Dispersal, survival, and reproduction of wild-born, yearling swift foxes in a reintroduced population

Abstract

From 1998 to 2002, the Blackfeet Tribe and Defenders of Wildlife reintroduced 123 captive-reared swift foxes ( Vulpes velox (Say, 1823)) to the Blackfeet Reservation in northern Montana. Because yearling swift foxes are colonizers of vacant habitats and are at the periphery of range expansion, we estimated 1st-year survival and explored aspects of dispersal to ascertain the contribution of wild-born juveniles to the reintroduction effort. First-year survival (post den emergence) of swift foxes averaged 0.38 and 0.36 for 2003–2004 and 2004–2005, respectively. Half of the females that survived to 1 June of their 1st year reproduced. Most dispersal (77%) and mortality (85%) occurred in autumn, with 80% of mortalities attributable to predation. Dispersal distance was not different among sexes and averaged 10.4 km. Understanding the contribution of yearling swift foxes — the colonizers — to reestablishing populations is important because several entities are currently reintroducing swift foxes and some states have expanding populations.