When more is less: the fitness consequences of predators attacking more unpalatable prey when more are presented

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Fritz Müller hypothesized that shared warning signals in mimicry reduce predator education costs.
• Müller's assumption of a fixed predator learning rate lacks empirical validation.

Purpose of the Study:

• To empirically test Müller's hypothesis on predator education costs in mimicry.
• To quantify the fitness costs and benefits of Müllerian mimicry under varying prey densities.

Main Methods:

• Experimental manipulation of unpalatable prey numbers presented to avian predators.
• Observation and quantification of predator attack rates on mimic prey.
• Calculation of fitness costs to unpalatable prey based on attack rates.

Main Results:

• Avian predators increased attack rates as the number of presented unpalatable prey rose.
• Increased attacks on mimic prey can impose substantial fitness costs.
• These costs diminished in significance with increased overall prey availability.

Conclusions:

• Müller's hypothesis may overestimate mimicry benefits due to predator learning dynamics.
• The survival advantage of mimicry is context-dependent, influenced by prey density.
• Predator learning rates and prey availability are critical factors in mimicry evolution.