The red-eared slider is primarily diurnal. It is in the daylight when most of its interesting behaviors can be observed. Some of these include feeding habits, basking, and overwintering.

Feeding Habits

Alderton, 1988

The red-eared slider, like many turtles is known for its opportunistic feeding strategy (Gibbons, 1990). It forages using both visual and olfactory cues. However it is the visual detection of food items, particularly moving prey that is of primary importance to its foraging success. The red-eared slider’s special interest in moving prey has been observed personally in my own turtles while feeding them live arthropods. They both appear to get very exited at the site of a struggling insect floating on the surface of the water, and will waste no time being the first to ingest it. It would seem that the movements of prey act as a visual cue that elicits feeding behavior. This phenomena has also been observed in the wild (Gibbons, 1990).

Red-eared sliders can usually be found foraging at depths between one to three meters deep. Water with depths greater than three meters are traversed quickly or avoided altogether (Moll and Legler, 1971; Hart, 1983). The red-eared slider’s preference of shallow water may explain its success in Cootes Paradise. Since Cootes is generally very shallow, this allows for a large foraging area as opposed to being limited to the shoreline vicinity.

Trapping records indicate that the greatest feeding activity occurs during the hours of early morning (Earnst, 1972). On average these turtles spend 6.8 hours of and 11 hour day foraging. It has been observed that while searching for food juvenile turtles spend between 20 seconds to 5 minutes underwater compared to the 5 to 6 minutes of adults (Moll and Legler, 1971).

While foraging the red-eared slider swims slowly beneath the water’s surface, periodically poking its head into clumps of vegetation. Presumably it does this in order to flush out any hidden invertebrates. Once prey is detected a chase ensues that ends in either capture or abandonment of the pursuit depending on the speed of the prey. Red-eared sliders (particularly juveniles) are known to chase small fish, tadpoles, frogs and small invertebrates. Once captured the prey is swallowed whole if possible, however if it is too large these turtles can rip their victims into smaller pieces using their powerful jaws and clawed forelegs (Gibbons, 1990).

Another interesting behavior associated with foraging in pond sliders is neustophagia. This type of feeding is similar to that of a baleen whale and acts as a crude filtration process. This process starts by the turtle skimming the water’s surface with it’s lower jaw. In doing this it ingests any small floating food particles along with some water, and stores these in its pharynx. The turtle then closes its mouth and forces the water out through the nostrils. The remaining food particles are then swallowed (Gibbons, 1990).

Within red-eared slider populations a foraging strategy shift has been observed between the adult and juvenile stages. It would seem that as the juvenile turtle matures its habitat shifts from the relatively quiet shallows to the deeper waters. This shift in foraging habitats is believed to be linked to the dietary shift that these turtles make as they mature, and will be discussed later (Hart, 1983).

Basking

Photograph by Roland Planeta

Basking is perhaps the turtles most well know behavior. Like most other turtles red-eared sliders frequently climb up onto rocks, logs or shoreline in order to bask in the sun. However they can also bask while floating at the surface. These turtles can even be seen stacked on top one another while basking. This phenomena has been observed with my two turtles. It starts with one turtle climbing up onto the basking rock in the aquarium. It then settles under the heat of the lamp and proceeds to stretch out its hindlegs orienting them perpendicular to the lamp rays. This orientation has been observed to be effective in heat transfer (Crawford, Spotila and Standora, 1983). The second turtle takes notice and also begins climbing onto the basking rock. The interesting part is that even though the basking rock is big enough for both turtles, the second one will usually attempt to climb onto of the first one in order to bask (presumingly to get closer to the heat source). However as the second turtle attempts to mount, the first one will begin a series of movements in order to shake off it’s neighbour. These movements include simply moving away, quick vertical displacement by raising it’s aboral end, and rocking. The latter is accomplished by standing on it’s hindlegs thereby raising its back end, and then initiating a rocking motion (wiggling it’s behind). This procedure usually displaces the invading turtle. However if these movements do not succeed after a period of time the turtle will stop and allow the second one to climb on top.

Photograph by Roland Planeta

Red-eared sliders usually bask from midmorning to midafternoon on sunny days, and late afternoon on days with cloud cover. Basking behavior is believed to be primarily used for thermoregulation, however it is also thought to serve other purposes. One such purpose is drying which hinders the growth of epizoic algae (Neill and Allen, 1954) and induces the removal of ectoparasites. Another is a means of promoting the synthesis of vitamin D from the sun’s rays which are essential for proper shell growth (Cagle, 1950).

Thermoregulation is an important issue in the life of a red-eared slider, and basking is the primary source of heat (Cagle, 1950). Being poikilotherms, these turtles rely on body temperature to dictate their activities. For example at low temperatures the movement of red-eared sliders (as with most turtles) becomes very limited.

The effects of temperature on digestion has also been an area of continued study. Some experts believe that the efficiency of the digestive system increases with elevated temperatures. For example higher body temperatures induce greater gastric acid and enzyme secretion. Therefore basking behavior may allow red-eared sliders to optimally regulate digestion through the control of body temperature. The fact that elevated body temperatures aid in digestion, and basking is a means of obtaining these body temperatures, can be used in explaining why these turtles feed during the morning hours and bask in the afternoon (Kenyon, 1925; Gibbons, 1990).

Overwintering

Red-eared sliders are active at temperatures between 10 C to 37 C, with the critical maximum around 41 C (Cagle, 1950). This data would indicate that when the temperature drops below 10 C (usually around October) and these turtles can no longer feed, they must go into hibernation in order to survive the winter months. Most red-eared sliders hibernate underwater by burying themselves in the sediment or mud. However some seek protected places near the water-line such as muskrat burrows or hollow stumps. Red-eared sliders are known to come out of hibernation on warm days and can be found basking out on logs and rocks (Earnst, 1972).