Interactive effects of prey and p,p'-DDE on burrowing owl population dynamics

Area of Science:

• Ecology
• Wildlife Population Dynamics
• Environmental Toxicology

Background:

• Organochlorine contaminants like p,p'-DDE can negatively affect wildlife.
• Burrowing Owl (Athene cunicularia) populations are influenced by prey availability, particularly voles.
• Prior research suggests an interaction between low vole biomass and p,p'-DDE exposure causing reproductive issues in Burrowing Owls.

Purpose of the Study:

• To investigate the combined effects of p,p'-DDE and fluctuating vole availability on Burrowing Owl population dynamics.
• To model the impact of different vole population states (average, peak, crash) and contaminant exposure on owl demographics.

Main Methods:

• Utilized periodic and stochastic matrix population models.
• Incorporated three distinct vole population states: average, peak, and crash years.
• Modeled varying frequencies of vole crash years and assessed the impact on owl demographic rates.

Main Results:

• Vole availability had a greater influence on owl population growth rate than reproductive impairment when vole populations experienced frequent peaks and crashes.
• This difference diminished as vole crash frequency decreased to once per decade.
• Fecundity, though impacted by p,p'-DDE, had less effect on population growth than adult or juvenile survival rates.

Conclusions:

• Vole availability is a critical factor in Burrowing Owl population dynamics, with survival rates being particularly sensitive during vole crash years.
• Population models can effectively elucidate complex ecological interactions, especially when field experiments are limited by scale.
• Understanding these dynamics is crucial for effective conservation strategies for Burrowing Owls facing environmental contaminants and prey fluctuations.