Perturbation drives changing metapopulation dynamics in a top marine predator

Area of Science:

• Marine mammal ecology
• Population genetics
• Metapopulation dynamics

Background:

• Metapopulation theory posits a balance between local extinction and colonization.
• Recent declines in UK harbour seal populations raise concerns about metapopulation health.

Purpose of the Study:

• To determine if UK harbour seal population declines represent normal metapopulation dynamics or a perturbation.
• To assess the viability of UK harbour seal metapopulations.

Main Methods:

• Analysis of 20 years of population trends.
• Utilizing location tracking data (n=380) and population genetic data (n=269).
• Microsatellite data to identify distinct metapopulations (northern and southern).

Main Results:

• Confirmed distinct northern and southern harbour seal metapopulations.
• Identified source-sink dynamics within the northern metapopulation.
• Observed a disruption in migration across the northern metapopulation coinciding with population declines.

Conclusions:

• The northern harbour seal metapopulation is exhibiting signs of decay.
• Local population changes can significantly impact overall metapopulation persistence.
• The observed declines suggest a perturbation rather than normal metapopulation fluctuations.