Using effect size benchmarks to assess when alien impacts are actually alien.

Area of Science:

• Ecology
• Invasive Species Biology
• Wildlife Management

Background:

• Alien predators pose a significant global threat to native wildlife, often with greater impact than native predators.
• Quantifying the impact of alien predators requires comparison to native predator benchmarks.
• The Australian garden skink (Lampropholis delicata) and the invasive black rat (Rattus rattus) were used as a model system.

Purpose of the Study:

• To determine if black rats are an additive source of predation for the Australian garden skink.
• To assess whether the impact of black rats on skinks aligns with that of an alien or native predator.

Main Methods:

• Replicated exclusion experiments were conducted at local and landscape scales.
• The experiments manipulated the presence of black rats to observe effects on skink activity and trapping frequency.

Main Results:

• Excluding black rats positively affected skink activity and trapping frequency.
• The population-level effect size of rat predation on skinks was lower than typical alien predators but comparable to native predators.

Conclusions:

• Australian skinks may possess adaptations to cope with predatory rats, possibly due to co-evolution with native Rattus species.
• This research provides novel insights into the variable impacts of alien predators on native prey populations.