[flyyyguy]

sound slike a prime circumstance for a 8 hour heat pack. It will burn out by the time you dont want/need it anymore. be careful though as those short time ones burn hot. make sure it is well insulated from the clam by either wrapping/inuslating it well and keeping it at least a few inches from the bag with the animal in it, or simply tape it to the outside top of the box if using a quailty thick walled cooler sealed well.

still insulate it from the styrofoam with a thin piece of cardborad or soemthing. If you dont they can sometimes burn right through the styro