Why Do Humans And Animals Get Goosebumps?
The Reason Why Animals Fluff Up Their Fur Or Feathers
Jun 1, 2009
Humans and other animals experience goosebumps (also called gooseflesh or goosepimples), known as piloerection, when they are cold or scared. The hair or fur stands up due to contraction of pili muscles (pili = hair).
Why do Humans and Animals get Goosebumps When They are Cold?
Animals (including humans) use different mechanisms to regulate the exchange of heat between the environment and themselves. This may include:
- Behavioural modifications, for example moving somewhere else
- Long-term morphological changes, for example a long-haired dog shedding its winter coat in spring
- Autonomic changes in blood flow and sweating
Internal physiological adjustments can alter heat flow. Many vertebrates (animals with backbone / vertebrae) have autonomic control of blood flow to the periphery, especially the skin, that can change the temperature gradient between the environment and skin surface.
Autonomic mechanisms modify the insulation qualities of the body surfaces. By activating the piloerector muscles, this increases the extent of fluffing of pelage and plumage, which increases the amount of, trapped, unstirred air next to the skin, and thus increases insulation. Their insulating properties can be changed very quickly in response to the environment. Through pilomotor control, fur, hair or feathers can be fluffed up or flattened as needed
Changes in blood flow to the skin regulate heat conductance. Vasomotor (regulating constriction and dilation of blood vessels) control of peripheral arterioles sends blood either to skin or away from it. In endotherms (warm blooded animal), peripheral blood vessels constrict in response to cold, keeping blood away from the body surface.
Of course most humans don’t have much hair anymore so fluffing or goosebumps don’t do much to keep them warm, but the physiological reaction is ever present and is a reminder that humans are descended from a much hairier species.
Why do Humans and Animals get Goosebumps When They are Scared?
Piloerection is also a defense mechanism, in particular with animals more that humans. When an animal feels threatened, piloerection causes the fur or feathers to stick out, make the animal appear much larger and more threatening, and thus, hopefully put off any potential attacker. Piloerection is an involuntary reaction controlled by the sympathetic nervous system.
In humans the reaction is less useful then it would have been for their ancestors, however, it can still occur as a response to fear or stress, preparing them for ‘fight or flight’.
Resource and further reading:
Silverthorn, D.U, 2007, ‘Energetic Costs of Meeting Environmental challenges’, in Human Physiology, ed. Benjamin Cummings, San Francisco, chap. 17.
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