Foraging behavior of female Guadalupe fur seals (Arctocephalus townsendi) and the implications for offspring dependence

Female fur seals and sea lions are central place foragers during the lactation period. Understanding foraging behavior is key to informing conservation and management of otariids, particularly for species whose populations are still recovering from near extinction like the Guadalupe fur seal (Arctocephalus townsendi; GFS). This is the first study to examine the movements of lactating female GFS beyond the second month of maternal care and assess how these movements relate to pup and maternal body mass at the time of tagging. Satellite-linked time-depth recorders with Fastloc® GPS technology were glued to 15 lactating females at Guadalupe Island, Mexico, and morphological data were collected from the females (mass and length) and eight of their pups captured at the same time (mass only). Biologgers were not retrieved. Females foraged in oceanic regions of the Northeastern Pacific Ocean, undertaking a broad range of foraging excursions from short trips around the island (< 600 km and 20 days) to extreme foraging trips northwest of the colony (up to 1665 km and 48.8 days). Heavier females traveled significantly farther from the colony (p = 0.018, SE = 0.014) and had smaller pups at the time of instrumentation (p = 0.018, SE = 0.007). Increased distance from the colony was also associated with longer maternal attendance periods (p = 0.0001, SE = 0.0001). Additionally, during mid to late lactation, female GFS were primarily shallow, nocturnal divers with 80% of dives to depths 2–40 m, with 70% of these occurring at night. The movement capabilities of female GFS described in this study can be key for their population recovery. Specifically, mothers’ extensive movement capacity and the possible capability of pups to endure long fasting periods could be crucial factors for pup survival, particularly in anomalously warm water years with reduced prey availability.