Multiple-stage decisions in a marine central-place forager

Area of Science:

• Marine biology
• Animal behavior
• Ecology

Background:

• Baleen whales (Mysticeti) are central place foragers.
• Diving challenges influence marine mammal foraging decisions.
• Understanding prey depth and density interactions is crucial for baleen whale foraging strategies.

Purpose of the Study:

• To investigate how Antarctic humpback whale foraging behavior is influenced by krill depth and density.
• To quantify the relationship between prey availability and feeding rates in humpback whales.

Main Methods:

• Utilized multi-sensor archival tags to record whale behavior.
• Employed active acoustics (echosounders) to assess krill distribution and density.
• Correlated whale foraging lunge rates with environmental and prey data.

Main Results:

• Humpback whales exhibit multi-stage foraging decisions influenced by krill depth and density.
• Feeding rates were highest when krill were shallowest and decreased with increasing dive depth.
• Whales foraged when krill were more broadly distributed and shallower, not necessarily in the densest patches.

Conclusions:

• Humpback whale foraging strategy optimizes efficiency by maximizing net energy gain over time.
• This complex predator-prey interaction highlights the importance of considering prey distribution in central place forager studies.
• The findings suggest a previously unrecognized level of complexity in marine foraging behavior.