Scientific American 201907

(Rick Simeone) #1

18 Scientific American, July 2019


DANITA DELIMONT

Alamy

ADVANCES


CONSERVATION

Slow-Motion


Extinction


Turtles’ famed longevity can mask
their decline—until it is too late

Nearly four decades ago zoologist Mi­
chael Thompson, then at the University of
Adelaide in Australia, made an alarming
discovery: invasive red foxes were gobbling
up more than 90 percent of all the turtle
eggs laid along the banks of Australia’s
Murray River. Thompson’s surveys also re­
vealed a disproportionate number of older
turtles, suggesting that fox predation had
already reduced the amount of juve niles in
the river. If no one took action, he warned,
the formerly abundant turtles would even­
tually disappear.
Very little was done, and Thompson’s
prediction now appears to be on its way to
coming true. A recent study confirms that
several turtle species have either drastically
declined or disappeared from various sec­
tions of the Murray River. “The problem is
that the longevity of turtles gives the per­
ception of persistence,” says Ricky Spencer,
an ecologist at Western Sydney University
and a co­author of the study, which was
published in February in Scientific Reports.
“It’s human nature that only when some­
thing is gone do we start missing it.”
Spencer and his colleagues tallied pop­
ulations of three once common turtle spe­
cies—the broad­shelled turtle, the eastern
long­necked turtle and the Murray River

turtle—at 52 sites along the southern
reaches of the river. The researchers in ­
ferred the species’ population sizes from
the number of individuals they trapped in
a given amount of time. They found the
turtles have been extirpated in places
where they were previously abundant, and
most of the specimens they managed to
capture elsewhere were large—and likely
old—adults. Spencer and his colleagues
blame the losses on ongoing nest predation
by foxes, compounded by other problems,
including environmental degradation and
severe drought in the 2000s.
“We have known about [the turtle die­
off] for decades, and despite intense media
hype in Australia about the ‘plight of our riv­
ers,’ nothing has been done to reverse that
decline,” says Rick Shine, a herpetol o gist at
Macquarie University in Sydney, who was
not involved in the research. “This paper is
a wake­up call that unless we begin to do
something about turtle conservation on a
landscape scale, we may lose a fas cinating
component of our native fauna.”
The turtles could recover quickly if
action is taken to protect nests from foxes
and restore habitat, Spencer notes. But
governments tend to respond only when
losses reach crisis levels, and the Murray
River species currently lack federal protec­
tion, he says. He and his colleagues have a
work­around, however: “Our next step
is to start designing community conserva­
tion efforts for common turtle species,”
he explains, “so people can actually do
things without having to wait for gov­
ernment funding.” — Rachel Nuwer

Juvenile Murray River turtle ( Emydura
macquarii ). Such turtles are growing rarer.

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