Snapping Turtles Flashcards
What is the taxonomy of snapping turtles?
Reptilia
Eurepetilia
Testudines
Cryptodira
Chelydridae
Chelydra
serpentina
(Vitt & Caldwell, 2014 pg.533)
How can you tell a male and female snapping turtle apart?
Males are usually bigger than females.
Males have the anal vent posterior to the carapacial rim and a preanal tail length usually >120% of the length of the posterior plastron lobe.
Females have the anal vent beneath or just under the carapace rim; their preanal tail length is usually <110% of the length of the posterior plastron lobe.
i.e.,
(posterior lobe = PL; plastron base to cloaca = BC)
length PL > length BC = cloaca closer to shell = F
length PL < length BC = cloaca further from shell = M
(Ernst and Lovich, 2009)
What DO levels can snapping turtles withstand? When is this most important?
They have been found to hibernate in a wide range of dissolved oxygen levels (e.g., 0.55–15.63 mg/L).
Dissolved oxygen levels impact turtles the most during the winter.
(G. P. Brown & Brooks, 1994; Marshall et al., 2021).
What is the home range of a snapping turtle?
Their home ranges vary by season and by sex with females having larger home ranges.
One study in Ontario found the home range to be anywhere from 0.95 to 8.38 ha.
(Obbard & Brooks, 1981; Paterson et al., 2012)
What is the scientific name for the snapping turtle?
Chelydra serpentina
What habitat do snapping turtles prefer? How does it change as they age? Why?
Turtles in general have a high preference for using wetlands globally.
Snapping turtles are capable of living in most freshwater habitats within its range but show a preference for muddy bottoms, slow-moving water, and abundant vegetation or submerged tree trunks.
When young, they’re usually in shallower water - the shift to deeper water could be due to need for larger prey.
(Cox et al, 2022; West, 2008; Ernst and Lovich, 2009)
Why are snapping turtles special concern?
Has a unique life history that makes it especially vulnerable to anthropogenic threats.
These turtles only have one clutch per year, though some females skip a year of nesting and the eggs are heavily predated on.
Furthermore, snapping turtles are not able to reproduce until they are between 11 and 16 years old and of the eggs that do survive predation, up to half can be infertile.
These reproductive challenges result in snapping turtle recruitment rate being so low that any death of an adult (e.g., by road mortalities to find nesting sites, or by predation during hibernation) can ultimately cut the size of the population in half.
For these reasons, snapping turtles are listed as special concern under the Species at Risk Act as well as specifically within in Ontario.
How do snapping turtles breathe under ice? Reduced DO?
They reduce their activity/hibernate so they don’t require as much oxygen.
Cutaneous gas exchange has been suggested to be part of it.
But they are also able to survive in anoxic conditions and thus also use anaerobic respiration.
(West, 2008)
How is temperature related to snapping turtle reproduction?
It triggers the depression (in fall) and stimulation (in spring) of gonadal growth.
(Mahmoud & Alkindi, 2008)
Describe snapping turtle reproduction.
Don’t start reproducing until ~17 years old in ON.
They have one clutch per year (or sometimes none).
Usually nest near water. Soil must be moist and sandy and in an open area.
Large clutch sizes with small eggs.
Their reproductive period is roughly from May to September.
In Algonquin Park they have been found to lay their eggs between
mid-May to late June (find ref I read this in).
Migrate to find nests - sometimes more than 11km and over same routes.
Frequently nest early in the morning or in the evening.
Take 75-100 days to hatch - they emerge from late August to early October.
(Congdon et al, 2008; Mahmoud & Alkindi, 2008)
How does stress impact snapping turtles?
It increases production of various hormones such as glucocorticoids which can suppress immunity, growth, and reproduction.
(Mahmoud & Alkindi, 2008)
Describe basking and thermoregulation in snapping turtles.
Basking is a form of thermoregulation.
They don’t bask as much as other turtles - they are much more aquatic. More often, they thermoregulate by finding an area with the appropriate water temperature.
Therefore their body temperature is usually the same as water temperature, however, because of their large size they can often keep their body temperature slightly above water temperature.
It’s thought the purpose of basking is to aid digestion and reproduction.
(Spotilla & Bell, 2008)
What do snapping turtles eat? How is this related to their size?
They are mostly carnivorous.
Eat annelids, crustaceans, insects, gastropods, amphibians, turtles, snakes, birds, muskrats, and some plant material.
They are also attracted to and eat carrion.
Their carnivorous diet is why they are much bigger than other freshwater turtles.
(Spotilla & Bell, 2008)
Describe the overwintering of snapping turtles.
Snapping turtles overwinter underwater though sometimes hatchlings overwinter within their nests during the first year (though this often results in the hatchlings freezing and dieing).
Can survive up to 150 days in 3 degrees C water.
Often hibernate in shallower flowing water since its well oxygenated i.e, stream bottoms and beneath debris. Also found to hibernate in marshy areas burried in mud.
They have been found to hibernate in groups and individually and they don’t always use the same site.
Usually start hibernating from late August to late September in ON.
(Ultsch & Reese, 2008)
When are snapping turtles most active?
They are diurnal - so most active during the day and rarely at night.
“Most summer activity in Ontario is in the morning or early evening.”
Females are mostly inactive in May while males are very active looking for mates.
Females very active late May and early June while nesting.
(Ernst and Lovich, 2009)
When do snapping turtles emerge from hibernation in Ontario?
Usually late April when water temperatures reach ~5-7.5C.
(Ernst and Lovich, 2009)
When do snapping turtles enter hibernation?
Usually by late October when water temperatures reach 5C.
(Ernst and Lovich 2009)
At what temperature do snapping turtles feed?
Usually above 15-16 C.
(Ernst and Lovich 2009)
What are some variables associated with the preferred hibernacula for snapping turtles?
- Water shallow enough to let the turtle reach the surface to breathe without having to swim upward but deep enough to prevent its freezing to the bottom.
- A location that is likely to be the last to freeze over and/or the first to thaw.
- Mud deep enough for the turtle to bury itself.
- Some additional cover, such as vegetation, brush, a muskrat or beaver dwelling, or an overhanging bank.
(Ernst and Lovich 2009)
Why do snapping turtles survive better in normoxic waters in the winter than some other turtles?
They can “use extrapulmonary gas exchange, and at 4C they can derive over 11% of their aerobic O2 demand from the water” unless it buries itself too deep in the mud as mud is anoxic.
(Ernst and Lovich 2009)
