Which animals sweat?

Nikki - Hi. My name is Nikki and I live in Perth, Western Australia. My question is, what type of animals sweat? I know that horses do, but do others too?

Hannah - So, sweat - do the birds and bees do it and even educated flees? Or is sweating just limited to humans and horses?

Jonathan - My name is Jonathan Holmes. I'm fellow of Queens College in the University of Cambridge and I'm a part time lecturer in veterinary anatomy. Humans have two sorts of sweat gland and two sorts of sweat. The first type with which we are most familiar are in our skin all over the body and produce watery droplets. The droplets evaporate from the surface and cool the skin so they are important in regulating our body temperature. This sort of sweat gland and sweating however is very uncommon in animals. Very few animals use sweating to keep their bodies cool. A second type of gland forms sweat by breaking off bits of cell rather than secreting a droplet. The product is much more granular and fatty. In humans, this is the smelly sort of sweat we associate especially with our armpits. Most animals do have this sort of sweat gland, but they are fairly few and far between and mostly concentrated around the face and mouth, and around the anus. They seem to be important for keeping the skin soft and flexible. Dogs and cats incidentally have a large number of these sweat glands on their footpads. They're probably there to keep the pads which are just very thick skin, supple, but may also help with grip in the same way that we lick our fingers to make them slightly moist when counting bank notes or turning pages. As Nikki has noted, horses do sweat abundantly. There is a type of protein related to albumin in their sweat which often causes it to froth.

Hannah - Thanks, Jonathan. So, humans can sweat out as much as 10 to 14 litres per day and they mainly due this to reduce their body temperature by evaporating water from their skin. Plus, they secrete a second type of sweat to release a more oily fatty fluid that eventually smells and can be used as a territorial marker or signal fear and anxiety. Most other animals don't do the first type of sweating. Instead, dogs pant for example to keep cool. But most animals do have the second type of sweat, oozing out of areas of their body and the fat is also keeping the skin soft and supple. With what question sweated out, we turn to this...

Paul - Hello. My name is (Paul) in the Northwest of England and my question is, do smaller organisms evolve faster than larger organisms?