Heleioporus australiacus   

Conservation Status

Vulnerable species in New South Wales (Threatened Species Conservation Act). Also listed as Vulnerable in the national Environmental Protection and Biodiversity Conservation Act.

What does it look like?

This striking amphibian is built for burrowing. Its legs are dense and muscular and its round body is a rich chocolate brown, with a white or yellowish spots on its sides.  The back, sides and arms of the male frog are covered in black warts capped with spines. 
The spines are used to grip the female during spawning, to protect itself against predators, and as armour when in conflict with other males.

To protect against dirt being flung into their eyes when digging, its eyelids have a protective flap, similar to an eyelid.  And if you look closely at their prominent eyes, you will see these frogs have a feature that distinguishes them from similar species: a vertical pupil sitting within a silver iris.

The Giant Burrowing Frog is one of Australia's largest frogs: adult frogs can grow up to 95mm.  It is also commonly known as the Owl Frog, Southern Owl Frog and Spotted Owl Frog.

Where does it live?

There are two distinct populations of the Giant Burrowing Frog in south-eastern Australia. The 'northern' population lives in the Sydney basin, and as far south as Jervis Bay. 
In general, the Giant Burrowing Frog prefers the following habitat:

• eucalypt forest
• woodland
• heathland 

However, in the Pittwater area, Giant Burrowing Frogs are most likely to be found in bushland on sandstone plains. Records show them in the upper reaches of Narrabeen Creek and Fern Creek. Between 1993 and 1996 they were recorded in Ingleside howeve most of the records are from the Kuring-gai Chase National Park.

For most of the year, you will find the Giant Burrowing Frog on a ridge within several hundred metres of a small, densely vegetated creek.  During the day, it likes to shelter from harsh conditions and predators; and while they prefer a burrow, you may also find them under a log or in dense undergrowth.  Like most frogs, they are most active directly during or directly after rain. 

True to its name, the Giant Burrowing Frog uses burrows for several purposes:

• Temporary burrows -  to escape predators, the frog quickly digs into the ground by rotating its fleshy hind legs. They hide in this shallow depression, often with only a few centimetres of soil overhead.
• Aestivation burrows -  to survive the harsh conditions of summer, the frog may find an empty yabby burrow in the bank of a stream or pond. Deep beneath the base of the watercourse, this burrow will be the last place to dry out if there is a drought.
• Breeding burrows - during mating season, males call from inside or next to a burrow in the bank of a creek or pond.  These burrows may have one or two openings.

What does it eat?

In the 1960s, scientists studying the Giant Burrowing Frog examined a pellet of its faeces. They discovered that ants made up the majority of the frog's diet. 

However, they also found remains of:

• Ground dwelling beetles
• Weevils
• Scorpions
• Spiders
• Cockroaches
• Centipedes

The adult frogs feed on insects and invertebrates on or near the ground, or in the water.  Their tadpoles feed on plant material and debris in the water.

What is its lifecycle?

When it's time to breed, the Giant Burrowing Frog makes its way to a nearby creek, dam or drainage line.  It needs a watercourse that is pure and unpolluted. Here it builds a burrow in the bank, ready for mating.  Calling from the bank,or from within its burrow, the male frog gives a resonant, low-pitched call. This soft "ou-ou-ou-ou" is sometimes mistaken for an owl hooting! 

Mating takes place within the burrow; the male frog grasps the female tight with the spines on his fingers and thumbs. The female frog then lays up to 1,250 colorless eggs in a foamy mass near the opening of the water-filled burrow, or under thick vegetation at the water's edge.  Tadpoles are grey, with grey fins speckled with lighter flecks.  They depend on a generous rain storm to raise the water level, flooding the watercourse and flushing them to a creek or shallow pool. Here they will complete their metamorphosis into adult frogs.  The Giant Burrowing Frog breeds in both autumn and spring, although this can vary depending on rainfall.

What are the threats?

In the Sydney basin, the main threat to the Giant Burrowing Frog is urban development of ridge top habitat sites.  Additional threats include:

• Pollution, degradation and siltation of creeks (especially minor creeks that drain sandstone plateaus, ridges and upper slopes)
• Bushfires - fires can kill frogs directly, as well as affecting their food supply
• Predation by dogs, cats and foxes
• Predation by the introduced Plague Minnow (Gambusia holbrooki)

Sadly, Giant Burrowing Frogs are also sometimes mistaken for cane toads, and killed.

What can we do to protect it?

There are many things we can do to protect this remarkable amphibian.  Their remaining habitat needs to be conserved.  To help its remaining populations we must:

• Protect waterways from further degradation
• Provide wildlife corridors between habitat areas
• Develop a fire management plan to reduce the impact of bushfire on this species
• Keep cats and dogs indoors and keep them out of national parks
• Educate the community about this unique species

Updated: 21 Jun 2011