our three interns, who have kindly helped us during the first months of the project, have presented their results. We include here a translation of their abstracts:
Impact of bromadiolone (anticoagulant rodenticide) on populations of small mustelids: The stoat, Mustela erminea and weasel, Mustela nivalis in the Doubs.
Tiphaine FRAINCARD (M1 – Biologie des Organismes et des Populations, Université de Bourgogne, http://bop.u-bourgogne.fr/m1-bop).
Bromadiolone is an anticoagulant rodenticide used in agricultural plots to control outbreaks of voles, which can greatly reduce forage production grasslands. It has been shown that the pesticide could also kill carnivores by secondary poisoning. Specialist predators of voles as the weasel (Mustela nivalis) and the stoat (Mustela erminea) could be partly the cause of voles population dynamics. Until now, knowledge about the exposure of these small mustelids to this pesticide are few and no study refers to possible consequences to a population level. The objective of this study is to determine whether bromadiolone impact on population densities of small weasels and vole consumption in several sites in the Doubs department, Franche-Comté, France. To do this, a density index, represented by a percentage of presence of small mustelids is compared between sites with use of bromadiolone and sites without treatment. A presence of 8.21% in the first sites and 7.03% in the second were found, not allowing to conclude on a real impact of bromadiolone on populations of small mustelids. Vole consumption did not give significant results to suggest a change on the feeding behaviour among small mustelids. An improved protocol is therefore conceivable.
Does the use of bromadiolone impact vole population density?
Alexandre VOZ (Biology degree, Université de Franche-Comté, http://www.univ-fcomte.fr/)
The intensification of the agriculture and the changes in the agricultural habits are disturbing the ecosystem functioning. Because of that, the meadow vole (Microtus arvalis) and the water vole (Arvicola terrestris) find favourable conditions for their growth (less predators, abundance of food). Thus, they are producing big damages to agricultural plots, and the farmers have to react, so some of them are choosing the chemical method, by using bromadiolone, a rodenticide that eradicate rodents by inhibiting their blood’s coagulation. The effect of this treatment on the vole populations density is tested in this report by the development of a protocol: two study sites located on the Doubs department and 2 groups of parcels are used, one lot that are treated with bromadiolone, the other by untreated parcels. On these parcels we conducted transects to estimate the relative abundance of the two species in question. Our results are showing the there is no significant differences of abundance between the treated parcels and the untreated parcels. Many hypotheses can explain these results, nevertheless the most likely is that we should revise our protocol to improve it, by increasing our sampling effort for example. The study is not finished yet and the project continues.
Though not analysed statistically at the site level, we found higher vole abundance in the untreated site.
Are bromadiolone treatments affecting vole predation by red foxes?
Cécile ROSE (Biology degree, Université de Franche-Comté, http://www.univ-fcomte.fr/)
Second generation anticoagulant rodenticides are the main means of controlling voles, but they also affect predators like raptors or foxes. A secondary poisoning causes the decline of predators’ populations, however the decrease of the prey’s number can also be involved. To see the effects of bromadiolone, we wanted to determine if the Red foxes predation on voles was changing with quantities of treatment. Therefore, we decided to study the diet of foxes in three municipalities of Haut-Doubs which use different quantities of bromadiolone. To calculate an index of predation we collected and analysed the faeces from the three communes.
Though not included in her abstract, Cécile did not find significant differences in the vole consumption by foxes. Comparing two sites, vole predation by foxes (fox abundance x vole consumption) was stronger in the site with lowest vole abundance and bromadiolone use. However, results should be taken cautiously because no statistical analyses were conducted in this case.
To sum up, in general we did not obtain many significant results because of low sample size, for instance. These results are in any case preliminary and should be taken cautiously. The beginning of the project is very recent and it continues until November 2017, so we will increase the datasets, and with the help of interns and colleagues, we expect to have a clearer picture of the effects of bromadiolone in this system.