(Halifax) The small, critically endangered population of North Atlantic right whales has long struggled with inbreeding. But a new scientific study by researchers at Saint Mary’s University in Halifax has made an encouraging finding.
Although inbreeding appears to limit the number of calves born each year, it does not impact genetic diversity, a trait essential to the survival of any species.
“The fact that they’re retaining this genetic diversity is a very good sign for their future,” said Carla Crossman, a doctoral student in the university’s biology department. “We’re not losing genetic diversity as fast as we would otherwise. (But) we don’t know why.”
As of October, the North Atlantic Right Whale Consortium estimated that there were 356 North Atlantic right whales remaining on the planet.
The new peer-reviewed study, published Wednesday in the journal Royal Society Open Science, says researchers initially found that most female North Atlantic right whales were not giving birth every three years, as females in the much larger southern population typically do.
“The interval is much higher in the (northern) population,” Mr.me Crossman, adding that some mature females in the North Atlantic never gave birth.
The research team, which included scientists from other parts of Canada and the United States, determined through genome sequencing that the level of inbreeding of each female had nothing to do with her ability to give birth.
“There was no clear relationship between the degree of inbreeding of a female and her reproductive success,” Crossman said. “But what we found was that all individuals in the population had greater genetic diversity than would be expected, given the size of the population.”
Great genetic diversity despite everything
The team reported another key finding based on previous research on known mother-calf pairs and known mother-father-calf triads: Highly inbred calves did not appear in the population. The researchers believe that inbred fetuses die in the womb.
“We believe there is an increased rate of fetal loss due to inbreeding,” Mr.me Crossman.
“This partly explains the low reproductive success we observe. […] Whatever the mechanism, it maintains genetic diversity in the population, because all calves are more genetically diverse than expected.”
This “mechanism” likely allowed the whales to avoid harmful mutations caused by inbreeding, she said.
“That means they can persist a little better with a small population size.”
Number of injuries on the rise
The team’s results could be used to “recalibrate” the expectations of those responsible for managing the North Atlantic right whale population, she said.
Despite the good news about genetics, Mme Crossman said none of these findings make much sense unless there is a substantial decrease in the number of whales killed by ship strikes and entanglements in fishing gear, which are the leading causes of mortality for the species.
Last fall, the North Atlantic Right Whale Consortium — a group of scientists, industry members and government officials who study the whales — said the latest data showed the number of human-caused injuries was increasing.
In 2022, deaths did not exceed births – a good sign – but environmental activists remain concerned that the species is still on the verge of extinction, as many of these injuries will result in death, while other injured whales may not be able to reproduce.
So far this season, five entangled North Atlantic right whales have been spotted in Canadian waters, including an adult male known as Dropcloth, spotted Saturday off the northeast coast of New Brunswick near Miscou Island.