• Question from:Ant

I've read about mammals whose testicles remain inside the body throughout development. Do these animals have less efficient sperm production, or have they evolved some type of cooling system? If they have a cooling system, how does it work?

Thanks,
Ant

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Hi Ant,

we have answered a testicular question before that touches on this: http://www.askabiologist.org.uk/punbb/v … php?id=653

In short, there are many mammals that maintain their testes internally for the majority of the time, but when they are needed (i.e. in the breeding season) they undergo rapid development and they briefly emerge to allow efficient sperm production.

There are also some mammals that do not maintain internal temperatures as high as humans, so sperm production doesn't necessarily become impaired by testicular retention inside the body.