To feed or not to feed? Bioenergetic impacts of fear-driven behaviors in lactating dolphins

Authored by William E Grant, Mridula Srinivasan, Todd M Swannack, Jolly Rajan, Bernd Wuersig

Date Published: 2018

DOI: 10.1002/ece3.3732

Sponsors: United States Army Engineer Research and Development Center (ERDC)

Platforms: No platforms listed

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

In mammals, lactation can be the most energetically expensive part of the reproductive cycle. Thus, when energy needs are compromised due to predation risk, environmental disturbance, or resource scarcity, future reproductive success can be impacted. In marine and terrestrial environments, foraging behavior is inextricably linked to predation risk. But quantification of foraging energetics for lactating animals under predation risk is less understood. In this study, we used a spatially explicit individual-based model to study how changes in physiology (lactating or not) and the environment (predation risk) affect optimal behavior in dolphins. Specifically, we predicted that an adult dolphin without calf would incur lower relative energetic costs compared to a lactating dolphin with calf regardless of predation risk severity, antipredator behavior, or prey quality consumed. Under this state-dependent analysis of risk approach, we found predation risk to be a stronger driver in affecting total energetic costs (foraging plus locomotor costs) than food quality for both dolphin types. Further, contrary to our hypothesis, after accounting for raised energy demands, a lactating dolphin with calf does not necessarily have higher relative-to-baseline costs than a dolphin without calf. Our results indicate that both a lactating (with calf) and non-lactating dolphin incur lowered energetic costs under a risk-averse behavioral scheme, but consequently suffer from lost foraging calories. A lactating dolphin with calf could be particularly worse off in lost foraging calories under elevated predation risk, heightened vigilance, and increased hiding time relative to an adult dolphin without calf. Further, hiding time in refuge could be more consequential than detection distance for both dolphin types in estimated costs and losses incurred. In conclusion, our study found that reproductive status is an important consideration in analyzing risk effects in mammals, especially in animals with lengthy lactation periods and those exposed to both biological and nonbiological stressors.

Tags

Bioenergetics Predation risk Life-history Orcinus-orca New-zealand Marine mammals Predator-prey interactions Food availability Body condition Lagenorhynchus-obscurus Lactation Predation risk effects Bottle-nosed-dolphin Dusky dolphin Hiding behavior