Each animal species has an optimal temperature at which it can metabolise food and its immune system can best fight off pathogens.

As our recent research shows, temperature directly affects the immune systems of vertebrates – regardless of how they moderate their own body temperatures. At first, slightly hotter temperatures actually give many animal immune systems a boost. But when temperatures get still hotter, conditions favour pathogens – organisms which cause disease.

This is a real problem, given many pathogens found in warmer areas are likely to expand their range as the climate changes.

The good news: learning more about how temperatures affect animal immune systems gives us new options, such as using “frog saunas” to help frogs fight off the lethal chytrid fungus.

How do animals maintain body temperatures?

Different types of vertebrates have very different ways of maintaining an optimal body temperature.

Mammals and birds are endotherms. In cold conditions, they can keep their body temperature close to optimal by burning energy stored as fat. Animals such as reindeer are able to live in temperatures as low as -40°C while keeping their core body temperature at 38-40°C.

At the other extreme are snakes, lizards and other poikilotherms – so-called “cold blooded” animals who rely on the environment to modify their temperature. If they’re too cold, they seek the sun. If too hot, they seek the........

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