May 2020 BBC Wildlife 25
WILD NEWS
LesserBermudasnail
CONSERVATION REPORT
This month, Gerardo Garcia shines a spotlight
on a tropical mollusc that nearly vanished.Why did the lesser Bermuda snail
go extinct in the wild?
The last live individuals were seen in
Bermuda more than 15 years ago. The
introduction of other snail species such
as the predatory rosy wolf snail, which
was introduced as biocontrol, has proved
troublesome to the native population. In
2005 seven species of terrestrial worm
were recorded on Bermuda, of which three
are known to eat snails. Also, Bermudian
land snails have not been observed sealing
their shells and may be prone to drying
out during warm conditions.What about changes to habitat?
Natural habitats are confined to a few
isolated patches mainly within parks and
nature reserves. These areas continue
to be degraded by invasive species,
and it is reasonable to assume that the
composition of the litter layer (where
the snails find food and refuge) and
associated fungi on the forest floor has
changed. Feral chickens also continue
to modify the forest floor through their
scratching. Plus, rats and introduced
Argentine ants predate the snails and
impede the regeneration of habitat.How was the species saved?
Specimens from the last
known populationsof greater and lesser Bermuda snails
in the wild were rescued. ZSL London
Zoo received the first snails and Chester
Zoo initiated an intensive breeding
programme for both species with the
objective to run reintroductions in
select locations. The government of
Bermuda started surveying sites to
consider reintroductions in parallel with
local habitat restoration. One of the
key approaches for the lesser Bermuda
snail reintroduction was to follow in the
success of the greater Bermuda snail
reintroduction (a close relative).Where were the snails reintroduced?
Eight hundred were released on to
Nonsuch Island in areas that have good
leaf litter, limestone blocks for refuge and
also endemic palmetto, which provides
the snails with food and shelter. The first
reintroduction of the lesser Bermuda snail
occurred early this year with the support
of wildlife ecologist Dr Mark Outerbridge.
We will continue to breed both species
until we establish stable populations. JPFrom land to sea
to sea otter
WILDLIFE HEALTHA
parasite known only to be hosted
in North America by the Virginia
opossum is infecting sea otters along
the West Coast. Sea otters ranging from
Southern California to Alaska were tested
for the presence of Sarcocystis neurona, a
parasite and important cause of death in
the marine mammals.
Several infected sea otters were found
in the northern part of Vancouver Island
in British Columbia, where Virginia
opossums are not known to live.
“We were pretty sure it comes from
the land, but we didn’t really know how
this pathogen finds them,” says lead
author Tristan Burgess. Results suggest
the pathogen may be carried by water
runoff from land to sea, where it can be
concentrated through ocean movement
and prey species, such as clams.
Most infections occurred in California
and Washington, more so than Alaska
and British Columbia. Higher risks of
exposure were associated with habitats
of soft sediment such as the mouths
of rivers and estuaries and otters
consuming a diet rich in clams. Human-
dense habitats, some wetlands and
croplands were also a factor – although
wetlands can help filter and deactivate
some pathogens, the study noted they
may be potential opossum habitat.
“We should remember the value of
marine mammals as sentinels, not just
of the health of their marine habitat, but
of nearby terrestrial environments, too,”
statesBurgess.JoPriceFIND OUT MORE
Scientific Reports:
go.nature.com/2wUV0ajGERARDO GARCIA is curator of
lower vertebrates and invertebrates
t esterZRED LIST
STATUS:
CRITICALLY
ENDANGEREDFINDOUT MORE Chester Zoo:
bit.ly/2VeDWUZOnce driven to the brink
of extinction, the lesser
Bermuda snail has been
given a second chance.Parasites may be
concentrated in clams
eaten by sea otters.