Conditioned prey aversion could be used as a non-lethal tool to reduce predation and contribute to the recovery of wild rabbit populations, a key prey species in Mediterranean ecosystems.
The dramatic and continuing decline in wild populations of European rabbit (Oryctolagus cuniculus), mainly due to diseases and the loss of suitable habitats, has led to its declaration by the International Union for Conservation of Nature (IUCN) as an endangered species in the Iberian Peninsula. The rabbit, which paradoxically can be a pest species in certain agricultural areas, faces a threat situation in forest environments -even with local extinctions-, for which reason it is urgent to adopt measures that contribute to improving their populations.
One of the most used measures to improve rabbit populations are translocations, which basically consist of capturing wild specimens in areas of high density to release them in areas of low or no density. One of the factors that most determines the effectiveness of translocations is the high mortality suffered by translocated specimens, largely due to predation, until they adapt to their new habitat. In fact, the fox (Vulpes vulpes) and birds of prey (which are the main predators of the wild rabbit) can prey on a large part of the rabbits released in the first 2-3 weeks after a translocation.
The wild rabbit (Oryctolagus cuniculus) is a key prey species in Mediterranean ecosystems. Its state of conservation is paradoxical, since in the Iberian Peninsula it can be a pest in certain agricultural areas but it is in danger of extinction in forest environments.
Scientists from the Research Group in Game Resources and Wildlife Management of the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM) and the Institute for Advanced Social Studies (IESA-CSIC), have evaluated the use of conditioned prey aversion as a measure to reduce the incidence of fox predation during rabbit translocations.
Conditioned aversion consists of using chemicals on the prey (or an imitation of it) that produce an unpleasant adverse effect –such as vomiting, nausea and/or diarrhea– in the predator, so that it learns to reject this prey in subsequent encounters. It is about triggering a survival mechanism that many animals develop to avoid the consumption of toxic or spoiled food once they have had a first bad experience.
This methodology, which has already been developed to protect partridge nests from fox predation by inducing taste aversion, has been used on this occasion introducing a new variant: the odor aversion. It is about generating aversion to an artificial smell (in this case vanilla smell), causing the predator to avoid areas with that smell, so that it allows protecting the specific areas where the artificial vivares are located in which they are going to be carried out. rabbit translocations.
The fox (Vulpes vulpes) is a generalist and opportunistic predator that includes the wild rabbit in its menu, especially in areas where the lagomorph is abundant, and can significantly influence the effectiveness of the translocations.
The experiment consisted of conditioning the foxes from forest areas in which rabbit translocations were going to be carried out, creating an aversion to the smell of vanilla as a scent signal using rabbit baits located in the treatment areas. Subsequently, every week all the entrances of the artificial stores were sprayed with the smell of vanilla to maintain their smell.
The response of the rabbit population to treatment and translocation was evaluated using mathematical models to estimate their abundance, while the establishment of rabbits in their new habitat was evaluated using a burrow usage index and their individual survival using radius. monitoring of marked rabbits. The results were compared with control areas in which the translocations were done at the same time and in the same way, but without generating conditioned aversion to the prey.
A total of 148 rabbits were distributed in artificial pens and 68 of them were equipped with radio collars to determine their survival rates.
The results showed that both the establishment of the translocated rabbits and the growth of the rabbit population were significantly higher in treatment areas compared to control areas. Short-term survival of translocated rabbits was also higher in treatment areas than in control areas.
Therefore, this work shows that conditioned prey aversion by scent cue may reduce fox predation of rabbits and may have a positive effect on rabbit population growth, significantly improving the effectiveness of translocations.
In the field of hunting management, this method could contribute to the rabbit recovery in areas of low abundance, eliminating the inconveniences and risks associated with predator control for other non-target species. In addition, it is not only applicable to the wild rabbit, but it would also be useful for other vulnerable prey species that require translocations or that must be protected in specific areas, such as breeding areas.
Finally, this method, used as a non-lethal tool to reduce predation and contribute to the recovery of a key prey species in Mediterranean ecosystems such as the rabbit, could be used to increase the success of endangered predator species recovery programs which, like the Iberian lynx (lynx pardinus) or the Iberian imperial eagle (Aquila Adalberti), find in the rabbit a fundamental trophic resource.
The scientific publication of this research is available at:
- Tobajas, J., Descalzo, E., Villafuerte, R., Jimenez, J., Mateo, R., Ferreras, P. 2020. Conditioned odor aversion as a tool for reducing post-release predation during animal translocations. Animal Conservation (2020)