April Flowers for redOrbit.com – Your Universe Online
Using six years of data collected during regular aerial surveys, combined with genetics data obtained by a consortium of research teams, a new study adds evidence that points to a central Gulf of Maine mating ground for North Atlantic right whales.
One of the most endangered marine mammal species, the North Atlantic right whale (Eubalaena glacialis) has been intensively studied for decades. Scientists have discovered much about the species habitat, behavior and population demographics, but until now, had little evidence to indicate where the whales mated. This left a large hole in the life history of the whales.
“A high proportion of potential mates aggregated in the central Gulf of Maine between November and January, and these same individuals produced a calf a year later. We concluded that this is a pretty strong indication of a mating ground if the gestation period is 12 months,” said Tim Cole, biologist at the Woods Hole Laboratory of NOAA’s Northeast Fisheries Science Center (NEFSC).
The research team used aerial surveys to document not only how many, but also which right whales were present in the study area between 2002 and 2008. A photo identification catalog maintained at the New England Aquarium that includes most of the adults in the population was used to identify individual whales. The team used genetic data collected in other field work to identify known fathers. Known mothers were identified by association with a calf.
The study findings, published online in the journal Endangered Species Research, revealed a higher proportion of reproductively successful animals in the study area than were present in other areas these whales used seasonally. The research team extrapolated a 12-month gestational period for the North Atlantic right whale, similar to that estimated for the closely-related southern right whale (Eubalaena australis) by Dr. Peter Best, South African whale biologist.
Cole says while this study is a strong indicator of a mating ground, there could be other mating areas not identified. It is also not entirely clear how fixed the mating grounds might be. Since the study ended, fewer right whales have been seen in the study area during what should be mating season. The researchers found less dramatic evidence that Roseway Basin, south of Nova Scotia, may also be a mating ground for the whales.
“We are still seeing right whales in the central Gulf of Maine, just not in the same numbers. They are still out there, but where they all are is the big question. The decline is significant, so something appears to have changed,” Cole said. “The good news is that calf production has been fairly good, with 22 calves born in 2011, 7 in 2012, and 20 this past winter. It will be interesting to see how many calves are born next year.”
During spring and summer, most of the North Atlantic right whale population can be found on feeding grounds off the northeastern US and Canadian Maritimes. The pregnant females migrate to waters off the southeastern US to give birth in the fall and early winter. Intense aerial surveys conducted from December through March off the coasts of Florida, Georgia, South Carolina and North Carolina detect the mothers and calves that return to the northeast feeding ground in early spring. The calves stay with their mothers for the first year following their births.
Successful reproduction is the key to recovery of this endangered animal, but the current reproduction rates are much lower for the North Atlantic right whale than for the recovering populations of southern right whales. Scientists do not yet understand the reasons for this disparity, but think the answers may include a low level of genetic variability and /or inbreeding, disease, biotoxins, pollutants, food supply limitations and habitat loss. Behavioral changes might also be triggered by increased ocean noise cause by coastal development. These changes could negatively impact reproduction as well. These factors all make finding the right whale’s conception period and mating grounds important steps in learning about the factors that may be impairing reproduction.