When you see a Snapping Turtle on land, its head is often only a few inches out of its shell, but don’t be fooled! The length of its neck can be up to two-thirds the length of its shell and if threatened it can quickly extend its neck all the way out. (Keeping yourself out of reach is wise. However, come June, when female Snapping Turtles often are found crossing roads when they leave their ponds to lay eggs, rescuing them from oncoming cars usually calls for close proximity to them. To hold and transport them (to the side of the road they were headed), just grab the back end of the shell, where their head can’t quite reach your hands.)
Their long neck allows Snapping Turtles to capture prey such as fish, frogs and crayfish from a distance. When in shallow water, they can lie on the muddy bottom of the pond with only their heads occasionally exposed in order to take an occasional breath. If you look closely at a Snapping Turtle’s head (see photo), you will see that their nostrils are positioned on the very tip of their snout, effectively functioning as snorkels.
It’s that time of year again, when female Snapping Turtles are leaving ponds, digging holes in sandy soil and depositing up to 80 eggs (20-30 is typical) before covering them up and returning to their ponds. While the sex of most snakes and lizards is determined by sex chromosomes at the time of fertilization, the sex of most turtles is determined by the environment after fertilization. In these reptiles, the temperature of the eggs during a certain period of development is the deciding factor in determining sex, and small changes in temperature can cause dramatic changes in the sex ratio.
Often, eggs incubated at low temperatures (72°F – 80°F) produce one sex, whereas eggs incubated at higher temperatures (86°F and above) produce the other. There is only a small range of temperatures that permits both males and females to hatch from the same brood of eggs. The eggs of the Snapping Turtle become female at either cool (72°F or lower) or hot (82°F or above) temperatures. Between these extremes, males predominate. (Developmental Biology by S. Gilbert)
If the cool temperatures we’ve experienced thus far this spring continue, there could be a lot of female Snapping Turtles climbing up out of the earth come September. (Thanks to Clyde Jenne and Jeffrey Hamelman for photo opportunity)
Congratulations to Elizabeth Hall, the first reader to correctly identify the trail blazer in the previous NC post!
As you can see from the dirt piled on this Snapping Turtle’s head, it has just emerged from hibernation. After extracting themselves from their muddy hibernacula, Snapping Turtles have two missions: to raise their body temperature and to secure food. According to Jim Andrews, Director of the Vermont Reptile and Amphibian Atlas (https://www.vtherpatlas.org/ ), the first movement of the year for these turtles is often to seek shallow water where they can bask in the sun and heat their internal organs. They also are on the move in order to get from their overwintering site (shallows of ponds, marshes, and lakeshores, in a spring or a stream) back to a feeding area. It won’t be long before they will be searching for mates.
Most Snapping Turtles have entered hibernation by late October. To hibernate, they burrow into the debris or mud bottom of ponds or lakes, settle beneath logs, or retreat into muskrat burrows or lodges. Once a pond is frozen over, how do they breathe with ice preventing them from coming up for air?
Because turtles are ectotherms, or cold-blooded, their body temperature is the same as their surroundings. The water at the bottom of a pond is usually only a few degrees above freezing. Fortunately, a cold turtle in cold water/mud has a slow metabolism. The colder it gets, the slower its metabolism, which means there is less and less of a demand for energy and oxygen as temperatures fall – but there is still some.
When hibernating, Snapping Turtles rely on stored energy. They acquire oxygen from pond water moving across the surface of their body, which is highly vascularized. Blood vessels are particularly concentrated near the turtle’s tail, allowing the Snapper to obtain the necessary amount of oxygen to stay alive without using its lungs.
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Newly-hatched Common Loon chicks can swim as soon as they hit the water, which they do as soon as their down dries after hatching, usually within 24 hours. Their buoyancy and lack of maneuverability, however, leave them vulnerable to predators. Parents usually don’t stray far from their young chicks due to the omnipresent threat of eagles, hawks, gulls, large fish and snapping turtles. During their first two weeks, young loon chicks often seek shelter (and rest) on the backs of their parents.
Leeches are segmented worms (annnelids) which feed predominantly on blood, although some species do eat insects. Of the 700 species of leeches, 500 inhabit fresh water, as opposed to salt water or land. Blood-sucking leeches are common parasites of many freshwater vertebrates including turtles, amphibians and fish.
Generally speaking, leeches of the genus Placobdella are commonly found on turtles. Bottom-dwelling species such as the Common Snapping Turtle, Mud Turtle and Musk Turtle usually have more leeches than other turtles, and they are often attached to the skin at the limb sockets. Aerially-basking species such as Painted Turtles often have fewer of these parasites, possibly because basking forces leeches to detach in order to avoid desiccation.
A leech can ingest several times its weight in blood from one host before dropping off and not feeding again for weeks, or even months. Leeches inject hirudin, an anesthetic, to keep the hosts from feeling them break the skin. They also inject an anticoagulant to keep the blood from clotting so that they can feed. Although leeches (especially large ones) can be a significant health detriment to smaller animals, they are not harmful to most large animals, such as Snapping Turtles.
Some of the most common predators of leeches include turtles, fish, ducks, and other birds. Map Turtles allow Common Grackles to land in basking areas and peck at leeches clinging to their skin, and minnows have been seen cleaning leeches from Wood Turtles in the water. At times turtles bury themselves in ant mounds to rid themselves of these pesky parasites.
For those readers who may hesitate before going into a leech-laden pond, it may be comforting to know that leeches are mainly nocturnal. (Photo by Jeannie Killam)
Female Snapping Turtles spend a lot of time and effort finding suitable sandy soil in which to dig their nest and lay their eggs. Some turtles have been found laying their eggs as far as a mile from the nearest water source. Once she has laid her eggs and covered them with soil, the female snapper returns to her pond, leaving her eggs to hatch on their own, and the hatchlings to fend for themselves.
It is estimated that as many as 80 to 90 percent of all turtle nests are destroyed by predators, weather conditions and accidental disturbances. Most of the damage is done by predators – skunks, raccoons, foxes, crows, among others. Most nests are discovered by smell, and most are raided at night. The fluid that coats the eggs, that is lost by the mother during egg laying or is lost through breaks in the eggs, produces a smell that is easily detected by predators. While a majority of nest raids happen within the first 48 hours of the eggs being laid, studies have shown that predation occurs over the entire incubation period (June – September). The pictured Snapping Turtle nest was dug up and the eggs consumed 10 days after they were laid.
If you are aware of a spot where a turtle dug a nest and laid eggs, you can try to protect the nest from predators by placing either a bottomless wire cage or an oven rack over the nest site, and putting a heavy rock on top. The tiny hatchlings will be able to escape through the openings but hopefully, if the rock is heavy enough, raccoons and skunks will become discouraged and give up trying to reach the nest.
The next Naturally Curious post will be on 7/5/17.