Modeling total predation to avoid perverse outcomes from cat control in a data-poor island ecosystem

Area of Science:

• Ecology
• Conservation Biology
• Invasive Species Management

Background:

• Complex ecosystem models are data-intensive and often impractical for threatened species management in data-poor systems.
• Invasive predators, such as cats and rats, pose significant threats to native wildlife, with potential for one species to release the other.

Purpose of the Study:

• To develop and demonstrate a minimum realistic modeling approach for guiding conservation decisions in data-limited ecosystems.
• To assess the threat posed by invasive cats and rats to the red-tailed tropicbird population on Christmas Island.

Main Methods:

• Utilized biophysical constraints (metabolic demand) and observable parameters (prey preferences) to create a minimum realistic model.
• Assessed the combined abundances of cats and rats that would threaten the tropicbird population, considering predator-prey dynamics.

Main Results:

• The red-tailed tropicbird population cannot be sustained with 1607 rats or 21 cats alone.
• Removing one cat improves the bird's population growth rate if rat numbers do not increase by more than 77 individuals.
• One cat is ecologically equivalent to 30-174 rats in this specific context.

Conclusions:

• The minimum realistic model approach effectively guides predator control in data-poor systems.
• This method helps determine if current predator levels threaten prey, if managing one predator is sufficient, or if multi-species control is necessary.
• The study shifts conservation focus from predicting future states to identifying immediate threats in data-limited scenarios.