Skinks cooperate to build ‘mansions’
SKINKS MAY NOT BE known for their family ties but a certain species uses the might of many to build elaborate dwellings.
Family groups of the great desert burrowing skink (Egernia kintorei) work together to build and maintain a long-term labyrinth of tunnels, some up to 13m in diameter and 1m deep. None of the world’s other 5000 species of lizard are known to collaborate in family groups this way – a behaviour usually reserved for mammals and birds.
The find is the accumulation of two decades of work in Uluru-Kata Tjuta National Park by conservation biologist Steve McAlpin and colleague Dr Adam Stow from Macquarie University.
“The study has contributed to our understanding of how cooperative behaviour evolves,” says Adam. “At present, there is discussion as to whether individuals need to be related for social behaviour to exist”.
Skink habitats in burrow clusters
Clusters of desert skink burrows often comprise 10 or more individuals, including one pair of parents with several cohorts of offspring spread throughout the burrow system. The burrows may have up to 20 entrances.
“Interestingly, the skinks have distinct latrines in the burrow cluster. All individuals in the burrow use the same latrine.” says Adam.
The skinks, which often grow to 44cm long, may inhabit the same dwelling for several years, often keeping the same partner throughout. Such monogamous behaviour is unusual in lizards, Adam says.
The ‘mansions’, as Adam calls them, offer protection from high temperatures and predators. The skinks are also calculated in their positioning of the tunnel homes, building their burrows next to along-lived termite colony on which they can feed for quite some time.
“This is a major step forward in research into social interaction” says Michael Bull, professor of biology at Flinders University in South Australia. “It refutes a hypothesis that had been discussed for sometime that social organisation [in lizards] derives from lack of refuge areas.” Further research is needed in lizard ecology to explain why it is “still obscure as to why this sociality has emerged”, he adds.
Aboriginal elders offer knowledge
Though Steve has been known to perch for hours in a hide observing the curious reptiles, he says working closely with the local indigenous Anangu people has been invaluable to the ongoing study. The research was conducted on the traditional lands of Anangu people and many of the elders in the community assisted Steve with their knowledge.
“I would walk around with one of the elders and he’d say ‘the males dig holes and then go off to find mates to bring back there'” Steve says. “They knew all that stuff from thousands of years of observation.”
In the local Aboriginal languages, the skinks are also known as: tjakura (Pitjantjatjara/Ngaanyatjarra), warrarna (Walpiri), or mulyamiji (Manyjilyjarra)
The species is regarded as vulnerable in the Northern Territory, while smaller populations in SA are considered endangered. The skink is thought to be long-lived, but scientists don’t yet know their average life span. Other species in the Egernia group, such as Cunningham’s skink, have been known to live for up to 40 years in captivity, Adam says.