Figure 7.11

Allen’s rule. Allen’s rule states that appendage length in mammals decreases as latitude increases. This anatomical variation helps animals to maintain suitable body temperatures in these different climates. Among hares and rabbits in North America, the southernmost species have long appendages as a means to radiate body heat for cooling. Appendage length decreases to the north as a means of conserving heat. Fur length and thickness in these animals also increases northward.