Emydura macquarii (Gray, 1830) (Bellinger River) - species delisting

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to remove the Emydura macquarii (Gray, 1830) (Bellinger River) from the Schedules of the Act by omitting reference to this species from Part 1 of Schedule 2 (Vulnerable species). The omission of species from the Schedules is provided for by Part 2 of the Act.

 

The Scientific Committee has found that:

 

1. Emydura macquarii (Bellinger River) is a short-necked freshwater turtle (tortoise) with a light-coloured shell, pale belly, cream jaw-stripe and yellow eyes. It may be distinguished from similar species as follows: (a) the similarly short-necked Georges’ Turtle Elseya georgesi has a serrated hind edge to the shell, a dark belly with black seams, two distinct barbels (short spikes) on the chin, a distinct head shield, and silver eyes, (b) the Eastern Snake-necked Turtle (Chelodina longicollis) has a long neck (extended head and neck longer than the shell) and black seams on the belly. The Bellinger River Emydura was believed to differ morphologically from other populations of the widespread Murray Turtle Emydura macquarii complex (Gray 1830), but is now thought to be within the range of normal genetic and morphological variation for this species (Georges et al. 2007). The few individuals with unusual characteristics that were previously the basis for segregating the Bellinger River taxon are believed to be hybrids with the Georges’ Turtle Elseya georgesi (Georges et al. 2007) which is endemic to the Bellinger-Kalang River system.

 

2. The populations of Emydura macquarii in the Clarence and Macleay River Catchments have been previously classified as subspecies (E. m. binjing and E. m. dharra, respectively), but analysis of DNA samples has shown that they cluster with populations from the Nambucca and Hastings as a single genetic clade (Georges et al. 2007). Other genetic clades identified by Georges et al. (2007) include a Hunter River clade E. m. gunabarra, a Sydney Basin clade E. m. dharuk, a Murray-Darling clade E. m. macquarii, a NSW/southern Queensland clade E. m. signata, and a Richmond River clade (not formally named as a subspecies). The Richmond clade has been suggested as a subspecies (Cann 1998), but it is genetically close to the Hunter and southern Queensland clades (Georges et al. 2007).

 

3. Although it is possible that E. macquarii has always been in the Bellinger River in some form, the haplotypes identified in a recent survey of Bellinger Emydura, and their segregated spatial distribution within the river system, argue against such an interpretation (Georges et al. 2007). Of six haplotypes found, two are shared with the Clarence River and two are shared with the Macleay, Nambucca and Hastings Rivers (Georges et al. 2007). The remaining two are not currently known from outside the Bellinger River, which may be due to low sampling effort in adjacent drainages. Georges et al. (2007) conclude that the Bellinger River Emydura has probably arisen from translocated individuals originating from several genetic sources (i.e. the adjoining Clarence, Nambucca, Macleay and Hastings drainages). There is a confirmed case of accidental release of three individuals originating from Coffs Harbour, and the two unique haplotypes are suspected to be from the Coffs Creek drainage (Georges et al. 2007).

 

4. Emydura may exist as a single, mobile population in the Bellinger-Kalang system (Spencer 2006) although genetic data suggest little movement. This population is geographically isolated (c. 5-10 km) from other populations in the Clarence and Nambucca drainages by rugged, forested ridge systems, which limit the turtles’ ability to disperse overland.

 

5. Only 20 Emydura have been captured in the Bellinger River during surveys dating back three decades, leading to previous assessments of a “small population”, “extremely low numbers”, “exceptionally rare” and potentially “one of Australia’s rarest turtles” (Cann 1998; Spencer & Thompson 2000; NSW NPWS 2001; Blamires et al. 2005). Conversely, an intensive three-week effort in March 2007 captured 76 Emydura (Spencer et al. 2007). Results suggested a patchy distribution and a density of c. five Emydura per hectare, which is very low compared to populations of E. macquarii found elsewhere (e.g. over 200/ha: Spencer 2001). No estimate has been made of total population size in this river (Blamires et al. 2005; Spencer et al. 2007). However, in light of recent genetic re-assessment, the subspecies of which the Bellinger River Emydura is part, has an extensive occurrence that comprises coastal drainages from the Clarence catchment to the Hastings catchment (c. 37 500 km2).

 

6. This population is currently managed under the Fox Threat Abatement Plan, and the recovery actions (NSW NPWS 2001) are thought to be effective in maintaining the turtle’s numbers in the Bellinger River (Eco Logical 2007). There is currently no evidence of a population decline, but modelling suggests that viability of the population may be extremely sensitive to mortality rates. Although most demographic parameters are not available for the Emydura in the Bellinger River, annual rates for adult female and juvenile survival (95% and 65% respectively) are known for E. macquarii in the Murray River (Spencer and Thomson 2005). Trampling by cattle and flooding destroy nests, and predation by goannas and foxes along the Bellinger accounts for c. 72% of nest failures (Blamires et al. 2005). Assuming an initial population of 300 Emydura (100 mature, 100 juvenile, 100 hatchlings) modelling of these parameters suggests that population size in the Bellinger River is stable or slightly increasing (Spencer et al. 2007, R. Spencer pers. comm. July 2008). However, applying even a slightly lower adult survival rate of 90% results in a modelled decline of over 30% in a decade. If the survival values recorded for Georges’ Turtle (Blamires et al. 2005) in the Bellinger River (86% and 58%) and known nest predation rates apply, the Bellinger Emydura is predicted to decline by 60% over the next decade (R. Spencer pers. comm. July 2008). Even complete elimination of nest predation under these lower survival values does not prevent gradual demise of the local population (Spencer et al. 2007). This dependence on high adult female survival for population stability is typical of freshwater turtles (Spencer et al. 2007). Any reduction in local conservation efforts, including current control of one of the major nest predators (foxes), may lead to loss of turtles in the Bellinger River, and would therefore warrant a review of the species status.

 

7. The main threat to the population is nest predation by goannas and foxes, and possibly predation on adults by the latter. ‘Predation by the European Red Fox Vulpes vulpes (Linnaeus, 1758)’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995. Other threats include water pollution and river sedimentation, human construction works (e.g. bridges and fords), extraction of river sand and gravel, removal or degradation of riparian vegetation, road kill, and line fishing. The Bellinger River has received substantial conservation effort by the local community which has ameliorated these threats over the past decade. Hybridisation and competition with the Georges’ Turtle are potential long-term threats to Emydura macquarii in the Bellinger River catchment.

 

8. Emydura macquarii Bellinger River is currently listed under the Environment Protection and Biodiversity Conservation Act 1999, as vulnerable under the name of the Murray Turtle Emydura macquarii signata (Bellinger River, NSW).

 

9. The current status of Emydura macquarii in the Bellinger-Kalang system no longer meets the criteria for listing under the Threatened Species Conservation Act 1995. Turtles of this catchment are now thought to be part of a much larger population extending over north-east NSW, and current knowledge indicates that the total number of mature individuals of the taxon is not low. There is no evidence of a moderately large reduction in the taxon, nor is it moderately restricted.

 

10. In view of the above the Scientific Committee is of the opinion that Emydura macquarii Gray, 1830 (Bellinger River) is no longer eligible to be listed as a Vulnerable species in Part 1 of Schedule 2 of the Act.

 

 

Dr Richard Major

Chairperson

Scientific Committee

Proposed Gazettal date: 11/12/09

Exhibition period: 11/12/09 – 29/01/10

 

References:

 

Blamires SJ, Spencer RJ, King P, Thompson MB (2005) Population parameters and life-table analysis of two co-existing freshwater turtles: are the Bellinger River turtle populations threatened? Wildlife Research 32, 339-347.

 

Cann J (1998) Australian Freshwater Turtles. Beaumont Publishing Pty Ltd. Singapore.

 

Eco Logical (2007) ‘Implementation review of eleven threatened species recovery plans in north-east NSW: Final report.’ Unpubl. report to NSW DECC. Eco Logical, Coffs Harbour.

 

Georges A, Walsh R, Spencer RJ, Welsh M, Shaffer HB (2007) ‘The Bellinger Emydura: Challenges for management.’ Unpubl. report to NSW NPWS. Institute for Applied Ecology, University of Canberra: Canberra.

 

NSW NPWS (2001) ‘Approved recovery plan for the Bellinger River Emydura Emydura macquarii (Bellinger River)’. NPWS, Hurstville.

 

Spencer, RJ. (2001) The Murray River turtle, Emydura macquarii: population dynamics, nesting ecology and the impact of the introduced red fox, Vulpes vulpes. PhD thesis, University of Sydney.

 

Spencer RJ (2006) ‘The Bellinger River Emydura survey: Effects of foxes and interspecific competition.’ Report to NSW NPWS, Dorrigo.

 

Spencer RJ, Georges A, Welsh M (2007) ‘The Bellinger Emydura: Ecology, population status and management’. Unpubl. report by Institute for Applied Ecology, University of Canberra, for NSW NPWS.

 

Spencer RJ, Thompson MB (2000) ‘The ecology and status of Emydura macquarii and Elseya georgesi in the Bellinger River’. Unpubl. report by Institute of Wildlife Research, University of Sydney, for NSW NPWS.

 

Spencer RJ, Thompson MB (2005) Experimental analysis of the impact of foxes on freshwater turtle populations. Conservation Biology 19, 845-854.

 

Page last updated: 28 February 2011