Identifying biases in the detection of poisoned animals

    A study reveals that the current system for tracking cases of wildlife poisoning due to the illegal use of poisoned baits can lead to significant biases in detection rates. His estimate of the real scope of this conservation problem must be taken with caution.


    The use of poison baits It has its origin in certain conflicts between humans and certain species of wildlife, mainly predators, as it is conceived as a relatively easy way to avoid the potential damage that these species can cause to activities such as livestock or hunting.

    But the poisons and the baits that contain them, and that are abandoned in natural spaces, They are not selective and can seriously affect protected and/or threatened species.. In fact, this illegal practice, penalized as a crime against wildlife by legislation in force for more than two decades, currently continues to be a major problem for the conservation of wildlife, the effects of which can even be felt at the biological community level. .

    Effectively combating the illegal use of poison baits depends to a large extent on the development of protocols that allow adequate detection of poisoned wild animals, as well as gather precise information on the species of fauna involved, the locations where these events occur and the number of individuals affected.

     

    The illegal use of poisoned baits constitutes a major problem for the conservation of wildlife that seriously affects scavenger birds, such as the griffon vulture (Gyps fulvus).

    Throughout the last decades, various procedures have been developed for the detection of poisoned animals. However, these procedures are biased towards the detection of the species most commonly affected by cases of poisoning, or the largest ones, or the detection of specific threatened species, which are the protagonists of the monitoring programmes. This bias can lead to underestimations or overestimations of the actual number of poisoning events or affected individuals in each event based on the species, providing data that may not reflect the real situation of the problem.

    Scientists from the Miguel Hernández University, the University of Granada, the International Center for Environmental Law Studies (CEIDA), the University of Lleida and the Research Group in Game Resources and Wildlife Management of the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM), have evaluated the biases in the detection of wildlife species that are intentionally poisoned in the Iberian Peninsula. To do this, they have compared data from the Antidote Program with those obtained from a series of field experiments in different regions of the Iberian Peninsula, based on the monitoring of baits (pieces of meat, sausages, eggs, etc.) not poisoned with camera traps, and which were aimed at quantifying the community animal that can potentially feed on really poisoned baits.

     

    Individuals of the 9 groups of species that, according to the results of the experiments, feed on baits: (a) wild carnivores, fox (Vulpes vulpes); (b) domestic carnivores, dog; (c) suidae, wild boar (Sus scrofa); (d) small mammals, dormouse (Eliomys quercinus); (e) corvids, crows (Corvus corone); (f) vultures, black vulture (Aegypius monachus), griffon vulture (Gyps fulvus) and Egyptian vulture (Neophron percnopterus); (g) other raptors, common kestrel (Falco tinnunculus); (h) other birds, great tit (Parus major); (i) reptile, ocellated lizard (Timon lepidus).

    The results of the field experiments showed that animals from up to 9 different faunal groups were the commensals in the simulation of baits (not poisoned) used as lure. If we compare the data from the Antidote Program with those obtained in these experiments, it can be seen that domestic animals (dogs) and vultures are overrepresented in the databases of wildlife species affected by the illegal use of poison baits, while the presence of corvids and small mammals are undervalued.

     

    The map on the left shows the animal poisoning events recorded by the Antidote Program between 1990 and 2015. On the right is a comparison between the data from the Antidote Program and the results of the field experiments carried out in the context of this work. research: (a) frequency of appearance of individuals of each faunal group according to the Antidote Program (orange bars) and according to the experiments (black bars); (b) Number of study areas in which each faunal group was overrepresented (orange dots) or underrepresented (black dots) in the Antidote Program database compared to the experiments. White dots indicate faunal groups for which there were no significant differences between both sources of information.

    This work shows that the current system for monitoring cases of poisoning in wildlife, based on heterogeneous sources, can lead to significant biases in detection ratesTherefore, their data must be interpreted with caution when inferring the real extent of the problem that the illegal use of poisoned baits entails for the conservation of wildlife.

    In this way, the results obtained could be very useful to improve the existing system in favor of a bias-free coordinated national poison control strategy, and whose results allow realistic estimates of the extent of the problem caused by the illegal use of poisoned baits.

    The scientific publication of this research is available at: