Striking longevity in a hibernating lemur

Body mass correlates with life span across mammals; larger species tend to live longer than small ones. There are, however, exceptions to this pattern. One metabolic strategy that has been linked to increased longevity is hibernation; that is, small-bodied hibernating mammals live longer than expected based on their size alone. Hibernation may be beneficial in seasonal and unpredictable habitats because individuals can reduce metabolic rates to conserve energy in times of resource scarcity. On the downside, the extended periods of dormancy hibernating mammals undergo afford them fewer reproductive opportunities per year compared with their similarly sized non-hibernating relatives. One strategy to compensate for a reduced reproductive rate is to extend reproductive life span. Increased longevity may also be expected if hibernators possess cellular machinery resilient to metabolic stress, which is generally associated with aging. Here we present data on life span and other life-history variables for four small-bodied strepsirrhine primates: (1) the fat-tailed dwarf lemur Cheirogaleus medius, a hibernator; (2) the gray mouse lemur Microcebus murinus, a closely related species, which opportunistically expresses torpor and/or hibernation; (3) the Northern giant mouse lemur Mirza zaza another closely related species, which does not hibernate, but may employ daily torpor; (4) the bushbaby Galago moholi, a non-lemur, non-hibernating strepsirrhine that employs torpor only as an emergency response to harsh conditions. We analyzed newly compiled captive data from the developing Duke Lemur Center Database, and report that dwarf lemurs live significantly longer, reproduce longer and show later incidences of both morphologic and reproductive senescence than the other species analyzed. That these correlations hold in captive populations with no predation indicates that intrinsic biologic effects must play some role.