What we don't know about walruses

Last week, Netflix's Our Planet series featured a segment in which walruses plunged to their deaths over cliffs. This was said to be as a result of global warming. Many media outlets subsequently reported Susan Crockford's comments that the claims were 'tragedy porn' and highly contrived, and that it was probably actually a documented occasion when polar bears drove walruses over cliffs near the village of Ryrkaypiy in eastern Siberia.

Subsequently, by matching rock shapes in the footage to archive images of Ryrkaypiy, I was able to show that this obscure corner of Russia was indeed the source (see my article here).

The producers are now tacitly admitting - they could hardly deny it - that although they were in Ryrkaypiy, and polar bears had indeed been driving walruses over the cliffs there, on the particular occasion captured by their cameras, bears were at a safe distance. This is remarkable, because at no point in the footage is the presence of polar bears mentioned.

However, their story is not impossible. As I documented in the article linked above, walruses have a tendency to fall from cliffs, even without the attentions of polar bears. There is video footage from the 1980s. I came across someone who said she had spent several months working at the Round Island walrus sanctuary in Alaska, where her only job had been to keep her charges away from the cliffs. Another sanctuary had tried to build a fence. A record of a trip to Ryrkaypiy in 2007 reports that there were hundreds of walrus deaths from natural causes. I've also found photos of what appear to be dead walrus at Ryrkaypiy from 2016. Walrus brains, it seems, are not in proportion to their brawn.

But what of the chain of logic that is being used to claim that these deaths are being caused by global warming? We know that walrus hauled out on land long before global warming was thought of, so global warming can at worst be only an exacerbating factor: "cause" is not a word that should be used therefore.

And it turns out that even the idea that global warming is increasing the number of fatal falls rests on shaky ground. While walruses undoubtedly prefer hauling out on ice, they want broken ice, both because it allows them to feed and because it protects them from predators. In years when ice is thick in the western Chukchi Sea, walrus apparently tend to move to clearer waters around Alaska. In other words, the feeding grounds on the Russian side are lost.

So global warming and the concurrent loss of sea ice is a cloud with a considerable silver lining. Walrus may need to haul out on land, with the concurrent problems of predation and cliff-diving, but the feeding grounds of the western Chukchi remain open, and for longer.

And if you are trying to demonstrate a correlation between land haulouts and sea ice, you have a problem. The records of haulouts are very thin: the recently published Pacific Walrus Haulout Database project has got as far as documenting places where walruses are known to haul out from time to time, but there is little detail of how many walruses hauled out at which locations and when. (Interestingly, however, there is a record of a haulout at Ryrkaypiy in the 1930s.)

And even then, as Susan Crockford has pointed out, there is no obvious correlation between land haulouts and sea ice levels. There are years with very low ice in which no haulouts are observed and years with lots of ice when walrus choose to haul out on land anyway. Beach haulouts seem to have more to do with population explosions than sea ice. As Crockford puts it:

The notion that females and calves are never found hauled out anywhere except the sea ice in late summer and autumn and never use beaches as foraging platforms in late summer/autumn – except when sea ice is low – is simply not true.

So what you are left with is supposition and anecdote. Scientists imagine that the lack of sea ice is having an adverse effect, and call for further monitoring. But they are not able to demonstrate these problems through data.

The reality may well be very different. But with 100,000 walrus hauling out at Cape Serdtse-Kamen alone in recent years, previous estimates of walrus numbers are starting to look rather low. Reasonable people will conclude that the Pacific walrus is doing very well.

Despite global warming.