The Rattle Is a Deterring Signal That Works Best with Sympatric Species

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Mead, L. Miles Horne This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7697892/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The rattlesnake rattle is one of the most iconic communication signals in nature, yet its evolutionary function remains poorly understood. To test the long-standing hypothesis that rattling acts as a deterrent, we developed a 3D-printed robotic rattlesnake capable of displaying the multimodal sensory stimulus produced by a rattlesnake. This robot was presented to 38 species of zoo-housed animals in a series of behavioral trials. Animals displayed aversive response to the rattling signal, suggesting that the rattle functions as a deimatic signal by triggering reflexive avoidance response. Sympatric species exhibited even stronger fear response to rattling, suggesting an evolved, innate fear to the signal. These results offer insights into how complex antipredator signals can originate and diversify in the animal kingdom. Animal Behavior Communication deimatism aposematism rattlesnakes Figures Figure 1 Figure 2 Figure 3 INTRODUCTION The rattlesnake rattle is perhaps one of the most emblematic communication signals found in nature. The profound impact of the rattle extends beyond the natural world by leaving a lasting imprint on human culture, where it has been symbolized in various art forms throughout history (Reiserer, 2016 ). Despite the fascination the rattle creates, the evolutionary origins and functions of this signal remain poorly understood (Reiserer & Schuett, 2016 ; Caine, Muñoz & Mulholland, 2020 ). The rattle is an extraordinary and uniquely evolved trait that emerged as a singular evolutionary event (Greene, 1988 ; Meik & Schuett, 2016 ), exclusively found in the genera Crotalus and Sistrurus (Klauber, 1956 ). Based on phylogenetic analyses, rattlesnakes rapidly diversified as they invaded a variety of habitats (Blair & Sánchez-Ramírez, 2016 ; Myers et al., 2024 ). Nowadays, rattlesnakes constitute a significant portion of the snake biomass across many habitats in the Western hemisphere, demonstrating their success as a group (Beaupre & Duvall, 1998 ; Nowak, Theimer & Schuett, 2008 ). Given their rapid diversification and ecological success, the rattle has been previously proposed as an important driver of the radiation of rattlesnakes (Meik & Schuett, 2016 ). The rattlesnake rattle is composed of loosely interlocking keratin segments, and its overall structure is conserved across all rattlesnakes species (Klauber, 1956 ). The rattle’s characteristic sound is produced when rattlesnakes contract highly specialized tailshaker muscles, causing the keratin segments to vibrate rapidly against each other (Moon, 2001 ). Because the rattle does not have any obvious morphological precursors (Allf, Durst & Pfennig, 2016 ), scientists have tried to solve the enigma of its evolution by identifying behaviors that may have preceded its development (Cope, 1871 ; Klauber, 1956 ). However, even the current function of the rattle remains poorly understood and uncovering the role of the rattle could shed light on its evolutionary origins and adaptative significance. Two main hypotheses have been proposed regarding the adaptative role of the rattle. The first hypothesis suggests that the rattle evolved as a caudal lure to attract prey (Schuett, Clark & Kraus, 1984 ), a behavior commonly observed in several snake taxa, especially within the Viperidae family (Reiserer & Schuett, 2016 ). The second hypothesis proposes that the rattle evolved to deter animals potentially dangerous to rattlesnakes, such as large grazing omnivores (Hay, 1887 ) or crevice-probing carnivores (Greene, 1997 ). The rattle has been proposed to act as a deterrent through two different mechanisms: deimatic signaling (Fenton & Licht, 1990 ), which triggers reflexive avoidance, and aposematic signaling, which conveys a warning of potential danger (Drinkwater et al., 2022 ). It is also important to recognize that the rattle is part of multimodal display, i.e. a display conveying information through multiple sensory channels (Rowe & Guilford, 1999 ). Indeed, when a rattlesnake rattle, its behavior combines auditory cues (the sound produced by the rattle) with visual signals, such as tail vibration, body posture, and sometimes conspicuous tail coloration. Multimodal displays often enhance communication, especially in high-stakes context, such as predator deterrence (Rowe & Guilford, 1999 ). In rattlesnakes, these sensory cues are typically expressed simultaneously and may work together to increase the receiver’s perception of threat. However, direct evidence supporting the hypothesis that rattling acts as a deterrent is lacking, especially in controlled settings (Caine et al., 2020 ). To test the hypothesis that the rattle acts as a deterring signal, we developed a 3D-printed robot rattlesnake and exposed 38 species of zoo-housed animals to three different behavioral trials and scored their behavior. The main objective was to determine whether rattling serves as a deterrent to other animal species. The second objective was to test whether its effectiveness was greater among species sharing their present distribution with rattlesnakes. We expected species sharing their present distribution with rattlesnakes (sympatric) to exhibit a stronger fear response to the rattling signal than species that do not share their current distribution with rattlesnakes (allopatric). Because all animals in this study were assumed to be naïve to rattlesnakes due to being in captivity, any observed differences in behavioral responses between sympatric and allopatric species would likely reflect an evolved, potentially innate sensitivity to the rattling signal, rather than learned avoidance. If the rattle deters both sympatric and allopatric species, this would support the idea that the rattle functions as a deimatic signal. However, if sympatric species exhibit stronger fear responses than allopatric species, it would suggest that the rattle also serves an aposematic function. Together, these possibilities support the hypothesis that the rattle may have a dual function by acting both as a deimatic and aposematic signal. This duality could suggest that the rattle began as general startle mechanism that gradually evolved as an aposematic warning. MATERIALS AND METHODS Rattlesnake robot design The 3D-printed rattlesnake model was designed and printed by the Fab Lab (501(c)3 Tech and Education Nonprofit Organization) located in El Paso, Texas. A preserved specimen of Crotalus atrox from the UTEP Biodiversity Collection (Catalogue #: 12333) was scanned in a defensive position (coiled, head and rattle up). The digital model created from the scan was then adjusted and printed with polylactic acid using a Creality Ender 3 FDM printer (Shenzhen Creality 3D Technology Co., Ltd., Shenzhen, China) . The 3D-printed model was approximately 15.5 cm length, 13 cm width, and 7.5 cm height. An interchangeable thermoplastic polyurethane (TPU) sheath was designed to attach at the tail end of the model and hold real rattles. The TPU sheaths were printed in different sizes to accommodate different rattle sizes. Rattles were collected from deceased rattlesnakes ( Crotalus sp.) found on roads in the El Paso area. To animate the 3D-printed model, the circuit board from a remote-controlled car toy (Model: Stunt Runner; Brand: Adventure force™, Buzz Bee Toys HK Ltd., Mt Laurel, USA) was recovered and refurbished to vibrate the rattle of the 3D-printed rattlesnake model on command. To do so, one of the wheels was replaced by a vibration motor (Tatoko DC 1.5-3V 7,000–14,000 RPM vibrating micro coreless brushed motor). The other wheels were removed from the circuit board. The vibration motor was inserted into the TPU sheath under the rattle and the circuit board was inserted into a compartment within the 3D-printed model, making none of the circuitry visible. The remote had a range of approximately 40 meters and was used to vibrate the rattle during trials. The 3D-printed model was painted according to the coloration and pattern of a western-diamond-backed rattlesnake with acrylic paint (Acrylicos Vallejo, Barcelona, Spain). The TPU sheaths were painted to follow the black and white banding found on the tail of Crotalus atrox . A layer of varnish (Liquitex professional matte varnish) was applied on the 3D-printed model to protect the paint from damage (Fig. 1 A). Behavioral trials All behavioral trials adhered to the ethical guidelines of The University of Texas at El Paso and were pre-approved by the University of Texas at El Paso Institutional Animal Care and Use Committee (protocol number: A-201101-1_1701402-1) and by the Association of Zoos and Aquariums (AZA). Behavioral trials were conducted at the El Paso Zoo (TX, USA). To limit stress, trials were conducted in the animal’s home enclosure (indoorsor outdoors enclosure). Trials were conducted in the presence of two observers and at least one El Paso Zoo personnel. All animals tested in this study were assumed to be naïve to rattlesnakes as they had spent most or all their lives in captivity. All trials were recorded using a camera (Sony handycam HDR-CX405, Sony, Tokyo, Japan) and the behavioral responses were evaluated from the video records. Three behavioral trials were conducted for each individual. For the first trial ( control ), the test individual was released in the enclosure after a food reward was placed in the enclosure to motivate the animal to come forward. For the second trial ( snake ), the robot rattlesnake was placed about 50 cm from the food reward, but the rattle was not triggered when the animal approached the food or the model. For the third trial ( snake + rattle ), the robot rattlesnake was placed about 50 cm away from the food reward and the rattle was triggered with the remote control when the animal was within one meter of food or the model (Fig. 1 B-D). The order of the trials was not randomized to minimize the risk of carryover fear response. Trials always started with the control trial, then the snake trial, and finally the snake + rattle trial. The food reward was adapted to the species tested. A trial consisting solely of the rattling sound was not included in this study for both theoretical and methodological reasons. First, the primary objective was to evaluate behavioral responses to the combined audiovisual stimulus a rattlesnake would produce, rather than to isolate the contribution of individual sensory modalities (visual and sound). In natural encounters, visual and auditory cues from a rattlesnake often co-occur, especially in close-range interactions, as simulated in this study. We aimed to replicate an ecologically relevant scenario, where rattling is almost always accompanied by the visible presence of a rattlesnake. Second, the acoustic environment of the zoo was challenging as it presented background noises that were highly variable and difficult to control. We were concerned that animals would have difficulty localizing or interpreting a sound in the absence of a visual cue, reducing the likelihood of detecting or responding meaningfully to a sound-only trial. We acknowledge that the same acoustic challenges also apply to the snake + rattle trial. However, the rattle was only triggered when animals were within close range of the robot, helping them localize the sound source and associate it with the visual of the robot. For each of these trials, the behavioral response of the individual tested was measured. Individual behavior was scored following a behavioral scale adaptable to any species tested and for all three trials (see Table 1 ). Specifically, individual behavior was measured using a 4-point ordinal scale reflecting increasing levels of aversion: no reaction, apprehension, startled, and flee. This ordinal structure captured a progression from passiveness (no reaction) to hesitation (apprehension), to defensive or avoidant behavior (startled), to full retreat from the testing area (flee). Two observers who were not present during the trials at the zoo rated the videos independently. The raters were not blind to the treatment. Table 1 Behavioral scale used to score the behavioral response of animal during trials. Behavior Description No reaction Individual readily approached the testing area. Individual did not exhibit any behavior showing that the model was detected if present. Model was detected, individual smells or look at the model but do not show any fear response. Apprehension Model/food reward approached with caution by the individual. Individual’s body twitched when approaching food reward or model. Individual first ate and then backed up. Individual paused eating and then continued. Startled Individual did not approach the model or the food reward. Individual was exhibiting threat displays such as vocalizations. Individual dropped the food reward. Flee Individual moved away quickly from the model or food reward to completely leave the testing area. Species tested The list of species tested is presented in supplementary materials (Fig S1). Species were classified as allopatric or sympatric based on their distribution relative to the distribution of extant rattlesnake species. Species distribution ranges were gathered from the IUCN red list (IUCN, 2024 ). Species were considered sympatric if any part of its range overlapped with at least one species of rattlesnake ( Crotalus sp. or Sistrurus sp. ). We tested a total of 38 species, 22 of which were allopatric and 16 of which were sympatric with rattlesnakes. The number of individuals tested per species varied between one individual to seven individuals. Statistical analysis All statistical analysis were performed in R (version 4.2.2) (R Core Team, 2025 ). The inter-rater reliability was estimated using Gwet’s AC1 from the package irrCAC (Gwet, 2019 ) for the behavioral scores. To determine whether evolutionary relationships influence behavioral responses to rattling, the phylogenetic signal among taxa in this study was examined. First, a phylogenetic tree encompassing all taxa tested was created using data from the Open Tree of Life with the package rotl (Michonneau, Brown & Winter, 2016 ). The branch lengths for this phylogenetic tree were computed using Grafen’s method (Grafen & Hamilton, 1997 ) using the package ape (Paradis & Schliep, 2019 ). The phylogenetic signal was tested for the behavioral response of each trial type ( control, snake, snake + rattle ) using Pagel’s lambda calculated with the package phytools (Revell, 2014 ). Cumulative link mixed models were conducted using package ordinal (Christensen, 2023 ). Regressions were performed with the behavioral score as response variable and species distribution (sympatric or allopatric) and trial type ( control, snake, snake + rattle ) as explanatory variables. Individual identity was included as a random variable to account for repeated measures of the same individual across treatments. Because of the small sample size, only one explanatory variable at a time was included in each model. RESULTS Inter-rater reliability and phylogenetic signal Gwet’s AC1 was estimated to be 0.76357 between the two raters for the behavioral scores. As such, the agreement between the two raters was considered to be substantial (Gwet, 2008 ) and thus, only the behavioral scores from one rater were used for the rest of the analysis. This rater was chosen randomly. The estimated value of Pagel’s λ varied between less than 0.001 for the negative and positive control trials and 0.0245 for the experimental trial, indicating minimal phylogenetic signal in the behavioral response of animals. Therefore, phylogenetic corrections were not included in the following analyses. Behavioral responses between trials Cumulative link mixed models indicated that the trial type had a significant effect on the behavioral responses with individuals showing significant stronger fear response in in the snake + rattle trial (Estimate = 5.50, SE = 0.90, z = 6.10, p < 0.001) and in the snake trial (Estimate = 2.68, SE = 0.80, z = 3.35, p < 0.001) compared to the control trial (Fig. 2 A). Moreover, individuals were significantly more likely to exhibit stronger fear response in the snake + rattle than in the snake trials (Estimate = 2.81, SE = 0.495, z = 5.68, p < 0.001). For allopatric species, individuals were significantly more likely to exhibit stronger fear response in the snake + rattle trial than in the control (Estimate = -5.30, SE = 1.2, z = -4.40, p < 0.001) or snake trial (Estimate = 3.33, SE = 0.743, z = 4.481, p < 0.001; Fig. 2 B). For sympatric species, individuals were more significantly more likely to exhibit a stronger fear response in the snake + rattle trial (Estimate = -5.95, SE = 1.420, z = -4.20, p < 0.001) and in the snake trial (Estimate = -3.34, SE = 0.726, z = 3.601, p < 0.001) than in the control trial (Fig. 2 C). Behavioral responses between sympatric and allopatric species Cumulative link mixed models were used to test whether species distribution (allopatric or sympatric) had a significant effect on their behavioral responses for each trial type. Sympatric species were significantly more likely to exhibit stronger fear response than allopatric species during the snake + rattle trial (Estimate = 0.59, SE = 0.001, z = 306.7, p < 0.001; Fig. 3 ). On the other hand, no significant differences in behavioral responses were observed between allopatric and sympatric species for the control trial (Estimate = -3.92, SE = 97.15, z = -0.04, p = 0.968) and the snake trial (Estimate = 2.60, SE = 1.516, z = 1.716, p = 0.09). DISCUSSION The main objectives of this study were to determine: 1) whether rattling serves as a deterrent to other animal species and 2) whether its effectiveness is greater among species sharing their present distribution with rattlesnakes. The results of this study demonstrated that rattling generally acts as a deterrent, with sympatric species exhibiting stronger fear response than allopatric species. These results support the long-standing hypothesis that the rattlesnake rattle is perceived as a deterring signal by other animals and align with anecdotal evidence documented throughout the years (Klauber, 1956 ; Sherbrooke & Westphal, 2006 ; Rogers et al., 2014 ) and the limited number of controlled studies that investigated this topic (Rowe & Owings, 1978 ; Swaisgood, Rowe & Owings, 1999 ; Caine et al., 2020 ). These findings are further supported by the fact that rattlesnakes usually rattle in defensive context (Greene, 1992 ) and that some species mimic rattling behavior as a defensive strategy (Owings, Rowe & Rundus, 2002 ; Allf, Sparkman & Pfennig, 2021 ). Indeed, burrowing owls ( Athene cunicularia ) defend themselves against predators by producing hisses that resemble the sound of a rattling rattlesnake (Owings et al., 2002 ) and gopher snakes ( Pituophis catenifer ) vibrate their tails similarly to a rattle (Allf et al., 2021 ). While animals exhibited a stronger fear response during the snake trial compared to the control trial, their response was even more pronounced during the snake + rattle trial. While these results indicate that rattling elicits a stronger fear response, the possibility that animals were responding to a novel sound and object cannot be totally ruled out. Despite this, these results suggest that the rattling signal alters animals’ perception of the robot, leading them to change their behavior. Animals might change their behavior in response to rattling as it triggers a reflexive avoidance response, causing animals to slow or stop their approach, suggesting that the rattle functions as a deimatic signal (Drinkwater et al., 2022 ). The rattle has been previously proposed as a deimatic signal (Fenton & Licht, 1990 ; Swaisgood et al., 1999 ; Caine et al., 2020 ; Drinkwater et al., 2022 ) but this hypothesis remained unconfirmed due to a lack of empirical evidence. All animals tested in this study were assumed to be naïve to rattlesnakes as they had spent most or all their lives in captivity. Despite this, rattling elicited a wide range of fear responses, from apprehension to fleeing, suggesting that rattling triggers existing reflexive neural mechanisms and works as a deimatic signal. Deimatic behaviors function by triggering reflexive responses such as startle reflexes, looming reflexes, fear responses, sensory overloads, confusions, or neophobia (Umbers et al., 2017 ; Drinkwater et al., 2022 ). Previous studies have shown that naïve predators respond more strongly to deimatic behavior when compared to experienced predators, potentially because experienced predators learn to ignore or avoid this display (Umbers et al., 2019 ). Numerous species of snakes are known to vibrate their tail when threatened (Greene, 1988 ), an especially common behavior in the families Colubridae and Viperidae, suggesting a shared origin between these families (Allf et al., 2016 ). Given the context in which tail vibration is expressed, tail vibration appears to function as a deterring behavior, likely to be deimatic. Its widespread occurrence and persistence across snake species suggest that it is likely to provide a survival advantage. Ancestral character state reconstructions analyses indicate that the rattlesnake rattle and rattling behavior could have evolved from the widespread tail-vibrating behavior (Allf et al., 2016 ). According to this, the rattle seems to follow the startle-first hypothesis, which states that the act of performing a defensive behavior (in this case, tail vibration) provides protective value and can facilitate the evolution of additional defenses, such as the rattle (Umbers et al., 2017 ). This further suggests that rattling functions as a deimatic signal, similar to tail vibration, which may explain why allopatric species and naïve individuals exhibit fear responses when exposed to the rattle. However, this does not explain why sympatric species exhibited significantly stronger reactions to the rattle than allopatric species, even if they were all naïve to rattlesnakes. Sympatric animals might be more sensitive to the rattle than allopatric species because they have evolved an innate fear of the rattling signal, suggesting that rattling serves as an aposematic signal for sympatric species. Indeed, while deimatic displays trigger reflexive response that do not require learned or innate aversion, aposematism relies on aversion that is either innate or learned from the focal species itself (Umbers et al., 2017 ). The innate avoidance of aposematic species or patterns have been previously found in several species, including humans (Souchet & Aubret, 2016 ). For example, hand-reared naïve great kiskadee ( Pitangus sulphuratus ) and turquoise-browed motmots ( Eumomota superciliosa ) both show a strong innate aversion to the aposematic yellow-red pattern of coral snakes (Smith, 1975 , 1977 ). While several species of tail-vibrating snakes are non-venomous (Young, 2003 ; Allf et al., 2016 , 2021 ), all species with a rattle are venomous (Klauber, 1956 ). What likely began as a deimatic signal through tail vibration may have evolved into an aposematic signal as species started to associate the rattle with the threat of a venomous bite. While avoidance may have initially been a learned behavior, selection may have acted upon individuals with a higher propensity for aversion responses and subsequently evolved into an innate response to the rattle. Evidence showed that aversion can evolve relatively quickly within populations: red-bellied black snakes ( Pseudechis porphyriacus ) developed an innate avoidance for the invasive marine toads ( Rhinella marina ) in Australia in less than 23 generations (Phillips & Shine, 2006 ). While our study does not quantify the strength of rattlesnake impact on selection, this could be a crucial next step in understanding how innate fear become fixed in sympatric populations. In conclusion, this study demonstrated that the rattle functions as a deterrent signal, a hypothesis widely accepted over time and previously supported, until now, by a few controlled-studies (Rowe & Owings, 1978 ; Swaisgood et al., 1999 ) and anecdotal evidence (Klauber, 1956 ; Sherbrooke & Westphal, 2006 ; Rogers et al., 2014 ). More importantly, this study highlighted the dual functionality of the rattle, suggesting that the rattle potentially acts both as a deimatic and aposematic signal. Although the distinction between aposematism and deimatism was not directly tested during this study, the difference in behavioral responses between allopatric and sympatric species allows us to infer potential mechanisms. The rattle effectively deters animals by triggering reflexive avoidance responses regardless of their geographic origin or past experience, supporting the role of the rattle as a deimatic signal. Sympatric species demonstrated significantly stronger fear responses than allopatric species, potentially due to an evolved innate aversion to the rattle, refining the function of the rattle as an aposematic signal in these species. This dual signaling strategy provides insight into the evolutionary trajectory of the rattle, suggesting that it likely originated as a general startle mechanism and gradually evolved into a more specialized aposematic warning. This study raises several intriguing questions, including the role of experience in shaping responses to a deterring signal, the extent of selective pressure required for a deimatic signal to evolve into an aposematic one, and the overall efficiency of the rattle in preventing predation. Further studies are needed to address these questions and gain a deeper understanding of the evolution and ecological significance of the rattle. Declarations Author’s contribution Conceptualization: OD, JJM, LMH. Implementation and data collection: OD, JJM, LMH. Data analysis: OD. Writing of first draft: OD. Reviewing and editing: OD, JJM, LMH. Acknowledgments: We would like to thank the personnel of the El Paso Zoo for allowing us to conduct our behavioral trials with their animals, with a special thanks to Carrie Trudeau who helped us along the way. We would also like to thank the Fab Lab for helping us design the robotic rattlesnake and Vicky Zhuang from the UTEP Biodiversity Collections for letting us borrow a specimen. We would like to acknowledge the help of Shawn Walls in the video analysis, and the Seymoure lab for providing feedback on the manuscript. We also would like to acknowledge the support of Jerry Johnson, Allyson Benson-Pedraza, and Vicente Mata-Silva for this project. We would like to thank the UTEP IACUC and AZA committee for allowing us to conduct this study. Data availability The datasets and R code generated during the current study are available in the following GitHub repository: https://github.com/OceaneD3/Rattle-is-a-deterring-signal . References Allf, B.C., Durst, P.A.P. & Pfennig, D.W. (2016). Behavioral Plasticity and the Origins of Novelty: The Evolution of the Rattlesnake Rattle. Am. Nat. 188 , 475–483. Allf, B.C., Sparkman, A.M. & Pfennig, D.W. (2021). Microevolutionary change in mimicry? 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Black Bear Reactions to Venomous and Non-venomous Snakes in Eastern North America. Ethology 120 , 641–651. Rowe, C. & Guilford, T. (1999). The Evolution of Multimodal Warning Displays. Evolutionary Ecology 13 , 655–671. Rowe, M.P. & Owings, D.H. (1978). The Meaning of the Sound of Rattling by Rattlesnakes to California Ground Squirrels. Behaviour 66 , 252–267. Schuett, G., Clark, D.L. & Kraus, J. (1984). Feeding mimicry in the rattlesnake Sistrurus catenatus, with comments on the evolution of the rattle. Anim. Behav. 625–626. Sherbrooke, W.C. & Westphal, M.F. (2006). Responses of Greater Roadrunners during Attacks on Sympatric Venomous and Nonvenomous Snakes. The Southwestern Naturalist 51 , 41–47. Smith, S.M. (1975). Innate Recognition of Coral Snake Pattern by a Possible Avian Predator. Science 187 , 759–760. Smith, S.M. (1977). Coral-snake pattern recognition and stimulus generalisation by naive great kiskadees (Aves: Tyrannidae). Nature 265 , 535–536. Souchet, J. & Aubret, F. (2016). Revisiting the fear of snakes in children: the role of aposematic signalling. Sci Rep 6 , 37619. Swaisgood, R.R., Rowe, M.P. & Owings, D.H. (1999). Assessment of rattlesnake dangerousness by California ground squirrels: exploitation of cues from rattling sounds. Animal Behaviour 57 , 1301–1310. Umbers, K.D.L., De Bona, S., White, T.E., Lehtonen, J., Mappes, J. & Endler, J.A. (2017). Deimatism: a neglected component of antipredator defence. Biology Letters 13 , 20160936. Umbers, K.D.L., White, T.E., De Bona, S., Haff, T., Ryeland, J., Drinkwater, E. & Mappes, J. (2019). The protective value of a defensive display varies with the experience of wild predators. Sci Rep 9 , 463. Young, B.A. (2003). Snake Bioacoustics: Toward a Richer Understanding of the Behavioral Ecology of Snakes. The Quarterly Review of Biology 78 , 303–325. Additional Declarations The authors declare no competing interests. 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Mead","email":"","orcid":"","institution":"The University of Texas at El Paso","correspondingAuthor":false,"prefix":"","firstName":"Joshua","middleName":"J.","lastName":"Mead","suffix":""},{"id":519633314,"identity":"2836f4bf-9db7-40cc-a2ae-a90c2f08d99b","order_by":2,"name":"L. Miles Horne","email":"","orcid":"","institution":"The University of Texas at El Paso","correspondingAuthor":false,"prefix":"","firstName":"L.","middleName":"Miles","lastName":"Horne","suffix":""}],"badges":[],"createdAt":"2025-09-23 22:31:14","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":true,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":true},"doi":"10.21203/rs.3.rs-7697892/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7697892/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":92190206,"identity":"902a6201-dbd0-44c3-890b-ccc18d3aafbb","added_by":"auto","created_at":"2025-09-25 15:05:51","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":80879,"visible":true,"origin":"","legend":"","description":"","filename":"JoZZoo23SEP25.docx","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/b20d8bbc744c1e220b3441f5.docx"},{"id":92190460,"identity":"b4e2beca-339c-43ea-806b-27b688dd7d23","added_by":"auto","created_at":"2025-09-25 15:05:57","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":342,"visible":true,"origin":"","legend":"","description":"","filename":"rs7697892.json","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/6f549fe000deb523e1797ffb.json"},{"id":92190455,"identity":"a346cd77-faf1-453c-95eb-c45481fa97b4","added_by":"auto","created_at":"2025-09-25 15:05:57","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":82601,"visible":true,"origin":"","legend":"","description":"","filename":"rs76978920enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/f201788a441281a8d7434c40.xml"},{"id":92190375,"identity":"6a9efe34-4ca7-4f23-954d-7f65530eca47","added_by":"auto","created_at":"2025-09-25 15:05:56","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":80989,"visible":true,"origin":"","legend":"","description":"","filename":"rs76978920structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/6d96857a0449a716465c3c33.xml"},{"id":92190424,"identity":"aee57b49-4d55-4fff-8e28-3553a492756b","added_by":"auto","created_at":"2025-09-25 15:05:57","extension":"html","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":87300,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/1ec2fb32782d3921c47195ac.html"},{"id":92190167,"identity":"7878d566-25c2-4083-8af5-986bfd012af1","added_by":"auto","created_at":"2025-09-25 15:05:48","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":822072,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe robotic rattlesnake and experimental set-up. \u003c/strong\u003e(\u003cem\u003e\u003cstrong\u003eA\u003c/strong\u003e\u003c/em\u003e) Diagram of the 3D-printed robot rattlesnake. (\u003cem\u003e\u003cstrong\u003eB-D\u003c/strong\u003e\u003c/em\u003e) Behavioral responses of a collared peccary (\u003cem\u003ePecari tajacu\u003c/em\u003e) during each of the three trial types. In all trials, a food reward was placed in the enclosure to encourage approach. (\u003cem\u003e\u003cstrong\u003eB\u003c/strong\u003e\u003c/em\u003e) The test individual was released in the enclosure after the food reward was placed in the enclosure. (\u003cem\u003e\u003cstrong\u003eC\u003c/strong\u003e\u003c/em\u003e) The robot rattlesnake was placed in the vicinity of the food reward, but the rattle was not triggered when the animal approached the food or the model. (\u003cem\u003e\u003cstrong\u003eD\u003c/strong\u003e\u003c/em\u003e) The robot rattlesnake was placed in the vicinity of the food reward and the rattle was triggered with the remote control when the animal approached the food or the model.\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/fef5083e977591289a8637c2.jpg"},{"id":92190357,"identity":"931e568d-f007-4fb7-b6fe-a88fb5a53109","added_by":"auto","created_at":"2025-09-25 15:05:55","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":207903,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe rattle acts as a deterrent. \u003c/strong\u003eStatistical significance between groups is denoted by the letter on top of each bar.\u003cstrong\u003e \u003c/strong\u003eIndividuals tested as a group are included as one observation.\u003cstrong\u003e \u0026nbsp;\u003c/strong\u003e(\u003cem\u003e\u003cstrong\u003eA\u003c/strong\u003e\u003c/em\u003e)\u003cstrong\u003e \u003c/strong\u003eBehavioral counts per trial type.\u003cstrong\u003e \u003c/strong\u003e(\u003cem\u003e\u003cstrong\u003eB\u003c/strong\u003e\u003c/em\u003e) Behavioral responses exhibited by allopatric species for each trial type. (\u003cem\u003e\u003cstrong\u003eC\u003c/strong\u003e\u003c/em\u003e) Behavioral responses exhibited by sympatric species for each trial type.\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/b9da70ae28bfe52b82203c2e.jpg"},{"id":92190373,"identity":"3372f213-2e35-41e4-b580-92a66b51c204","added_by":"auto","created_at":"2025-09-25 15:05:56","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":128625,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSympatric species are more sensitive to the rattle than allopatric species. \u003c/strong\u003e\u003cem\u003e*** \u003c/em\u003edenotes statistical significance while \u003cem\u003en.s \u003c/em\u003edenotes non-significance. Individuals tested as a group are included as one observation (\u003cem\u003e\u003cstrong\u003eA\u003c/strong\u003e\u003c/em\u003e) Behavior counts per species distribution relative to rattlesnake (allopatric or sympatric) per trial type. (\u003cem\u003e\u003cstrong\u003eB\u003c/strong\u003e\u003c/em\u003e) Behavioral response exhibited by allopatric and sympatric species for each trial type.\u003c/p\u003e","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/3961707ca9d7a80a9e45ccf2.jpg"},{"id":92190621,"identity":"ab72539f-783f-4d1d-9c94-aa53e4a83065","added_by":"auto","created_at":"2025-09-25 15:06:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1789126,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7697892/v1/56eaf001-286b-41b3-8d73-77a738c223ba.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eThe Rattle Is a Deterring Signal That Works Best with Sympatric Species\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION ","content":"\u003cp\u003eThe rattlesnake rattle is perhaps one of the most emblematic communication signals found in nature. The profound impact of the rattle extends beyond the natural world by leaving a lasting imprint on human culture, where it has been symbolized in various art forms throughout history (Reiserer, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Despite the fascination the rattle creates, the evolutionary origins and functions of this signal remain poorly understood (Reiserer \u0026amp; Schuett, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Caine, Mu\u0026ntilde;oz \u0026amp; Mulholland, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe rattle is an extraordinary and uniquely evolved trait that emerged as a singular evolutionary event (Greene, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Meik \u0026amp; Schuett, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), exclusively found in the genera \u003cem\u003eCrotalus\u003c/em\u003e and \u003cem\u003eSistrurus\u003c/em\u003e (Klauber, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1956\u003c/span\u003e). Based on phylogenetic analyses, rattlesnakes rapidly diversified as they invaded a variety of habitats (Blair \u0026amp; S\u0026aacute;nchez-Ram\u0026iacute;rez, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Myers et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Nowadays, rattlesnakes constitute a significant portion of the snake biomass across many habitats in the Western hemisphere, demonstrating their success as a group (Beaupre \u0026amp; Duvall, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Nowak, Theimer \u0026amp; Schuett, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Given their rapid diversification and ecological success, the rattle has been previously proposed as an important driver of the radiation of rattlesnakes (Meik \u0026amp; Schuett, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The rattlesnake rattle is composed of loosely interlocking keratin segments, and its overall structure is conserved across all rattlesnakes species (Klauber, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1956\u003c/span\u003e). The rattle\u0026rsquo;s characteristic sound is produced when rattlesnakes contract highly specialized tailshaker muscles, causing the keratin segments to vibrate rapidly against each other (Moon, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Because the rattle does not have any obvious morphological precursors (Allf, Durst \u0026amp; Pfennig, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), scientists have tried to solve the enigma of its evolution by identifying behaviors that may have preceded its development (Cope, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1871\u003c/span\u003e; Klauber, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1956\u003c/span\u003e). However, even the current function of the rattle remains poorly understood and uncovering the role of the rattle could shed light on its evolutionary origins and adaptative significance.\u003c/p\u003e\u003cp\u003eTwo main hypotheses have been proposed regarding the adaptative role of the rattle. The first hypothesis suggests that the rattle evolved as a caudal lure to attract prey (Schuett, Clark \u0026amp; Kraus, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1984\u003c/span\u003e), a behavior commonly observed in several snake taxa, especially within the Viperidae family (Reiserer \u0026amp; Schuett, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The second hypothesis proposes that the rattle evolved to deter animals potentially dangerous to rattlesnakes, such as large grazing omnivores (Hay, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1887\u003c/span\u003e) or crevice-probing carnivores (Greene, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). The rattle has been proposed to act as a deterrent through two different mechanisms: deimatic signaling (Fenton \u0026amp; Licht, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), which triggers reflexive avoidance, and aposematic signaling, which conveys a warning of potential danger (Drinkwater et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). It is also important to recognize that the rattle is part of multimodal display, i.e. a display conveying information through multiple sensory channels (Rowe \u0026amp; Guilford, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). Indeed, when a rattlesnake rattle, its behavior combines auditory cues (the sound produced by the rattle) with visual signals, such as tail vibration, body posture, and sometimes conspicuous tail coloration. Multimodal displays often enhance communication, especially in high-stakes context, such as predator deterrence (Rowe \u0026amp; Guilford, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). In rattlesnakes, these sensory cues are typically expressed simultaneously and may work together to increase the receiver\u0026rsquo;s perception of threat. However, direct evidence supporting the hypothesis that rattling acts as a deterrent is lacking, especially in controlled settings (Caine et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTo test the hypothesis that the rattle acts as a deterring signal, we developed a 3D-printed robot rattlesnake and exposed 38 species of zoo-housed animals to three different behavioral trials and scored their behavior. The main objective was to determine whether rattling serves as a deterrent to other animal species. The second objective was to test whether its effectiveness was greater among species sharing their present distribution with rattlesnakes. We expected species sharing their present distribution with rattlesnakes (sympatric) to exhibit a stronger fear response to the rattling signal than species that do not share their current distribution with rattlesnakes (allopatric). Because all animals in this study were assumed to be na\u0026iuml;ve to rattlesnakes due to being in captivity, any observed differences in behavioral responses between sympatric and allopatric species would likely reflect an evolved, potentially innate sensitivity to the rattling signal, rather than learned avoidance. If the rattle deters both sympatric and allopatric species, this would support the idea that the rattle functions as a deimatic signal. However, if sympatric species exhibit stronger fear responses than allopatric species, it would suggest that the rattle also serves an aposematic function. Together, these possibilities support the hypothesis that the rattle may have a dual function by acting both as a deimatic and aposematic signal. This duality could suggest that the rattle began as general startle mechanism that gradually evolved as an aposematic warning.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS ","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eRattlesnake robot design\u003c/h2\u003e\u003cp\u003eThe 3D-printed rattlesnake model was designed and printed by the Fab Lab (501(c)3 Tech and Education Nonprofit Organization) located in El Paso, Texas. A preserved specimen of \u003cem\u003eCrotalus atrox\u003c/em\u003e from the UTEP Biodiversity Collection (Catalogue #: 12333) was scanned in a defensive position (coiled, head and rattle up). The digital model created from the scan was then adjusted and printed with polylactic acid using a Creality Ender 3 FDM printer \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003e(Shenzhen Creality 3D Technology Co., Ltd., Shenzhen, China)\u003c/span\u003e. The 3D-printed model was approximately 15.5 cm length, 13 cm width, and 7.5 cm height. An interchangeable thermoplastic polyurethane (TPU) sheath was designed to attach at the tail end of the model and hold real rattles. The TPU sheaths were printed in different sizes to accommodate different rattle sizes. Rattles were collected from deceased rattlesnakes (\u003cem\u003eCrotalus sp.)\u003c/em\u003e found on roads in the El Paso area. To animate the 3D-printed model, the circuit board from a remote-controlled car toy (Model: Stunt Runner; Brand: Adventure force™, Buzz Bee Toys HK Ltd., Mt Laurel, USA) was recovered and refurbished to vibrate the rattle of the 3D-printed rattlesnake model on command. To do so, one of the wheels was replaced by a vibration motor (Tatoko DC 1.5-3V 7,000–14,000 RPM vibrating micro coreless brushed motor). The other wheels were removed from the circuit board. The vibration motor was inserted into the TPU sheath under the rattle and the circuit board was inserted into a compartment within the 3D-printed model, making none of the circuitry visible. The remote had a range of approximately 40 meters and was used to vibrate the rattle during trials. The 3D-printed model was painted according to the coloration and pattern of a western-diamond-backed rattlesnake with acrylic paint (Acrylicos Vallejo, Barcelona, Spain). The TPU sheaths were painted to follow the black and white banding found on the tail of \u003cem\u003eCrotalus atrox\u003c/em\u003e. A layer of varnish (Liquitex professional matte varnish) was applied on the 3D-printed model to protect the paint from damage (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eBehavioral trials\u003c/h3\u003e\n\u003cp\u003e All behavioral trials adhered to the ethical guidelines of The University of Texas at El Paso and were pre-approved by the University of Texas at El Paso Institutional Animal Care and Use Committee (protocol number: A-201101-1_1701402-1) and by the Association of Zoos and Aquariums (AZA).\u003c/p\u003e\u003cp\u003eBehavioral trials were conducted at the El Paso Zoo (TX, USA). To limit stress, trials were conducted in the animal’s home enclosure (indoorsor outdoors enclosure). Trials were conducted in the presence of two observers and at least one El Paso Zoo personnel. All animals tested in this study were assumed to be naïve to rattlesnakes as they had spent most or all their lives in captivity. All trials were recorded using a camera (Sony handycam HDR-CX405, Sony, Tokyo, Japan) and the behavioral responses were evaluated from the video records. Three behavioral trials were conducted for each individual. For the first trial (\u003cem\u003econtrol\u003c/em\u003e), the test individual was released in the enclosure after a food reward was placed in the enclosure to motivate the animal to come forward. For the second trial (\u003cem\u003esnake\u003c/em\u003e), the robot rattlesnake was placed about 50 cm from the food reward, but the rattle was not triggered when the animal approached the food or the model. For the third trial (\u003cem\u003esnake + rattle\u003c/em\u003e), the robot rattlesnake was placed about 50 cm away from the food reward and the rattle was triggered with the remote control when the animal was within one meter of food or the model (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB-D). The order of the trials was not randomized to minimize the risk of carryover fear response. Trials always started with the \u003cem\u003econtrol\u003c/em\u003e trial, then the \u003cem\u003esnake\u003c/em\u003e trial, and finally the \u003cem\u003esnake + rattle\u003c/em\u003e trial. The food reward was adapted to the species tested. A trial consisting solely of the rattling sound was not included in this study for both theoretical and methodological reasons. First, the primary objective was to evaluate behavioral responses to the combined audiovisual stimulus a rattlesnake would produce, rather than to isolate the contribution of individual sensory modalities (visual and sound). In natural encounters, visual and auditory cues from a rattlesnake often co-occur, especially in close-range interactions, as simulated in this study. We aimed to replicate an ecologically relevant scenario, where rattling is almost always accompanied by the visible presence of a rattlesnake. Second, the acoustic environment of the zoo was challenging as it presented background noises that were highly variable and difficult to control. We were concerned that animals would have difficulty localizing or interpreting a sound in the absence of a visual cue, reducing the likelihood of detecting or responding meaningfully to a sound-only trial. We acknowledge that the same acoustic challenges also apply to the \u003cem\u003esnake + rattle\u003c/em\u003e trial. However, the rattle was only triggered when animals were within close range of the robot, helping them localize the sound source and associate it with the visual of the robot. For each of these trials, the behavioral response of the individual tested was measured. Individual behavior was scored following a behavioral scale adaptable to any species tested and for all three trials (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Specifically, individual behavior was measured using a 4-point ordinal scale reflecting increasing levels of aversion: no reaction, apprehension, startled, and flee. This ordinal structure captured a progression from passiveness (no reaction) to hesitation (apprehension), to defensive or avoidant behavior (startled), to full retreat from the testing area (flee). Two observers who were not present during the trials at the zoo rated the videos independently. The raters were not blind to the treatment.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eBehavioral scale used to score the behavioral response of animal during trials.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBehavior\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDescription\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNo reaction\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eIndividual readily approached the testing area. Individual did not exhibit any behavior showing that the model was detected if present. Model was detected, individual smells or look at the model but do not show any fear response.\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eApprehension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eModel/food reward approached with caution by the individual. Individual’s body twitched when approaching food reward or model. Individual first ate and then backed up. Individual paused eating and then continued.\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStartled\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eIndividual did not approach the model or the food reward. Individual was exhibiting threat displays such as vocalizations. Individual dropped the food reward.\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFlee\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cem\u003eIndividual moved away quickly from the model or food reward to completely leave the testing area.\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eSpecies tested\u003c/h3\u003e\n\u003cp\u003eThe list of species tested is presented in supplementary materials (Fig S1). Species were classified as allopatric or sympatric based on their distribution relative to the distribution of extant rattlesnake species. Species distribution ranges were gathered from the IUCN red list (IUCN, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Species were considered sympatric if any part of its range overlapped with at least one species of rattlesnake (\u003cem\u003eCrotalus sp.\u003c/em\u003e or \u003cem\u003eSistrurus sp.\u003c/em\u003e). We tested a total of 38 species, 22 of which were allopatric and 16 of which were sympatric with rattlesnakes. The number of individuals tested per species varied between one individual to seven individuals.\u003c/p\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eAll statistical analysis were performed in R (version 4.2.2) (R Core Team, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The inter-rater reliability was estimated using Gwet’s AC1 from the package \u003cem\u003eirrCAC\u003c/em\u003e (Gwet, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) for the behavioral scores.\u003c/p\u003e\u003cp\u003eTo determine whether evolutionary relationships influence behavioral responses to rattling, the phylogenetic signal among taxa in this study was examined. First, a phylogenetic tree encompassing all taxa tested was created using data from the Open Tree of Life with the package \u003cem\u003erotl\u003c/em\u003e (Michonneau, Brown \u0026amp; Winter, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The branch lengths for this phylogenetic tree were computed using Grafen’s method (Grafen \u0026amp; Hamilton, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) using the package \u003cem\u003eape\u003c/em\u003e (Paradis \u0026amp; Schliep, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The phylogenetic signal was tested for the behavioral response of each trial type (\u003cem\u003econtrol, snake, snake + rattle\u003c/em\u003e) using Pagel’s lambda calculated with the package \u003cem\u003ephytools\u003c/em\u003e (Revell, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eCumulative link mixed models were conducted using package \u003cem\u003eordinal\u003c/em\u003e (Christensen, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Regressions were performed with the behavioral score as response variable and species distribution (sympatric or allopatric) and trial type (\u003cem\u003econtrol, snake, snake + rattle\u003c/em\u003e) as explanatory variables. Individual identity was included as a random variable to account for repeated measures of the same individual across treatments. Because of the small sample size, only one explanatory variable at a time was included in each model.\u003c/p\u003e\u003c/div\u003e"},{"header":"RESULTS","content":"\u003ch2\u003eInter-rater reliability and phylogenetic signal\u003c/h2\u003e\u003cp\u003eGwet’s AC1 was estimated to be 0.76357 between the two raters for the behavioral scores. As such, the agreement between the two raters was considered to be substantial (Gwet, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) and thus, only the behavioral scores from one rater were used for the rest of the analysis. This rater was chosen randomly. The estimated value of Pagel’s λ varied between less than 0.001 for the negative and positive control trials and 0.0245 for the experimental trial, indicating minimal phylogenetic signal in the behavioral response of animals. Therefore, phylogenetic corrections were not included in the following analyses.\u003c/p\u003e\u003ch3\u003eBehavioral responses between trials\u003c/h3\u003e\u003cp\u003eCumulative link mixed models indicated that the trial type had a significant effect on the behavioral responses with individuals showing significant stronger fear response in in the \u003cem\u003esnake + rattle\u003c/em\u003e trial (Estimate = 5.50, SE = 0.90, z = 6.10, p \u0026lt; 0.001) and in the \u003cem\u003esnake\u003c/em\u003e trial (Estimate = 2.68, SE = 0.80, z = 3.35, p \u0026lt; 0.001) compared to the control trial (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). Moreover, individuals were significantly more likely to exhibit stronger fear response in the \u003cem\u003esnake + rattle\u003c/em\u003e than in the \u003cem\u003esnake\u003c/em\u003e trials (Estimate = 2.81, SE = 0.495, z = 5.68, p \u0026lt; 0.001). For allopatric species, individuals were significantly more likely to exhibit stronger fear response in the \u003cem\u003esnake + rattle\u003c/em\u003e trial than in the \u003cem\u003econtrol\u003c/em\u003e (Estimate = -5.30, SE = 1.2, z = -4.40, p \u0026lt; 0.001) or \u003cem\u003esnake\u003c/em\u003e trial (Estimate = 3.33, SE = 0.743, z = 4.481, p \u0026lt; 0.001; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). For sympatric species, individuals were more significantly more likely to exhibit a stronger fear response in the \u003cem\u003esnake + rattle\u003c/em\u003e trial (Estimate = -5.95, SE = 1.420, z = -4.20, p \u0026lt; 0.001) and in the \u003cem\u003esnake\u003c/em\u003e trial (Estimate = -3.34, SE = 0.726, z = 3.601, p \u0026lt; 0.001) than in the control trial (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC).\u003c/p\u003e\u003ch3\u003eBehavioral responses between sympatric and allopatric species\u003c/h3\u003e\u003cp\u003eCumulative link mixed models were used to test whether species distribution (allopatric or sympatric) had a significant effect on their behavioral responses for each trial type. Sympatric species were significantly more likely to exhibit stronger fear response than allopatric species during the \u003cem\u003esnake + rattle\u003c/em\u003e trial (Estimate = 0.59, SE = 0.001, z = 306.7, p \u0026lt; 0.001; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). On the other hand, no significant differences in behavioral responses were observed between allopatric and sympatric species for the control trial (Estimate = -3.92, SE = 97.15, z = -0.04, p = 0.968) and the \u003cem\u003esnake\u003c/em\u003e trial (Estimate = 2.60, SE = 1.516, z = 1.716, p = 0.09).\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThe main objectives of this study were to determine: 1) whether rattling serves as a deterrent to other animal species and 2) whether its effectiveness is greater among species sharing their present distribution with rattlesnakes. The results of this study demonstrated that rattling generally acts as a deterrent, with sympatric species exhibiting stronger fear response than allopatric species.\u003c/p\u003e\u003cp\u003eThese results support the long-standing hypothesis that the rattlesnake rattle is perceived as a deterring signal by other animals and align with anecdotal evidence documented throughout the years (Klauber, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1956\u003c/span\u003e; Sherbrooke \u0026amp; Westphal, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Rogers et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) and the limited number of controlled studies that investigated this topic (Rowe \u0026amp; Owings, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Swaisgood, Rowe \u0026amp; Owings, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Caine et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These findings are further supported by the fact that rattlesnakes usually rattle in defensive context (Greene, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1992\u003c/span\u003e) and that some species mimic rattling behavior as a defensive strategy (Owings, Rowe \u0026amp; Rundus, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Allf, Sparkman \u0026amp; Pfennig, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Indeed, burrowing owls (\u003cem\u003eAthene cunicularia\u003c/em\u003e) defend themselves against predators by producing hisses that resemble the sound of a rattling rattlesnake (Owings et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) and gopher snakes (\u003cem\u003ePituophis catenifer\u003c/em\u003e) vibrate their tails similarly to a rattle (Allf et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWhile animals exhibited a stronger fear response during the \u003cem\u003esnake\u003c/em\u003e trial compared to the control trial, their response was even more pronounced during the \u003cem\u003esnake + rattle\u003c/em\u003e trial. While these results indicate that rattling elicits a stronger fear response, the possibility that animals were responding to a novel sound and object cannot be totally ruled out. Despite this, these results suggest that the rattling signal alters animals’ perception of the robot, leading them to change their behavior. Animals might change their behavior in response to rattling as it triggers a reflexive avoidance response, causing animals to slow or stop their approach, suggesting that the rattle functions as a deimatic signal (Drinkwater et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The rattle has been previously proposed as a deimatic signal (Fenton \u0026amp; Licht, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Swaisgood et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Caine et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Drinkwater et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) but this hypothesis remained unconfirmed due to a lack of empirical evidence. All animals tested in this study were assumed to be naïve to rattlesnakes as they had spent most or all their lives in captivity. Despite this, rattling elicited a wide range of fear responses, from apprehension to fleeing, suggesting that rattling triggers existing reflexive neural mechanisms and works as a deimatic signal. Deimatic behaviors function by triggering reflexive responses such as startle reflexes, looming reflexes, fear responses, sensory overloads, confusions, or neophobia (Umbers et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Drinkwater et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Previous studies have shown that naïve predators respond more strongly to deimatic behavior when compared to experienced predators, potentially because experienced predators learn to ignore or avoid this display (Umbers et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eNumerous species of snakes are known to vibrate their tail when threatened (Greene, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1988\u003c/span\u003e), an especially common behavior in the families Colubridae and Viperidae, suggesting a shared origin between these families (Allf et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Given the context in which tail vibration is expressed, tail vibration appears to function as a deterring behavior, likely to be deimatic. Its widespread occurrence and persistence across snake species suggest that it is likely to provide a survival advantage. Ancestral character state reconstructions analyses indicate that the rattlesnake rattle and rattling behavior could have evolved from the widespread tail-vibrating behavior (Allf et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). According to this, the rattle seems to follow the startle-first hypothesis, which states that the act of performing a defensive behavior (in this case, tail vibration) provides protective value and can facilitate the evolution of additional defenses, such as the rattle (Umbers et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). This further suggests that rattling functions as a deimatic signal, similar to tail vibration, which may explain why allopatric species and naïve individuals exhibit fear responses when exposed to the rattle. However, this does not explain why sympatric species exhibited significantly stronger reactions to the rattle than allopatric species, even if they were all naïve to rattlesnakes.\u003c/p\u003e\u003cp\u003eSympatric animals might be more sensitive to the rattle than allopatric species because they have evolved an innate fear of the rattling signal, suggesting that rattling serves as an aposematic signal for sympatric species. Indeed, while deimatic displays trigger reflexive response that do not require learned or innate aversion, aposematism relies on aversion that is either innate or learned from the focal species itself (Umbers et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The innate avoidance of aposematic species or patterns have been previously found in several species, including humans (Souchet \u0026amp; Aubret, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). For example, hand-reared naïve great kiskadee (\u003cem\u003ePitangus sulphuratus\u003c/em\u003e) and turquoise-browed motmots (\u003cem\u003eEumomota superciliosa\u003c/em\u003e) both show a strong innate aversion to the aposematic yellow-red pattern of coral snakes (Smith, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1975\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1977\u003c/span\u003e). While several species of tail-vibrating snakes are non-venomous (Young, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Allf et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), all species with a rattle are venomous (Klauber, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1956\u003c/span\u003e). What likely began as a deimatic signal through tail vibration may have evolved into an aposematic signal as species started to associate the rattle with the threat of a venomous bite. While avoidance may have initially been a learned behavior, selection may have acted upon individuals with a higher propensity for aversion responses and subsequently evolved into an innate response to the rattle. Evidence showed that aversion can evolve relatively quickly within populations: red-bellied black snakes (\u003cem\u003ePseudechis porphyriacus\u003c/em\u003e) developed an innate avoidance for the invasive marine toads (\u003cem\u003eRhinella marina\u003c/em\u003e) in Australia in less than 23 generations (Phillips \u0026amp; Shine, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). While our study does not quantify the strength of rattlesnake impact on selection, this could be a crucial next step in understanding how innate fear become fixed in sympatric populations.\u003c/p\u003e\u003cp\u003eIn conclusion, this study demonstrated that the rattle functions as a deterrent signal, a hypothesis widely accepted over time and previously supported, until now, by a few controlled-studies (Rowe \u0026amp; Owings, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Swaisgood et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1999\u003c/span\u003e) and anecdotal evidence (Klauber, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1956\u003c/span\u003e; Sherbrooke \u0026amp; Westphal, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Rogers et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). More importantly, this study highlighted the dual functionality of the rattle, suggesting that the rattle potentially acts both as a deimatic and aposematic signal. Although the distinction between aposematism and deimatism was not directly tested during this study, the difference in behavioral responses between allopatric and sympatric species allows us to infer potential mechanisms. The rattle effectively deters animals by triggering reflexive avoidance responses regardless of their geographic origin or past experience, supporting the role of the rattle as a deimatic signal. Sympatric species demonstrated significantly stronger fear responses than allopatric species, potentially due to an evolved innate aversion to the rattle, refining the function of the rattle as an aposematic signal in these species. This dual signaling strategy provides insight into the evolutionary trajectory of the rattle, suggesting that it likely originated as a general startle mechanism and gradually evolved into a more specialized aposematic warning. This study raises several intriguing questions, including the role of experience in shaping responses to a deterring signal, the extent of selective pressure required for a deimatic signal to evolve into an aposematic one, and the overall efficiency of the rattle in preventing predation. Further studies are needed to address these questions and gain a deeper understanding of the evolution and ecological significance of the rattle.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor\u0026rsquo;s contribution\u003c/h2\u003e\u003cp\u003eConceptualization: OD, JJM, LMH. Implementation and data collection: OD, JJM, LMH. Data analysis: OD. Writing of first draft: OD. Reviewing and editing: OD, JJM, LMH.\u003c/p\u003e\u003ch2\u003eAcknowledgments:\u003c/h2\u003e\u003cp\u003eWe would like to thank the personnel of the El Paso Zoo for allowing us to conduct our behavioral trials with their animals, with a special thanks to Carrie Trudeau who helped us along the way. We would also like to thank the Fab Lab for helping us design the robotic rattlesnake and Vicky Zhuang from the UTEP Biodiversity Collections for letting us borrow a specimen. We would like to acknowledge the help of Shawn Walls in the video analysis, and the Seymoure lab for providing feedback on the manuscript. We also would like to acknowledge the support of Jerry Johnson, Allyson Benson-Pedraza, and Vicente Mata-Silva for this project. We would like to thank the UTEP IACUC and AZA committee for allowing us to conduct this study.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e\u003cp\u003eThe datasets and R code generated during the current study are available in the following GitHub repository: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://github.com/OceaneD3/Rattle-is-a-deterring-signal\u003c/span\u003e\u003cspan address=\"https://github.com/OceaneD3/Rattle-is-a-deterring-signal\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAllf, B.C., Durst, P.A.P. \u0026amp; Pfennig, D.W. (2016). Behavioral Plasticity and the Origins of Novelty: The Evolution of the Rattlesnake Rattle. \u003cem\u003eAm. Nat.\u003c/em\u003e \u003cstrong\u003e188\u003c/strong\u003e, 475\u0026ndash;483.\u003c/li\u003e\n\u003cli\u003eAllf, B.C., Sparkman, A.M. \u0026amp; Pfennig, D.W. 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Snake Bioacoustics: Toward a Richer Understanding of the Behavioral Ecology of Snakes. \u003cem\u003eThe Quarterly Review of Biology\u003c/em\u003e \u003cstrong\u003e78\u003c/strong\u003e, 303\u0026ndash;325.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"The University of Texas at El Paso","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Communication, deimatism, aposematism, rattlesnakes","lastPublishedDoi":"10.21203/rs.3.rs-7697892/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7697892/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe rattlesnake rattle is one of the most iconic communication signals in nature, yet its evolutionary function remains poorly understood. To test the long-standing hypothesis that rattling acts as a deterrent, we developed a 3D-printed robotic rattlesnake capable of displaying the multimodal sensory stimulus produced by a rattlesnake. This robot was presented to 38 species of zoo-housed animals in a series of behavioral trials. Animals displayed aversive response to the rattling signal, suggesting that the rattle functions as a deimatic signal by triggering reflexive avoidance response. Sympatric species exhibited even stronger fear response to rattling, suggesting an evolved, innate fear to the signal. These results offer insights into how complex antipredator signals can originate and diversify in the animal kingdom.\u003c/p\u003e","manuscriptTitle":"The Rattle Is a Deterring Signal That Works Best with Sympatric Species","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-25 14:55:57","doi":"10.21203/rs.3.rs-7697892/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6ee6568a-b06d-4a61-b27f-bba30faa9032","owner":[],"postedDate":"September 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":55227805,"name":"Animal Behavior"}],"tags":[],"updatedAt":"2025-09-25T14:55:57+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-25 14:55:57","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7697892","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7697892","identity":"rs-7697892","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}