Individual Specialization in a Generalist Apex Predator: The Leopard Seal

Area of Science:

• Marine Biology
• Ecology
• Wildlife Conservation

Background:

• Apex predators are often viewed as generalists, but individual specialization in resource use is common.
• Leopard seals (Hydrurga leptonyx) are key apex predators in the Southern Ocean, yet their trophic ecology is poorly understood at the individual level.

Purpose of the Study:

• To investigate trophic variation and individual specialization in leopard seals.
• To determine the drivers of this intraspecific variation and its ecological implications.

Main Methods:

• Analysis of stable isotopes (δ13C and δ15N) in leopard seal whiskers (n=46) from the Western Antarctic Peninsula.
• Assessment of individual consistency over time using repeat samples (n=7) over 2-10 years.
• Comparison of population and individual isotopic niche space.

Main Results:

• Leopard seals exhibit a broad population-level trophic niche, functioning as generalists.
• However, the majority of individuals are dietary specialists (59%), with only a few generalists.
• Individual specialization, sex, and mass were significant drivers of trophic variation, with some seals specializing consistently over time.

Conclusions:

• Individual specialization is a critical factor in leopard seal trophic ecology, potentially leading to disproportionate impacts on prey populations.
• Long-term specialization by a few individuals may have significant ecosystem consequences, such as contributing to declines in prey populations.
• Understanding individual specialization in apex predators is crucial for effective ecosystem management and conservation.