Introduction: The two subspecies of the West Indian manatee (Trichechus manatus), Florida manatees (T. m. latirostris) and Antillean manatees (T. m. manatus), face different environmental challenges. While Florida manatees have to cope with winter water temperatures below their lower critical temperature of ~ 20 °C and air temperatures below freezing, Antillean manatees live in year-round warm Caribbean waters. Sirenians lack effective thermal insulation and have limited capability of controlling peripheral heat loss. Although severe cold related health issues and mortality are primarily known in Florida manatees, it can be assumed that Antillean manatees and other extant sirenians share the cold-sensitivity, but hardly ever experience it. Contrarily, during summer, Antillean manatees may face the opposite form of thermal stress by being exposed to water temperatures close to their body temperature. However, the upper critical temperature of manatees is not known.
Objective: To improve understanding of the impact of high ambient temperatures on manatee physiology.
Methods: We measured skin temperature in six Antillean manatees in two different habitats in Belize, and compared the results to skin temperatures measured in two captive Florida manatees.
Results: We found a similar temperature distribution pattern over the body surface in both subspecies, but significantly higher temperatures and larger temperature ranges among measuring points in Antillean manatees as compared to Florida manatees. In one Antillean manatee, skin temperature was consistently lower than ambient water temperature by up to 2.5 °C. This implies potential heat uptake from the environment, in contrast to the heat loss experienced by Florida manatees at low water temperatures, apparent in skin temperatures above ambient water temperature.
Conclusions: Our findings suggest that heat stress may be a more likely risk for manatees in warm tropical waters. Despite the small sample size, our results present important findings towards understanding thermal tolerance and impact of high ambient temperatures on manatee physiology.
Anderson, P. K. (1986). Dugongs of Shark Bay, Australia - Seasonal migration, water temperature, and forage. National Geographic Research, 2, 473–490.
Bossart, G. D., Meisner, R. A., Rommel, S. A., Ghim, S.-j., & Jensen, A. B. (2002). Pathological features of the Florida manatee cold stress syndrome. Aquatic Mammals, 29, 9–17. https://doi.org/10.1578/016754203101024031
Bryden, M. M., Marsh, H., & Macdonald, B. W. (1978). Skin and hair of the dugong, Dugong dugong. Journal of Anatomy, 126, 637–638.
Castelblanco-Martínez, D. N., Slone, D. H., Landeo-Yauri, S. S., Ramos, E. A., Alvarez-Alemán, A., Attademo, F. L. N., … Mignucci-Giannoni, A. A. (2021). Analysis of body condition indices reveals different ecotypes of the Antillean manatee. Scientific Reports, 11, 19451. https://doi.org/10.1038/s41598-021-98890-0
Erdsack, N., McCully Phillips, S. R., Rommel, S. A., Pabst, D. A., McLellan, W. A., & Reynolds, J. E., III. (2018). Heat flux in manatees: an individual matter and a novel approach to assess and monitor the thermal state of Florida manatees (Trichechus manatus latirostris). Journal of Comparative Physiology B, 188, 717–727. https://doi.org/10.1007/s00360-018-1152-7
Fawcett, D. W. (1942). A comparative study of blood-vascular bundles in the Florida manatee (Trichechus latirostris) and in certain cetaceans and edentates. Journal of Morphology, 71, 105–133. https://doi.org/10.1002/jmor.1050710106
Gallivan, G. J., & Best, R. C. (1980). Metabolism and respiration of the Amazonian manatee (Trichechus inunguis). Physiological Zoology, 53, 245–253. https://www.jstor.org/stable/30155787
Gallivan, G. J., Best, R. C., & Kanwisher, J. W. (1983). Temperature regulation in the Amazonian manatee Trichechus inunguis. Physiological Zoology, 56, 255–262. https://10.1086/physzool.56.2.30156057
Hales, J. R. S. (1984, June17-21). Skin arteriovenous anastomoses, their control and role in thermoregulation. In K. Johansen & W. W. Burggren (Eds.), Cardiovascular Shunts: phylogenetic, ontogenetic, and clinical aspects : proceedings of the Alfred Benzon Symposium 21, held at the premises of the Royal Danish Academy of Sciences and Letters, , Munksgaard, Copenhagen, Denmark.
Hardy, S. K., Deutsch, C. J., Cross, T. A., de Wit, M., & Hostetler, J. A. (2019). Cold-related Florida manatee mortality in relation to air and water temperatures. PLoS One, 14, e0225048. https://doi.org/10.1371/journal.pone.0225048
Horgan, P., Booth, D., Nichols, C., & Lanyon, J. M. (2014). Insulative capacity of the integument of the dugong (Dugong dugon): thermal conductivity, conductance and resistance measured by in vitro heat flux. Marine Biology, 161, 1395–1407. https://doi.org/10.1007/s00227-014-2428-4
Irvine, A. B. (1983). Manatee metabolism and its influence on distribution in Florida. Biological Conservation, 25, 315–334. https://doi.org/10.1016/0006-3207(83)90068-X
Iverson, S. J. (2009). Blubber. In W. F. Perrin, B. Würsig, & J. G. M. Thewissen (Eds.), Encyclopedia of Marine Mammals (2nd ed., pp. 115–120). Academic Press.
Kaufman, K. W., & Thompson, R. C. (2005). Water Temperature Variation and the Meteorological and Hydrographic Environment of Bocas del Toro, Panama. Caribbean Journal of Science, 41, 392–413.
Marsh, H., O’Shea, T. J., & Reynolds, J. E., III. (2011). Ecology and Conservation of the Sirenia: Dugongs and Manatees. Cambridge University Press.
Martony, M. E., Isaza, R., Erlacher-Reid, C. D., Peterson, J., & Stacy, N. I. (2020). Esophageal measurement of core body temperature in the Florida manatee (Trichechus manatus latirostris). Journal of Wildlife Diseases, 56, 27–33. https://doi.org/10.7589/2019-02-049
National Oceanic and Atmospheric Administration. (2022). Coastal Water Temperature Guide. NOAA National Centers for Environmental Information. https://www.ncei.noaa.gov/access/coastal-water-temperature-guide/all_table.html
Neises, V. M., Karpovich, S. A., Keogh, M. J., King, R. S., & Trumble, S. J. (2021). Regional, seasonal and age class blubber fatty acid signature analysis of harbour seals in Alaska from 1997 to 2010. Conservation Physiology, 9, coab036. https://doi.org/10.1093/conphys/coab036
Reynolds, J. E., III, & Lynch, W. (2017). Florida manatees: Biology, behavior, and conservation [Photographs]. John Hopkins University Press.
Schmidt-Nielsen, K. (1997). Animal Physiology: Adaptation and Environment (5th ed.). Cambridge University Press.
Scholander, P. F., & Irving, L. (1941). Experimental investigations on the respiration and diving of the Florida manatee. Journal of Cellular and Comparative Physiology, 17, 169–191. https://doi.org/10.1002/jcp.1030170204
Wong, A. W., Bonde, R. K., Siegal-Willott, J., Stamper, M. A., Colee, J., Powell, J. A., Reid, J., Deutsch, C. J., & Harr, K. E. (2012). Monitoring Oral Temperature, Heart Rate, and Respiration Rate of West Indian Manatees (Trichechus manatus) During Capture and Handling in the Field. Aquatic Mammals, 38, 1–16. https://doi.org/10.1578/am.38.1.2012.1
Worthy, G. A. J., Miculka, T. A., & Wright, S. D. (1999, August 24-25). Manatee Response To Cold: How Cold is Too Cold? [Paper presentation]Florida Manatees and Warm Water: Proceedings of the Warm-Water Workshop, Jupiter, Florida, United States..
Zeh, D. R., Heupel, M. R., Hamann, M., Jones, R., Limpus, C. J., & Marsh, H. (2018). Evidence of behavioural thermoregulation by dugongs at the high latitude limit to their range in eastern Australia. Journal of Experimental Marine Biology and Ecology, 508, 27–34. https://doi.org/https://doi.org/10.1016/j.jembe.2018.08.004
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