Fact 1: Mammals can also generate little bursts of heat by shivering.

Fact 2: Heat production is increased by shivering and non-shivering thermogenesis .

Given the two facts above, answer the question "what do mammals use for heat?" with the following options: 
- thermogenesis
 - Animal fur
 - feet
 - Chemical energy
 - fur and fat
 - layers of fat
 - convection
 - ice


 

 thermogenesis        