Fishing in your backyard: otters that prey on urban resources

Abstract We monitored the incidence of predation behavior in Eurasian otters (Lutra lutra) from urban ponds in southern Spain, following reports of the mustelids’ presence in various urban locations. In one of the case studies, 30 small common carp and 35 Koi fish were released in May 2017 and April 2018, respectively, into two different ponds. Otters extensively predated on these fish over a period of 75–80 days. Only two small carp (6.6%) survived in one of the ponds and 10 Koi fish (28.5%) in the other. The surviving Koi were relocated. We determined that fish survival functions and mortality rates between these two years were not significantly different. At the second urban location, otters extensively predated on Iberian frogs over a period of 5–6 days in May 2018, left the area, and repeated this pattern in May 2019. Finally, at the third urban location, otters consumed 20 goldfish in 16 days in August 2018. Our results indicate that available food resources in urban settings can become a viable option for certain bold individuals of wildlife species and that otters appear to explore urban habitats when it suits them. Appropriate management and damage control strategies are therefore needed to ensure the survival of this protected species in case food resources in the wild become limited and urban raids become habitual.