Happy New Year!
I don’t know about yours, but one of my resolutions for 2018 is to pay a lot more more attention to bugs. Or rather, insects in general, and how they interact with all the other critters around them.
So the year was off to a good insect-oriented start when I took this photo just down the hill from the spectacular lookout at West Head in Kuring-gai Chase National Park.
What’s this little monitor doing as she peeps out of this termites’ nest, a few metres up a gum tree?
What’s her story? And what’s she up to with those termites?
At first, I thought she might have been after kingfisher eggs or nestlings.
A couple of years ago my bird watching brother told me to keep an eye out for termites nests in trees, pointing out that kingfishers often made the hollows in these “termitaria” to nest in. Since then, I’ve seen plenty of arboreal burrows on my paddles around the Hawkesbury, and occasionally a sacred kingfisher lurking suspiciously nearby.
Many species of kingfishers, including (to my great surprise – I’m not sure why), kookaburras, often nest in termite mounds. I had assumed that birds would choose abandoned arboreal termitaria, but in most cases where animals reuse mounds, it seems, the original builders are still in situ when the new residents move in.
Unlike other birds, such as the hooded parrots of Arnhem Land, kingfishers don’t wait to build until the mud of the mound is softened by rain. They do construction the hard way, through sometimes lethal collision flights into outer wall of the nest. Both members of the pair participate in this headbanging activity until a 25 cm tunnel is dug. As you can see in the picture of the burrow above, the tunnel slopes downward a little, to help with keeping the it clear of the young’s faeces. If only dealing with human children’s ordure was a simple as a gently sloping bedroom and hallway, eh? Once the initial tunnel is dug, the kingfisher sometimes leaves the excavation for the termites to tidy up inside, sealing the interior walls of the nest.
But kingfishers aren’t alone in using termite mounds as a handy place to breed. I’m not quite sure what was using this big nest near Port Stephens. I suspect it’s not kingfishers. Like many Australian birds, they are cooperative breeders, with their youngsters from previous broods helping raise the new babies, but they don’t seem to nest colonially. As these burrowholes or just access points for some insect-eating predator to have a crunchy snack?
But back to our termite loving monitor lizard. As a bird-savvy informant pointed out, had my lizard been munching baby kingfisher eggs, the parents would have had something to say about it. In fact, what I saw wasn’t a nest-raid but most likely the aftermath of a hatching.
Because, as it turns out, lace monitors also lay their eggs in termite mounds, using the warmth generated by the insects to incubate their young. Once the eggs are laid, the lizards lets the termites seal them in, safe from predators in their incubation chamber in the treetops. Or perhaps slightly safer.
No-one seems to research lace monitors – too damn common it seems. But, researchers studying the related Rosenberg Monitors found that females defended the nests for a few weeks after the eggs were deposited. Some hard core conflict was observed:
“The most aggressive fighting observed was between a defending female and a marauder, with females fighting males more than twice their body mass. Both attacker and defender sustained injuries, including dislocated or broken limbs; broken ribs; spinal injuries; and severe bites to head, throat, and abdomen” (Rismiller, McKelvey, Green, 2010).
Baby rosenberg monitors dig their own way out of their natal termite heap, but everyone’s a bit vague about how the baby lace monitors escape their birthplace/prison. Despite the female’s willingness to break a spine or limbs to ensure the safety of their young at the point eggs are laid, herpetologists don’t give goanna mothers a lot of credit for subsequent interest in their offspring. Some researchers think that the mothers come back to dig their babies out of captivity when the right time comes. Others seem to think they just happen to be digging randomly in likely-looking termite mounds when they accidentally happen upon their young (Kirshner, 2007). This sounds all rather implausible to me .
I’m still not 100% clear about what I saw up a tree at West Head. Was the lizard I spotted was one of the little ones, lolling around in its birthplace after its mysterious liberation. Or a female spending some time hanging out in the nest, having helped her young to freedom? I’m just not sure.
One way or another, one of our common-as-muck goannas was doing its thing in its ordinary, fascinating way. With the help of a multitude of insect Mary Poppinses.
Kirshner, D. (2007) Multiclutching in captive Lace Monitors, Varanus varius. Mertensiella (16): 403-
Rismiller, P.D., McKelvey, M.W., Green, B. (2010) “Breeding phenology and behavior of Rosenberg’s Goanna (Varanus rosenbergi) on Kangaroo Island, South Australia” Journal of Herpetology 44(3):399-408. 2010