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DeRango EJ, Schwarz JFL, Piedrahita P, Páez‐Rosas D, Crocker DE, Krüger O. Hormone-mediated foraging strategies in an uncertain environment: Insights into the at-sea behavior of a marine predator. Ecol Evol 2021; 11:7579-7590. [PMID: 34188836 PMCID: PMC8216952 DOI: 10.1002/ece3.7590] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/30/2021] [Accepted: 04/01/2021] [Indexed: 12/22/2022] Open
Abstract
Hormones are extensively known to be physiological mediators of energy mobilization and allow animals to adjust behavioral performance in response to their environment, especially within a foraging context.Few studies, however, have narrowed focus toward the consistency of hormonal patterns and their impact on individual foraging behavior. Describing these relationships can further our understanding of how individuals cope with heterogeneous environments and exploit different ecological niches.To address this, we measured between- and within-individual variation of basal cortisol (CORT), thyroid hormone T3, and testosterone (TEST) levels in wild adult female Galápagos sea lions (Zalophus wollebaeki) and analyzed how these hormones may be associated with foraging strategies. In this marine predator, females exhibit one of three spatially and temporally distinct foraging patterns (i.e., "benthic," "pelagic," and "night" divers) within diverse habitat types.Night divers differentiated from other strategies by having lower T3 levels. Considering metabolic costs, night divers may represent an energetically conservative strategy with shorter dive durations, depths, and descent rates to exploit prey which migrate up the water column based on vertical diel patterns.Intriguingly, CORT and TEST levels were highest in benthic divers, a strategy characterized by congregating around limited, shallow seafloors to specialize on confined yet reliable prey. This pattern may reflect hormone-mediated behavioral responses to specific risks in these habitats, such as high competition with conspecifics, prey predictability, or greater risks of predation.Overall, our study highlights the collective effects of hormonal and ecological variation on marine foraging. In doing so, we provide insights into how mechanistic constraints and environmental pressures may facilitate individual specialization in adaptive behavior in wild populations.
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Affiliation(s)
| | | | - Paolo Piedrahita
- Facultad de Ciencias de la VidaEscuela Superior Politécnica del LitoralGuayaquilEcuador
| | - Diego Páez‐Rosas
- Universidad San Francisco de QuitoGalápagos Science CenterIsla San CristobalEcuador
- Dirección Parque Nacional GalápagosOficina Técnica San CristóbalIsla San CristóbalEcuador
| | | | - Oliver Krüger
- Department of Animal BehaviourBielefeld UniversityBielefeldGermany
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Kroeger CE, Crocker DE, Orben RA, Thompson DR, Torres LG, Sagar PM, Sztukowski LA, Andriese T, Costa DP, Shaffer SA. Similar foraging energetics of two sympatric albatrosses despite contrasting life histories and wind-mediated foraging strategies. ACTA ACUST UNITED AC 2020; 223:223/23/jeb228585. [PMID: 33268565 DOI: 10.1242/jeb.228585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 10/12/2020] [Indexed: 11/20/2022]
Abstract
Understanding the environmental and behavioral factors that influence how organisms maintain energy balance can inform us about their potential resiliency to rapid environmental changes. Flexibility in maintaining energy balance is particularly important to long-lived, central-place foraging seabirds that are constrained when locating food for offspring in a dynamic ocean environment. To understand the role of environmental interactions, behavioral flexibility and morphological constraints on energy balance, we used doubly labeled water to measure the at-sea daily energy expenditure (DEE) of two sympatrically breeding seabirds, Campbell (Thalassarche impavida) and grey-headed (Thalassarche chrysostoma) albatrosses. We found that species and sexes had similar foraging costs, but DEE varied between years for both species and sexes during early chick rearing in two consecutive seasons. For both species, greater DEE was positively associated with larger proportional mass gain, lower mean wind speeds during water take-offs, greater proportions of strong tailwinds (>12 m s-1), and younger chick age. Greater proportional mass gains were marginally more costly in male albatrosses that already have higher wing loading. DEE was higher during flights with a greater proportion of strong headwinds for grey-headed albatrosses only. Poleward winds are forecasted to intensify over the next century, which may increase DEE for grey-headed albatrosses that heavily use this region during early chick rearing. Female Campbell albatrosses may be negatively affected by forecasted slackening winds at lower latitudes due to an expected greater reliance on less energy efficient sit-and-wait foraging strategies. Behavioral plasticity associated with environmental variation may influence future population responses to climate change of both species.
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Affiliation(s)
- Caitlin E Kroeger
- Department of Ocean Sciences, 1156 High Street, University of California at Santa Cruz, Santa Cruz, CA 95064, USA
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, 1801 E Cotati Avenue, Rohnert Park, CA 94928, USA
| | - Rachael A Orben
- Department of Fisheries and Wildlife, Oregon State University, 2030 SE Marine Science Drive, Newport, OR 97365, USA
| | - David R Thompson
- National Institute of Water and Atmospheric Research Ltd (NIWA), 301 Evans Bay Parade, Hataitai, Wellington 6021, New Zealand
| | - Leigh G Torres
- Department of Fisheries and Wildlife, Marine Mammal Institute, Oregon State University, 2030 SE Marine Science Drive, Newport, OR 97365, USA
| | - Paul M Sagar
- National Institute of Water and Atmospheric Research Ltd (NIWA), 10 Kyle Street, Riccarton, Christchurch 8011, New Zealand
| | - Lisa A Sztukowski
- Marine Biology & Ecology Research Centre, Plymouth University, Plymouth PL4 8AA, UK.,Department Commonwealth of the Northern Mariana Islands, Department of Lands and Natural Resources, Division of Fish and Wildlife, PO Box 10007, Saipan, MP 96950
| | - Timothy Andriese
- Department of Biological Sciences, San Jose State University, One Washington Square, San Jose, CA 95192, USA
| | - Daniel P Costa
- Department of Ecology and Evolution, University of California Santa Cruz, Santa Cruz, CA 95062, USA
| | - Scott A Shaffer
- Department of Biological Sciences, San Jose State University, One Washington Square, San Jose, CA 95192, USA
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Glucs ZE, Smith DR, Tubbs CW, Bakker VJ, Wolstenholme R, Dudus K, Burnett LJ, Clark M, Clark M, Finkelstein ME. Foraging behavior, contaminant exposure risk, and the stress response in wild California condors (Gymnogyps californianus). ENVIRONMENTAL RESEARCH 2020; 189:109905. [PMID: 32738723 DOI: 10.1016/j.envres.2020.109905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/05/2020] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
Wild California condors (Gymnogyps californianus) are frequently exposed to lead via lead-based ammunition ingestion, and recent studies indicate significant exposure to organochlorines (e.g. dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs)) for condors feeding on beach-cast marine mammals. We investigated the influence of contaminant exposure on condor glucocorticoid response through comparisons between wild and captive populations and identification of modifiers of glucocorticoid release in wild condors. We assessed the glucocorticoid response to routine trapping and handling events through measurement of plasma corticosterone and urate glucocorticoid metabolites (GCM). Comparison of peak urate GCM levels showed wild condors exhibited higher responses to handling-associated stressors (2300 ± 1400 ng/g dry wt, average ± SD, n = 27) than captive condors (910 ± 490 ng/g dry wt., n = 6, U = 28, p = 0.003). Multiple linear regression models and an information theoretic approach (AICc) identified several extrinsic variables (e.g., time captive in flight pen before sample collection) that were negatively associated with plasma corticosterone and urate GCM levels in wild condors, which explained ~25% of glucocorticoid variation. When accounting for these extrinsic variables we found that behavioral variables associated with increased lead and organochlorine exposure risk were positively associated with GCM levels, explaining an additional 15% of glucocorticoid variation among wild condors. Days absent from management area, a variable associated with reduced survival attributed to increased lead exposure risk, had a positive influence on plasma corticosterone levels (β = 53 ± 20 SE) and peak urate GCM levels (β = 1090 ± 586 SE). Years observed feeding on marine mammals, a variable positively associated with DDE and PCB exposure, positively influenced peak urate GCM (β = 1100 ± 520 SE) and the magnitude of GCM response (peak GCM - 1st urate GCM) (β = 1050 ± 500 SE). Our findings suggest that individual propensities for contaminant-associated foraging behaviors predict higher stress-induced glucocorticoid levels in wild condors, and that accounting for variables associated with trapping and handling is essential for assessing the impact of environmental stressors such as contaminants on the condor stress response. As an abnormal glucocorticoid response to stress is associated with reduced reproduction and survival in vertebrates, this work indicates the need for further investigations into the physiological impacts of sub-lethal contaminant exposures in scavenging species worldwide.
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Affiliation(s)
- Zeka E Glucs
- Predatory Bird Research Group, University of California, Santa Cruz, CA, USA; Microbiology and Environmental Toxicology Department, University of California, Santa Cruz, CA, USA.
| | - Donald R Smith
- Microbiology and Environmental Toxicology Department, University of California, Santa Cruz, CA, USA
| | - Christopher W Tubbs
- San Diego Zoo Global, Institute for Conservation Research, Escondido, CA, USA
| | | | - Rachel Wolstenholme
- National Park Service, Interior Regions 8, 9, 10, 12, San Francisco, CA, USA
| | - Kristina Dudus
- National Park Service, Interior Region 2, Gulf Breeze, FL, USA
| | | | | | - Michael Clark
- Los Angeles Zoo and Botanical Gardens, Los Angeles, CA, USA
| | - Myra E Finkelstein
- Microbiology and Environmental Toxicology Department, University of California, Santa Cruz, CA, USA
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