One of the northern hemisphere’s most famous extinct birds could have disappeared at the hands of humans and humans alone.
A nearly three-foot-tall flightless bird called the great auk was once abundant in the north Atlantic Ocean, from the US Atlantic Coast, north to Greenland and Iceland, and throughout European waters. It looked like a penguin – in fact, penguins take their name from an older term for the great auk. The bird went extinct in 1844 after hunters killed the last one. But there’s still question as to whether the cause of decline is due to human behaviour alone, or whether other factors like changing climate helped. According to new evidence published in eLife on Tuesday, it was mostly the former.
“It was shocking that they were hunted so intensely, that humans could cause their extinction in just a short period of time,” the study’s first author Jessica Thomas, now a scientific officer based at Swansea University, told Gizmodo. “That’s why we were looking to see whether they were already in decline or at risk of extinction.”
The researchers gathered and sequenced ancient mitochondrial DNA samples from 41 of 66 great auk bones they found in museums in Europe and North America, representing individuals that lived anywhere from 15,000 to 170 years ago. They also evaluated ocean current data and made models of how extinction could have played out for various initial populations of the bird, including how many individuals would need to have been killed annually to extinction to occur.
Had some other forces been partially responsible for the great auk’s overall decline, genetic evidence should reveal either loss of genetic diversity or the species fragmenting into smaller populations. But the researchers observed no evidence of either prior to the start of intensive hunting in the 16th century, according to the new paper.
Mathematical modelling seems to show humans alone had a strong enough effect to kill the bird off. Had the population started with two million birds followed by humans beginning to take 210,000 birds annually, the bird would have gone extinct in 350 years. The researchers report that actual hunting pressure on the bird was likely much higher. One of the sources the paper cites notes that two ships took 1,000 birds in a half hour in Newfoundland.
“If each of the 400 vessels in the region spent only half an hour a year harvesting great auks at this rate, that would already correspond to 200,000 birds a year,” the researchers wrote in the paper.
All model-based studies have their drawbacks, and work like this inevitably requires speculation. Plus, the researchers point out that their data sample is relatively small for population analysis, and that some smaller-scale declines might not be reflected in the genetic data. The study relies on bones, which had reliable date and sample information. The paper’s reviewers pointed out that there are better DNA sources than bones, though.
Still, the study provides even more evidence that unchecked industrial hunting was the primary, if not the only, reason for the great auk’s extinction. More importantly, it shows that even species that don’t show evidence of a declining population could go extinct at the hands of humans. The authors write: “Our findings emphasise the need for thorough monitoring of commercially harvested species, particularly in poorly researched environments such as our oceans.”
Featured image: Illustration: John James Audubon