The thought of animals in hibernation, usually conjures images of grizzly bears in freezing arctic climates seeking shelter from icy temperatures. In Australia, there are few landscapes as cold and harsh, but during the colder months, one of the Park’s most common reptilian residents – the freshwater turtle – escapes the winter chills by going into a period of hibernation.
Like all cold-blooded creatures, turtles cannot control their own body temperature, so they have developed the unique ability to go into a state of inactivity to cope with the lower temperatures. During this dormant period, turtles rest on the bottom of the pond or beneath a fallen log, sometimes huddling together in groups. Their pulse rate and breathing slows down and their appetites decrease. Instead of feeding, they use the fat reserves in their body stored during summer, to provide just enough energy to keep their body functioning.
The drop in water temperature that triggers this sleepy winter existence varies from place to place but is usually around 11° celsius. Turtles require little oxygen during their winter siesta, but an amazing, although somewhat unusual practise, is for them to ‘breath’ through their bottoms! This enables them to exchange oxygen and carbon dioxide from the water.
When warmer conditions return at the start of spring, turtles will become more active again and search the ponds for aquatic insects and small fish to replenish their food stores in preparation for the busy mating season ahead.
The Sydney basin turtle (Emydura macquarii), and the snake-necked turtle (Chelodina longicollis) are the most commonly seen of the five native species recorded in Centennial Parklands.
They can sometimes be seen basking on tree branches, drain covers and the banks of the ponds during warmer months. Turtles have been spotted in Randwick, Lily, Busby’s and Kensington ponds where the vegetation offers shelter and sloping banks provide good access to the water.
Less commonly seen species are the northern snapping turtle (Elseya Dentata) and the broad-shelled turtle (Chelodina Expansa). There has also been one recorded sighting of the Mary River turtle (Elusor macrurus).
The female turtle comes ashore to nest, laying her eggs in sandy substrate with enough sun to aid incubation. Predators of turtle eggs include dogs and foxes, which are drawn to the nest by smell.
The freshwater turtle’s diet varies and includes insects, algae and weeds. In Centennial Park, turtles can often be seen crossing roads to travel between different ponds so drivers need to be careful, especially during warmer months.