Interactions between the short-tailed mouse (Mus spretus) and the wood mouse (Apodemus sylvaticus): diet overlap revealed by stable isotopes

Abstract

Extensive niche overlap between closely related species generally leads to aggressive interactions and competition. The short-tailed mouse (Mus spretus Lataste, 1883) and the wood mouse (Apodemus sylvaticus (L., 1758)) show a large habitat overlap without aggressive interactions. The present study investigates the existence of food competition between these species, based on an analysis of carbon and nitrogen stable isotopes. An almost exhaustive sample of plants, which were potential food resources, was taken and analyzed to infer the consumed plants in mouse diets. The main result showed that both species had a similar diet composition, consisting exclusively of seeds and fruits. This suggests that no competition for food between these species is apparent, or if it exists it would be minimized by a differential exploitation of resources. In the absence of food and space competition,the short-tailed mouse may be using the presence of the wood mouse as an indicator of habitat food quality. In the case of wood mice, we hypothesize that the level of competition with short-tailed mice may be low because of the abundance of resources and because the wood mice may perceive the smaller short-tailed mouse as being equivalent to a young of their own species.

Expansion of great cormorant colony immediately increased isotopic enrichment in small mammals

“…Plants enriched in guano 15 N may occur at distances exceeding 100 m from nesting sites and colonies (Millus and Stapp, 2008). Few plant samples (Carex and Sambucus) were highly 25 Rodents usually eat foods that are most abundant (Bauduin et al, 2013) or have preferences characteristic to the species (Fisher and Türke, 2016;Schneider et al, 2017), however, choices in the Juodkrantė great cormorant colony are limited to several plant species (mainly nitrophilous) and invertebrates. Nitrophilic plants usually grow abundantly, being the food source for herbivores living in the territory of a colony (Cassaing et al, 2007).…”

“…SIA using mammal hair is a method suitable for diet analysis and for comparing 25 intrapopulation groups as well as different species. When analyzing diet, hair isotopic signatures are compared with the signatures of possible food sources (Bauduin et al, 2013). In identifying diet sources, carbon and nitrogen isotope ratios are most widely used.…”

“…We used hair of the rodents as metabolically inert samples, preserving the isotopic record of the animal's diet (Crawford et al, 2008;Bauduin et al, 2013). Hair samples were cut off with scissors from between the shoulders of all trapped specimens of A. flavicollis and M. glareolus (88 and 29 individuals, see Table 1).…”

“…Considering isotopic signatures in the 10 hair of small mammals as dietary proxies (according Fernandes et al, 2014) reflecting proteins of the food sources (Perkins et al, 2014), we found that diets differ in the various zones of the colony and depending on the small mammal species. Therefore, differential exploitation of resources minimizes competition (Bauduin et al, 2013).…”

Comparative bite force in two syntopic murids (Rodentia) suggests lack of competition for food resources

“…caught in the same trap lines) in southern France-84 are good candidates to run such a study. The two species share several habitats and most 85 food items (Bauduin et al 2013;Cassaing et al 2013). Therefore, they may be considered to 86 be in a situation of competition for food, yet they seem to coexist at least since the Holocene 87 period.…”