Mammal body heat and local or global climate

Can anyone tell me if the effect on local or global climate from the body heat of animals had been observed?

If there is no noticeable effect on a local or global level, what kind of population density for human animals would you need to have an effect on local climate? Would the effect be similar to urban heat islands?

Any info would be very much appreciated.

Probably not, no. Basically body heat comes from breaking up food, which stored solar energy for a while. If there weren’t animals there, the plants would die and release the same heat by being decomposed by bacteria.

I’m not doing the math, but I think you’d need a huge amount of animals in one place to make an appreciable difference on climate, even locally. As viking points out, you’d have the same effect by heaping up and burning the animal’s food each day. Think how much you’d need to burn to make an effect.
Urban heat islands are all about removing vegetation (which CAN have an effect), adding very solar-absorbent surfaces like black roofs and roads, and heating buildings using fossil fuels; they have nothing to do with the body heat of the residents: each person only puts out about as much heat as a single incandescent light bulb.

A human puts out ~415 Btu/hour, or ~125 watts worth of of heat. That’s good enough for warming rooms, but you’d have to pack them pretty close to affect the climate.
Look at the thread Heat from candles for more calculations.