ROADS AND TURTLES
Mortality of turtles crossing roads is a significant threat to turtle populations in regions undergoing rapid human development. A project directed to understand the threats that roads pose to freshwater turtles, and methods to mitigate such threats, has been established by the Institute for Applied Ecology at the University of Canberra. The project receives funding from the US Society for Wetlands Scientists with additional support from Booderee National Park and the New South Wales Parks and Wildlife Service.

For further information ...
John Roe, Institute for Applied Ecology
University of Canberra, ACT 2601
Phone (02) 6201 2937
roe@aerg.canberra.edu.au

Arthur Georges, Institute for Applied Ecology,
University of Canberra, ACT 2601.
Phone (02) 6201 5786
georges@aerg.canberra.edu.au

Growing demands upon our freshwater resources to meet human needs for industry, agriculture, and cities have caused the decline, disappearance, or alteration of freshwater wetlands and associated aquatic animal communities worldwide, including in Australia. A large proportion of our wetlands has been destroyed or seriously disturbed, and the banks of most rivers have been damaged. As a result of these changes to Australia's inland waters, many species of aquatic animals are endangered, in decline or already extinct.
The value of services to the community provided by healthy inland waters and their ecosystems – the quality of the water we use and the non-consumptive values – is becoming better appreciated, especially as we count the cost of replacing those services through desalinization plants and other techno-fixes or the prohibitive costs of restoring those services through habitat rehabilitation. It is widely recognized that maintaining aquatic habitats in good condition is also important for the unique biodiversity they support – the waterfowl, fishes, turtles, platypuses and the like. Pollution, over-alloation of water, changed flow regimes and exotic and displaced species are all affecting native species.

A wetland is not isolated and independent of what happens in the surrounding terrestrial habitat – the health of a wetland depends critically on the quality and quantity of inputs from the surrounding terrestrial ecosystems – inputs of nutrients, carbon, sediment and other particulates, and pollutants. Terrestial vegetation provides important structural elements to streams and rivers through logfall, and provides seeds, fruits, flowers and insects that are important windfall foods for aquatic animals of all persuasions. The quantity of water run-off is itself greatly influenced by attributes of the surrounding terrestrial environment, particularly tree, shrub and ground cover. The impact of the terrestrial environment on the aquatic ecosystem includes important influences on aquatic species and their ability to survive and thrive. These ecosystem processes have been relatively well studied.

One term in nature's equations has been largely ignored. Many aquatic species depend directly on both the aquatic and terrestrial environments. Many insects have aquatic and terrestrial life phases, frogs live and feed terrestrially, but breed in water where their tadpoles live and grow, and a number of species of bird, mammal and reptile live in riparian zones where they draw on both aquatic and terrestrial resources. Conservation planning for wetlands in the context of development often fails to consider potential threats to aquatic animals that arise from habitat alteration and destruction beyond the immediate wetland boundary. This failure stems in part from misconceptions about the life history and ecology of aquatic organisms, such as turtles.

Why consider what happens in adjacent terrestrial habitats when we attempt to protect wetlands and their biota? How much of the surrounding terrestrial environment must be conserved also? These are questions that are increasingly occupying the minds of conservation biologists, as the dependency of many aquatic animals on terrestrial habitat is revealed. Our study addresses this question in the context of a very special animal, the Eastern Long-necked Turtle.

OUR FAVOURITE BEAST
The Eastern Long-necked Turtle (Chelodina longicollis) was the first Australian freshwater turtle to come to the attention of science. The first specimens were collected by Joseph Banks in 1770 during the Cook voyage. It is well known to most people living in eastern and south-eastern Australia because of its propensity to move overland in the warmer months, following rain. Well intentioned attempts to return the wayward beasts to water results in an unforgettable pungent odour, no doubt designed to deter predators, but also serving the purpose of reducing the resale value of the family car.

It is a long-necked turtle, its head and neck are about as long as its shell, and one of our most terrestrially adapted, though all Australian turtles must be in water to feed. To avoid predation and minimize water loss, the turtles can withdraw their head, tail and limbs completely beneath the shell, unlike many other species, and when they walk, they can lift their shell well clear of the ground to avoid abrasion.

The species is an opportunistic carnivore, feeding on a wide range of benthic, pelagic and planktonic foods. They breed in the spring and early summer, laying between 10 and 25 eggs in a nest with a flask-shaped chamber sealed with a soil plug. Males and females are difficult to distinguish, even as adults.

For more information on this interesting animal, refer to John Cann's wonderful book Australian Freshwater Turtles (Beaumont Press, Singapore, ISBN 0646339778).

WHY DID THE TURTLE CROSS THE ROAD?
What causes a turtle to leave the relative safety of its aquatic habitat? It is a complex question. All but one species of Australian turtle lay their eggs in a chamber that they dig in the ground, so each year female turtles migrate from water to suitable terrestrial nesting sites before returning to water. Some do this several times per year. For many, an ability to move over land is a matter of survival, when drought strikes and their wetlands dry. Moving overland to permanent water is a matter of life and death.

One might expect wetlands that periodically dry to be avoided by turtles, but there are great benefits to being able to invade ephemeral waters when they are flooded. First of all, drawdown and drying of wetlands is important for releasing nutrients that have accumulated and become trapped in the sediments. This explains the great flush of productivity that occurs when an ephemeral wetland first fills after a period of dry. There is considerable benefit to those aquatic organisms that can sit and wait out the dry, or that can move overland to invade the wetlands when they again flood. There is also the advantage of less competition than would be present in permanent waters, because relatively few competing species are able to invade the ephemeral wetlands.

The Eastern Long-necked turtle is one species that capitalizes on these benefits, showing a great preference for life in ephemeral swamps, ponds, farm dams, small seasonally dry streams and even rain pools.

This propensity to move overland in search of ephemeral wetlands when they become inundated makes them an ideal species to investigate the role of the terrestrial environment and the impact of terrestrial habitat modification on populations of aquatic species. Of particular interest is the impact of roads on turtle populations. Regardless of the reason for their migration, when a road lies along the path of where a turtle needs to go, they must cross it.

A CASE STUDY
We are addressing the question of potential road-impacts on turtles with the help of the eastern long-necked turtle, Chelodina longicollis, in southeastern Australia. We plan to:

• Describe their movement patterns and habitat use, with a particular emphasis on their terrestrial ecology;
• Assess their behavioural responses to roads and vehicles;
• Develop predictive models that identify areas of potential high road mortality for turtles in the region;
• Determine if turtle populations inhabiting areas with many roads are structurally different than those at more pristine sites.

To achieve the first objective, we have begun a study at Booderee National Park near Jervis Bay. We have equipped a number of turtles with small radio-transmitters that allow us to locate turtles and follow them throughout their daily and annual movements. We also capture turtles and mark them with a unique identifier code, and when captured again we can determine important information such as growth rates, survivorship, longevity, and movement rates.

Results of this work are beginning to flow in, including a number of surprising aspects of the life of eastern long-necked turtles. They are extremely mobile, moving frequently to and from up to five different wetlands. They often move long distances overland in the process, as much as two kilometres (Figure 1).

Their terrestrial sojourns are not brief. The turtles often move hundreds of meters away from wetlands to burry themselves in sand and leaf litter, where they will remain for months at a time. Why an aquatic turtle would do this, when free-standing water is readily available, is a complete mystery. These turtles are living a secret life on land.

Is it for thermoregulation? Is it for energetic reasons, with the turtles aestivating on land to wait out periods of relative food scarcity? Is it to assist in reducing parasite load? Although significant progress has been made, much more work is needed to provide a satisfactory description this behaviour of the eastern long-neck turtle, before we can formulate ideas and begin testing them.

Given their propensity to use terrestrial habitats, it seems likely that eastern long-necked turtles would encounter roads and vehicles more frequently that would more fully aquatic animals. But what do turtles do when they encounter a road? Do some turn back? Do they move quickly (for a turtle) across? Do they withdraw inside their shell? How many are crushed by vehicles? We plan to provide answers to all of these questions.

Using information gathered for turtle movements and habitat use, their behavioural responses to roads and vehicles, and data on road extent and traffic volumes, we will develop a model to predict the overall impact of vehicular mortality on eastern long-necked turtles. This model will allow us to identify regions where turtle populations may be especially vulnerable to road mortality, which will help to direct future mitigation measures.

A final phase of the project will be to head back into the field and study turtle populations over a broader geographic area. We will compare turtle populations inhabiting areas with heavily trafficked and dense road networks to populations inhabiting relatively pristine regions with very few roads. Such a comparison should allow us to determine whether roads have impacted turtle populations, and if so, to what degree.

COMMUNITY INVOLVEMENT
Success of this project depends on community involvement. We are grateful to have obtained permission for studies on National Park land, Australian Department of Defense land, and Wreck Bay Aboriginal Community land. We are seeking permission from other private land owners to carry out other phases of the study.

PROJECT OUTCOMES
Turtles are a critical component of freshwater ecosystems, but they and other animals are likely suffering from the drastic changes to the landscape associated with human populations. This study aims to provide a detailed description of the ecology and natural history of the eastern longnecked turtle, with the ultimate goals to highlight specific threats to freshwater turtles and identify management actions, commensurate with production goals that will enhance their conservation both on and off reserves.

FURTHER READING
Georges, A., Norris, R.H. and Wensing, L. (1986). Diet of the Eastern Long-necked Tortoise, Chelodina longicollis, from the coastal dune lakes of the Jervis Bay Nature Reserves. Australian Wildlife Research 13:301-308.

Kennett, R. and Georges, A. (1990). Habitat utilization and its relationship to growth and reproduction of the eastern long-necked turtle Chelodina longicollis (Testudinata: Chelidae). Herpetologica 46:22-33.

Palmer-Allen, M., Beynon, F. and Georges, A. (1991). Hatchling sex ratios are independent of temperature in field nests of the long-necked turtle Chelodina longicollis (Testudinata: Chelidae). Australian Wildlife Research 18:225-231.

Kennett, R. and Georges, A. (1995). The Eastern Longnecked Turtle -- Dispersal is the key to survival. Pp. 104-106 in Cho, G., Georges, A. and Stoujesdijk, R. (Eds) (1995). Jervis Bay: A place of cultural, scientific and educational value. Australian Nature Conservation Agency, Canberra.

Graham, T., Georges, A. and McElhinney, N. (1996). Terrestrial migration by the eastern long-necked turtle, Chelodina longicollis from Australia. Journal of Herpetology 30:467-477.

Roe, John H., Kingsbury, Bruce A., Herbert, Nathan R. (2003). Wetland and upland use patterns in semiaquatic snakes: implications for wetland conservation. Wetlands 23:1003-1014

This document was first published as a Research Flyer, Institute of Applied Ecology, University of Canberra, Issue #3, November 2005.

For further information and copies of the above publications, refer to our web page http://aerg.canberra.edu.au/staff/georges/

An earlier issues of this newsletter on Aboriginal harvest can be found at http://aerg.canberra.edu.au/documents/IAE_flyer_1.pdf