Predator-mediated interactions through changes in predator home range size can lead to local prey exclusion

Area of Science:

• Ecology
• Community Ecology
• Behavioral Ecology

Background:

• Indirect biotic interactions can significantly influence community composition but are challenging to quantify in natural settings.
• Understanding predator-mediated interactions is crucial for predicting species dynamics and community structure.
• The numerical response of predators, influenced by prey availability and behavior, plays a key role in indirect effects.

Purpose of the Study:

• To quantify the strength of indirect biotic interactions in a natural vertebrate community.
• To investigate how the presence of one prey species (geese) affects the population growth rate of another prey species (sandpipers) through a shared predator (arctic fox).
• To develop and parameterize an empirically based model integrating mechanistic predation and behavioral processes.

Main Methods:

• Utilized a multi-prey mechanistic model of predation and a population matrix model.
• Parametrized models using behavioral, demographic, and experimental data from a community including arctic foxes, lemmings, sandpipers, and geese.
• Quantified predator-mediated interaction strength by analyzing the effects of goose presence on sandpiper nesting success and fox density.

Main Results:

• The positive effect of goose colonies on sandpiper nesting success (reduced search time) was negated by increased arctic fox density.
• Arctic fox numerical response was driven by changes in their home range size, influenced by prey availability.
• The net indirect interaction from geese on sandpipers was negative, potentially leading to sandpiper local exclusion.

Conclusions:

• Indirect interactions mediated by predators can have significant negative consequences for prey populations, even when direct benefits exist.
• Empirically based models integrating mechanistic functional responses and behavioral processes are essential for accurately assessing predation impacts on community dynamics.
• This study provides a robust framework for quantifying indirect effects and their role in shaping ecological communities.