Being incredibly mobile ocean predators, it is tricky to get tissue samples from wild orcas. To get a high-quality genome assembly requires a living specimen - so dead animals that wash up won’t do either.
Morgan’s tragic case in 2010 provided a rare opportunity. She was rescued after becoming stranded on a beach in the Netherlands, and taken to the Dolphinarium in Harderwijk. Judging by her size, Morgan was still very young.
Andy Foote was initially brought in to identify the killer whale population to which Morgan belonged. Using genetics, and the expertise of a colleague, Dr Filipa Samarra, who managed to identify the ‘family dialect’ of Morgan’s calls, they discovered that Morgan belonged to a Norwegian group of herring-eating orcas.
The team at Harderwijk has a history of rehabilitating porpoises into the wild. But this was a more difficult proposition for Morgan. “Killer whales are very group based, they tend to stay with their mother for life. And the stability of that family group is essential to the survival of the individuals within it,” explains Andy.
Then, a heart-sinking realisation. Morgan’s calls were becoming more variable over time, a sign of acute hearing loss. For an animal reliant on acoustics to hunt and stay with the group, this was a death sentence in the wild.
While there are cases of orcas being successfully released into the wild, this would not be the fate of Morgan. She is living out the rest of her days in the Loro Parque zoo in Tenerife.
But Morgan’s stranding still offered an opportunity to better understand, and ultimately protect, her species. “We could get blood samples with really good DNA that wasn’t broken up or fragmented, the kind that would be needed for these long-read genome sequencing techniques,” says Andy.
Even that wasn’t easy! Geneticists only need a small sample to sequence a genome, but extracting the DNA from Morgan’s blood proved tricky. Killer whale blood has very high levels of haemoglobin, which makes it very viscous. A standard silicon-filter approach didn’t work: “The blood simply wouldn’t go through the filter.” Andy’s team had to switch to a different PAXgene technique.