Abstract:
Historical exploitation, and a combination of current anthropogenic impacts, such as climate
change and habitat degradation, impact the population dynamics of marine mammalian
megafauna. Right whales (Eubalaena spp.) are large cetaceans recovering from hunting, whose
reproductive and population growth rate appear to be impacted by climate change. We apply
noninvasive genetic methods to monitor southern right whale (E. australis, SRW) and test the
application of noninvasive genetics to minimise the observer effects on the population. Our
aim is to describe population structure, and interdecadal and interannual changes to assess
species status in the Great Acceleration period of Anthropocene. As a basis for population
genetic analyses, we collected samples from sloughed skin during post-migration epidermal
moult. Considering the exploration-exploitation dilemma, we collaborated with whale
watching companies, as part of a citizen science approach and to reduce ad hoc logistic operations
and biopsy equipment. We used mitochondrial and microsatellite data and population
genetic tools. We report for the first time the genetic composition and differentiation of the
Namibian portion of the range. Population genetic parameters suggest that South Africa hosts
the largest population. This corresponds with higher estimates of current gene flow from Africa
compared to older samples. We have observed considerable interannual variation in population
density at the breeding ground and an interdecadal shift in genetic variability, evidenced
by an increase in the point estimate inbreeding. Clustering analyses confirmed differentiation
between the Atlantic and Indo-Pacific, presumably originating during the ice ages. We show
that population monitoring of large whales, essential for their conservation management, is
feasible using noninvasive sampling within non-scientific platforms. Observed patterns are concurrent to changes of movement ecology and decline in reproductive success of the South
African population, probably reflecting a large-scale restructuring of pelagic marine food
webs.
