February 2022, ScientificAmerican.com 17CLIMATEBreaking Up
Albatross “marriages” cool
as the climate warmsFew animals appear more affectionate
than the black-browed albatross. These
large seabirds, whose dark eyebrows
shadow their eyes like mascara, are
socially monogamous and often mate for
life. Their romantic-seeming “marriages”
have a practical purpose: staying with the
same partner builds trust, which is essen-
tial as the pair alternates between lengthy
foraging trips and egg-incubation duties.
But “divorce” is not unheard of. As is
the case with other monogamous animals,
a female albatross will leave a partnership
that lacks breeding success. The process is
relatively understated and free from noisy
squabbles, says University of Lisbon biolo-
gist Francesco Ventura. Often when a
female deems the partnership unsuccess-
ful over the course of a year, she will simply
appear with a different male in the follow-
ing breeding season.
Although divorce is natural among
these birds, Ventura recently began notic-
ing that its rates seemed to vary from year
to year for the roughly 15,500 pairs of black-
browed albatross breeding on New Island,
a rocky outcrop in the Falkland Islands.“There were clearly years in which more
pairs split up, compared with the previous
years,” says Ventura, whose team combed
through about 15 years of breeding data.
To investigate, the group focused on
two environmental variables vital to alba-
tross: wind speed and sea-surface temper-
ature. Each affects the birds in different
ways. Higher winds make it easier for them
to soar for greater distances to gather food.
Increasing sea-surface temperatures, on
the other hand, limit the nutrients available
to foraging albatross by curbing the pro-
duction of phytoplankton, which has cas-
cading effects on the rest of the marine
food web. As a result, albatross must travel
farther and struggle more to find enough
food. This throws breeding schedules into
disarray and increases stress levels among
partnerships—both factors that can
decrease breeding success.
In a paper published in the Proceedings
of the Royal Society B , Ventura and his team
concluded that warmer sea temperatures
are linked to higher divorce rates among
New Island’s black-browed albatross—
providing the first evidence of environ-
mental conditions increasing such rates
among a wild monogamous animal popu-
lation, the researchers say.
Warmer sea conditions were associ-
ated with more albatross divorcing
because of breeding failures. And diggingdeeper, the team found that in warmer
years female albatross were more likely
to leave their mate even after successful
breeding attempts.
“Previous successful females are the
ones that are most affected by this [warm-
ing],” Ventura says. “They divorced more
often, when in theory they should have
remained together with their previous
partner.” This may be a manifestation of
what Ventura calls the “partner-blaming
hypothesis,” in which the female conflates
the stress caused by environmental condi-
tions with poor performance by a partner.
Ventura hypothesizes that similar pat-
terns may manifest in other seabird popula-
tions and possibly among some monoga-
mous mammals, highlighting a potentially
overlooked consequence of climate change.
According to Natasha Gillies, a researcher
at the University of Liverpool in England,
who studies seabird-breeding behavior and
was not involved in the new study, similar
scenarios could have “profound” impacts on
smaller populations of birds by decreasing
breeding options. “If you have a situation
where increasing sea-surface temperature
is leading to higher divorce rates, that
reduces breeding success for the population
as a whole,” she says. “Ultimately you’re
sending fewer albatrosses out into the
world, and that’s going to impact the popu-
lation more widely.” — Jack TamisieaEnrique Aguirre Aves/Getty Images