Optimal diving: patch quality, depth, and marginal value

Area of Science:

• Behavioral Ecology
• Foraging Theory
• Marine Biology

Background:

• The Marginal Value Theorem (MVT) is commonly used to predict optimal foraging patch times for diving animals.
• Assumptions of the MVT, particularly diminishing returns, may not accurately reflect diving foraging scenarios.

Purpose of the Study:

• To address limitations of the MVT in predicting underwater foraging time for diving animals.
• To clarify the roles of ecological and physiological factors in patch residency time.
• To resolve confusions in interpreting environmental quality effects on foraging time in different habitats.

Main Methods:

• Analysis of the MVT's core assumption of diminishing returns in foraging.
• Modeling the interplay of prey abundance (ecological) and aerobic capacity (physiological) on patch residency.
• Examination of optimal foraging time in homogeneous and heterogeneous habitats.
• Investigation of foraging gain dependent on time and depth.

Main Results:

• Diminishing returns are not always necessary for MVT application; ecological and physiological factors interact significantly.
• Environmental quality's impact on optimal foraging time differs between homogeneous and heterogeneous habitats.
• Optimal foraging depth is not solely determined by the peak energetic rate of gain.

Conclusions:

• The MVT requires adjustments for diving animals, incorporating interacting ecological and physiological influences.
• Clarified interpretations of environmental quality and depth effects enhance models of optimal diving foraging.
• This work provides a more robust framework for understanding diving animal foraging strategies.