Why do mice need to have a high metabolism?

Question

Why do mice need to have the highest metabolism if it has the least amount of weight?

Is it something to do with not having much surface area for exchange of materials so they have to be efficient?

Thanks =)

Answer 1

You're correct about the surface area part, but it's not a matter of material exchange; it's a matter of heat exchange.

Because mice are mammals, and mammals are endothermic, they rely on their metabolism to produce body heat.  However, they have a rather large surface area for their small volume, which allows a lot of this heat to escape.  They must constantly replace this heat, and they require a high metabolism to do that.  An elephant, by contrast, doesn't have very much surface area for its heat to escape, so it doesn't need a high metabolism to replenish heat rapidly.