In the mid 19^th century Carl Bergmann, a German biologist, observed that birds and mammals in cold regions tended to be bigger and bulkier than individuals of the same species in warmer regions. He proposed to account for an adaptive mechanism to conserve or to radiate body heat depending on climate. The principle known as Bergmann’ rule states that homoeotherm animals from higher altitudes and latitudes or bred at lower temperatures tend to be bigger.

Because heat exchange occurs mainly at an animal's surface, large animals cool down more slowly than small ones, due to a lower surface to mass ratio. Further factors like insulation (fat, fur, feathers,...) and behaviour (huddling, selection of favourable microhabitat,...) have great impacts on the temperature balance of an animal.

The following model should demonstrate these principles. The inserted values for the parameters are only exemplary and do not exactly match real data.

Select parameters and check their effect on core temperature drop after 100 seconds. Then answer the questions that follow.

1) How many degrees does the core temperature of a dog-like animal with thin fur and no specific heat conserving behaviour drop after 100 sec?

2) How many degrees does the core temperature of a mouse-like animal with thick fur and living below the snow surface drop after 100 sec?

3) Compare the heat loss of animals with the same insulation and behaviour and find out how important the size of an animal is with regard to its thermoregulation.

View details of model

29 August 2011
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