A familiar face with a novel behavior raises challenges for conservation: American mink in arid Patagonia and a critically endangered bird

Abstract

Invasive American mink is a severe threat to endangered waterbird populations. In Europe and South America, control efforts have been increasing in the last decades. Mink has a proven acute impact on the Hooded Grebe, a critically endangered specialist of highland plateau lakes in Patagonia where a single mink attack can deplete up to 4% of the global population. We aimed to examine mink ecology in Austral Patagonia to inform ongoing control programs in the region and contribute to efforts elsewhere to counteract mink impact. We evaluated mink distribution at a regional scale and found that its distribution extends across the steppe-arid environment, often assumed to be an obstacle for mink colonization. Consequently, its current distribution fully overlaps with the Hooded Grebe breeding grounds. At a finer scale, we used 3 techniques to detect American mink at different times of the year and found a temporal sex-biased occupation-dispersion pattern: permanent presence of both sexes in areas around the plateaus used by grebes and upstream male biased dispersion in late summer (which leads young mink to the grebes’ lakes). Therefore, plateau perimeters function as an invasion front that resets yearly. Lastly, from scat content analysis we detected a shift in mink diet from a generalist type in lowland rivers to a diet specialized on birds in highland lakes, where attacks are exclusively directed towards Hooded Grebes and where waterbird presence might be a determinant of mink presence (regardless of other prey). All of these findings have profound relevance for control schedules and priorities.