Optimal foraging: the difficulty of exploiting different feeding strategies simultaneously.

Area of Science:

• Behavioral Ecology
• Aquatic Ecology
• Predator-Prey Dynamics

Background:

• Optimal foraging theory predicts predators maximize energy intake by balancing encounter rates and handling times.
• Visually feeding fish, like perch (Perca fluviatilis), face complex foraging decisions when multiple prey types are available.
• Prey species often exhibit diverse anti-predatory behaviors, potentially complicating predator efficiency.

Purpose of the Study:

• To investigate the foraging efficiency of perch (Perca fluviatilis) when presented with single versus mixed prey species.
• To determine if perch foraging efficiency is affected by the differing anti-predatory behaviors of Daphnia magna and Chaoborus obscuripus.
• To evaluate the congruence of empirical results with existing optimal foraging models.

Main Methods:

• Experimental trials were conducted using perch (Perca fluviatilis) as the predator.
• Prey consisted of Daphnia magna and Chaoborus obscuripus, presented individually and in mixed-meal scenarios.
• Foraging efficiency was quantified by measuring capture success and prey proportions.

Main Results:

• Perch foraging efficiency was significantly reduced when presented with a mixture of Daphnia magna and Chaoborus obscuripus compared to single-prey presentations.
• The predator captured both prey species in equal proportions in mixed-meal experiments, contradicting models assuming independent prey encounter and handling times.
• Observed foraging patterns align with optimal foraging models that incorporate short-term learning influencing handling time and encounter rates.

Conclusions:

• Predator foraging efficiency is impaired when faced with prey exhibiting distinct anti-predatory strategies.
• Simple optimal foraging models may not accurately predict predator behavior in complex environments with multiple prey types.
• Short-term learning likely plays a crucial role in a predator's ability to adapt foraging strategies to mixed-prey conditions.