Stuttering frog (Mixophyes balbus)

Also known as: Silver-eyed barred frog, southern barred frog
KingdomAnimalia
PhylumChordata
ClassAmphibia
OrderAnura
FamilyMyobatrachidae
GenusMixophyes (1)
SizeLength: 60 – 85 mm (2)

The stuttering frog is classified as Vulnerable (VU C1 + 2a(i)) on the IUCN Red List 2004 (1). It is listed under Schedule 1 of the Threatened Species Conservation Act of Australia (3).

So named due to the stuttering sound of its call, the stuttering frog is a large, well-built frog with strong hind limbs. It has mid to dark brown bars on the hind limbs and a dark line running from the eye towards the shoulder against the yellow-grey skin (2) (3). The eye has a blue crescent under the upper lid (2). The tadpoles are large with dark grey bodies, and dark grey fins with black speckling (2).

The stuttering frog is found from northeast Victoria to New South Wales, Australia (3), in a range of 110,400 km² (1). It occupies low altitudes in the south and high altitudes in the north (1).

Occupying permanent streams through temperate and sub-tropical rainforest, the stuttering frog is also found in the moist gullies of dry forest (1).

Breeding occurs from September to April (4). Males call from the edges of small streams, from under leaf litter or within holes, making a soft, short, pulsed call, ‘kook kook kook kra-a-ak kruk kruk’ that last for just a couple of seconds (2). A nest is constructed in shallow running water and between 500 and 550 coloured eggs are deposited in a shallow excavation in the stream bed. The tadpoles develop in pools and shallow water where they remain for up to one year, depending upon when the eggs are laid (1) (4).

Habitat fragmentation and degradation as a result of forest grazing and land clearance for agriculture has isolated populations of the stuttering frog (1) (3). These small, isolated populations risk local extinctions as they become more vulnerable to catastrophic events, such as wildfires, droughts or disease, as well as to reduced fitness through inbreeding (4).

The stuttering frog is found in more than 20 national parks (4), and is the subject of a recovery plan which aims to determine the factors causing the decline in numbers, at the same time as researching and maintaining the current populations (5). A three year research programme has just been completed which assessed the distribution and abundance of this species, as well as its ideal habitat vegetation and water quality (5). There is also ongoing monitoring of the stuttering frog at a number of sites by researchers at the Australian University of Newcastle (4).

For further information on this species see:

Authenticated (25/11/2005) by Frank Lemckert, Senior Research Scientist for Forest Biodiversity, Forest Resources Research, NSW Department of Primary Industries, Australia.

  1. IUCN Red List (November, 2004)
    http://www.redlist.org
  2. Frogs of Australia (November, 2004)
    http://frogs.org.au/frogs/fov.php?frog_id=23
  3. New South Wales National Parks and Wildlife Service (November, 2004)
    http://www.nationalparks.nsw.gov.au/npws.nsf/Content/Stuttering+frog+endangered+species+listing
  4. Lemckert, F. (2005) Pers. comm.
  5. Department of the Environment and Heritage – Australian Government (November, 2004)
    http://www.deh.gov.au/biodiversity/threatened/action/frogs/22.html