Some problems in the management of the Green and Golden Bell FrogLitoria aurea(Anura: Hylidae) at Coomonderry Swamp on the South Coast of New South Wales

4 Pages·1996·0.9 MB·English

by  Garry Daly

Some problems in the management of the
Green and Golden Bell Frog Litoria aurea (Anura: Hylidae)
at Coomonderry Swamp on the South Coast of
~ e swout h Wales
Gamy Daly
ci- No~.thN orvra P.O., New South Wales 2511.
ABSTRACT
Cwmonderry Swamp, the largest freshwater coastal wetland in New South Wales, lies 15 km
north east of Nowra. The wetland and its catchment are utilized for a number of purposes including
dairy farming, beef cattle production, turf farming, plant nurseries and a national park. Coomonderry
Swamp provides habitat for several species of fauna currently recognized as endangered in New
South Wales including the Green and Golden Bell Frog (Litoria aurea). There have been several
attempts to drain the wetland in order to converl the area to other land uses including dairying, a golf
course and housing. Currently there is a proposal to rezone parl of the wetland's catchment from rural
to rural residential. All such proposals would compromise to some extent the habitat value of this
significant wetland. If regional biodiversity is to be maintained planning authorities, need to adopt local
environmental planning instruments that protect habitats identified as significant for rare and
endangered species such as L. aurea.
INTRODUCTION on the New South Wales coast (Fig. 1) and
represents 3470 of this type 01. wetland in the
Litoria auren has undergone a I-ecent popula-
state (Goodrick 1970). It is fed largely by ground
tion decline in New South Wales and is now
water (Mitchell McCotter 1992). The swamp is
listed on part 1 of Schedule 12 of the amended
a ~azetted wetland (No. 370) under State
National Parks and Wildlqe Act as threatened.
Environmental Planning Policy (SEPP) No. 14
Currently, populations in New South Wales are
and 169 ha of it (25%) lies within Seven Mile
scattered along the coast from Yuragir National
Beach National Park (Mitchell McCotter 1992).
Park (Clancy 1996) to Jervis Bay (Daly 1995a,h).
This is one of the fe~vn ational pal-ks where L.
In Sydney the species has been located at several
aurea is known to occur. The Illawarra Regional
heavily disturbed sites, including quarries
Landscape and Envil-onment Study (Depart-
(Cogger 1993; Greer 1994, pers. obs.). The
ment of Environment and Planning 1981)
colonization of fish-free quarries may be a
categorizes the wetland as IIc-Priority Protection
response of L. aurea to the presence of Mosquito
requiring protection against polluting land uses.
Fish (Gambtuia holhrooki) in srvamps that they
previously utilized fbr breeding. The draining Coomonderry Swamp is significant lor L.
and filling of many li-eshwater wetlands during area because it is the most extensive wetland in
the last 35 years may also have driven L. aurro which the [rag has yet been discovel-ed in New
to constructed ponds. South Wales (G.D aly, pers. ohs.). Unfortunately
the introduced hIosquito Fish (Caotbusia) is
There is a need to mallage remaining coastal
+videspread in the swamp, although the impact
freshrvater wetlands as they represent critical
this predator of small tadpoles has had on
habitat Tor adult frogs and may also serve as
breeding sites. Coomonde~-ryS wamp provides the local li-og population is unkrrowt~. To
an appropl-Late case study Lbl- the management date the frog is known to occur on both the
of the L. aurea's natural habitat. The aim of this caste^-n and urestcr~ls ides ol the wetland. On
paper is to examine how one I-. aurea habitat the eastern edge it occurs in swamp mahogany
has been managed and to offer a I-angc of con- ( E u c u ~ ~r~u~buuJ~ t~a~nd) blackhutt/harrgalay
senration measures to preserve the existence of (E. pilulari.slE. hotqoide~)f orest (Murphy 1994).
the species. On the western edgc it occurs in cumbungil
spikerush (Tjpha sppl Eleochoris sp.) and in farm
dams containing kikuyu (Penn&tum clandestislim,.m)
Cwmonderry Swamp
and water primrose (Ludzui@a peploides) Breeding
Coomonderry Swamp (34"48'S, 150°44'E) is a bchaviour and spawn have only been found on
670 ha wetland 15 krn north east 01. Nowra the rrrestcrn side of Coomonderry S~vampi,n two
on the New South Wales south coast. It is farm dams which were fish free (Daly l995a).
the largest semi-permanent freshwater swamp Frogs were not present in a nearby dam which
May 1996 Australian Zwlogist 30(2) 233
Fig. I. Locadon of Coornonderry Swamp near Nowra, New South Wales
contained Mosquito Fish. The fish-free water the Endangered Fauna (Interim Protection) Act
bodies around Coomonderry Swamp may be 1991. In other cases, development applications
critical for the successful breeding of the frog in have been granted prior to a proper assessment
the area. having been made. Daly 11993) conducted a
fauna assessment on land proposed for turf
Coomonderry Swamp has an extensive area
farming adjacent to Coomonderry Swamp. This
of natural habitat which is potentially suitable
land was previously evaluated by Mitchell
for L. aurea, and the wetland maintains a large
McCotter (1992) as "unacceptable to develop-
population (Daly 1995a). The majority of the
ment" and for zoning as Environmental
extant populations of L. aurea in New South
Protection (7a). In future, environmental
Wales occur in coastal wetlands south of Sydney,
surveys should be undertaken, prior to consent,
particularly in the Wollongong-Kiama and
for all development in the vicinity of the swamp
Nowra Municipalities (G. Daly, pers. obs.). The
and L. aurea should he included in these surveys.
fact that part of Coomonderry Swamp is in a
National Park is significant since in New South Much of the current land management near
Wales the species is now only known from three Coomonderry Swamp is inappropriate for
national parks: Yuraygir (Clancy 1996), Seven sustaining L. aurea. For example, the siting of
Mile Beach (Murphy 1994) and Jervis Bay roads close to the wetlands, especially where
Nature Reserve (Commonwealth controlled they may traverse suitable frog habitat, can be a
land) (Daly 1995b). problem. A road killed, gravid female L. aurea
was found close to the BolonglCerroa Road
intersection (Daly 1995a). Future development
Threats to Coomondeny Swamp
that involve additional roads or an increase in
Several threats to Coomonderry Swamp as a traffic should be considered with respect to L.
viable habitat for L. aurea are outlined below. aurea.
They are listed in order to illustrate improve-
The continued draining of land leads to an
ments which could be made in conservation
obvious loss of frog habitat. In the early 1900s
practices for the species.
various drainage canals were constructed across
Recent environmental assessments have failed the Shoalhaven flood plain in an attempt to
to consider adequately L. aurea. One report drain low-lying areas in order to make them use-
commissioned by the Shoalhaven City Council ful for agriculture. Such drainage canals were
(Mitchell McCotter 1992) ignored amphibians subsequently enlarged in the 1960s and 1970s
totally, even though it concluded that the assess- (Shoalhaven City Council 1992). In the Shoal-
ment provided sufficient information to satisfy haven and adjacent Kiama Shires the following
234 Australian Zoologist 30(2) May 1996
Plate 6a. A pair of L. aurea in amplexus at Shoalhaven Plate 66. A road-killed L. aurea. In s~tuationsw here roads
Heads, New South Wales. occur close to breeding sites, vehicles may contribute
to a significant source of mortality.
fresh water swamps have been drained: (1) Foys encouraged to drain or poison them (Barlow et
Swamp (adjacent to Coomondeny Swamp); (2) al. 1990).
the extensive flood plains west of Coomonderry
Other exotic predators besides Mosquito Fish
Swamp, extending from Coolangatta Mountain
are also a potential threat to the frog. Bell Frogs
west to Bomaderry and north to Berry; (3) the
are eaten by Foxes Vulpes uulpes (Mr. P. Meek,
extensive flood plains to the east and south-east
pers. comm.) and probably Cats Felis catus. The
of Nowra; (4) several unnamed swamps beside
degree of impact this has on L. aurea is
the Shoalhaven River (east of Ski Park, adjacent
unknown.
to bridge at Bomaderry and Ben's Walk); and
(5) Omega Swamp (Kiama) (G. Daly, pers. obs.). Another potential threat to Coomonderry
Swamp is mining. There are considerable
The preservation of L. aurea requires a resources of peat and sand within Coomonderry
re-examination of drainage canals. It may be Swamp (Mitchell McCotter 1992). Immediately
appropriate to fill in canals to re-establish wet- to the north of the wetland is a sand mine. The
lands. The permanent canals which are required owners of this mine (Cleary Brothers) also have
to keep the water table low after initial drainage freehold title to the northern section of
also provide a potential route for Mosquito Fish Coomonderry Swamp. The sand mining
to penetrate to isolated farm dams during flood- activities at Seven Mile Beach have resulted
ing. At one site adjacent to Coomonderry in the removal of native vegetation and the
swamp, a flood allowed Mosquito Fish and construction of a large permanent water body.
Goldfish Carassius auratus to enter a dam where The impact of this operation on L. aurea is
L. aurea had spawned (Daly 1995a). No Bell unknown.
Frog tadpoles were located in this pond after
Rezoning land for subdivision has an obvious
this event. These problems may be overcome by
effect on frogs as this involves the removal
filling in drainage canals and altering dams so
of habitat and leads to an increase in roads
they are ephemeral.
and traffic. During 1995 the Shoalhaven City
Isolated dams adjacent to wetlands can also be Council prepared a Local Environmental Plan
rendered unsuitable for frogs by the deliberate (LEP). Coomonderry Swamp was excluded from
introduction of fish into them. Concessional lot this assessment because it is subject to a separate
subdivision has resulted in the establishment of LEP. There has been some subdivision of land
several small privately owned portions of land in the catchment of this wetland and there is a
adjacent to the wetland, all of which have at least deferred application to rezone tracts of land to
one dam. One lot has a dam in which the owners the north-west of the wetland to rural residential
have placed Carp Cyprinus carpio and Mosquito (G. Watson, Councillor Shoalhaven City Council,
Fish (C. Virtue, pers. comm.). Prior to the Minutes of the Lower Shoalhaven Catchment
addition of these fish, the pond was utilized by Management Meeting 2/5/95). The appropriate-
L. aurea (C. Virtue, pers. comm.). Such small ness of land use intensification is questionable
farm dams that have become populated by in respect to L. aurea habitat.
Mosquito Fish serve as a reservoir for colonization
Conservation Measures
of new areas. There is also a strong possibility
that additional species of exotic fish will colonize Litoria aurea is a species which is difficult
Coomonderry Swamp. Dams adjacent to to conserve because it may make seasonal
Coomonderry Swamp should be inspected and movements from cumbungi swamps through
if exotic fish are detected their owners should be environments modified by humans to fish-free
May 1996 Australian Zoologist 30(2) 235
ponds for spawning (Daly 199.5a). Adult frogs REFERENCES
have different habitat requirements to tadpoles
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and hence conservation measures need to
Dams. Agfacts F3.1.1. New South Wales Agiculrure
accommodate the animals' requirements at all and Fisheries: Sydney.
stages of their life cycle.
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ing: (1) rezoning all of the Coomonderry Swamp
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wetland to National Park; (2) establishing a forum
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ACKNOWLEDGEMENTS
Murphy, M. J.. 1994. Reptiles and amphibians of Seven
I thank P. Beck, R. Goldingay, A. Greer, Mile Beach National Park. New South Wales
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W. Osborne for their critical review of the
Shoalhaven City Council, 1992. State of the Environment.
manuscript and M. Murphy for his company
in the field. This paper has benefited from
discussions with W. Buttemer and L. Morgan.
236 Australian ZooIogisl30(2) May 1996