Captive-reared European hamsters follow an offensive strategy during risk-assessment

Abstract

Understanding whether captive-reared animals destined to reintroduction are still able to discriminate predators has important implications for conservation biology. The endangered European hamster benefits from conservation programs throughout Europe, in which several thousand individuals are released into the wild every year. Despite this, the anti-predator strategy of hamsters and their ability to maintain predator discrimination in captivity remain to be investigated. Here, we explore the predator discrimination behaviour of captive-reared European hamsters and their response to different predation cues. When first exposed to the urine of cats and goats in a Y-maze test, hamsters spent more time close to the cat scent rather than to the goat scent. In a second experiment, during which hamsters were exposed to a non-mobile European ferret (inside a cage), hamsters significantly increased the time spent close to the ferret’s cage and displayed aggressive behaviour towards the ferret. Furthermore, they did not take refuge inside an anti-predation tube (APT), a device designed to upgrade wildlife underpasses and reconnect wild hamster populations. Finally, when exposed to a mobile ferret (but without physical contact), hamsters displayed mobbing and aggressive behaviours towards the ferret, before taking refuge inside the APT. Taken together, our results show that captive-reared hamsters are still able to detect and react to predation cues, but that they initially adopt an offensive strategy (grunting, spitting, mobbing) during the risk-assessment phase. After risk assessment, however, hamsters used the APT as a refuge. Our study provides important insights into the anti-predator behaviour of hamsters. Testing the efficacy of the APT, a device that will allow upgrading wildlife underpasses for the hamster and other rodents, is also of great importance and is instrumental in conservation efforts for these species.

Aposematism in mammals

“…This result was unexpected, as we had predicted that aposematic defenses would be more effective in larger animals. However, there are a handful of small mammals that behave aggressively when threatened, including some lemmings, hamsters (Family Cricetidae), and polecat species (Family Mustelidae); displays of aggression in these species successfully deter predators (Andersson 2015;Tissier et al 2019). It is, therefore, possible that larger body size may serve to make morphological defenses more effective, but not behavioral defenses.…”

Improving the success of reinforcement programs: effects of a two-week confinement in a field enclosure on the anti-predator behaviour of captive-bred European hamsters

“…However, due to habitat fragmentation, agriculture intensification, and climate change, it is now one of the most threatened mammal species in Western Europe ( Weinhold, 2009 ; Tissier et al, 2016 ) and has recently been classified as “Critically Endangered” by the IUCN (International Union for Conservation of Nature; Banaszek et al, 2020 ). In a recent study, European hamsters that were bred in captivity over 15 generations in France showed a marked aggressive response when confronted with a mobile predator (European ferret, Mustela putorius furo ), rather than fleeing and hiding in an available shelter ( Tissier et al, 2019 ). Such behavioural response is not consistent with the common assumption that prey species only display aggressive behaviour towards a predator when freezing or fleeing are not viable options ( Eilam, 2005 ).…”

“…Such behavioural response is not consistent with the common assumption that prey species only display aggressive behaviour towards a predator when freezing or fleeing are not viable options ( Eilam, 2005 ). Attacking an unknown predator is likely to be fatal for hamsters in the wild, questioning the appropriateness of such a response ( Tissier et al, 2019 ). Non-appropriate behavioural responses to predation risk can be a major problem for reinforcement programs, especially when animals face a high predation pressure upon their release into the wild ( Moseby et al, 2011 ; La Haye et al, 2020 ).…”

“…This was mainly due to (1) avian predation (2) terrestrial predators overcoming fences or (3) the dispersal of released hamsters to areas with little or no vegetation cover, resulting in predation. Hence, while the reinforcement program has allowed to maintain the relict hamster population in France, it has so far failed to restore a viable, self-sustaining population ( Tissier et al, 2019 ). Given the high mortality rates following release, it would seem obvious that efforts should focus on increasing the post-release survival of captive-bred hamsters to improve the effectiveness of this conservation measure.…”

“…To study whether potential behavioural differences after such confinement persisted over time, hamsters were confronted again with the same predator model 1 month after their return to the captive indoor facility. The objective of the confrontation with the predator model was not to condition hamsters to react more appropriately to the risk of predation ( i.e ., not to conduct an antipredator training), but to assess how a short period in a semi-natural environment might modify their anti-predator behaviour and elicit a more appropriate response ( Tissier et al, 2019 ). In parallel, we investigated whether the repeated confrontation with a predator model alone could alter the behavioural responses in a group of hamsters that remained inside the captive facility throughout experimentation (control group).…”