Harpooning genetic diversity
Harpooning genetic diversity
The intergenerational impact of whaling for centuries
The devastating impact of whaling is immediately obvious. Great whales were hunted so incessantly that the humpback has only recently reached healthy numbers again and mostly thanks to the 1986 IWC moratorium putting a ban on commercial whaling. The Right whale has never quite recovered and remains one of the most endangered whales in the world with a population of just 350, facing ongoing threats of entanglement and vessel collisions. And even modern whaling persists, as Iceland resumes their yearly quota with approval from the Icelandic government following a temporary ban. After great whales declined to such an extent that demand for their commercial hunting dwindled, smaller whales such as minke and pilot have been targeted. Though their current populations are at healthy levels around the world, they are in immediate danger.
If things didn’t seem bad enough, a new study suggests the repercussions of whaling on great whale species like the humpback and blue whale1 run even deeper than we first thought. Given that they were once hunted to near extinction, it isn’t shocking to hear that there are more lasting consequences to killing over two million whales in the southern hemisphere alone. New research conducted by Oregon State University has uncovered a notable loss of genetic diversity specifically linked to whaling in the 20th century.
Using bones found scattered across the island of South Georgia, where commercial whaling was once rife and cold temperatures have perfectly preserved the samples, scientists have been able to compare the bones to those of modern-day whales. Including humpback, blue and fin whales in their analysis, the study found that although there is still high genetic diversity among the species, there is also a clear loss of maternal DNA lineages among blue and humpback whales.2
Maternal lineage is linked to an animal’s cultural memories like feeding and breeding locations. So for example, whales who journey to South Georgia to feed during the summer months know where to go, and when, because of the DNA passed down to them through their maternal lineage. But as hundreds of thousands of them were killed3 this information is lost to the whales forever and they will no longer return to these areas. This might sound like it’s for the best if they’re being hunted there anyway but it also makes it more difficult for the remaining population to find new locations with a healthy abundance of food and/or safe areas to breed.
The knowledge which should have been passed down from one generation to the next was lost, and whale populations disappeared from South Georgia. Though there is hope that more whales will return to the region, things are likely to get worse before they get better. As these whales can live up to 100 years, some may have been alive during the rampant whaling years, and so when they die it could result in a further reduction of the maternal lineage DNA.
Navigating the unforgiving ocean is difficult enough for our whale friends without the human-inflicted loss of the memories they need to survive out there in the harsh and unforgiving big blue.
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Amie 🐋
Only 0.15% of the Antarctic blue whale population survived their incessant hunting.
The same data for fin whales wasn’t as easily comparable due to a scarcity of post-whaling samples. It’s worth noting that fin whales aren’t afforded the same protection as other great whales today, and so they’re hunted just as they were throughout the 20th century.
Specifically 345,755 Antarctic blue whales, 215,848 humpback whales and 726,461 fin whales, in the southern hemisphere.