Bergmann 's rule is most often applied to mammals and birds which are endotherms , but some researchers have also found evidence for the rule in studies of ectothermic species such as the ant `` Leptothorax acervorum '' .
Bergmann 's rule is most often applied to mammals and birds which are endotherms , but some researchers have also found evidence for the rule in studies of ectothermic species .