Spring: Where are all Ocracoke’s frogs and toads?
By PAT GARBER
Rachel Carson published her environmental classic, "Silent Spring," in
1962, she was referring to the silence of songbirds, quoting a line
from a John Keats’ poem that reads, "The sedge is withered from
the lake and no birds sing."
silence Ocracokers have been noticing recently is not that of
songbirds, but of the tree frogs and the Fowler’s toads, whose
voices used to echo through the village from spring until fall. Chubby
toads lounged in flower gardens and spry green and squirrel tree frogs
clung to windows and slipped through open doorways. Children played
with them, stuffing them into their pockets. Sometimes a little green
frog would jump down someone’s shirt.
last year or two, however, they have been noticeably absent, and more
and more people are wondering why.
have always been scarce on Ocracoke. No salamanders are recorded living
here, and only four members of the order known as Salientia (frogs and
toads) have been identified on the island.
herpetologist Alvin Braswell, who works at the North Carolina State
Museum in Raleigh, identifies them as the Fowler’s toad (Bufo
woodhousei), the green tree frog (Hyla cinerea), the squirrel tree frog
(Hyla squirella), and, less commonly, the Southern leopard frog (Rana
moist, sensitive skin which makes them extremely sensitive to changes
in their environment.
Fowler’s toads are 2 to 3 1/4 inches long and have brown, olive
or gray dorsums, speckled with darker spots, warts, and a light stripe
down the back. They breed, according to Braswell, in spring and early
summer and live an average of five to seven years. The males emit a
loud, discordant mating call that lasts one to four seconds and sounds
like "wa-a-a-ah.” It takes about two months for the 7,000 or so
eggs the females lay to transform to tadpoles and then to tiny toads.
It takes three to four more years before they are of breeding age.
green and squirrel tree frogs may live three to five years. They
typically breed from April to July, but their mating calls may be heard
into September. Green tree frogs have long legs and smooth skin and
sometimes reach a length of 2 1/2 inches. Their call is a bell-like,
nasal "queenk," repeated once a second. Females lay about 400 eggs.
Squirrel tree frogs are smaller, 1 to 1 1/2 inches. They can change
skin tone from dull brown to green, with or without spots. It is the
call of squirrel tree frogs which often resound after summer storms,
sounding like a flat, nasal, duck-like "waaaak," repeated every half
three species depend on ephemeral fresh water sites that are hydrated
every year to lay their eggs and hatch their tadpoles. Drought during
their breeding seasons could cause them to die off.
there are only a few species, individual tree frogs and toads have
until recently been prolific. Lots of full and part-time residents have
noticed the change.
S. National Park Service ranger Kenny Ballance remembers seeing only
one at his cottage on Back Road, and two at the Pony Pens. Park
bio-tech Jocelyn Wright has seen none in the two years she has worked
here. Some of the men working on the Ocracoke Airport building, located
within the park, do recall seeing some of the tree frogs this past
summer and fall.
islanders say they blame mosquito spraying for the decrease in toads
and frogs on Ocracoke. During the months of mosquito season, which can
last from spring through fall, the hum of the mosquito truck is a
familiar evening sound, and residents and guests rush to close their
windows when they hear its approach.
of Rachel Carson’s book presents evidence that the pesticide DDT
was responsible for the death of birds and other organisms during the
1950s and ‘60s, and she predicted that unless its use was
curtailed, there would indeed be a silent spring.
resident Thomas Midgett remembers the days following World War II,
during which DDT use was heavy on the island. Trucks drove around the
village spraying the pesticide behind them. It felt good on hot summer
days, and laughing children followed it, playing in the mist.
toads and frogs disappeared, recalls Thomas, along with other wildlife.
After DDT was banned the amphibians made a gradual come-back. But, says
Midgett, who lives near Pamlico Sound and the salt marsh, "There used
to be lots of those toads back where I am, and frogs as well. I saw a
few of the little brown frogs last summer, but the toads and the green
frogs are gone.
don’t see a lot of things you used to see here," he adds, shaking
his head. "A lot of the birds and what we used to call furry worms
(probably what some people call wooly bears-caterpillars) are not here
Joliff, who has lived on the island most of her life, recalls the time
years ago when the frogs and toads disappeared.
DDT, they said. The DDT killed the toad-frogs."
she sees very few of the green tree frogs and has not seen any
Fowler’s toads near her home on Howard Street, and she misses
pesticide now being sprayed at Ocracoke is not DDT, however, but a
product called Master Line Kontrol 4-4. The active ingredients in this
product, Permethrin and Piperonyl Butoxide, are claimed to be
environmentally safe and are approved by the Environmental Protection
Engber, medical entomologist for the North Carolina Department of
Environment and Natural Resources, said that it is a commonly used
mosquito pesticide believed to be harmless.
people think that they (the sprayers) are trying to coat
surfaces,” he said. “Not true. Droplets have to hit
mosquitoes in flight. The droplets, which are much smaller than
raindrops, have a very short half-life, and should lose their potency
by the next morning."
about the warning on the label?" I asked him, reading aloud the
statement written under environmental hazards: "This pesticide is
extremely toxic to aquatic organisms, including fish and aquatic
conceded that if used incorrectly the chemical could kill amphibians
and that it might impact frog and toad populations by killing insects
they depend on for food. He concluded that "I can’t say for sure,
but I kind of doubt that it’s killing frogs."
toxicology report on Master Line Kontrol 4-4, which Braswell found on
the Internet, stated that "Amphibians are much more tolerant of
Permethrin than the fish and arthropods." It added, however, that "It
should be noted that ‘much more tolerant’ can mean they do
not die in a short time frame."
report also said that "Permethrin disrupts the growth and development
of tadpoles (and) affects brain function in tadpoles."
Austin, president of Ocracoke’s Mosquito Control Committee, said
that he does not think the pesticide would kill frogs or toads and said
that because it was so dry, they hadn’t had to do a lot of
spraying the last two years.
committee has recently spent about $11,000, he added, on new improved
equipment which fine-tunes the direction and speed of the spray, so
that it does not enter waterways and is safer in general.
trying to be as efficient and safe as we can be," he said.
discussing the disappearance of the frogs and toads, he noted that on
Portsmouth Island, where no chemicals are sprayed, there are few or no
frogs and toads.
If this is
true, then what else might have caused the disappearance of most of
Ocracoke’s hopping amphibians?
the state herpetologist, mentioned several possibilities.
is the drought that Rudy Austin had mentioned. Ocracoke, along with the
rest of the state, experienced unusually dry spring and summer seasons
in 2008 and 2009. If Ocracoke’s freshwater ponds and puddles
dried up during breeding season, said Braswell, there would have been
no offspring -- what he called recruitment -- to replenish the adult
stock. The lack of rain could also have caused increased salinity,
which the tadpoles might not be able to survive.
overall pollution, brought about by more people living on and visiting
the island, is what part-year resident Serge Gracovetsky thinks may be
wrong. Braswell confirmed that it could certainly contribute. Motor
oil, either dumped or accidentally leaked into waterways, is deadly to
aquatic life. Fertilizers, pesticides, sewage -- all products of a
growing human presence, combined with fewer undeveloped areas for
breeding and spawning, make Ocracoke a less hospitable habitat for
frogs and toads.
the burgeoning feral cat population have an effect on the amphibians?
It could. Both dogs and cats sometimes kill the amphibians, along with
natural predators, such as eastern hognose and ribbon snakes and black
racers. There are also a lot more ducks and minks here than before,
noted Rudy Austin, and now raccoons live on the island -- all of which
may contribute to the decline.
more ominous possibility is the introduction of Chytrid fungus or
Ranavirus, two diseases which have been ravaging frog and toad
populations worldwide. It is not known for sure where they originated,
says Braswell, but both have now been detected in North
fungus has already led to the extinction of several species. It is the
worldwide food and pet markets that led to the introduction of these
exotic diseases. Frog legs and aquarium frog pets have become big
business and are transported all over the world by airlines and
shipping lines. According to an article published in "New Scientist" by
Catherine Brahie, "Global trade is spreading two severe diseases, one
of which is blamed for driving amphibians towards extinction."
scientists blame the global loss of amphibians on an increase of
ultraviolet rays entering earth’s atmosphere through a "hole" in
the ozone layer caused by manmade CFCs (hydroflourocarbons). Because of
their sensitive, highly absorbent skins, frogs, toads, and salamanders
are exceptionally vulnerable to the rays.
same phenomenon does not seem to be affecting the northern Outer Banks.
Retired National Park Service biologist Marcia Lyons and North Carolina
Coastal Federation coastkeeper Jan DeBlieu said that last summer they
saw or heard lots of tree frogs. Dare County does spray for mosquitoes,
Lyons added. She was not sure about whether Fowler’s toads were
to Jeff Hall, writing for the N.C. Wildlife Resources
Commission’s magazine, “Wildlife in North Carolina,”
coastal plain amphibian diversity is “in trouble...” The
species most at risk are not found at Ocracoke, but the decrease in
frogs and toads could be related to what is happening on the
it was the drought conditions of the past two years that reduced their
populations, Braswell said that they may rebound soon. Because of all
the winter rain, he expects this year to be a good breeding season for
amphibians. It will probably take several years, however, before the
improvement will be noticeable -- the time it takes for this
year’s tadpoles to reach breeding age.
the decline in Ocracoke’s frogs and toads should turn out to be
caused by mosquito spraying, what other options are available?
mentioned larval control with a product called methaprene, which is put
into the water to regulate mosquito growth.
was an issue for a while where it was blamed for frog
deformities,” he said, “but that doesn’t seem to be
is also a product – BTI -- which uses bacteria that are very
specific to mosquitoes. It is being used in parts of North Carolina.
Proper drainage of standing water is also a way to control mosquitoes.
The ditches that crisscross Ocracoke village were created for the
purpose of mitigating mosquitoes.
well may be that the decline in frogs and toads is due to a combination
of all of these causes. The good news is that all of the species are
common in other parts of the state and could be re-introduced, if
Joliff told me a charming tale of how, after the toad-frogs were killed
off by DDT, Mrs. Eleanor Burrus went to Hatteras, where toads still
lived, and filled up a shoe box with them. She brought them back to
Ocracoke, and they have lived here ever since.
now, that is. If they do not replenish themselves naturally, someone
could indeed bring back a shoe box full of toads and frogs, thus ending
Ocracoke’s silent spring.