Captive Dwarf and Mouse Lemurs Have Variable Fur Growth

SIMPLE SUMMARY: Next to nothing is known about fur or hair growth for any primate species aside from humans. Researchers have typically assumed that fur and hair growth is constant, but the available data suggest this is not the case. I investigated how quickly fur grows for two closely related species of small-bodied lemur, dwarf lemurs, and mouse lemurs at the Duke Lemur Center. I found that fur growth varied considerably both within and among individuals. Additionally, growth was overall slower and quite seasonally variable for dwarf lemurs. Seasonal fluctuations in fur regrowth likely reflect changes in metabolism related to photoperiod, a phenomenon that is widespread among vertebrates. Variable fur growth is problematic for any study that uses keratin to investigate seasonal changes in diet or health. Further research examining how variable fur and hair growth is across a larger array of species, between sexes, and across seasons is needed. ABSTRACT: Researchers typically assume constant fur and hair growth for primates, but the few studies that have investigated growth explicitly suggest this may not be the case. Instead, growth may vary considerably among individuals and across seasons. One might expect this variability to be most pronounced for species that have seasonally variable activity patterns (e.g., Madagascar’s Cheiorogaleidae). In particular, dwarf lemurs (Cheirogaleus spp.) undergo considerable changes in their daily activity levels (torpor) in the austral fall, when nights get shorter. I monitored regrowth of shaved fur patches for eight adult captive fat-tailed dwarf lemurs (Cheirogaleus medius) and gray mouse lemurs (Microcebus murinus) on a bi-weekly basis for 21 months in total. Regrowth varied considerably both within and among individuals. Overall, fur regrew in spurts and was faster for mouse lemurs (0–14 to 215–229 days) than dwarf lemurs (27–40 to 313–327 days). There were significant differences between species and an obvious influence of season for dwarf lemurs, but no clear influence of shave location, age, or sex. Similar trends have been previously reported for captive lemurids, suggesting that seasonal fur growth may be widespread across Lemuroidea. Researchers are cautioned against using primate fur or hair to investigate variables confounded by seasonality (such as diet and body condition) until patterns of growth are better understood.