Faecal avoidance and selective foraging: do wild mice have the luxury to avoid faeces?

Abstract

Host–parasite interactions are a key determinant of the population dynamics of wild animals, and behaviours that reduce parasite transmission and infection may be important for improving host fitness. While antiparasite behaviours have been demonstrated in laboratory animals and domesticated ungulates, whether these behaviours operate in the wild is poorly understood. Therefore, examining antiparasite behaviours in natural populations is crucial for understanding their ecological significance. In this study, we examined whether two wild rodents (white-footed mice, Peromyscus leucopus, and deer mice, Peromyscus maniculatus), selectively foraged away from conspecific faeces or avoided faeces altogether, and whether faecal gastrointestinal parasite status affected their behaviour. We also tested whether wild mice, when nesting, avoided using material that had previously been used by healthy or parasite-infected conspecifics. Our results, in contrast to laboratory mouse studies, suggest that wild mice do not demonstrate faecal avoidance, selective foraging or selective use of nesting material; they preferred being near faeces and did not differentiate between faeces from parasitized and uninfected conspecifics. Behavioural avoidance to reduce parasite infection may still represent an important strategy; however, mice in our study population appeared to favour the opportunity to feed and nest over the risks of coming into contact with faecal-transmitted parasites. Furthermore, the presence of conspecific faeces may actually provide a positive cue of a good foraging or nesting location. Ultimately, balancing the trade-off of performing antiparasite behaviours to reduce infection with missing an important feeding or nesting opportunity may be very different for animals in the wild facing complex and stochastic environments.

Environmental Parasitism Risk and Host Infection Status Affect Patch Use in Foraging Wild Mice

“…On the other hand, this lack of fecal avoidance may be due to methodological differences between Walsh et al. () and previous studies on ungulates. Specifically, the food patches were not directly contaminated with conspecific feces in Walsh et al.…”

“…In fact, a recent study by Walsh et al. () failed to demonstrate fecal avoidance in wild mice Peromyscus leucopus and P. maniculatus . This is not to say that parasitism has trivial impacts on the fitness of the mice, and consequently, they do not need behavioral means to detect infection risk.…”

“…Specifically, the food patches were not directly contaminated with conspecific feces in Walsh et al. (). Rather, the feces were placed in close proximity to the food patches without directly contacting the food.…”

“…A likely explanation for the lack of fecal‐avoidance foraging in Walsh et al. () is that the benefits of food outweigh the costs of parasitic infection for these mice due to their higher metabolism (e.g., basal metabolic rate of P. maniculatus is c . 1.95 cm 3 O 2 /g/h, which is higher than that of ungulates ranging from 0.1–0.5 cm 3 O 2 /g/h among 12 species in the order of Artiodactyla; Hayssen & Lacy ) and constant needs for food acquisition.…”

“…Another explanation might be that predation risk outweighs parasitism risk for these mice when they are making foraging decisions in the wild (Walsh et al. ). On the other hand, this lack of fecal avoidance may be due to methodological differences between Walsh et al.…”