You may not have heard of the Gulbaru Gecko but you’d love it if you met it. Ancient and spectacular, this endangered gecko has one of the smallest distributions of any Australian animal.
Australia is a global centre of gecko diversity, with a remarkable 140 species at last count. Australia’s geckos fall into three families: Diplodactylidae, Gekkonidae and Carphodactylidae. The last of these, Carphodactylidae, is a uniquely Australian group; in fact it’s the only lizard family endemic to Australia.
These are all large, spectacular geckos with flamboyant or bizarre tails; very different to the “typical” gecko most would have seen on a house wall.
Among the genera within Carphodactylidae is Phyllurus, which means “leaf tail”. There are nine species, restricted to coastal eastern Australia. The most southerly is found in the sandstones of the Sydney region.
The remaining eight species are all restricted to tiny distributions along the Queensland coast, in many cases to a single mountain or range. All these species are found in rocky rainforest. No two species are found in the same patch and their distribution reflects the gradual contraction and fragmentation of rainforest in eastern Australia to small isolated pockets over millions of years.
The most northerly species is the Gulbaru Gecko (Phyllurus gulbaru). The Gulbaru Gecko occurs approximately 35 km west of Townsville, in Patterson’s Gorge at the southern end of the Paluma Range. Despite being highly distinctive and close to a city, the Gulbaru Gecko was only discovered in 2001 and named in 2003.
This large gecko, growing to 18 cm, is restricted to rocky rainforest, generally dominated by Hoop Pines (Araucaria cunninghamii). It hides in rock cracks during the day and emerges at night to hunt invertebrates on the rock surfaces. It is slow moving and highly camouflaged. Females lay two eggs, which develop slowly.
The Gulbaru Gecko is listed internationally as Critically Endangered, and is listed at the state level as Endangered.
It is one of Australia’s most narrowly-distributed species. The total distribution is extremely small and almost certainly fragmented into two areas. The larger area of suitable habitat is approximately 10km2, the other patch is about 4km2. In the larger patch the gecko is reasonably common, in the smaller patch it is rare.
Between the two patches there is a narrow band of unsuitable habitat, which almost certainly separates the geckos. The total population size is not known, and we have to be careful not to overestimate the abundance of the gecko. Even within suitable habitat their distribution is patchy.
The larger population is protected within Mt Cataract Forest Reserve and Paluma Range National Park.
Because of the small size of the Gulbaru Gecko’s habitat and population, it is vulnerable to anything that reduces or degrades the rainforest.
The primary threat is unmanaged burning, particularly late dry season fires that encroach into the rainforest from nearby open forest and pastoral areas. Fires are a natural part of the landscape in this region but intense burning can chip away at the rainforest edge. This has happened over the last decade at one of the Gulbaru sites I’ve been visiting.
Invasive grasses growing at the rainforest boundary provide a thick, highly flammable fuel load that can exacerbate these effects. Restriction of the Gulbaru Gecko to rocky areas such as gully lines affords the species some protection from fire; but, it is dependent on surrounding rainforest vegetation which is vulnerable. Even small incursions from fire could further fragment populations.
Climate change is a potential threat to the species, for example if it leads to drier conditions and greater potential for fire. An unlikely but obvious direct threat to the species is quarrying, an activity that doesn’t occur within the distribution but does occur nearby in the region.
Recently the larger fragment of the gecko’s habitat was protected under the state reserve system.
The smaller fragment is not formally protected but the leaseholders are aware of the species and its habitat requirements.
Further surveys are required to determine the fine-scale distribution of the Gulbaru Gecko and to estimate population size. An active program to reduce late dry season hot fires should be implemented.
The Gulbaru Gecko is a spectacular reptile that persists in a tiny area. It has clearly done so for a long time and with a little management to protect its rainforest habitat it will continue to do so.