Date of Award
Doctor of Philosophy (PhD)
Dr. Bradley N. White
Nineteen years of monitoring the highly endangered North Atlantic right whale (Eubalaena glacialis ) has led to the photo-identification of 388 individuals of which 283 were alive in 1997. To assess the status of the population, microsatellite markers were developed and used to establish individual-specific genetic profiles for 209 whales. Genetic profiles based on nine microsatellite loci and mitochondrial control region haplotypes were used to examine the population for evidence of inbreeding and to assess the current levels of genetic variability. At the population level, genetic variability was found to be lower than that reported for other large-bodied cetaceans, including the closely-related South Atlantic right whale. No evidence was found to indicate that the low genetic variability is the result of the most recent population bottleneck (19th century). Rather, the loss of genetic variability appears to have occurred over several hundred years, starting as far back as the 16th century. To examine the current population for evidence of inbreeding, the nature of the mating system was identified and used to estimate the effective number of breeders in the population. Based on a promiscuous mating system, the effective population size is estimated at between 103 and 154, which places the ratio of the census population size to the effective population size within those reported for other large-bodied mammals. Despite the random nature of the mating system, population structuring was identified between calves born to two groups of females that differ in their use of nursery habitat. The identification of two reproductively discrete populations suggests the existence of two mating areas for the North Atlantic right whale population. Although mating is not entirely random within the population, no evidence of inbreeding was detected in the population. Mating pairs were no more related than unrelated whales (Rxy = 0.0007 ± 0.24 versus -0.035 ± 0.28). While 74% of females produced at least one calf during a period of 17 years, only 55% had multiple birthing events. The failure of the population to increase in size during the past few hundred years may reflect an overall reduction in the reproductive fitness of females that may be associated with the historic loss of genetic variability. The ability of the population to remain at a stable size (∼300) throughout the past 400 years suggests that the current decline in the size of this population is the result of more contemporary influences. The combination of contemporary influences, such as resource shortages and accidental mortality, with the low intrinsic calving rate, appear to be compromising the long-term persistence of this species. (Abstract shortened by UMI.)
Waldick, Ruth Carolin, "Assessing the status of the endangered North Atlantic right whale using genetic and demographic data" (1999). Open Access Dissertations and Theses. Paper 1797.