Thermoregulatory Adaptations of

Terrestrial Polar Mammals

Thermoregulation

Thermoregulation is the result of biofeedback to control systems in the central nervous system responsible for regulating internal body temperature.

Thermoneutral Zone

Determines an animal’s cost of heat production in a cold environment.

The range in which metabolic rate is unaffected by temperature.

Arctic mammals vs. Warm climate mammals Sweating Threshold Sweating Threshold

Thermoneutral Zone Thermoneutral Zone

Shivering Threshold Shivering Threshold

Critical Temperature

Lowering Critical Temperature Arctic mammals tend to have a low critical

temperature and only increase metabolic rates when the temperature drops to a certain point

Example: The Arctic Fox, Vulpes lagopus

Metabolic rate does not increase until temperature drops below -40ºC At -70ºC metabolic rate has only

increased by 50%

Non-shivering Thermogenesis Heat production without an actual

increase in muscular activity. Brown fat is the main site of non-

shivering thermogenesis. Brown fat is a vascular adipose tissue

found in the neck, thorax and around major blood vessels supplying the heart and brain.

Hibernating and newborn terrestrial mammals have an abundance of brown fat.

Counter-current Exchange

Heat Conservation Circulation to the periphery is restricted. Heat is transferred from high

temperatures to lower temperatures through conduction.

Counter-current Exchange

Counter-current Exchange

Heat Dissipation Increased blood supply from the

peripheries circulates through the body as opposed to warmer blood from the core

Fur Layers

Animal Behaviour

Hibernation

Snow Dens

Walking Slowly

Swimming

Conclusion

Because of such harsh environments in the Arctic, many animals have evolved unique adaptive mechanisms that allow them to survive and flourish in these environments.

References

Best, R. (1982). Thermoregulation in resting and active polar bears. Journal of Comparative Physiology, 146, 73-63.

Blix, A., & Steen, J. (1979). Temperature regulation in newborn polar homeotherms. Physiological Reviews, 59(2), 285- 304.

Gordon, M. (1968). Animal function: Principles and adaptations. Toronto: Macmillan. Hoar, W. (1983). General comparative physiology (3rd ed.). New Jersey: Prentice-Hall. Noren, S., Pearson, L., Davis, J., Trumble, S., & Kanatous, S. (2008). Different

thermoregulatory strategies nearly weaned pup, yearling, and adult weddell seals (Leptonychotes weddelli). Physiological and Biochemical Zoology, 81(6), 868-879.

Schmidt-Nielson, K. (1997). Animal physiology: Adaptation and environment (5th ed.). Cambridge England: Cambridge University Press

SeaWorld Parks & Entertainment. (2002). Polar Bears. Retrieved from http://www.seaworld.org/infobooks/polarbears/pbadaptations.html

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