For the first time, we know more than we ever expected to know about the sex lives of the majestic beluga whale. It's complicated, to say the least, but it also shows just how strategic nature is at keeping an isolated group of animals alive.
Research led by the Florida Atlantic University’s (FAU) Harbor Branch Oceanographic Institute have, for the first time, discovered how wild beluga whales mate – and it's a picture of evolutionary survival.
The beluga whale (Delphinapterus leucas) has been an infamously challenging species to study, even in terms of the normal difficulties in researching marine mammals. Over a massive 13 years, the scientists focused on a small whale population in Alaska’s Bristol Bay, connecting genetic information on 623 individuals as well as observing their social groups and ages. Overall, this population is made up of around 2,000 whales that are essentially isolated from any other belugas.
What they found was that their mating habits are impressively strategic. Each mature individual – male and female – will mate with multiple partners over several years, meaning they're polygynandrous. The result is that many calves are half-siblings, ensuring genetic diversity – which is critically important in an isolated population.
“What makes this study so thrilling is that it upends our long-standing assumptions about this Arctic species," said senior author Greg O’Corry-Crowe, a research professor at FAU. "Because males are much larger than females and appear to spend little time associating with mothers and calves, scientists believed belugas were likely to be highly polygynous, where males spend a lot of time competing for mates and only a few dominant males fathering most of the calves.
"Our findings tell a very different story. In the short term, males are only moderately polygynous. One explanation we think lies in their incredible longevity – belugas can live perhaps 100 years or more. Rather than competing intensely in a single season, males appear to play the long game, spreading their reproductive efforts over many years. It appears to be a ‘take your time, there’s plenty of fish in the sea’ strategy."
While the boys play "the long game," the females frequently swap mates from one breeding season to the next. The scientists believe this helps them avoid being stuck with "low quality males" and again protects genetic diversity.
"It’s a striking reminder that female choice can be just as influential in shaping reproductive success as the often-highlighted battles of male-male competition," said O’Corry-Crowe. "Such strategies highlight the subtle, yet powerful ways in which females exert control over the next generation, shaping the evolutionary trajectory of the species."
The researchers also found that while older females had more surviving calves than younger ones – possibly due to experience and mate choice – most adults had only a few offspring at a time. This appeared to be guided by the female's slow reproduction.
If you're wondering why scientists would devote more than a decade to watching whales get it on, understanding the reproductive strategies and success or failures of such an elusive, isolated group of animals is critical for protecting their numbers.
"Understanding these dynamics matters for conservation," said O’Corry-Crowe. "If only a few males father most calves, the effective population size becomes much smaller than the number of whales actually present. This loss of genetic diversity increases the risk of inbreeding and reduces the population’s ability to adapt to environmental change. Frequent mate switching combined with low reproductive ‘skew’ and possibly the active avoidance of mating with close relatives, may be effective strategies to maintaining the genetic health of relatively small populations."
The scientists also worked closely with the Bristol Bay indigenous communities in an effort to better protect the whales as they face a rapidly changing Arctic and sub-arctic environment.
"We cannot afford to be complacent," said O’Corry-Crowe. "Small populations still face the dangers of genetic erosion. But we can be optimistic that beluga whale mating strategies provide evidence of nature’s resilience and offers hope for those working to save and recover small populations of any species."
The study was published in the journal Frontiers in Marine Science.
Source: Florida Atlantic University
