Ecological variation among island foxes relative to reproductive events

Abstract

Ecological attributes of a species can vary as resource requirements and social interactions change in response to the annual reproductive cycle. We examined variation in home range size, home range overlap, activity (2005–2006), and food item selection (2006–2007) of island foxes (Urocyon littoralis) on San Nicolas Island relative to reproduction-related events. Home ranges, particularly for males, were larger during the mating period compared with the post-mating, pup-rearing, and non-reproduction periods. Home range overlap with non-mate neighbors also increased during the mating period. The greater home range size and overlap during the mating season is consistent with foxes, particularly males, traveling into the ranges of neighboring pairs in an attempt to secure extra-pair copulations. Daily activity patterns did not vary among the reproductive periods. Use of vertebrate prey items increased during the period when adults would have been provisioning weaning young. These items (e.g., mice, birds, lizards) are protein-rich and easier to transport compared with smaller items (e.g., fruits, snails, insects) that also are commonly consumed by island foxes. Variation in ecological attributes among island foxes across the different seasons defined by reproductive events likely represents efforts to maximize mating opportunities, particularly among adult males, and to secure optimal resources for provisioning growing young. These patterns are consistent with those observed among other small canid species.