Associations between glucocorticoids and habitat selection reflect daily and seasonal energy requirements

Levi Newediuk; Gabriela F Mastromonaco; Eric Vander Wal

doi:10.1186/s40462-024-00475-9

Associations between glucocorticoids and habitat selection reflect daily and seasonal energy requirements

Mov Ecol. 2024 Apr 22;12(1):30. doi: 10.1186/s40462-024-00475-9.

Authors

Levi Newediuk^{1

2}, Gabriela F Mastromonaco³, Eric Vander Wal⁴

Affiliations

¹ Department of Biology, Memorial University, St. John's Newfoundland, A1B 3X9, Canada. levi.newediuk@umanitoba.ca.
² Current address: Biological Sciences Department, University of Manitoba, Winnipeg Manitoba, R3T 2N2, Canada. levi.newediuk@umanitoba.ca.
³ Reproductive Physiology, Toronto Zoo, Toronto, ON, M1B 5K7, Canada.
⁴ Department of Biology, Memorial University, St. John's Newfoundland, A1B 3X9, Canada.

Abstract

Background: Glucocorticoids are often associated with stressful environments, but they are also thought to drive the best strategies to improve fitness in stressful environments. Glucocorticoids improve fitness in part by regulating foraging behaviours in response to daily and seasonal energy requirements. However, many studies demonstrating relationships between foraging behaviour and glucocorticoids are experimental, and few observational studies conducted under natural conditions have tested whether changing glucocorticoid levels are related to daily and seasonal changes in energy requirements.

Methods: We integrated glucocorticoids into habitat selection models to test for relationships between foraging behaviour and glucocorticoid levels in elk (Cervus canadensis) as their daily and seasonal energy requirements changed. Using integrated step selection analysis, we tested whether elevated glucocorticoid levels were related to foraging habitat selection on a daily scale and whether that relationship became stronger during lactation, one of the greatest seasonal periods of energy requirement for female mammals.

Results: We found stronger selection of foraging habitat by female elk with elevated glucocorticoids (e^ß = 1.44 95% CI 1.01, 2.04). We found no difference in overall glucocorticoid levels after calving, nor a significant change in the relationship between glucocorticoids and foraging habitat selection at the time of calving. However, we found a gradual increase in the relationship between glucocorticoids and habitat selection by female elk as their calves grew over the next few months (e^ß = 1.01, 95% CI 1.00, 1.02), suggesting a potentially stronger physiological effect of glucocorticoids for elk with increasing energy requirements.

Conclusions: We suggest glucocorticoid-integrated habitat selection models demonstrate the role of glucocorticoids in regulating foraging responses to daily and seasonal energy requirements. Ultimately, this integration will help elucidate the implications of elevated glucocorticoids under natural conditions.

Keywords: Fitness; Hormones; Integrated step-selection analysis; Physiology; State-dependent habitat selection; Stress.