Lonely
George the tree snail dies, and a species goes extinct
The world’s loneliest snail is no more.
George,
a Hawaiian tree snail—and the last known member of the species Achatinella
apexfulva—died on New Year’s Day. He was 14, which is quite old for a snail
of his kind.
George
was born in a captive breeding facility at the University of Hawaii at Mānoa in
the early 2000s, and soon after, the rest of his kin died. That’s when he got
his name—after Lonesome George, the Pinta Island
tortoise who was also the last of his kind.
For
over a decade, researchers searched in vain for another member of the species
for George to mate with, to no avail. (Though these snails are hermaphrodites,
two adults must mate to produce offspring, and researchers refer to George as a
“he.”)
“I’m
sad, but really, I’m more angry because this was such a special species, and so
few people knew about it,” says Rebecca Rundell, an evolutionary
biologist with State University of New York who used to help care for George
and his kin.
Throughout
his life, George was a public face for the struggles facing Hawaiian land
snails. His death highlights both the vast diversity of indigenous snails—and
their desperate plight.
“I
know it’s just a snail, but it represents a lot more,” says David Sischo, a
wildlife biologist with the Hawaii Department of Land and Natural Resources and
coordinator of the Snail Extinction
Prevention Program.
Silencing the forest
Snails
were once incredibly numerous in Hawaii, and the loss of a species is a blow to
the ecosystem. Records from the 19th century claim that 10,000 or more shells
could be collected in a single day.
“Anything that is abundant in the
forest is an integral part of it,” says Michael Hadfield, an invertebrate
biologist who ran the captive breeding program for rare native Hawaiian snails
until the late 2000s.
And
these creatures are incredibly diverse: There were once more than 750 species
of land snail in Hawaii, including a little over 200 in
the tree snail family.
When
they arrived on the islands, the snails branched out and took on a variety of
ecological roles. Some of these species came to function as decomposers—like
earthworms, which are not native to the islands—and fulfill the essential
ecological role of breaking down detritus.
The
Hawaiian tree snails specialize on the gunk that grows on leaves. Upon feeding,
they reduce the abundance
of fungi on leaves while increasing fungal diversity—and because of that,
they may have helped protect their host trees from diseases. Some biologists
think healthy snail populations could have prevented the current outbreak of Rapid ʻŌhiʻa Death, a new fungal
pathogen wiping out native trees.
In
some ways, these snails are more like mammals or birds than other
invertebrates: They regularly live well into their teens, take five or more
years to reach sexual maturity, and give birth to less than ten offspring per
year. They’re revered in Native Hawaiian legends which hold that tree snails can sing
beautifully,
and are known as the ‘voice of the forest’. (It’s not clear why since they
aren’t known to make audible noises.)
Diverse but endangered
About
a decade ago, it was commonly believed that over 90 percent of Hawaii’s snail
species were gone. Researchers have re-discovered dozens of species that they
thought were extinct, however, and found several new species.
The
snails that remain in Hawaii are in serious trouble, though. Most are only
found on a single ridge or valley, and in recent years, declines have
accelerated as introduced predators have started invading their last refuges.
“We’ve
had populations that have been monitored for over a decade, and they seemed
stable… then, within the past two years they’ve completely disappeared,” says
Sischo. “We’ve all broken down and cried in the field.”
These
snails are likely to go extinct within months or a few years, Sischo says,
unless they’re protected in the wild or brought into the lab.
And
the same thing is happening around the world. Land snails and slugs represent about 40
percent of the known animal extinctions since 1500, more likely disappeared before becoming known to science, and many species
are now on the edge. If there’s any silver lining to George’s death, it’s that
it might draw attention to this hidden
extinction crisis
hitting the globe’s mollusks while there’s still time to do something.
Rapid fall
The
snails’ decline can be blamed on invasive species, which are eating them to
extinction. In particular, they’re falling victim to the rosy wolfsnail (Euglandina
rosea), a snail and slug specialist that was brought to the islands to eat other
mollusks: giant African snails. It found the endemic snails to be much more
palatable, and has been eating through entire species at an alarming rate since
its introduction in 1955.
Researchers
suspect increased rainfall and higher temperatures have allowed the rosy
wolfsnails to venture up in altitude into the Hawaiian snails’ last refuges.
Also, the snails’ long lives may have masked their declining health, as
populations could persist long after they’ve stopped producing new generations.
The
downfall as been swift. Melissa Price, a molecular
ecologist with University of Hawaii at Mānoa who uses genetic methods to learn
more about the animals’ ecology and evolution, found out that her favorite
species A. lila, went extinct in the wild last April. She helped count
the last population three years ago, and at the time, there were about 300 left
on ridge overlooking Punaluʻu valley and Kāneʻohe Bay.
“It
was just the most magical spot on Earth, and then you had these beautiful,
rainbow-colored snails hanging from the trees,” she recalls. But when
scientists returned last year, they searched for 20 hours and only found a
single individual.
The
same thing is happening to other snails on the other islands. “Stuff is just
blinking out,” she laments. “This entire taxonomic group is about to fall off
the face of the planet.”
In
the 1980s, the entire genus of Hawaiian tree snails was listed as endangered.
This led Hadfield to establish a captive breeding facility in the hopes of
saving the rarest species. “We knew we were seeing the last of those snails,”
he says.
What remains
And
it was in that laboratory at the University of Hawaii at Mānoa that George was
born in the early 2000s. George’s parents, along with a handful of other
members of the species, were collected from the last known population found in
a few trees near Oahu's Poamoho trail in 1997.
Only
a few offspring were produced, but they and their parents didn’t make it long.
By the mid 2000s, “all of the Achatinella apexfulva died, except for one
juvenile snail, which was George,” says Sischo.
It
became a tradition amongst the snail researchers to stop at the spot where the
last A. apexfulva were found and pull out binoculars to scan the trees.
“We kept hoping we’d find more,” says Hadfield. But they never saw another.
Thus, though George became sexually mature in 2012, he never had a mate. The
snail lived over a decade in a terrarium of his own, and then, on the first day
of 2019, he died.
George’s
remains were preserved in ethanol and his shell will join the more than 2
million other Hawaiian land snail specimens in the Bernice Pauahi Bishop
Museum’s malacological collection. (Malacology is the study of mollusks.)
And
back in 2017, a tiny piece of George’s foot was carefully cut off and sent to
scientists with the San Diego Zoo
Institute for Conservation Research’s “Frozen Zoo” to provide DNA
should scientists ever desire to clone him—which isn't currently possible, but
likely will be in the near future. Every animal that dies in the captive breeding
program is preserved, and Hadfield notes that it’s sometimes possible to get
DNA from old shells as well, so there may be enough genetic diversity to bring
the species back. But unless the forests they lived in are restored as well,
and the invasive animals removed, there will be nowhere safe to put them.
The love shack
George
spent the last two years inside a 12-foot by 44-foot modular trailer in Oahu
which some have taken to calling “the love shack.” In the captive breeding
program, which was officially taken over by Sischo and the Snail Extinction
Prevention Program in 2016, there are 30 species of Hawaiian snail that are
either extinct in the wild or exceedingly rare. Several of those species are
down to fewer than 50 individuals.
Taking
care of 2,000 snails isn’t easy. The animals housed in carefully designed
terrariums that live inside six large environmental chambers with controlled
lighting, temperature, and humidity. Roughly every other day, loads of freshly
clipped branches from the snails’ host plants are brought in so the snails can
feed on the algae and fungi that naturally grow on the leaves. The team also
cultures a native tree fungus to add to their diet.
Researchers
hope these efforts keep more species from going extinct—and that in death, as
in life, George will help raise awareness of the problem.
“The
land snail extinction crisis hasn’t gotten as much publicity,” Rundell notes,
even though “these species are an important part of life on earth, and when
they start going extinct, it means that something is really wrong with the
environment that supports us.”
“As we are all
mourning George, I hold tighter the thought that hope still does exist for
these native snails,” says Norine Yeung, the malcology
collection manager at the Bernice Pauahi Bishop Museum. “Please don't forget
them.”
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