New York Times, 3/11/17 by
Nicholas Caseymarch, Charles Darwin Research Station, Galápagos — Of all the
giant tortoises on these islands, where the theory of evolution was born, only
a few have received names that stuck.
There was Popeye, adopted by
sailors at an Ecuadorean naval base. There was Lonesome George, last of his
line, who spent years shunning the females with whom he shared a pen.
And there is Diego, an ancient
male who is quite the opposite of George.
Diego has fathered hundreds of
progeny — 350 by conservative counts, some 800 by more imaginative estimates.
Whatever the figure, it is welcome news for his species, Chelonoidis hoodensis, which was stumbling toward extinction in the
1970s. Barely more than a dozen of his kin were left then, most of them female.
Then came Diego, returned to the
Galápagos in 1977 from the San Diego Zoo.
“He’ll keep reproducing until
death,” said Freddy Villalva, who watches over Diego and many of his
descendants at a breeding center at this research facility, situated on a rocky
volcanic shoreline. The tortoises typically live more than 100 years.
The tales of Diego and George
demonstrate just how much the Galápagos — a province of Ecuador — have served
as the world’s laboratory of evolution. So often here, the fate of an entire
species, evolved over millions of years, can hinge on whether just one or two
individual animals survive from one day to the next.
Diego, and his offspring, are
part of one of the most high-profile efforts to keep Galápagos tortoise
populations thriving. The tortoise, estimated to be perhaps a century old, is
one of the main drivers of a remarkable recovery of the hoodensis species — now
more than 1,000 strong on their native island of Española, one of the dozen
Galápagos islands.
His story stands in contrast to
Lonesome George, who was perhaps the most famous Galápagos resident when he
died in 2012, at about 100 years old. His species, Chelonoidis abingdonii, now lives only on T-shirts and postcards
because George, found in 1971 by a snail biologist on the island of Pinta,
never produced any offspring in captivity.
An estimated 11 of about 115
known animal species have gone extinct since scientists began keeping records
on the Galápagos. But the establishment of a national park, and the efforts of
scientists, mean that extinctions are now a rarity. Which is why the death of
George was such a blow.
Scientists did all they could to
coax more abingdonii out of George and his mates. Only when George had died did
an autopsy reveal it wasn’t lack of potency that impeded his reproduction, but
a more anatomical ailment affecting his reproductive organ.
“We don’t like to talk about it,”
said James P. Gibbs, a professor of vertebrate conservation biology at the
State University of New York College of Environmental Science and Forestry in
Syracuse, and one of the world’s experts on the tortoises, only half joking.
Dr. Gibbs had returned to the
Galápagos that week from upstate New York to bring the stuffed remains of
George and several expensive air-conditioning units and UV filters that would
preserve the reptile in perpetuity in a mausoleum of sorts on one of the
islands.
Both George and Diego had shells
much smaller than many other species, and long necks to reach the few cactuses
growing on their wind-swept island. In a way, those small shells were a curse
on both their houses: Abingdonii and hoodensis were easy prey for the
buccaneers and whalers who poured onto their islands in previous centuries and
saw only defenseless, slow-moving meals that could easily be carted away.
Nor did it help that the giant
tortoises of the Galápagos can survive for up to a year in the hull of a ship,
meaning they provided a near-endless supply of fresh meat as they were stacked
below decks by the hundreds. They were even tossed overboard when a ship needed
to lose ballast for a quick getaway.
Among those who dined on giant
tortoise flesh: Charles Darwin.
“We lived entirely on tortoise
meat, the breastplate roasted … with flesh on it, is very good; and the young
tortoises make excellent soup,” Darwin wrote in 1839, near the peak of the
tortoise plunder in which some 200,000 were killed or carried away from the
islands.
In the end, finches led him to
the theory of evolution, not tortoises.
“He may have eaten his best
specimens,” Dr. Gibbs said.
The recovery of Diego’s hoodensis
species also brings up a quandary, one that perplexed Darwin during his adventures
in the Galápagos more than a century ago, when he studied the fauna.
As Diego produces more offspring,
and as those he has produced reproduce with one another, the entire hoodensis
species could begin to look like Diego.
Evolutionary scientists call this
process the bottleneck effect — when survivors’ genes come to dominate the gene
pool as populations rebound. It’s particularly true on islands like Española,
where tortoises from other lines will not breed with Diego’s kin.
Tortoise experts were divided on
what risk that presents for hoodensis on a recent afternoon. Dr. Gibbs called
it a “dangerous zone,” where little genetic diversity could mean susceptibility
to a dangerous disease or changes in habitat because of climate change.
But Linda Cayot of the Galápagos
Conservancy dissented, saying island species on the Galápagos have a long
history of being decimated to just a few survivors that rebounded without
incident — like a population of giant tortoises that chose to live in the
caldera of a volcano. After the volcano exploded 100,000 years ago, the
tortoises bounced back and returned to the caldera.
“Every species came from a
bottleneck,” Dr. Cayot said. “It’s what happens in the Galápagos.”Dr. Gibbs
noted that another male of Diego’s species, in captivity, is adding his own
progeny to the gene pool, possibly even beyond the numbers of Diego. He has not
been given as much credit, though, perhaps because he does not have a name. (He
goes only by “Male No. 3.”)
Two days later, the scientists’
attention was back on George, whose embalmed body was being revealed for the
first time on the Galápagos.
A kind of memorial ceremony was
underway around dusk at the Charles Darwin center, attended by national park
guards, air force officers and police officers. A government official stood to
declare the tortoise’s body “cultural patrimony of the people.”
Someone presented a death mask of
George, made shortly after he had died.
“It is a great honor to receive
this relic,” said Fausto Llerena, George’s longtime caretaker, who spoke below
a sign that read: “Lonesome George: A legacy, a future, a hope.
But maybe the real hope was
elsewhere at the Darwin center.
Diego lounged in his pen with the
females. His face was an old yellow color after four decades in the breeding
pen, his shell looking like a house that could use a new coat of paint. He
craned his neck to look around him.
“If you give him the chance, he
bites you,” warned Mr. Villalva, the breeding center manager.
Before long, Diego had found a
female. The act did not look easy, like one boulder trying to roll over
another. January to June is the mating season, Mr. Villalva explained.
But not that afternoon. The
female backed off into the bushes, and Diego landed with a thud that sent dust
flying. After a moment, he scooted away.
For some great photos go to the
original story at
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