ACT News

Gang-gang: Rosenberg's Monitors in courtship mode in 'jungle' of Mt Ainslie

A vulnerable species of goanna makes its home in our nation's capital.

While human Canberra figuratively snoozes in its summer holiday hammock (waiting for God's gift of Summernats to get the year really started), wild Canberra remains effervescently busy.

So, for example, January is the mating time for Rosenberg's Monitor (Varanus rosenbergi), a substantial (growing to 1.5 metres) and rather beautifully patterned (see our picture) goanna. Matthew Higgins, who with ACT government ecologist Don Fletcher is studying the species, suspects that "Most Canberrans don't even know they exist."

Rosenberg's Monitor, which is being monitored and studied by Matthew Higgins and ACT government ecologist Don Fletcher.
Rosenberg's Monitor, which is being monitored and studied by Matthew Higgins and ACT government ecologist Don Fletcher. Photo: Matthew Higgins.

But exist they do, although as Higgins points out Canberrans can be excused for not knowing that they exist since "the species' numbers are evidently quite low, so that any sighting is pretty special".

​"Our project aims to gather further information about Rosenbergs from Mt Ainslie, particularly breeding behaviour, through the use of remote automatic wildlife cameras.

<i></i>
 

"These goannas lay their eggs in active termite mounds; the termites repair the hole and so the eggs are incubated inside the mound for several months before the young hatch. It is an amazing piece of animal behaviour and one wonders how on earth did it evolve?  The young goannas feed on termites before they leave the mound – not much joy for the termites!

"I've seen the goannas at Googong, in Namadgi and on Mt Ainslie after considerable searching but I think that the paucity of my and others' sightings indicates a very small population."

"These goannas are very well camouflaged," he testifies, "and hard to see even if you're only a metre away; they are also good at staying very still when they want to. This makes finding them that much harder.

"Rosenberg's Monitor is a very beautiful creature and it is wonderful that they continue to live almost in the centre of Australia's national capital."

The species' relationship with and dependence upon termite mounds is, as Higgins says, really remarkable. A famous (among herpetologists) study done on Kangaroo Island between 1991 and 1996, told us a lot of what we know about V. rosenbergi. We can infer that all or most of what herpetologists Brian Green, Mike McKelvey and Peggy Rismiller​ reported of Kangaroo Island is true of the Rosenbergs (lucky Rosenberg to have such a splendid creature named after him!) of Mt Ainslie.

"V.rosenbergi mate over a period of about 12 days in January, and in late February/early March the female spends a couple of days digging into a termitarium (a termite mound). After digging about 0.7 metres into the mound she constructs a circular nest chamber ... and lays her eggs [up to 14 of them]. She then backfills the excavation and then within a few days the termites totally reseal the mound."

"Hatchlings first appear in spring ... they dig their own way [with a narrow tunnel] out of the termitarium without any adult assistance."

The three scholars found that the canny hatchlings do not emerge from the mound until the outside air temperatures are sufficiently warm. But even when that day temperature is ideal the hatchlings don't frolic away from ''home'' to seek their fortunes in the wider world. Instead for several months they come back to the mounds for "overnight refuge".

And OMG they need that refuge. They quickly find that it's a jungle out there (strictly, on Mt Ainslie, it is a dry sclerophyll woodland out there). The researchers found the hatchlings "subject to intense predation mainly by corvid birds" (ravens, magpies and related winged monsters). They found that "very few young [Rosenbergs] survive their first year."

And these mites, the hatchlings watched on Kangaroo Island (and surely something similar happens on violent Mt Ainslie), were even sometimes victims of a form of what our US military cousins call collateral damage. Echidnas, in search of toothsome termites and rampaging into the mounds by enlarging the Rosenbergs' exit tunnels, often punctured to death, with powerful claws and spines, Rosenberg hatchlings that got in the way of this feeding frenzy.

And on top of belligerent Nature's decimations of the Rosenbergs, they also suffer habitat loss, get skittled by cars and killed by cats. It is no wonder then that in NSW (they are, too, thinly sprinkled in niches of South Australia and Western Australia) they are classified as ''Vulnerable''.

We don't yet have a status classification for the ACT's Rosenbergs but they seem to be scarce and we must look after them. Matthew Higgins asks that we never, ever damage a termite mound (it used to be a sport for urchins to poke them with sticks to watch the termites get into frenzies). The mounds, as well as being essential for termites, are literally indispensable for any Rosenbergs thereabouts. 

Older Australians (this gnarled columnist is 70) will remember with a shudder of green horror the days when "ant bed" (crushed up termite mounds) was a popular surface for Australian tennis courts. Almost every sacrifice is worth making for tennis, the game they play in Heaven (and in Hell too, although there all they play is social tennis), but one shudders to think what strains those mound-plundering days put on the Rosenbergs and on echidnas, let alone on the termites themselves.

Dr Glenn Shea of the Australian Museum in Sydney informs us that the Rosenberg of the species' name was one Hans Rosenberg of Hamburg in Germany. He was somehow pivotal to herpetology. One imagines he is the same Rosenberg remembered in the scientific and common names of Hypsiboas rosenbergi, Rosenberg's Gladiator Treefrog. The species gets the evocative common name "gladiator" from the way in which the males fight one another, like amphibious Russell Crowes.