Relevance of body weight effects for the population development of common voles and its significance in regulatory risk assessment of pesticides in the European Union

Abstract

Background The common vole (Microtus arvalis) is typically the wild mammal species driving regulatory pesticide risk assessment (RA) in Europe. The risk assessment endpoint for wild mammals is taken from the studies conducted mainly with rodents for the toxicological part of the dossier. Body weight effects in these studies are often driving the selection of the No Observed Adverse Effect Level (NOAEL) used for wildlife risk assessment. Thus, assessing body weight effects in voles very frequently constitutes a key scenario in the RA. Although many studies on ecology, reproductive biology, population genetics, and other aspects of common voles are available, the relevance of body weight for their survival and reproduction has not yet been specifically analysed. There is also little guidance on how to quantitatively deal with body weight effects in the regulatory risk assessment of pesticides. Results We evaluated the population relevance of body weight effects on voles by analysis of a dataset from a multi-annual study with repeated life-trapping and genotyping, and have correlated body weight with reproductive success, taking account of the seasonality of body weight. Body weight and growth were similar between reproducing and non-reproducing females. The number of confirmed offspring indicated no correlation with parental body weight. Reproductive success of the voles was mainly influenced by the date of birth, i.e., animals born in spring have a higher chance to reproduce. Body weight did not correlate with life span during most of the year, except for autumn. Animals weighing < 15 g in October did not survive winter. Conclusions These results demonstrate no detectable influence of common vole body weight on reproductive success and survival during most times of the year. The results of this study suggest that, additional to the hazard information from toxicity studies, ecological information on voles as a typical species of concern should be considered in the regulatory risk assessment of pesticides.

Effects of an IgE receptor polymorphism acting on immunity, susceptibility to infection and reproduction in a wild rodent

“…Our measure of reproductive success was zero-inflated (50% zeros). This is consistent with a previous study of the closely-related common vole (Microtus arvalis) [66]. A…”

“…Our measure of reproductive success was zero-inflated (50% zeros). This is consistent with a previous study of the closely-related common vole ( Microtus arvalis ) [66]. A Poisson error distribution was therefore deemed inappropriate and it could not be modelled using hapassoc.…”

“…Instead, we ran a separate model for each sex. We included birth month as a covariate in this model, given that autumn-born voles (of the closely-related common vole) have been shown to have a lower chance to reproduce than spring-born voles [66]. Other covariates included in this model were, whether or not an individual was culled for the cross-sectional component of this study (again, reducing the opportunity to reproduce), site and the year in which an individual was most frequently captured (Table 1).…”

“…Initially, we ran a model in hapassoc to look for an association between Fcer1a haplotype and our measure of reproductive success. We included birth month as a covariate in this model, given that autumn-born voles have been shown to have a lower chance to reproduce than spring-born voles (Wang, Ebeling, & Hahne, 2019). Other covariates included in this analysis were, whether or not an individual was culled for the cross-sectional component of this study (again, reducing the opportunity to reproduce), whether or not an individual was given antiparasite treatment, site and year.…”

Early-life immune expression profiles predict later life health and fitness in a wild rodent

“…Il17 expression in early life was also found to be zero-inflated (117/131 or 89% zero values) and was simply coded as either expressed or not. We included birth month as a (continuous) covariate in the model, given that autumn-born voles have a lower chance of reproducing than spring-born voles 30 . Other (categorical) covariates included in the model as fixed effects were: sex, whether or not an individual was culled for the cross-sectional component of this study (again, reducing the opportunity to reproduce) and the year in which an individual was born.…”