Risk assessment based on indirect predation cues: revisiting fine-grained variation

Area of Science:

• Ecology
• Animal Behavior
• Evolutionary Biology

Background:

• Prey adaptively express inducible defenses by gauging predation risk using indirect cues.
• Information in indirect cues for fine-tuning prey phenotypes to risk variation remains unclear.
• Aquatic research often focuses on cue concentration, but risk varies with number or biomass killed.

Purpose of the Study:

• To investigate how tadpoles use indirect predation cues to assess and respond to risk.
• To determine if cue pulse frequency or concentration is a more reliable indicator of predation risk for tadpoles.
• To examine the relationship between tadpole growth and different metrics of predator cue exposure.

Main Methods:

• Laboratory experiments with red-eyed treefrog tadpoles assessing growth in response to predator cues.
• Analysis of total cue, cue per pulse, and cue pulse frequency.
• Reanalysis of a previous study on wood frog tadpoles and predator cue variation.

Main Results:

• Tadpole growth significantly declined with increasing cue pulse frequency in both red-eyed treefrog and wood frog studies.
• High-frequency cue treatments, even with low individual pulse intensity, led to reduced growth.
• Results suggest cue pulse frequency, reflecting the number of predation events, is a key factor in risk assessment.

Conclusions:

• Tadpoles assess predation risk using fine-grained variation in predator cues, specifically cue pulse frequency.
• This finding challenges previous conclusions that cue concentration is the primary driver of threat-sensitive responses.
• Prey utilize the frequency of predation events, not just cue intensity, for adaptive defense expression, aligning with consumer-resource theory.