The Turtles of Lake Champlain

Basking map turtles. Photo by Megan Epler Wood.

Basking map turtles. Photo by Megan Epler Wood.

by Lake Champlain Committee Staff Scientist Mike Winslow

Warm days, particularly in the spring and fall, bring out hordes of sunbathing turtles. Sometimes it can even be hard for them to find a place to set their shell. There are five species of turtle that might be spied on the lake. Most people are familiar with snapping and painted. The other three species are at the northern limit of their range in Lake Champlain. However, map turtles are the species most likely to be seen on the lake. Musk turtles or stinkpots are limited to scattered marshy locations in the Champlain Valley. Eastern spiny softshell turtles are restricted to the northeastern portion of the lake particularly around the Missisquoi Bay Causeway. A sixth species, the wood turtle, can be found in the Champlain Valley but it is more terrestrial and thus unlikely to be seen in the lake.

Basking is a necessary activity for turtles. They use external heat sources to maintain their body temperature, unlike mammals and birds. When basking they may extend their heads or legs to soak up even more sun. Their dark shells also aid in absorbing heat. While groups of turtles resting on a log may look like the epitome of laziness, they are actually performing a vital life function.

The heat absorbed from basking fuels physiological activities. Basking is essential for food digestion, so turtles that do not have sufficient exposure to sunlight grow more slowly; and time of first reproduction is tied more to turtle size than age. Basking is critical for egg development, and since many species lay eggs in May the turtles have to get to sunny spots very soon after leaving hibernation. Basking assists with immune response. Exposure to sunlight kill algae and microorganisms that might grow on the turtles’ shell and helps dry the area beneath the shell thus preventing bacterial and fungal infections.

On windy days less basking occurs because the wind sucks heat from the turtles. Instead, they sit partially submerged, absorbing sunshine but letting the water provide insulation from the wind.

Snapping turtles are the largest and perhaps most common turtles throughout our area. Adults average ten to thirty five pounds but specimens up to seventy five pounds have been recorded in the wild. Their aggressive nature and muscular jaws help protect them since the portion of their shell covering the belly is quite small compared to other turtles and they can’t pull their heads completely into their shells. Such traits are fine for the safety of a pond bottom but not for moving over land. Snappers rarely bask and when they do they are most likely to stay partially submerged. They are omnivorous and eat plants besides the occasional live bird. They lay large clutches, typically twenty to thirty eggs but clutches of over eighty have been reported. The temperature of eggs during key periods of incubation determines the sex of the young. Cooler eggs produce females, warmer eggs males, but hot eggs (over 77oF) produce females. Temperatures vary within a nest.

The painted turtle is another common turtle. They sport smooth unkeeled shells and have handsome red and yellow markings along their face, neck, and the outer scutes of their shells as well as a pair of bright yellow spots behind each eye. Like snappers, they prefer shallow weedy areas with muddy bottoms. Unlike snappers they bask in large groups sometimes atop one another. The typical nest contains six eggs but may have as few as two or as many as twenty. Females construct nests by digging a narrow four inch deep hole in sandy soils, roadsides, lawns, or fields near water. Once the eggs are laid and the nest covered they can be very difficult to find.

Unlike the previous two species, map turtles prefer large water bodies and in our region are restricted to Lake Champlain. In fact, if you are travelling on the lake this is the turtle species you are most likely to see basking. Their limbs and head are patterned with a maze of dark and light stripes and whorls as are the shells of young. Map turtles principally feed on snails and crayfish. They build nests on sandy unshaded beaches where they deposit six to twenty eggs. Young will occasionally overwinter in the nests.

The Northern musk turtle or stinkpot earns its name by releasing a musky secretion. These small turtles with two light yellow lines along the side of their head are strongly aquatic and only occasionally bask in the open. When they do they may climb thin slanting trees and have been recorded up to six feet above the water surface. They prefer still waters and have hair-like barbells on their chin and throat which help them hunt in murky environs. Their nests contain one to nine eggs with four or five typical. As with snapping turtles, nest temperature determines the sex of the young.

The Eastern spiny softshell turtle is the most distinctive of our turtle quintet. Instead of a hard rounded shell they wear a flat leathery one, and their nose is sharply pointed. Peterson reptile and amphibian field guide describes them as animated pancakes. In most of their range they inhabit large rivers, making the Lake Champlain population, which is separated from any nearby populations, somewhat distinct. They are strong, surprisingly fast swimmers. They are a threatened species in Vermont because of their very limited population.

If I ever get reincarnated I would like to come back as a turtle. You spend your summer days lazing in the sun and when it gets too hot, just drop in the water for a cooling dip. Then you sleep all winter. I am sure the algae and leeches get itchy after a while but all in all it sounds like an appealing life.