Musteloids and Mongoose

[Sully]

Low individual diet variation and high trophic niche overlap between native polecat and invasive American mink 

Abstract

Introductions of invasive species increase competitive interactions in a community
proportionally to the similarity between the ecological niches of invasive and native
species. Food represents one of the most important resources in uencing competi-
tion, and differences in the trophic niche of native and invasive species can affect
their ability to coexist. Moreover, in sympatric native and invasive species of simi-
lar body size and high sexual dimorphism, competition for food between individu-
als of the same sex may be higher than intraspecic competition between males
and females, thus making the overall competitive interactions more complex. The
aim of this study was to investigate the intraspecic and intrasexual competition
for food resources between two sexually dimorphic mustelids, the native polecat
Mustela putorius and invasive American mink Neovison vison, in riparian habitats
of Białowie
_
za Forest (Poland). Based on an analysis of 1215 scats, we studied the
food habits of eight polecat and 24 mink individuals. The trophic niches of the
polecat and mink were narrow and overlapped considerably. The diet of both
predators was dominated by amphibians (mainly the common frog Rana tempo-
raria), which comprised up to 94.1% and 89.7% of polecat and mink prey bio-
mass, respectively. Individual diet variation was low within each sex group of both
species. Interspecic similarities in body mass of the sexes and intraspecic differ-
ences in body mass between the sexes did not affect pairwise niche overlaps. How-
ever, we observed some mechanisms of food segregation between the sexes and
species that reduced intra- and interspecies competition. Polecat males hunted more
common toads Bufo bufo than polecat females, mink males and mink females.
They also hunted larger frogs than polecat females, and the opposite pattern was
recorded in mink. We conclude that two predator species exploiting abundant prey
can coexist despite a very high overlap in their food niches. Reply