Pulsed resource availability changes dietary niche breadth and partitioning between generalist rodent consumers

Area of Science:

• Ecology
• Animal Behavior
• Ecosystem Dynamics

Background:

• Understanding species interactions and ecosystem roles requires knowledge of niche breadth and overlap.
• Investigating the influence of foraging ecology and interspecific competition on diet is challenging without manipulative experiments.
• Resource pulses in ecosystems provide natural experiments to study consumer dietary niche drivers.

Purpose of the Study:

• To test if optimal foraging or competition structures dietary niche breadth and overlap in two congener rodent species, Peromyscus leucopus and P. maniculatus.
• To investigate the role of American beech mast-fruiting events as a natural experiment influencing rodent diets.
• To assess seasonal dynamics of dietary niches in relation to food availability.

Main Methods:

• Stable isotope analysis (δ13C, δ15N) of rodent hair and potential food items to reconstruct diets over two years.
• Utilized natural pulses of American beech mast-fruiting as a key environmental variable.
• Employed Bayesian framework to calculate standard ellipse area for measuring niche dynamics.

Main Results:

• Rodent niche breadth narrowed during mast years, consistent with optimal foraging theory, as they consumed more high-quality beechnuts.
• Dietary niches expanded in non-masting seasons, with increased consumption of lower-quality fungi.
• Dietary niche overlap increased during masting seasons, supporting competition theory.

Conclusions:

• Food availability, particularly beech masting, significantly influences rodent dietary niche dynamics and interspecific competition.
• Diet plasticity and potential niche partitioning between Peromyscus species may reduce competition during periods of low food availability.
• Shifts in rodent diets can have implications for ecosystem functions, such as fungal spore dispersal.