|Reed New Holland Publishing, 2002.|
My first challenge is to find a standing body of water, no small feat given that South-east Queensland has endured an El Nino-derived drought this summer; nearby Archerfield recorded its driest summer in 65 years. Luckily, while poring over satellite maps the preceding week, I found a densely vegetated area in the north of Algester near a new housing development, and where there’s scrub, there’s usually water. Parking the car in the quiet dead end of Mount Moogerah Drive, I glimpse water through the trees to my left, and walk down the embankment to find my breath taken away.
I have stumbled upon an oasis in suburbia.
|Potential frog habitat? Algester.|
A small, weakly-flowing stream extends between two concrete culverts, its banks protected by a revegetation effort that has used all native trees, not a camphor laurel (Cinnamomum camphora) in sight. The water itself is crystal clear and less than thirty centimetres deep, broken by aquatic vegetation and scattered rocks. The air is filled with the rustling of at least a hundred dragonfly wings—they are landing on every protruding boulder, gathering their strength momentarily before resuming their endless skirmishing with each other. Such activity is being closely watched by a hungry willie wagtail (Rhipidura leucophrys), and in the shrubs bordering the water, fairy-wrens and finches are twittering away. I lean over the stream bank and peer into the shallows, spotting my first tadpole in just a few seconds. Pleased with discovering a mini-paradise, I set up a little study camp in the shade, consisting of a folding chair, my camera, a container filled with water from the creek, a notepad and pen, and Anstis’s book.
I scoop my dip net into the water and immediately collect two fairly well developed tadpoles. Anstis’s book points out that there are 46 stages of development between fertilised egg and a metamorphed (newly-transformed) frog; these tadpoles appear to be around the 37th or 38th stage. The book has a detailed and easy-to-use key that allows you to work through all the tadpoles you are likely to find in southern Queensland, New South Wales and Victoria, however, I am lacking some of the necessary equipment—like measuring calipers and chlorobutol for anaesthetisation—to use this tool to its full ability. To study the tadpoles, I observe their behaviour in the wild before capture, I note their form and colour while in the container, and I deposit them onto a wet surface for twenty to thirty seconds while I take some macro photographs for later study.
These particular tadpoles are very dark, almost jet-black. Their back legs have partially formed and about the only non-black pigmentation detail I can see is a banded pattern developing on the toes. Such a feature suggests that this creature will turn into a ground-dwelling amphibian rather than a tree frog, so I begin to look through the detailed species information in my field guide. I have taken notes which will assist me: my tadpoles have large nares (nostrils) situated close the eyes, the tail fin tapers smoothly to a blunt, rounded tip, and the underside of the tadpole is black, obscuring the intestines from view. Unfortunately, it turns out these features are all consistent with these tadpoles being the offspring of introduced cane toads (Rhinella marina).
|'Toadpoles' and a metamorph, Algester.|
One thing I had not considered before is that the behaviour, microhabitat and life cycle specifics of each tadpole is different depending on the species. For example, Anstis’s book describes cane toad tadpoles as exhibiting ‘schooling behaviour’, which makes them quite unique from other Australian tadpoles. Sure enough, after a short walk along the water’s edge, I come across dense, dark masses of tadpoles seeking shelter among the water plants, as well as a tiny metamorph on the creek bank, all of which further confirms the toad identity.
That’s when I really begin to notice my surrounds. A drain flowing into the creek is releasing a reddish-brown sludge that can’t be good for the water quality. The aquatic vegetation consists mostly of kidneyleaf mudplantain (Heteranthera reniformis), an emerging invasive weed first recorded in South-east Queensland in 2007. And the willie wagtail vacates his creekside post when a dozen Indian mynas (Acridotheres tristis) arrive for a drink, chirping and quarrelling noisily at what must be their daily watering hole. This is no paradise, this is a highly damaged and degraded urban waterway, and suddenly I can’t imagine many native frogs having an easy life here.
I gather my belongings and head back to my car, a little disheartened that I couldn’t find any frog tadpoles. Maybe it’s the wrong time of year, maybe it’s the wrong kind of habitat—a lot of our local frogs specialise in using temporary flood waters—but at least I learned more about tadpole anatomy and identification thanks to Marion Anstis’s incredibly useful book. Come the first wet weekend next spring, Tadpoles of South-eastern Australia: A Guide With Keys will be accompanying me into the nearest flooded swamp I can find.
- Tadpoles of South-eastern Australia: A Guide With Keys, by Marion Anstis, is a Reed New Holland publication from 2002. Selected Brisbane City Council libraries feature it in their collection, and it can be bought easily from online booksellers.