Mary River crocodile: cold snap does not stop search
THE drop in temperature in the Gympie region this week has not impacted the search for two crocodiles spotted by wildlife officers in the Mary River near Maryborough last month.
An Environment and Heritage Protection spokesman said on Friday wildlife officers from the DEHR were continuing their efforts to capture two crocodiles known to be in the Mary, one of them 4.5m long and the other 2.5m.
There is no evidence that the crocodiles have left the area and it is very important for members of the public to continue to exercise CrocWise behaviour at all times, the spokesman said.
A floating trap has been deployed at Graham's Creek and is being monitored by remote camera. Wildlife officers are rebaiting the trap on a weekly basis.
It could take some time for the animals to lose their natural wariness around the trap and members of the public can assist by avoiding the area if possible.
A daytime vessel-based survey of the Mary River was conducted on Thursday, April 28, 2016, from Lamington Bridge downstream to Walker Point and Saltwater Creek at low tide. No evidence of crocodiles was observed.
"Survey cameras have been positioned along the river near Graham's Creek and are being checked regularly. Further river bank surveys in the area are also planned.
"Members of the public are strongly encouraged to report all crocodile sightings to EHP as soon as possible on 1300 130 372.
"Photographic evidence is helpful, but only if it can be obtained safely."
Crocodiles are highly mobile and capable of travelling long distances, with some animals known to cover more than 40km in a single day.
It is therefore not unexpected to receive multiple sightings of a single animal over a short period of time.
"Timely reports from the public of crocodile sightings greatly helps EHP to determine the movements of these animals and to plan their capture," the spokesman said.
"It is very important to exercise CrocWise behaviour at all times. In particular:
•Obey croc warning signs
•Don't swim or let domestic pets swim in waters where crocs may live
•Be aware that crocodiles also swim in the ocean
•Stand back from the water when fishing or cast netting
•Never provoke, harass or feed crocs
•Never leave food, fish scraps or bait near the water, a camp site or boat ramp
•Never interfere with or fish or boat near crocodile traps, and
•Always supervise children
•Remember, you are responsible for your own safety in croc country.
Things you might not have known about the Mary River crocodile
Estuarine crocodiles like the Mary River croc are found in India, throughout South-East Asia and New Guinea, in northern Australia, Vanuatu and the Solomon Islands. In Queensland, they are known to live between Gladstone and Cape York Peninsula, and throughout the Gulf of Carpentaria.
Although most commonly seen in tidal reaches of rivers, they also live in freshwater lagoons, rivers, and swamps hundreds of kilometres inland from the coast. They can even be found along beaches and around offshore islands in the Great Barrier Reef and Torres Strait.
Often observed basking on the banks of watercourses where they are generally inactive, crocodiles are less likely to be seen when they are in the water. Livelier in the water, crocodiles can swim just below the surface, with only their eyes and nostrils visible.
Crocodiles are one of the few reptiles to have a 4-chambered heart (like mammals). They can also stay underwater for extended time because they can slow their heart rate, allowing them to hold their breath for longer.
However, they cannot maintain strenuous activity for long periods and can easily become exhausted while capturing prey or fighting other crocodiles. Extreme exertion is done anaerobically (without oxygen) and must be followed by a period of rest so that the â€˜oxygen debtâ€™ can be repaid to their muscles. The result of anaerobic activity is a build-up of lactic acid in the blood. Although crocodiles can withstand higher levels of blood acidity than other animals, sometimes it can be fatal.
Crocodiles are large and skilful predators that hunt by stealth. Their muscular tail propels them through water and allows them to lunge forward with great power and speed. It can also be used to thrust them vertically to capture a bat or bird in mid-flight or in foliage.
Crocodiles can see underwater due to a transparent lid that closes over their eye to protect it. They also have excellent night vision, due to a specialised retina, as well as a good sense of smell. Small sensory buds around the top and bottom jaws allow crocodiles to detect vibrationsâ€"crucial when hunting in murky water.
Crocodiles are opportunistic feeders that eat a variety of animals. Their jaws have immense crushing power, enabling them to easily break through skulls and other bones. Prey is not chewed but swallowed as large chunks. If the chunks are too big to swallow whole, the crocodile may roll several times or shake its head in an attempt to break off a smaller piece. Although their stomach secretions are highly acidic, they cannot digest some items, such as fur, hooves and turtle shells. These items collect in the stomach and may either be passed through undigested or turned into â€˜hairballsâ€™ and regurgitated later.
Studies have shown that crocodiles can convert as much as 50-70% of their food into growth and energy. By contrast, humans use only up to 80% of our food is used to produce heat and maintain a constant body temperature. This efficiency in crocodiles means that they can go for months without eating.
People and crocodiles
Traditionally, Aboriginal and Torres Strait Islander peoples have had a special relationship with crocodiles. They are the focus of stories, songs, dances and art. Some groups regard crocodiles as religious icons or totems, while others believe they are spirits of ancestors. Crocodiles are also a food source for some traditional groups who take eggs from nests and hunt adults.
Commercially, crocodiles are now an important resource. Farmed crocodile meat is a gourmet item on many menus around the world, and their skins are recognised as a durable leather that is made into a variety of products. Crocodiles are also a major tourist attraction throughout northern Australia, both in the wild and in wildlife sanctuaries.
Vulnerable to extinction
Until 1974, estuarine crocodiles in Queensland were hunted close to extinction for their prized skins. Both species are now protected in Australia, but their numbers continue to be threatened.
It is estimated that less than 1% of eggs laid by estuarine crocodiles hatch and survive to adulthood. Overheating, flooding and predation by goannas and feral pigs claim an estimated 70-80% of unhatched embryos. From the small numbers that do hatch, more than half die in their first year of life, mainly from predation by birds of prey, fish, snake-necked turtles and other crocodiles. Once they reach maturity their only enemies are each other and humans.
Habitat destruction is now considered a major threat to crocodile survival in Queensland. Increasingly, humans are crowding crocodile territory developments in swamps, mangroves and rivers are displacing crocodiles from their homes.
The growing human population along the east coast of Queensland ultimately means more frequent encounters with crocodiles. Unless the community values crocodiles and their habitats, it will be a challenge to ensure their long-term conservation.