Kristin Stanford radio-tracking a Lake Erie watersnake along the
Downloadable Reports From the
Project: Hibernation, Seasonal
Activity, Movement Patterns and
Foraging Behavior of Adult Lake Erie

Annual Report 2001

Annual Report 2002

Annual Report 2003

All graphs and figures appearing on this
page come from the reports listed above.
Over 60 Lake Erie watersnakes were surgically implanted with radio-transmitters on 5 islands (Kelleys, South Bass,
Middle Bass, North Bass and Gibraltar) between July of 2000 and June of 2002. Initially, snakes were located almost
daily. However, when the number of snakes increased, we attempted to locate them about twice per week.

Over the course of the 3-year study, we learned several interesting things about Lake Erie Watersnakes.

Amount of Shoreline Used: By tracking snakes several times per week during their active season, we were able to
determine the average amount of shoreline snakes used during the active season.

When looking at these graph, the percentage listed at the top indicates the proportion of snakes using that
particular amount of shoreline. We found that 75% of snakes are using about 440 meters (about 1/4 mile) or less
of shoreline during the summer months and additionally that 75% of LEWS stay within the first 13 meters (about
45 feet) of shore. Neither of these variables was found to differ between males and females.

Timing of Hibernation Activity: In order to determine the approximate duration LEWS were utilizing hibernation
areas we calculated mean dates for both entrance into and emergence from hibernation sites. The dates of entry
into hibernation ranged from mid September to mid October. When these dates are compared with the mean
daily air temperatures, the data suggests that snakes begin entering into hibernation when the mean minimum
daily temperature falls below 60 degrees F. Additionally, the entrance into hibernation is typically completed by
the time the mean maximum daily temperature fails to exceed 60 degrees.
LEWS begin their emergence from hibernation in the spring from late April to late May and again were compared
to the mean daily temperatures. Snakes begin their emergence from hibernation when the mean maximum daily
temperature first exceeds 55 degrees F and are typically finished with their emergence when the mean daily
minimum temperature exceeds 57 degrees F.
It should be noted however, that snakes can and do emerge from their hibernation sites to bask on warm days.
Typically, they do not venture far from their refuge and only surface briefly to take advantage of warm

Hibernation Sites: Over the course of the study we were able to locate 50 hibernation sites for LEWS using
data from 49 snakes. All but 1 snake utilized the same hibernation location (within 10 meters or less) in
successive years. However, it should be noted that this snake failed to emerge from hibernation the following
Spring indicating that she may have died prior to being able to move to her hibernation site.
For some snakes, hibernation sites were located directly inland from the shoreline occupied during the summer
as seen from the bullseye point below:

However, for other snakes hibernation sites were located adjacent to shoreline that was not within their
summer active areas. In addition, we found that even though these snakes moved out of their active area to
hibernate, they did return to the same site the following spring:

Types and location of Hibernation Sites: Over the course of our studies, we discovered that LEWS will hibernate
in a variety of places. These included natural structures (rock crevices, existing small animal burrows, tree root
masses) as well as man-made (old foundations, drain tiles, beneath concrete patios). We examined all of the sites
for commonalities, but were unable to pinpoint anything specific. Telemetered Lake Erie water snakes were
found to hibernate individually, although there were a few exceptions where two snakes chose sites less than 10
meters from another. However, we sometimes observed other (non-telemetered) snakes emerging from the
same hibernation ares as in the photo below indicating that several snakes may be utilizes certain sites.

We also measured the distance of each hibernation site in relation to the shoreline. These distances did not
differ between males and females. We found that 75% of snakes hibernate within 69 meters (226 ft) of the
shoreline. Distances ranged from 1 -580 meters and averaged around 27 meters. We examined these distances
using the same percentages as noted above:

One of the interesting observations regarding the distance of the hibernation sites was that of one of our
female snakes on Kelleys Island that hibernated 580 meters from the nearest shoreline. That's over a quarter
mile! What's more interesting is that this snake found its way back to its active area (the area along the shore
where there are multiple dots) and spent the summer. For the remainder of the study, she made this journey
back and forth for 2 more winters to hibernate within 10 meters of the precise location the previous year.
In July of 2000, the project: Hibernation, Seasonal Activity,
Movement patterns and Foraging Behavior of Adult Lake Erie
Watersnakes was initiated by Rich King, Kristin Stanford
(Northern Illinois University) and Doug Wynn (Westerville
North High School). The primary goals of this project were to
obtain information on these little known aspects of LEWS
biology utilizing radio-telemetric observation. Of special
interest were the location of hibernation areas in relation to
the shoreline as well as the duration watersnakes used these
sites in order to update the management and construction

recommended by USFWS.

So just where do you stick a transmitter on a snake???
Actually, we put them inside the snake's body! All of our
transmitters are surgically implanted by a veterinarian or
skilled professional. Snakes are placed under anesthesia while
we preform the surgery.A small incision is made toward the
beginning of the lower third of the snake. The body of the
transmitter is inserted just under the rib cage of the snake
and attached to a rib.The 8 inch long antenna is placed just
under the skin running toward the head. We use transmitters
lasting between 1-3 years which vary in size (longer lasting
transmitters are larger) but can typically be described as
being the size of a AA battery. Following surgery, snakes are
stitched up and allowed to recover in the lab for three days
before being released back where they were initially captured.
One of the man-made structures on South Bass Island that we found LEWS
using for hibernation. As you can see, there were many snakes that seemed
to be using this particular site!
Natural rock crevices and large rock piles like the ones pictured above at
the South Bass Island State Park also serve as good LEWS hibernation
To see photos of us taking data on this
snake and to read more about the
telemetry project during the first year
of the study, visit the following link:
Doug Wynn surgically inserting a transmitter into an adult
Lake Erie watersnake.
Radio-Telemetry of the
Lake Erie watersnake