Soil habitat of the endangered five-clawed worm skink

The five-clawed worm skink makes its home in the cracking clays (Vertosols) of the slopes and plains of northern New South Wales. The Soil and Landscape Assessment Team have been working to help their colleagues in the Department of Planning and Environment to identify potential habitat to support this endangered species.

Black vertosol on the Liverpool plains

The five-clawed worm skink

The five-clawed worm skink (Anomalopus mackayi) is a brown, wormlike, burrowing lizard that can be up to 27 cm in length. It has short limbs and as the name suggests, 5 claws; 3 toes on the forelimbs and 2 on the hind.

It has a patchy distribution in northern New South Wales extending into southern areas of Queensland. It is considered endangered under the NSW Biodiversity Conservation Act and vulnerable under the Commonwealth Environment Protection and Biodiversity Conservation Act.

The five-clawed worm skink lives in permanent tunnel-like burrows and deep cracks in soils known as Vertosols. When the skink reaches the surface, it uses fallen logs and timber as shelter.

Whilst little is known about the skink's breeding, life cycle or feeding behaviours, scientists from Soil and Landscape Assessment Team have been using their soils knowledge to help identify potential skink habitat.

Brian Jenkins, Senior Team Leader for Soil and Landscape Assessment Team, says, 'The skink's dependence on these iconic soils for habitat highlights the critical role soil plays in supporting rare and endangered species in New South Wales.'

What are Vertosols and why do these skinks call them home

The cracking clay soils, which the skinks call home, are known as Vertosols under the Australian Soil Classification system. Australia has the greatest area and diversity of Vertosols anywhere in the world.

Vertosols are an iconic soil type in New South Wales and are generally regarded as having high fertility and agricultural productivity. Vertosols typically form on basaltic rocks or basaltic alluvium. These soils are usually black but can also be red, brown or grey, depending on drainage.

Vertosols are strongly structured soils with a high clay content throughout the profile. This is important as they develop with a particular type of clay that can absorb large amounts of water. These clays will swell when wet and shrink and crack when dry. This shrink-swell characteristic means these soils form a surface condition known as self-mulching. The strongly structured topsoil forms a loose mulch of soil peds or aggregates on the surface.

This shrink-swell characteristic makes these soils perfect homes for the five-clawed worm skink. The loose self-mulching topsoil provides easy access, and the deep cracks that form when the soil is dry make cosy burrows. Recent rain events have led to increased sightings of these skinks. When these soils become wet, the cracks will close, forcing the skinks out of their burrows onto the surface.

Soil information to predict skink habitat

Through identifying the distribution of Vertosols in northern New South Wales, the department's scientists have been able to predict potential areas for skink habitat. This information helps land managers understand and protect populations of these endangered skinks.

'The advice from the Soil and Landscape Assessment Team helped me to understand the soil mapping that is available and what scale it can be applied. The advice the team gave us helped build rigour into our impact assessment and management action decisions. The Soil and Landscape Assessment Team were fantastic; they gave me everything I needed really quickly' – Principal Project Manager, Renee Shepherd.

The soil expertise provided by Soil and Landscape Assessment Team has proved incredibly valuable and is helping to protect the endangered five-clawed worm skink.