Turtle Population Study 2012 _ Yellagonga Regional Park
Download a copy of the report from here.
Last Updated on Sunday, 31 March 2013 10:37
Summary of Turtle paper of 2010
Summary prepared by Kevin McLeod of a report by Dr. Jacqueline Giles for Friends of Yellagonga, Joondalup City Council, Wanneroo City Council and Department of Conservation of W.A. 15.3.2011
A POPULATION SURVEY OF THE LONG-NECKED FRESHWATER TURTLES OF LAKES Joondalup and Goollelal completed in November 2010.
The survey was designed by Dr. Jacqueline Giles and undertaken by members of the Friends of Yellagonga over a 20 day period. The report was prepared by Dr. Jacqueline Giles.
Statistics collected were the length, width, depth, sex, weight, algae presence and general condition.
These were used to
1. determine size structure, sex ratios and recruitment into the population
2. Assess the condition of turtles as a relative indicator of habitat quality
3. Establish a baseline for the turtle population within Lake Goollelal
Results show that in Lake Joondalup the ratio is 1.75 males to one female and in Lake Goollelal the ratio is 1.2 males to each female.
Juveniles or sub adults represented 10.06% of the population in Lake Joondalup and 11.3% of the population in Lake Goollelal.
Of particular note is the fact that no turtles under 8 cms. were caught in Lake Joondalup and no turtles under 10 cms. in Lake Goollelal.
Two deceased turtles from Lake Goollelal were tested for heavy metals and showed levels of Copper, Magnesium and Mercury at 400, 320 and 16 times the minimum reporting level respectively.
Since the report a deceased turtle from Lake Joondalup has been tested and shows 16 times and 140 times the minimum reporting level of mercury and magnesium. Unfortunately copper wasn’t tested for in this case.
The high concentrations of Magnesium, Copper and Mercury are of concern as their effect on turtles is unknown.
From the studies Dr. Giles has suggested that considering the size and quality of the habitat and the numbers of turtles present, the recruitment into the population is below what one would reasonably expect.
1. Monitoring to continue on a two to five year basis to inform managers of population trends and to assess the effectiveness of any actions taken to address concerns.
2. Turtle Studies should include Capture –Mark release programs, auditing for carcasses on roads and throughout terrestrial buffers and surveys of nest predation.
3. Improvement of nesting environments.
4. Coordinated pest animal control programs
5. Education of the public of the value of the long-necked freshwater turtles in their wetlands and to foster a sense of stewardship for them.
Last Updated on Sunday, 13 May 2012 15:05
Measuring Turtle Nest Predation of the Lake Joondalup Turtles (Chelodina oblonga) 2011/2012
Monitoring of Turtle (Chelodina oblonga) nest predation at Lake Joondalup as an indicator of the effectiveness of an ongoing fox control program.
The work was carried out on behalf of the Friends of Yellagonga by Kevin McLeod (Chairman) ably assisted by fellow member Sue Walker.
Predation of turtle nests has been known for some time. Historically Lake Joondalup carried a high population of turtles with large numbers being observed moving around during nesting events. These numbers no longer occur (pers. com.). No scientific work has been done to determine population size. A population study in 2010 (J.Giles) showed no turtles captured below 9cms and a skew towards older ages.
Foxes predate on a wide range of small native species and are extremely efficient in finding and eating turtle eggs. An effective fox control program should result in higher survival of turtle eggs, hatchlings and small native animals being available as a population buffer and a food source for native predators.
Since urbanization of the lake surrounds no fox hunting or control had been carried out. Foxes were regularly seen moving around the lake. A subsequent trapping effort saw 13 foxes removed. (Animal Pest Management Report 2010)
It has been decided to carry out continual fox control at least annually. Nest predation is still observed however.
Monitoring is an important part of any Pest Animal Control Program (Australian Pest Animal Strategy – NRM – Ministerial Council).
It was decided to monitor the results of fox predation on turtle nests as this was comparatively easy to observe over time. The nests dug up have no relationship to fox numbers other than that there was at least one involved and possibly more.
A path runs between Picnic Cove and Neil Hawkins Park along the Western edge of Lake Joondalup. It was proposed to walk along the path and note any nest dug up within two meters each side.
The path measures 2000 meters so the area inspected is 8000 square meters.
The exercise was done every two weeks from before the laying season until the end.
It’s planned to repeat the exercise annually for comparisons.
Note: Two main nesting events occurred, one in October and the second in December. In both cases the nests were dug up within 24 hours. Further minor nesting occurred with predation as shown in the graph.
In light of the data perhaps additional techniques could be tried such as an effort made to find the nest before the fox and supply a protective grid. The Friends of Yellagonga will continue efforts to increase hatchling recruitment into the Lake.
Image shows approximate positions of predated turtle nests with a yellow pin and the track followed.
Last Updated on Sunday, 13 May 2012 15:08
On Saturday October 2, 2010, Councillors and staff from the Cities of Joondalup and Wanneroo, together with members of the Friends of Yellagong Regional Park (FOY) attended the launch of the 2010 Long-Necked Turtle Study at Picnic Cove in Edgewater. Funding from both Cities has allowed the FOY sponsored study to continue with Dr Jacqueline Giles training up FOY members to do their own sampling. It is hoped that sufficient information will be gathered to accurately assess turtle numbers, their general health and level of recruitment.
Daniel Garlett from the South West Aboriginal Land & Sea Council and Dennis Simmons, the indigenous caretaker of the Yellagonga Regional Park (YRP) and surrounding area – attended and both spoke of their support for the project and gave a brief explanation of the aboriginal history of the area. Dennis is the late Ken Colbung’s grandson and is passing on the proud traditions of the aboriginal people to the younger generation.
Concern about fox predation on turtle hatchlings and incubating eggs was the motivation for the initial study in 2009. Two fox trapping programs have been carried out so far this year in the Yellagonga Regional Park. This is a program that the Perth Region Natural Resource Management hopes to promote throughout the whole metropolitan area north of the Swan River. Thanks to the FOY members Kevin, John and Frank who underwent the training with Dr Jacque Giles and the helpers who assisted them with the paddling, setting, pulling nets, marking the caught turtles and recording the information.
(photo: John Chester)
(above) Mayor Troy Pickard with son, Mason, examine turtle held by Dr Jacqueline Giles at the Launch Day of the Survey
Last Updated on Sunday, 13 May 2012 15:37
Friends of Yellagonga was successful in obtaining funding from the DEC, the cities of Wanneroo and Joondalup for a baseline study of the endemic long-necked freshwater Turtles (Chelodina oblonga). This initial research study was conducted in October 2009 by wetland ecologist - Dr Jacqueline C Giles PhD, BSC(Hons). Friends of Yellagonga plans to continue the study utilising our members.
Last Updated on Sunday, 13 May 2012 15:34
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