Waking Snakes: Discovery of a Nantucket Snake Hibernaculum
by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
As I write this, the world is celebrating the 42nd Earth Day. Today's story is a fitting tale of the entanglement of man-made and animal realms. Fortunately for all concerned, it has a happy ending. Wintertime is a time of
hibernation for many of us. We move slower, stay in more, and try to stay
warm. Many animals hibernate to conserve energy and increase their chances
for survival.
A new state-of-the-art septic system is being installed at the UMass Boston
Nantucket Field Station, and during the construction phase we discovered two
large, six foot deep, six foot wide, underground cisterns. To our even greater
surprise, when we opened the lids of both cisterns (which were connected by
a ceramic pipe), we found a nest of milk and garter snakes bedded down for
the winter. The name for this phenomenon is a hibernaculum. This word
comes from Latin word "hibernare" (to spend the winter) or "winter quarters." Hibernaculum is also used in biology to describe a protective case, covering,
or structure, such as a plant bud, in which an organism remains dormant for
the winter.
Previously in this column, we explored the life histories and stories of the
six species of snakes found on Nantucket. You may recall that snakes are "cold
blooded" creatures, or ectotherms (from the Greek "ektós" for "outside" and "thermos" for "hot"). Ectotherms control their body temperature through
external means from basking in the sun to cooling off in the shade. Lucky for
us when we had to become inadvertent snake wranglers, cold-blooded animals
are very sluggish in cold environments. Their metabolism decreases significantly
when it is cold, allowing them to survive on much less food and
water and extending their chances for survival. Unfortunately for us, wintertime
is a time of food and holidays and our endotherm nature doesn't help one
bit for lowering our appetite when it gets cold.
Most of us have heard of the term "snake den" and some scientists refer to
these as refugia. All of these words are used to describe the places where
many snakes spend the cold months of the winter and at times, the extreme
heat of summer. Hibernacula can range in form from natural structures such
as caves and sinkholes to man-made structures such as foundations, crawl
spaces and garages. Although seemingly very different, these structures have
one thing in common; they provide a thermally stable place for snakes to hide
while the temperatures are too extreme for activity.
Before I forget, I have to mention the extreme bravery my husband Len
Germinara exhibited when we found these snakes. It appeared we would be
removing these underground cisterns by breaking them up and pulling the
pieces out of the ground to make way for new septic tanks. We knew we had
exposed these snakes to the cold and that we needed to pull them out and figure
out a place to repatriate them that would allow them a couple more days
of warmth. Using "grabbers" which are extension pickers we use for the CleanTeam, Len was able to pull out each of these snakes, some quite long and large
and place them with some towels into a bucket. Fortunately the snakes were
definitely cold and moving slow and were quite content to be covered by a
towel. When gently handling them, Len was amazing by the muscular strength
and grip of the larger milk
snakes. Lots of people are
frightened by snakes, and there
weren't many volunteers
among the construction and
archeology workers at the site.
We are fortunate to have a
resident snake expert on
island, Andrew McKenna
Foster, the Director of Natural
Science Department at Maria
Mitchell Association. I called
Andrew, and he came over
within 30 minutes. We had
released two milk snakes, but
still had 10 milk snakes and
two garter snakes. He was able
to positively ID the snakes, weigh then and measure their lengths and try to
determine the gender of the snakes, which is not easy. There are two ways to
do it, one involves a probe and as this is a family show, I won't go into details.
The other method is relatively easy when snakes are fat and happy, but these
snakes had not been eating for some time. Because the male parts are located
just inside the cloaca opening (the exit point for waste and reproductive
fluid) males have a tail that is thicker and longer than in females, and also
tapers less evenly to the tip (thicker for a bit then suddenly thinning). Females
have a tail that is thinner and shorter
than in males and tapers smoothly,
evenly and more quickly. But allof these snakes were skinny and
hiding their genders because they
have not eaten.
Andrew was extremely excited
to learn about this discovery and
informed me that this is the first
documented case of a verified snake
hibernaculum on island. When you
think about some of the historical
accounts of snakes on island, it
makes sense to find a hibernaculum
near the Field Station. You may have
heard about "Rattlesnake Bank" which is off Polpis Road near the
Lifesaving Museum right across the marsh from the Field station. The name
comes from a local who saw what he believed to be a rattlesnake but who was most likely misidentifying a milk snake (which also rattles its tail) for the
dreaded rattlesnake. Somewhere on island was an area called "Snake Spring" where Nantucket's English settlers dispatched hundreds of snakes as they
emerged groggily from their inter home. We have come a long way from the
days of fear and loathing of snakes.
There are six species of snake found on Nantucket: garter snake, ring-neck
snake, eastern milk snake, northern water snake, ribbon snake, and smooth
green snake. All of these snakes are non venomous and cannot seriously hurt
you. Most of the snakes we found were milk snakes which are a boldly patterned
and quite beautiful snake as you can see from the accompanying picture
(photo by Len Germinara). The milk snake (Lampropeltis triangulum) has
a light gray to tan body covered with reddish-brown blotches bordered in
black. Larger blotches on the back alternate with smaller ones on each side.
The head is patterned, usually with a light colored "Y" or "V" within a reddishbrown
patch. Smooth scales give this attractive snake a shiny or glossy
appearance. The belly is patterned with an irregular checkerboard of black on
white.
Generally, you can recognize this most common of all New England
snakes, the garter snake (Thamnophis sirtalis) by its pattern of yellow stripes on
a black or brown background. Stripes may be tan, yellow or orange.
Nantucket garter snakes have a darker coloration and can be more reddish
brown on top to better camouflage themselves in our coastal habitat.
There are folks out there who build snake hibernaculums for snakes in
order to protect them in areas of construction or development. And I managed
to find a couple of web sites that talk about constructing experimental snake
hibernaculums. It just so happens that these cisterns are the perfect refuge for
snakes. We were able to leave these cisterns in place to shelter the snakes
over the incoming winters as they will most likely come back to the same spot
next year. I promised you a happy ending. We released the snakes appropriately
on Saint Patrick's Day which was warm and sunny. We placed the larger
ones some distance from the smaller ones and made sure we released them
close to food and water. The snakes were happy to be free of their pillowcase
enclosures and were much feistier in the warmer air.
Read more about recent snake research on island here and at www.yesterdaysisland.
com/2010/science/11-special2.php. The research is funded by
the Nantucket Biodiversity Initiative which is a partnership between Nantucket
conservation organizations, universities, non-governmental organizations,
and individuals interested in documenting the biodiversity of the islands and
adjacent waters and monitoring and conserving that biodiversity over time.
Members of the NBI include: the Linda Loring Nature Foundation, Maria
Mitchell Association, Massachusetts Audubon Society, Nantucket
Conservation Foundation, Nantucket Garden Club, Nantucket Islands Land
Bank Commission, Nantucket Land Council, Natural Heritage & Endangered
Species Program of Massachusetts Division of Fisheries & Wildlife, Science
Department of Nantucket High School, The Trustees of Reservations, the
Tuckernuck Land Trust, and the University of Massachusetts Boston Nantucket
Field Station.
I bring up the NBI to get everyone thinking about and planning to attend
the NBI's 5th Biennial Biodiversity Assessment Week which is May 16-22.
Biodiversity Week is a week-long series of walks, talks and events to celebrate
and explore the unique biodiversity of Nantucket. There are events for children,
the general public, researchers, and naturalists. Kit Noble will be showing
his film "Nantucket by Nature" on Wednesday May 16th at 6 pm in the Great
Hall at the Nantucket Atheneum to kick off the start of Nantucket Biodiversity
Assessment Week. Our keynote talk by moth and bee expert Dr. Paul Goldstein
entitled ""Beyond Bees: Pollinator diversity and invertebrate conservation on
the Cape and Islands" will be on Friday May 18 at 7 pm in the Great Hall of the
Atheneum.
Field trips will include morning and afternoon programs on insects, plants,
shorebirds, moths and butterflies, bird song, marine life, and more. Great Point
tours will be offered by the Trustees of Reservations. Family oriented programs
will also be offered in the areas of insects, shorebirds and plants. In addition
to the kickoff and keynote, evening presentations will be made on insect signs
and insect tracking, the offshore underwater world, and Nantucket's natural
history. A photography contest that is open to everyone will be held with the
winners in each category announced at an event to wrap up the week's programs
on the 21st at the Nantucket Conservation Foundation. I hope to see you
there and that you have emerged refreshed from your own hibernaculum.