Why These Three Specific Killer Whales Are Important

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Two researchers who have been monitoring a group of killer whales off the US Pacific coast are pretty sure that three of them might be pregnant.

The researchers compared drone photos that they took earlier this month with photos of the same whales from last year, and noticed that they looked a little bigger.

Southern resident killer whales are a particular group of orcas that live in the Northern Pacific Ocean and since 2005 they’ve been listed as endangered.

And the chance that these whales might be pregnant is a really positive step towards the conservation of their population.

Why Are These Killer Whales Endangered?

Population numbers of southern resident killer whales have been decreasing.

Today there are only 74 of them left in the world, and researchers think that’s mainly down to pollution and a general lack of food.

Chemical pollutants in the ocean – like PCBs – can concentrate in the whales’ blubber and reach dangerous levels that have been known to cause cancer and impair reproduction.

Noise pollution from ocean vessels can also prevent the whales’ echolocation, which they use to communicate with each other and to find food.

Chinook salmon makes up over 80% of a southern resident killer whale’s diet.

But various dams in Chinook salmon’s key habitats have disrupted their migration patterns, and led to a significant decline in their population.

How Rare Is Pregnancy In The Killer Whales?

Successful pregnancies in southern resident killer whales are few and far between.

They only give birth to one calf at a time, around every three to ten years, and have a 17-month gestation period.

Researchers think that a population of this size should be having six to eight calves be born every year.

But in the last 20 or so years, only 44 have been born, and another 81 have either died or disappeared.

Last year, there were several failed pregnancies in the killer whales, and over the past decade there’s been a generally high reproductive failure rate, with a 40 percent mortality rate for young calves.

Two years ago, one orca – known as J35 – made headlines after she carried her dead calf thousands of kilometres over 17 days, in what scientists at the time called a “tour of grief”.

So What Do Scientists Think About These Pregnancies?

Researchers remain hopeful that at least some of the three new pregnancies could contribute to this endangered population.

But they are cautious that the chance of mortality of the calves is quite high.

The Washington Department of Fish and Wildlife has said that it has lots of people looking at the science to understand how we can improve the odds for the population of the killer whales.

And it’s called for recreational boaters to follow regulations to give the whales extra space.

John Durban and Holly Fearnbach are the marine biologists who’ve been monitoring this group of southern residents, and they’re cautiously optimistic about the pregnancies.

Fearnbach said that she was reminded of J35 who – after her 2018 tour of grief – now has a healthy one-year-old calf, and she’s hoping that these three pregnancies could have a similarly happy ending.