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Cole MR, Ware C, McHuron EA, Costa DP, Ponganis PJ, McDonald BI. Deep dives and high tissue density increase mean dive costs in California sea lions (Zalophus californianus). J Exp Biol 2023; 226:jeb246059. [PMID: 37345474 DOI: 10.1242/jeb.246059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 06/14/2023] [Indexed: 06/23/2023]
Abstract
Diving is central to the foraging strategies of many marine mammals and seabirds. Still, the effect of dive depth on foraging cost remains elusive because energy expenditure is difficult to measure at fine temporal scales in wild animals. We used depth and acceleration data from eight lactating California sea lions (Zalophus californianus) to model body density and investigate the effect of dive depth and tissue density on rates of energy expenditure. We calculated body density in 5 s intervals from the rate of gliding descent. We modeled body density across depth in each dive, revealing high tissue densities and diving lung volumes (DLVs). DLV increased with dive depth in four individuals. We used the buoyancy calculated from dive-specific body-density models and drag calculated from swim speed to estimate metabolic power and cost of transport in 5 s intervals during descents and ascents. Deeper dives required greater mean power for round-trip vertical transit, especially in individuals with higher tissue density. These trends likely follow from increased mean swim speed and buoyant hinderance that increasingly outweighs buoyant aid in deeper dives. This suggests that deep diving is either a 'high-cost, high-reward' strategy or an energetically expensive option to access prey when prey in shallow waters are limited, and that poor body condition may increase the energetic costs of deep diving. These results add to our mechanistic understanding of how foraging strategy and body condition affect energy expenditure in wild breath-hold divers.
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Affiliation(s)
- Mason R Cole
- Moss Landing Marine Laboratories, San Jose State University, 8272 Moss Landing Rd, Moss Landing, CA 95039, USA
| | - Colin Ware
- Center for Coastal and Ocean Mapping, University of New Hampshire, Durham, NH 03924, USA
| | - Elizabeth A McHuron
- Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington, Seattle, WA 98105, USA
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95064, USA
| | - Paul J Ponganis
- Scripps Institution of Oceanography, University of California San Diego, Center for Marine Biodiversity and Biomedicine, 8655 Kennel Way, La Jolla, CA 92037, USA
| | - Birgitte I McDonald
- Moss Landing Marine Laboratories, San Jose State University, 8272 Moss Landing Rd, Moss Landing, CA 95039, USA
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Valenzuela-Toro AM, Mehta R, Pyenson ND, Costa DP, Koch PL. Feeding morphology and body size shape resource partitioning in an eared seal community. Biol Lett 2023; 19:20220534. [PMID: 36883314 PMCID: PMC9993223 DOI: 10.1098/rsbl.2022.0534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023] Open
Abstract
Body size and feeding morphology influence how animals partition themselves within communities. We tested the relationships among sex, body size, skull morphology and foraging in sympatric otariids (eared seals) from the eastern North Pacific Ocean, the most diverse otariid community in the world. We recorded skull measurements and stable carbon (δ13C) and nitrogen (δ15N) isotope values (proxies for foraging) from museum specimens in four sympatric species: California sea lions (Zalophus californianus), Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus) and Guadalupe fur seals (Arctocephalus townsendi). Species and sexes had statistical differences in size, skull morphology and foraging significantly affecting the δ13C values. Sea lions had higher δ13C values than fur seals, and males of all species had higher values than females. The δ15N values were correlated with species and feeding morphology; individuals with stronger bite forces had higher δ15N values. We also found a significant community-wide correlation between skull length (indicator of body length), and foraging, with larger individuals having nearshore habitat preferences, and consuming higher trophic level prey than smaller individuals. Still, there was no consistent association between these traits at the intraspecific level, indicating that other factors might account for foraging variability.
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Affiliation(s)
- Ana M Valenzuela-Toro
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA.,Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Rita Mehta
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA
| | - Nicholas D Pyenson
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA.,Department of Paleontology and Geology, Burke Museum of Natural History and Culture, Seattle, WA 98105, USA
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA.,Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Paul L Koch
- Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
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Hawkes LA, Fahlman A, Sato K. Introduction to the theme issue: Measuring physiology in free-living animals. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200210. [PMID: 34121463 PMCID: PMC8200652 DOI: 10.1098/rstb.2020.0210] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2021] [Indexed: 12/18/2022] Open
Abstract
By describing where animals go, biologging technologies (i.e. animal attached logging of biological variables with small electronic devices) have been used to document the remarkable athletic feats of wild animals since the 1940s. The rapid development and miniaturization of physiologging (i.e. logging of physiological variables such as heart rate, blood oxygen content, lactate, breathing frequency and tidal volume on devices attached to animals) technologies in recent times (e.g. devices that weigh less than 2 g mass that can measure electrical biopotentials for days to weeks) has provided astonishing insights into the physiology of free-living animals to document how and why wild animals undertake these extreme feats. Now, physiologging, which was traditionally hindered by technological limitations, device size, ethics and logistics, is poised to benefit enormously from the on-going developments in biomedical and sports wearables technologies. Such technologies are already improving animal welfare and yield in agriculture and aquaculture, but may also reveal future pathways for therapeutic interventions in human health by shedding light on the physiological mechanisms with which free-living animals undertake some of the most extreme and impressive performances on earth. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.
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Affiliation(s)
- L. A. Hawkes
- Hatherly Laboratories, University of Exeter, Prince of Wales Road Exeter EX4 4PS, UK
| | - A. Fahlman
- Global Diving Research Inc, Ottawa, Ontario, Canada
- Fundación Oceanogràfic de la Comunitat Valencia, Valencia, 46005 Spain
| | - K. Sato
- Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba Prefecture 277-8564, Japan
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