Direct interaction between roe deer and mountain hare suggestive of interference encounter competition

Direct interaction between roe deer and mountain hare suggestive of interference encounter competition | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 13 February 2026 V1 Latest version Share on Direct interaction between roe deer and mountain hare suggestive of interference encounter competition Authors : Simen Pedersen 0000-0002-9468-7098 [email protected] , Synnøve Hervik , and Hans Pedersen Authors Info & Affiliations https://doi.org/10.22541/au.177097912.29513684/v1 180 views 87 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Roe deer and mountain hares are known to select same food sources and engage in indirect exploitative competition. Here we report on a case of direct interaction between a roe deer doe and a mountain hare recorded by a camera trap in Tydal Municipality, Norway, suggestive of direct interference competition. The roe deer doe is as a minimum following and displacing the mountain hare for 2 minutes and 29 seconds, including a 19 second active chase phase. Although this could be just a case of curiosity, we suggest this is a case of interference encounter competition between these two herbivore species, previously not documented. Our traditional textbook understanding of ecology is based on the common and the easily observable, not the rare and difficult to observe. This observation paints a different picture of our understanding of the interactions between roe deer and hares, as roe deer may compete directly with mountain hares over food resources. INTRODUCTION Interspecific interactions among mammalian herbivores range from; 1) direct or interference competition (Schoener 1983), 2) indirect or exploitative competition (Schoener 1983) to 3) forage facilitation (Arsenault and Owen-Smith 2002) and 4) multispecies herds with shared vigilance for predators (Stears et al. 2020). According to niche theory, food competition occurs only if there is high overlap in use of limited forage resources. Herbivores are not expected to compete if they differ in body size (Demment and van Soest 1985), or if they differ in digestive systems (Duncan et al. 1990). However, due to an interaction between digestive systems and body mass, large ruminants such as cervids may compete with small hind gut fermenters such as hares (Belovsky 1984, Hofmann 1989, Johannessen and Samset 1994, Hulbert and Andersen 2001, Öhmark et al. 2015, Sangiuliano et al. 2016, Pedersen and Pedersen 2021). Roe deer ( Capreolus capreolus ) and Mountain hares ( Lepus timidus ) have previously been shown to compete indirectly over food resources during winter, expressing exploitative competition (Hulbert and Andersen 2001). Moreover, mountain hares are competitively inferior to roe deer, and (Hulbert and Andersen 2001) suggest that this may cause roe deer limiting mountain hare populations. Furthermore, roe deer and European brown hares ( L. europaeus ) are known to compete for forage (Sangiuliano et al. 2016), and moreover European hares are avoiding areas of high roe deer abundance (Viviano et al. 2021). The spatial partitioning between roe deer and European hares may be suggestive of interactions between the two species being a result of not only indirect exploitative competition, but also direct interference competition. Here we report on a case of a roe deer doe following and displacing a mountain hare, suggestive of interference encounter competition. METHODS As part of a project on behavioural responses to coat colour mismatch (HareKlima), we deployed cameratraps (Reconyx Hyperfire 4K Professional WhiteFlash) at 27 locations to monitor coat phenology of individually GPS marked mountain hares (Pedersen et al. in review). At one of our two studysites in Tydal Municipality, Trøndelag County, Norway. Between February 25 th 2025, and December 27 th 2025, 11 camera traps were placed in locations where the GPS tagged hares frequently passed, with the aim of documenting individual moult phenology. No bait, lure or any other attractant was used. Cameras were programmed to take continuous pictures if triggered by movement. A total of 350 hare and 137 roe deer observations were recorded across all 11 cameratraps. The one camera we report from here was located at 62.9537556 N, 11.7735995 E. The study area is situated between 600 and 900 m.a.s.l. and is dominated by downy birch ( Betula pubeschens) , interspersed with bogs, fields and Scots pine ( Pinus sylvestris ) and Norway spruce ( Picea abies ) forest. The area also contains recreational cabins. Other tree species like rowan ( Sorbus aucuparia ) and willow ( Salix spp.) are also present at lower abundance. The shrub layer is dominated by grasses, herbs, and dwarf shrubs such as bilberry ( Vaccinium myrtillus) and crowberry ( Empetrum nigrum ) . The mean daily temperature in Tydal ranges from -28.5°C to 22.2°C (2004 – 2025 data from www.senorge.no). Annual precipitation is around 900 mm (Rekdal 2013). RESULTS On June 21 st 2025 at 07:56:50, an unmarked mountain hare passed in front of the cameratrap, without stopping (Figure 1 A, Suppl. 1). From 08:25:01 to 08:25:10 there is a sequence of 9 pictures of a roe deer buck walking in front and away from the cameratrap (Figure 1B). At 08:25:43 the roe deer male can be seen in the background, while a mountain hare and a roe deer doe is in the foreground (Figure 1 C). The roe deer doe approaches the mountain hare, until she is approximately 1.5-2.0 m from the hare (estimated from the picture, and based on average dimensions of roe deer). The hare runs off towards the camera trap and to the right and disappears out of frame. The roe deer follows the hare, and the hare re-enters the frame, and stops (seemingly to forage). The roe deer doe continues approaching the hare, and the hare again runs off, this time at a longer distance from the roe deer (estimated distance 2-3m) (Figure 1 D). Both the hare and the roe deer leave the picture frame at 08:26:01. At 08:26:46 the hare re-enters the picture frame once again from the lower left corner and seems to be foraging before leaving the picture frame to the right at 08:26:53 (Figure 1 E). Seven seconds later at 08:27:00 the roe deer doe once again approaches from the left, nibbles a rowan leaf and continues to the right, following the path of the hare (Figure 1E). The roe deer doe leaves the frame at 08:27:14. At 08:27:52 to 08:27:54 the hare can be seen moving from the right to the left, this time without being followed by the roe deer (Figure 1F). This is the last activity on the camera for the rest of June 21 st 2025. As a minimum based on what we document through the frame of the cameratrap, the whole interaction between the roe deer and the hare lasted for 2 minutes and 29 seconds, while the “active chase phase”, where the roe deer is a few meters from the hare and the hare can be seen moving away from the roe deer lasted 19 seconds. What is interesting to note is that most likely the hare, and definitely the roe deer, were feeding within the patch. This further supports that this interaction was driven by competition for food sources and indeed was a case of interspecific encounter competition. Figure 1. Sequence of events from the interaction between the roe deer and the mountain hare. As a minimum the total interaction lasted 2 minutes 29 seconds, while the active chase lasted as a minimum for 19 seconds. See Suppl. 1 for a video of all still pictures DISCUSSION We fully acknowledge the limitations of this observation. We clearly see the roe deer doe following the mountain hare, however we do not know the intentions of the roe deer. We suggest this is a case of interference encounter competition, but we are open to alternative explanations that at one end of the spectrum is that it is only out of curiosity, while at the other extreme explanations may be that of a predation attempt (Pietz and Granfors 2000, Vazquez et al. 2023). Our traditional textbook understanding of ecology is based on the common and the easily observable, not the rare and difficult to observe. As pointed out in their study on roe deer and mountain hare competition Hulbert and Andersen (2001) states “…there was no evidence from personal observation or from the literature of either species interacting with the other in an antagonistic manner, e.g. chasing the other”. Direct encounters of roe deer and mountain hares are most likely infrequent and thus seldom observed, but that does not mean they are unimportant for structuring their foraging behaviour and space use (Viviano et al. 2021). As a comparison, since the dawn of science it has been established that mountain hares is a prey species, and predation is an important interaction shaping hare life history, morphology, behaviour and space use. Despite this, we did not record a single predation event on any of the camera traps, but that does not mean predation is not an important interaction in this system. This is yet another example of how the development of new technologies such as GPS collars and camera traps allows us to monitor animals for an extended amount of time, and with a detail level previously not possible gives us insights that previously were hidden (e.g. Lai et al. 2022, Spitzer et al. 2023, Pedersen et al. in review). This observation paints a different picture of our understanding of the interactions between roe deer and hares, as roe deer may compete directly with mountain hares over food resources. ACKNOWLEDGEMENTS This study received funding from Trygve Gotaas Fond, the Norwegian Environmental Agency (grant no. 2023/1082, 2024/805) and the Norwegian Agricultural Agency. We thank Lars Kristian Sekne for permission to deploy camera traps. AUTHOR CONTRIBUTIONS SP secured funding, had the idea of the paper and drafted the main manuscript. SH classified the cameratrap images. All authors contributed to field work and revised the manuscript draft. DATA ACCESSIBILITY STATEMENT No data except enclosed pictures and animation in Supplementary material was used in the creation of this paper. COMPETING INTEREST The authors have no competing interest. REFERENCES Arsenault, R., and N. Owen-Smith. 2002. Facilitation versus competition in grazing herbivore assemblages. Oikos 97 :313-318.Belovsky, G. E. 1984. 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Animals 11 :DOI10.3390/ani11020562.Öhmark, S. M., G. R. Iason, and R. T. Palo. 2015. Spatially segregated foraging patterns of moose (Alces alces) and mountain hare (Lepus timidus) in a subarctic landscape: different tables in the same restaurant? Canadian Journal of Zoology 93 :391-396. Information & Authors Information Version history V1 Version 1 13 February 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords behavioral ecology ecosystem natural history terrestrial vertebrate Authors Affiliations Simen Pedersen 0000-0002-9468-7098 [email protected] University of Inland Norway View all articles by this author Synnøve Hervik NMBU View all articles by this author Hans Pedersen Norwegian Institute for Nature Research View all articles by this author Metrics & Citations Metrics Article Usage 180 views 87 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Simen Pedersen, Synnøve Hervik, Hans Pedersen. 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