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

Monitoring large carnivores requires substantial effort, which is why indirect methodologies such as camera trapping with attractants or baits are commonly employed. The Iberian wolf (Canis lupus signatus) is one of the top predators in the Iberian Peninsula, and monitoring its packs is essential to understand its distribution and mitigate conflicts arising from livestock predation. We performed a captivity-based study evaluating the effectiveness of five attractants (beef extract, cadaverine, Fatty Acid Scent (FAS), lynx urine and valerian extract) on wolf detection. To accomplish this objective, Jacobs selectivity index and generalized linear models were employed to assess the attractiveness and induced behaviour of each attractant. Subsequently, the three most effective attractants, combined or not with a bait, were tested in the field and analyzed using generalized linear mixed models. The five attractants tested elicited different behavioural responses in the wolves in captivity, including smelling, rubbing, rolling, marking and licking. Among the captive wolves, cadaverine, FAS and lynx urine emerged as the top three preferred attractants. In the field tests with these three attractants cadaverine remained the most preferred option. The inclusion of bait did not have any significant effect on the wolf’s visitation rates. Our results show that employing species-specific attractants can significantly improve the efficiency of carnivore surveys conducted in the field. Specifically, cadaverine was the most effective attractant for wild Iberian wolves. Consequently, the careful selection of an appropriate attractant becomes crucial to attain the precise objectives of the study, such as camera trapping, bait deployment or DNA sampling.