Past ReSearch:
Telemetry
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 goal of this project was to obtain information on these little known aspects of LEWS biology by utilizing radio-telemetric observation. Of special interest were the locations 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 guidelines recommended by USFWS. So where do you stick a transmitter on a snake? Actually, we put them inside the snake's body (see photo to the right)! All of our transmitters were surgically implanted by a veterinarian or skilled professional. Snakes were placed under anesthesia while we performed the surgery. A small incision was made toward the beginning of the lower third of the snake, then the body of the transmitter was inserted just under the rib cage of the snake and attached to a rib. The 8-inch-long antenna was placed just under the skin running toward the head. We used 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 were stitched up and allowed to recover in the lab for three days before being released back where they were initially captured. |
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.
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 graphs, 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) inland from the 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 F. 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 temperatures.
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 watersnakes 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 areas as in the photo below, indicating that several snakes may be utilizing certain sites.
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 habitat.
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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!
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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 to the right. |