Which type of animal shows highest body heat retention?
A large bear retains body heat more effectively than a small bird, lizard, or amphibian because body size lowers the surface-area-to-volume ratio. Heat is produced throughout metabolically active tissue, which scales broadly with mass, but exchanged with the environment across body surface. As size increases, surface area grows more slowly than volume, so less heat is lost per unit mass. Bears also possess fur and subcutaneous fat that reduce conduction and convection. Birds are endothermic and insulated by feathers, but a small bird has high relative surface area and must sustain a very high
Ref: Evolutionary Analysis, Herron & Freeman, 5th Ed., Ch. 10