Risk induced by a native top predator reduces alien mink movements

Abstract

Summary 1.Nonlethal predation effects may have stronger impacts on prey populations than direct predation impacts, and this should also apply to intraguild predation. The consequences of such interactions become especially important if invasive, and potentially destructive alien predators act as intraguild prey. 2. We studied the predation-risk impacts of a re-colonizing native top predator, Haliaeetus albicilla (white-tailed sea eagle), on the movements of Mustela vison (American mink), an alien predator in Europe. We radiocollared 20 mink in two study areas in the outer archipelago of the Baltic Sea, South-west Finland, during 2004 and2005. In the archipelago, mink home ranges incorporate many islands, and mink are most predisposed to eagle predation while swimming between islands. Observed swimming distances of mink were compared to distances expected at random, and deviations from random swimming were explained by mink distance from nearest eagle nest, number of eagle observations near mink location, and mink home-range size. 3. Mink reduced their swimming distances with increasing sea eagle predation risk: for females, the reduction was 10% for an increase of 10 eagle observations, and 5% for each kilometre towards an eagle nest. Conclusions for males were restricted by their small sample size. 4. Our results suggest that female mink modify their behaviour according to eagle predation risk, which may reduce their population growth and have long-term cascading effects on lower trophic levels including bird, mammal and amphibian populations in the archipelago. Ecosystem restoration by bringing back the top predators may be one way of mitigating alien predator effects on native biota.

Induced changes in island fox (Urocyon littoralis) activity do not mitigate the extinction threat posed by a novel predator

“…Eagle predation risk is associated with reduced activity in minks (Salo et al 2008), and predation risk has been associated with changes in diurnal activity in guppies (Fraser et al 2004), salmon (Metcalfe et al 1998) and rats (Fenn and MacDonald 1995). Although shifting circadian patterns to avoid predation has been well documented in many systems, island fox response to golden eagles presented here and by Swarts et al (2009) represents the Wrst example we are aware of demonstrating shift in daily activity patterns as a result of a novel predator.…”

Impacts of Removing Badgers on Localised Counts of Hedgehogs

“…Larger predators may suppress smaller mesopredators either by direct predation/conflict, or by changing their behaviour such that they avoid habitats or locations where the larger predator is present [1], [28]. It is therefore possible that increased captures of hedgehogs in the current study were due not to changes in hedgehog numbers, but to changes in hedgehog behaviour, with hedgehogs being more visible or active in amenity grassland sites where badger numbers had been reduced.…”

Top‐down limitation of mesopredators by avian top predators: a call for research on cascading effects at the community and ecosystem scale

“…biological invasions (Ritchie et al 2012, Suraci et al 2016. For example, the recolonization of the White-tailed Eagle Haliaeetus albicilla in the Finnish archipelago reduced American mink Neovison vison movements, potentially mitigating their impact on native species (Salo et al 2008). Most recent research on trophic cascades has focused on determining how top predators shape and drive community structure (Terborgh & Estes 2010, Estes et al 2011, Ritchie et al 2012, leading to widespread predictions that the loss of large predators will release populations of smaller predators, as depicted by the mesopredator release hypothesis (Crooks & Soul e 1999, Ritchie & Johnson 2009).…”