Conditioned odor aversion as a tool for reducing post‐release predation during animal translocations

Abstract

Predation is a key factor in prey population dynamics and could impact population recovery. One common means employed to recover prey populations is that of translocations, but most fail owing to high predation during the early stages. We tested whether conditioned odor aversion can reduce predation during animal translocations by using the predation of the European rabbit Oryctolagus cuniculus by the red fox Vulpes vulpes as a case study. Following a before‐after control‐impact design (BACI), we deployed bait stations monitored using camera‐traps in two zones to which rabbits were translocated. One week before the rabbits were released, microencapsulated levamisole was added to rabbit baits located in the treatment zones, along with vanilla essence as an odor cue. A total of 148 rabbits were distributed in artificial warrens with the odor cue and 68 of them were fitted with radio collars in order to determine their survival rates. The response to the treatment and translocation as regards subsequent rabbit abundance was evaluated using N‐mixture models, while rabbit establishment was evaluated using a warren use index (WUI). The treatment decreased the proportion of baits consumed by foxes, but this decrease was partially compensated by other predators. WUI and rabbit population growth increased significantly more after translocations in the treatment zones than in the control zones. The short‐term survival of translocated rabbits was also higher in the treatment zones than in the control zones. Our study showed that conditioned odor aversion reduced rabbit predation by foxes, and had a positive effect on rabbit population growth after translocation, since there was an increase in rabbit survival and warren establishment. This method could be used as a non‐lethal tool for the recovery of a key prey when carrying out programs concerning the reintroduction of endangered predators or for other vulnerable species requiring translocations.

Effects on carrion consumption in a mammalian scavenger community when dominant species are excluded

“…Predator control is a tool used in both game and conservation management (Reynolds and Tapper 1996; Moreno-Opo et al 2015). In the case of Mediterranean ecosystems, the red fox is one of the most controlled species in managed hunting estates, where it is considered one of the main threats to game species (Delibes-Mateos et al 2013;Tobajas et al 2020b). As this study shows (Table 1), the red fox is one of the main facultative scavenger species in Mediterranean ecosystems (Mateo-Tomás et al 2015;Tobajas et al (in press), so its continuous depletion can reduce the efficiency of rabbit carrion removal, this being especially important at times of high incidence of diseases such as viral hemorrhagic disease that can remain infectious in carcasses for several weeks after death (McColl et al 2002;Henning et al 2005).…”

Conditioned Taste Aversion as a Tool for Mitigating Human-Wildlife Conflicts

“…Of these studies, two-thirds reported a (partial) success, while field experiments conducted during the season of conflict most often reported failure (Supplementary Data 1). Another option is to artificially increase novelty by adding a new stimulus to a familiar, conditioned stimulus, such as a visual or odor stimulus (Baker et al, 2007(Baker et al, , 2008Tobajas et al, 2021a). For example, domestic chicks avoided a particular taste sooner when a novel color or odor stimulus was added to quinine-flavored water (Roper and Marples, 1997).…”

“…It is thus important to implement methods to guarantee long-term or equal palatability. Many CTA interventions do this by regularly replenishing baits or eggs (e.g., Dimmick and Nicolaus, 1990;Indigo et al, 2018;Tobajas et al, 2020aTobajas et al, , 2021a.…”

“…TPOA might also protect prey from predation during animal translocations. This strategy consists of using TPOA to condition predators, and applying the odor stimulus to a buffer zone to protect areas with translocated prey (e.g., rabbits, Oryctolagus cuniculus), to reduce predation short after release, a time during which translocated animals are more vulnerable (Tobajas et al, 2021a). Similarly, TPOA may be used to protect domestic livestock from large carnivore predation by creating an odor buffer zone in fenced areas that confine livestock (Tobajas et al, 2020b).…”

Using lures for improving selectivity of bait intake by red foxes

“…Baiting programs are also used in contraceptive or vaccination campaigns of several animal species, to regulate fertility or reduce the incidence of diseases that potentially could affect humans or their economy (Bradley et al 1999;Dı ´ez-Delgado et al 2018). Other uses of baits in wildlife management include live trapping to attract the animals to the traps (Dı ´az-Ruiz et al 2016) and Conditioned Food Aversion (CFA) studies, where a chemical compound is added to baits to elicit its rejection after a non-lethal adverse effect induced by the chemical compound (Tobajas et al 2020b(Tobajas et al , 2021a. CFA with baits has been used to reduce the bait consumption of poisoned baits (Nielsen et al 2015), for monopolisation of baits in vaccination campaigns (Gentle et al 2004), for livestock predation (Gustavson et al 1976;Tobajas et al 2020c) and for post-release predation of prey species (Tobajas et al 2021a).…”