An empirical estimate of the generation time of mouse lemurs
The generation time of organisms drives the rate of change in populations and across evolutionary times. In long-lived species, generation time should also account for overlapping generations, and the average age of parents has been proposed as a best approximation under these conditions. This study uses this definition to estimate the generation time of a widely studied small primate, Microcebus murinus, based on parentage data generated for a free-living population over a 6-year period in northwestern Madagascar. The average age of parents was calculated separately for mothers and fathers of three different offspring cohorts that differed in the degree of demographic uncertainty. In addition, adult survival rates were calculated for males and females based on long-term capture data from the same population to estimate the possible upper limits of generation time. Adult survival was low with only 44% of adult females and 38% of adult males being recaptured at the beginning of their second breeding season. The average age of mothers was 1.56-1.91 years, pointing toward a 2-year female generation time due to the high proportion of 1-year old mothers in all three cohorts. Female generation time estimates were fairly stable across the three offspring cohorts. In contrast, the average age of fathers differed by more than 1 year from the first to the third offspring cohort (1.71-2.83 years) pointing toward a 3-year generation time, but also suggesting a higher degree of demographic uncertainty in the early years of the study. For future modeling purposes, we, therefore, propose to use the average, 2.5 years, of male and female values as new estimate for the generation time of mouse lemurs.