Abstract
Following nineteenth-century declines, polecats Mustela putorius are recolonising Great Britain. Polecat diet relates to two potential risks to recovery. First, rabbits Oryctolagus cuniculus, which are important prey for polecats, have experienced extreme population fluctuations, with near extirpation due to myxomatosis in the 1950s, recovery in 1960s–1990s and declines in 1990s–2010s. Second, polecats are secondarily exposed to anticoagulant rodenticides by eating contaminated rodents, and the frequency of polecat exposure to rodenticides is increasing. We analysed stomach contents from 99 polecats collected in 2012–2016 and compared results with earlier studies. Lagomorphs were the most abundant prey (66% frequency of occurrence, 95% confidence interval 53–74%), followed by other mammals (12%, 4–18%), amphibians (10%, 3–16%) and birds (7%, 1–13%). Diet varied seasonally; lagomorph occurrence was highest in spring and summer and lowest in autumn. Dietary niche breadth was greater in the 1960s, when rabbits were scarce, than in other decades, but did not differ between the 1990s and 2010s, indicating that diets have not diversified with recent rabbit declines. This may be because rabbit abundance is not yet low enough to cause dietary diversification or because polecats were collected in areas where rabbits were still abundant. Rodents did not increase in diet between the 1990s and 2010s and still occur with < 10% frequency, indicating that rodents need not contribute much to diet to expose polecats to rodenticides. This potentially limits the effectiveness of management actions designed to minimise polecat exposure to contaminated rodent prey.
Highlights
Colonizing species often demonstrate ecological flexibility during the process of populationCommunicated by: Andrzej Zalewski establishment and expansion (Rosecchi et al 2001; Lee and Gelembiuk 2008)
A significant element of this period of range expansion has coincided with extreme fluctuations in populations of rabbits Oryctolagus cuniculus (Sumption and Flowerdew 1985; Aebischer et al 2011; Harris et al 2018; Massimino et al 2019), which are a major source of food for polecats in Great Britain (Birks and Kitchener 1999)
As there is no evidence from previous dietary studies to suggest that polecats eat earthworms (e.g. Birks and Kitchener 1999), and since variation in microscopic remains do not relate to the primary processes of interest in this study, we considered only macroscopic remains in the remaining 90% of gut samples
Summary
Colonizing species often demonstrate ecological flexibility during the process of populationCommunicated by: Andrzej Zalewski establishment and expansion (Rosecchi et al 2001; Lee and Gelembiuk 2008). A significant element of this period of range expansion has coincided with extreme fluctuations in populations of rabbits Oryctolagus cuniculus (Sumption and Flowerdew 1985; Aebischer et al 2011; Harris et al 2018; Massimino et al 2019), which are a major source of food for polecats in Great Britain (Birks and Kitchener 1999). It is unknown whether polecats in Britain may have altered their feeding strategy in response to recent rabbit declines and whether these declines may have impacted on their continued recolonisation
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