Differential habitat use promotes sustainable coexistence between the specialist otter and the generalist mink

Abstract

2004. Differential habitat use promotes sustainable coexistence between the specialist otter and the generalist mink. Á/ Oikos 106: 509 Á/519.Optimal foraging and habitat selection theories predict that heterogeneous environments should favour the coexistence of competitors, especially when the dominant competitor is a specialist and the sub-ordinate is a generalist. In this paper, we analysed differential habitat use as a potential mechanism for the coexistence of two competing riparian mammals, the specialist and dominant Eurasian otter (Lutra lutra ) and the generalist and sub-ordinate American mink (Mustela vison ). We tested three hypotheses: H1: mink coexist with otters for longer in areas with abundance of habitats hosting terrestrial prey because, by not relying on aquatic prey, mink can segregate from its competitor. H2: the characteristics of the habitat closer to the riverbank will affect the length of time the two species coexist, because mink are still tied to the water even in the presence of otters. H3: denser vegetative cover along the bank increases the duration of coexistence of mink and otters because it reduces the frequency of their encounters. The first hypothesis was supported by the data and we found that in areas where terrestrial prey was abundant mink coexisted for longer with otters. The second hypothesis was also supported by the data and the characteristics of the habitat closer to the riverbank were the most important in determining coexistence time. Finally, we did not find supporting evidence for the third hypothesis. This study provides strong evidence that habitat heterogeneity plays an important role in determining the likelihood of coexistence of American mink with Eurasian otters. This result is particularly important from a conservation standpoint. Mink are invasive and a threat to endangered species in parts of their range. The knowledge that mink have a higher chance to persist in the presence of otters when terrestrial prey is abundant should be used to target areas for preferential mink management.

Feeding habits of American mink from Biebrza Wetlands affected by varied winter conditions

“…Interestingly, individuals that occupied neighbouring rivers showed different feeding habits, but during colder winters the changes in dietary habits followed similar trends for both areas: a decrease in the proportions of fish and amphibians in favour of mammals. Similar results have been reported for American mink (Maran et al 1998, Sidorovich 2000, Macdonald 2002, Bonesi and Macdonald 2004b) and other predators such as European polecat (Lode 1995, Sidorovich 2000, Macdonald 2002) and river otter (Sidorovich 2000, Macdonald 2002, Bonesi and Macdonald 2004b. The most interesting fact observed during the present study was that mink occupying neighbouring rivers showed different feeding habits, but under similar environmental conditions the niche shift between predators was almost identical.…”

Seasonal changes in American mink (Neovison vison) signs related to Eurasian otter (Lutra lutra) presence

“…Erlinge (1972) identified a similar pattern comparable to our study areas, observing that despite generally favourable conditions for mink, they disappeared seasonally and locally in response to the arrival of otters. In GBRL and Salamanca, it seems that there is an interaction between otters and mink, possibly a certain degree of displacement of the American mink by the Eurasian otter when this large species temporarily occupies the suitable habitat of the first one, as has been shown previously (Dunstone 1993, Ruiz-Olmo et al 1997, Lariviè re 1999, Bonesi and Macdonald 2004a,b, Bonesi et al 2004, McDonald et al 2007). …”

From Aquatic to Terrestrial Food Webs: Decrease of the Docosahexaenoic Acid/Linoleic Acid Ratio

“…Nevertheless, these species have to cope now with disturbed biotopes and prey populations. The re-colonising success of these species in their disturbed niches suggests a change in their foraging strategies [1,2]. However, these diet modifications are very difficult to evaluate in a low density context [3].…”