Identifying and quantifying prey consumption using stomach temperature change in pinnipeds

Area of Science:

• Marine biology
• Animal physiology
• Behavioral ecology

Background:

• Foraging behavior in marine predators is often inferred from diving and movement patterns, leading to incomplete ecological insights.
• Accurate quantification of prey consumption is crucial for understanding marine mammal feeding ecology.

Purpose of the Study:

• To assess the efficacy of stomach temperature telemetry for identifying and quantifying prey consumption in northern elephant seals and California sea lions.
• To differentiate between prey and water ingestion using stomach temperature recovery rates.

Main Methods:

• Stomach temperature telemetry was employed in phocid (northern elephant seal) and otariid (California sea lion) species.
• Prey and water ingestion events were identified by analyzing declines and recovery rates in stomach temperature.
• The integral of stomach temperature decline over time was used to estimate consumed prey mass.

Main Results:

• Over 96% of feeding events were identified via stomach temperature decline, even with short intervals between meals.
• Water ingestion showed significantly faster stomach temperature recovery rates than prey ingestion.
• A notable 30.6% of water ingestion events were misclassified as prey ingestion due to overlapping recovery rates.

Conclusions:

• Stomach temperature telemetry is a viable method for identifying prey consumption and estimating meal mass in marine mammals.
• While water ingestion can be distinguished, misclassification remains a challenge.
• This technique enhances the understanding of marine mammal foraging behavior beyond traditional movement analysis.