Using lures for improving selectivity of bait intake by red foxes

Abstract

Context The use of baits for reducing the populations of harmful animal species, eradicating invasive species, vaccination, contraception or producing conditioned aversion, is widespread worldwide. However, baiting programs are often not successful enough and affect non-target species, requiring new approaches for baiting methods. Aims The aim of the present study was to evaluate two attractants used in carnivore studies to improve bait intake probability by red foxes and minimise bait intake by non-target species. Methods Non-toxic baits were distributed across 1000 ha, with bait intake monitored by camera traps during 3-week trials. Baits were assigned to two treatments with lures (lynx urine and Fatty Acid Scent – FAS) and one control. Bait intake by red foxes and non-target species was analysed using Generalised Linear Mixed Model (GLMM) and Kaplan–Meier survival analyses. Key results Lynx urine significantly increased the bait intake by red foxes (58.8%) compared with control (5.7%) and FAS (16.7%) treatment. However, FAS did not significantly increase the bait intake by red foxes compared with control. Bait intake by non-target species differed significantly between treatments, with lower intake in lynx urine (23.5%) treatment than control (54.7%), but not regarding FAS (36.7%), and neither between FAS and control. The probability of bait persistence after the 3-week trial period differed significantly among treatments, being lower in lynx urine treatment (0.18) than FAS (0.50) and control (0.43). All baits taken by foxes with lynx urine treatment (58.8%) occurred within the first 10 days, whereas intake by non-target species (23.5%) stopped after Day 7. Conclusions The use of lynx urine lure increased the proportion of baits consumed by red fox and reduced bait intake by non-target species. Implications Lures can serve to optimise bait delivery methods for red foxes in their different applications, such as conditioned aversion studies, vaccination, live trapping or predator control, while minimising risks to non-target species and reducing the costs and application time.

Effectiveness of attractants and bait for Iberian wolf detection: captivity-based and free-ranging trials

“…The captivity tests were carried out in over a period of twenty days in February 2022 at Sendaviva zoological park located in Arguedas, province of Navarra, Northern Spain, where six wolves were kept in the same enclosure spanning approximately one hectare. We tested the following five attractants on the basis of previous studies with wolves and other carnivores: (1) a commercial concentrated beef extract (Bovril®; Roche 2008); (2) cadaverine, an own elaboration water solution of rotten fish (Avrin et al 2021;Jiménez et al 2023); (3) FAS containing a mixture of ten synthetic volatile fatty acids found in fermented egg (Roughton 1982;Monterroso et al 2011;Tobajas et al 2022) that is commonly used as a generalist carnivore attractant in North America (Roughton and Sweeny 1982); (4) lynx urine (obtained from captive specimens of Iberian lynx (Lynx pardinus), Monterroso et al 2011;Tobajas et al 2022); and (5) valerian-extract solution containing valeric acid found in urine and anal-sac secretions of coyote (Canis latrans) and red fox (Saunders and Harris 2000;Ferreras et al 2018). The six Iberian wolves were adults (four females and two males) and they had access to the attractants 24 h a day, as they were in the same enclosure as the wolves, during the 20 days of experiment.…”

“…Attractants for carnivores can be classified in three groups based on their characteristics: (i) natural attractants, which are naturally occurring in the environment with communicative function as faeces, gland secretions or urine; (ii) baits, typically consisting of food or its derivates, which are intended to be consumed and attract animals through smell or taste; and (iii) lures, which are substances that are not naturally present in the environment and attract animals through smell, sound or sight (Schlexer 2008). The use of these attractants improves the detectability, or even the selectivity of the target species (Steyer et al 2013;Ferreras et al 2018;Tobajas et al 2022), increasing the cost-effectiveness of the surveys, especially in areas of expansion with low abundances (Ferreras et al 2017;Buyaskas et al 2020). This is especially relevant in cases such as large carnivore surveys, where the large home ranges imply high sampling and economic efforts.…”

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

“…For example, a project to protect California condor (Gymnogyps californianus) eggs from ravens (Corvus corax) showed that the condor itself was most likely to be affected by the intervention, but could be safely protected with the compound landrin (Quick and Hill, 1988). Further, research should explore use of selective bait deployment methods to reduce ingestion by non-target animals and the smart use of lures or attractants to increase the food detectability specifically by the target species (Ferreras et al, 2018;Tobajas et al, 2021b). Another way to avoid bait consumption by nontarget species is to directly inject the substance into the subject after it has eaten the relevant food.…”