Uncoupling oceanic and life-history drivers to alternate foraging strategies in lactating long-nosed fur seals
TLDR: Are environmental or biological factors driving mother long-nosed fur seals to switch between making short or long foraging trips?
Lactating female fur seals are central place foragers i.e. they alternate between foraging at-sea and nursing their fasting pup on land (the central place). They forage on the shelf in summer, where their foraging trips last ~ 4 days. Towards autumn/winter, they transit to foraging in distant oceanic waters associated with the subtropical front (~ 1000 km from the colony), where their foraging trips can last up to 2 weeks.
Why do they make this transition? Is it because shelf waters are not productive anymore due to the cessation of seasonal localised upwelling (Bonney upwelling, most productive in summer – early autumn)? Or are oceanic waters at the subtropical front always more productive than shelf waters, but the constraint of nursing their young fasting pup limits them from traveling too far early in the lactation period? Is it better to transit earlier or later for short-term reproductive success?
Field research location
Long-nosed fur seals (previously New Zealand fur seal) colony at Cape Gantheaume, Kangaroo Island, South Australia.
Here’s a (pre-results) poster of my project! GRC_poster_v1b (final)