Emydura krefftiiKrefft’s River Turtle

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Geographic Range

The Fraser Island short-necked turtle is found only on Fraser Island off Australia's eastern coast. This is the world's largest sand island with a length of 124 km and a width of 24 km at it's maximum. The turtles live in numerous fresh water lakes on the island.

Habitat

A number of the lakes they reside in are murky. As a result, sunlight is unable to penetrate the surface, causing a deficiency in plant nutrients and high acidity. These lakes have low levels of phytoplankton as compared to the tea-colored and clear lakes on the island. The highest turtle populations occur in humified tea-colored lakes where there is complex vegetation growth near the shore. Turtles from the clear Lake MacKenzie appear to have optimal conditions, yet this lake contains one of the smaller populations. Since the turtles seem to survive in several types of lakes, it is undetermined which habitat characteristics best suit them.

Physical Description

The Fraser Island short-necked turtle is so called so because it's head and neck combined do not equal the length of the shell. The head is smooth and there are five claws on each of the webbed forelimbs and four on the webbed hindlimbs. The plastron is white, or a creamy gray. The carapace and limbs are very dark. Most Emydura present on the mainland have a yellow stripe behind the eye, however those on the island appear to be missing this feature. Yet, they both have a characteristic yellow stripe extending from the lower jaw to the side of the neck. Several populations on the island differ in carapace color, from dark to light brown, depending on which lake they reside in. Sexual dimorphism is represented by, the noticeably longer and stronger tails of mature males and the deeper shells and broader heads of the females.

Reproduction

Males are mature at about seven to ten years when their shells are 106-115 mm in length. Their spermatogenic activity is highest in autumn to early summer, coinciding with mating which occurs in autumn, late winter and spring. Females usually mature by seven to eight years and have shells 150-155 mm in length. Ovulation occurs from late winter until mid-summer. Three clutches of hard-shelled ellipsoid eggs are laid per season with each clutch containing 4-10 eggs. Recently mature females lay about 12 eggs per season whereas fully grown females may lay 30 eggs per season.

Nest sites are typically located close to the water in open sandy patches. After 69-74 days the turtles begin to hatch from their shells. This can take anywhere from 12-48 hours after the initial cracking of the shell. The newly hatched turtles crawl around for the first 12 hours before venturing into the water and usually do not eat within the first 48 hours.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    15.8 years
    AnAge

Behavior

The turtles are active throughout the year with seasonal cycles of activity correlating to the environmental temperature. They are diurnally active with peaks of activity in the mornings and afternoons. In addition, growth is also seasonal with a cessation in the winter months. Juveniles grown much faster than adults, and females faster than males.

Food Habits

The omnivorous Fraser Island short-necked turtles have a broad range of food considering their habit is often nutrient deficient. The smaller, younger turtles are mostly carnivorous, relying on aquatic and terrestrial insects, and crustaceans. The larger adults are more omnivorous, feeding on a greater variety of insects as well as plants. The turtles usually feed at or directly below the water's surface. They submerge their head, expelling bubbles through their nostrils and then swallow the food. This routine is completed eight to ten times before they rest and repeat it again.

Conservation Status

The turtles are protected under Queensland wildlife legislation, and exportation is prohibited under the 1982 Wildlife Protection Act. However, the turtle is vulnerable due to the instability of its habitat. Therefore, the Queensland Forestry Department has set aside 23 "Beauty Spots" for special protection, and has strictly regulated tourism activities in this region to prevent nutrient enrichment by detergents and sewage. In addition, the Queensland Government stopped logging of the island's forests in 1991, and the island has since been recognized as a World Heritage Area.

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

Suborder Pleurodira The precise species name of the Fraser Island short-necked turtle is still awaiting decision. It is most closely related to Emydura krefftii. Detailed comparisons with its mainland relatives should determine the species.

Contributors

Nicole Burns (author), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Georges, A. and McNicol, K. (1980). Observations on the eggs and hatchlings of Emydurakrefftii from Fraser Island. Herpetofauna 12(1):10-12.

Georges, A. (1982). Diet of Australian Freshwater Turtle Emydura krefftii (Chelonia:Chelidae), in an unproductive lentic environment.

Georges, A. (1983). Reproduction of Australian Freshwater Turtle Emydura krefftii. Journal of Zoology 201(3):330-350.

Georges, A. and Legler, J. (1997). The Fraser Island Short-Necked Turtle. http://aerg.canberra.edu.au/pub.acrg/hcrps/fnfraser.htm#taxonomy.

Gotch, A.F. (1995). Latin Names Explained. Cassell plc. pp60-63.

Legler, J. (1976). feeding Habits of Some Australian Short Necked Tortoises. Victorian Naturalist 93(2):40-43.