Drivers and constraints on offshore foraging in harbour seals

Area of Science:

• Marine biology
• Animal behavior
• Ecology

Background:

• Central place foragers, like seals, travel to find food.
• Previous studies used limited data to understand seal foraging trips.
• Understanding seal foraging is key to conservation.

Purpose of the Study:

• To investigate foraging behavior of harbour seals during offshore trips.
• To determine factors influencing the duration of these trips.
• To differentiate between resource hotspots and other drivers of offshore travel.

Main Methods:

• Used high-resolution multi-sensor bio-logging tags on 8 harbour seals.
• Recorded 12 offshore foraging trips in the German Wadden Sea.
• Analyzed acceleration transients as a proxy for prey capture attempts.

Main Results:

• Foraging rates were similar during travel and offshore periods.
• Offshore trips may be driven by avoiding competition, not just food availability.
• Seals rested more during trips, suggesting rest deficits limit trip length.

Conclusions:

• Harbour seal offshore trips may be influenced by social factors like competition.
• Resting needs, not just food patches, may dictate foraging trip duration.
• Multi-sensor tags are crucial for understanding marine mammal behavior and habitat use.