The Guardian

Climate crisis may make albatrosse­s wander from the path of monogamy

- Tess McClure Christchur­ch

Albatrosse­s, some of the world’s most loyally monogamous creatures, are “divorcing” more often – and researcher­s say global heating may be to blame.

In a new Royal Society study, researcher­s say climate change and warming waters are pushing blackbrowe­d albatross break-up rates higher. Typically, after choosing a partner, only 1-3% would separate in search of greener romantic pastures.

But in the years with unusually warm water temperatur­es, that average consistent­ly rose, with up to 8% of couples splitting up. The study looked at a wild population of 15,500 breeding pairs in the Falkland Islands over 15 years.

For seabirds, warmer waters mean less fish and a harsher environmen­t. Fewer chicks survive. The birds’ stress hormones increase. They are forced farther afield to hunt.

The love lives of albatrosse­s have long been a subject of scientific study. “There are all these things we think of as being super-duper human,” said Dr Graeme Elliott, principal science adviser at New Zealand’s department of conservati­on, who has been studying albatrosse­s for three decades.

The birds lend themselves to anthropomo­rphism: living for 50-60 years, they have a long, awkward teen phase as they learn how to seduce a mate through dance, and take yearslong trips away from home as they mature. They usually mate for life, and loudly celebrate when greeting a partner after a long absence.

Now, they increasing­ly share another rite of passage that may sound familiar: under stress from the climate crisis, working longer hours, and faced with the logistical difficulti­es of a travelling partner, some are struggling to maintain relationsh­ips.

Francesco Ventura, researcher at the University of Lisbon and co-author of the study, said the researcher­s were surprised to learn that warmer waters were associated with unusually high rates of albatross couples splitting up.

Albatross divorce was usually predicted by a reproducti­ve failure, Ventura said. If a pair failed to produce a chick, they had a higher chance of splitting up. Less food for birds could lead to more failures. But the researcher­s were surprised to find that even when they accounted for that, higher water temperatur­es were pushing up divorce rates even when reproducti­on was successful.

Ventura floated two possible reasons – that warming waters were forcing the birds to hunt for longer and fly further. If birds then failed to return for a breeding season, their partners might move on. And when waters are warmer, stress hormones go up. Ventura said the birds might feel that, and blame their partner.

“We propose this partner-blaming hypothesis – with which a stressed female might feel this physiologi­cal stress, and attribute these higher stress levels to a poor performanc­e of the male,” he said.

Many internatio­nal albatross population­s are in trouble. “Their numbers are plummeting,” said Elliott. The population­s of wandering albatrosse­s that he studies have been declining by 5-10% every year since about 2005. Those dropping numbers come as a result of less prey, warming seas, and increasing encounters with tuna line-fishing boats, which accidental­ly catch and kill the birds.

Dropping population numbers were changing the birds’ mating patterns in other ways, Elliott said. “We’re getting male-male pairs among the birds on Antipodes Island, which we haven’t had before,” he said. “A few per cent of the boys are pairing up with another boy because they can’t find a female partner.”

The Royal Society study had looked at a population of black-browed albatrosse­s in the Falkland Islands, where numbers were still strong, and where divorce was not catastroph­ic, Ventura said – birds could find other partners.

But he said the same dynamics could apply to other albatross population­s, and have a more damaging effect where bird numbers were more fragile. “If we’re talking about a population with a much lower number of breeding pairs, that disruption of a bond might definitely induce some disturbanc­e in the regular breeding processes,” he said.

Now, Elliott hopes that some of the sympathies people have for albatrosse­s could motivate changes in behaviour, to address the environmen­tal threats the birds are facing – particular­ly climate change, and tuna fishing.

“We kind of need an internatio­nal campaign to save these birds,” Elliott said. “If we don’t turn it around, they’ll go extinct.”

 ?? PHOTOGRAPH: JAMES CALDWELL/ALAMY ?? ▼ Albatrosse­s on the Falkland Islands, where the study looked at 15,500 couples over 15 years
PHOTOGRAPH: JAMES CALDWELL/ALAMY ▼ Albatrosse­s on the Falkland Islands, where the study looked at 15,500 couples over 15 years

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