Frogging

This went out originally as an ABC Radio National broadcast on Ockham's Razor. It has been edited to disguise locations.

It is a warm and moonless Saturday night.  It is raining, the cloud is down so low on the headland that it qualifies legally and scientifically as mist, and I am wandering around in the dark through dense heathland, half a kilometre from home, with the rain soaking through my broad-brimmed hat, and running down my neck.  Every so often, I stop and shout ‘FROG!’ as loudly as I can.  Then I raise my dripping hat to hear if anything answers.

It is probably fair to ask whether these are the actions of a sane man.  I say they are, but then I know what I am doing.  Or that is my story, at any rate, and I would like to stress here my non-membership of that strange breed, the compulsive froggers, people who sometimes care more for frogs and toads than they do for humans.

I know that I retain my sense of proportion, my sanity, for out there, alone in the dark, I am still rational enough to ask myself what I am doing there.

I am on a headland near Sydney Harbour, in a large patch of bush where there are three, or possibly four species of frog.  After steady rain, there will be equally steady seepage out of the sandy soil for some weeks, and the frogs have a chance to rebuild their numbers.  They gather near the trickling water, they call, and they mate.  Their tadpoles will hatch a few days later and rush through a hurried childhood into premature adolescence, before they join their parents on the drying land.

As a child, I collected tadpoles once or twice in a glass jar and brought them home, but I never succeeded in growing any up to be frogs.  As a young adult, I maintained a genial interest in frogs.  I learned to feed the tadpoles on lettuce, to get them to the adult stage.  Most importantly, I learned to provide them with a rock to rest on, a way out of the water.  Emergent frogs have lungs, not gills, and they will drown if they cannot scramble out.

Many years ago, as a young biology teacher, I acquired by devious means a lockable glass-fronted cupboard, designed for chemical storage.  I bolted it to a corridor wall where passing students could look in.  I bought a narrow glass tank and went through a number of frog-breeding cycles over several years, but I was still not a compulsive frogger.  I just thought it was good for students to have a small ‘zoo’ to look at.  Tadpoles and frogs were a major part of what happened there, along with assorted invertebrates and static demonstrations, but I was definitely not a compulsive frogger.

Later, I moved house, and we soon found that frogs had joined us in our garden.  We got up one rainy morning to find that we had a frothy mass of frog eggs in plastic bowl that lay abandoned in the garden.  Delighted, I dug a small pond, and transferred the eggs across.  Soon after, when I had to build some new stairs and a landing into the backyard, I constructed a much larger pond in the wasted space underneath the stairs.  Friends thought this a little eccentric, but I knew I was still not a compulsive frogger.  Even the friends could see that, when I explained it to them.

Some years later still, I found myself working in a museum, and I was cajoled into working on a project called Frog Watch, that involved both frogs and computers.  I was involved more as a writer and computer person, though I found myself getting more involved in froggy things.  But still I resisted the temptation to become a compulsive frogger.

I met quite a few compulsive froggers while I was there.  One of them noticed a small population of tadpoles sharing a pool with some mosquito fish.  This surprised him, for mosquito fishes will attack most tadpoles, and eat them, working up from the tail.  Most people would have passed on to other things, but this frogger thought about it, and concluded that the tadpole must taste rather awful.  A true man of science, he tried eating several of the raw tadpoles.  They tasted vile, a discovery which may have waited forever, but for the dedicated commitment of this compulsive frogger.

I met a fellow worker, who kept several pet frogs in a tank in his office, where they responded every time his phone rang.  Later, I edited a frog book for another colleague, who kept a one-eyed tree frog in his workshop (it lost the other eye when a truck ran over it, but my colleague nursed it back to health).  I knew I was still not a compulsive frogger, not by any of the rational standards that I could construct.

Pseudophryne australis, otherwise the Sydney red-crowned toadlet.
CC BY-SA 3.0, 
https://commons.wikimedia.org/w/index.php?curid=1185340

Then I moved house again.  Soon I started to notice the several frogs living around my house.  I bought tapes to identify them (you ‘earball’ frogs rather than eyeballing them), and I started to learn how to provoke certain species to call.  Then one day I found a small frog in my front yard, did a quick double-take.

With delight, I realised that the seepage drain near my front gate was home to a member of an endangered species, a Sydney Red-crowned Toadlet.  I was still not a compulsive frogger, but now I was distinctly interested.

Since then, I have been trying to map the frog's distribution in the local area by going out in wet weather and listening for the toadlet's distinctive call.  Somebody in Canberra told me once that the Corroboree Frog, another member of the same genus, will answer if a male human voice bellows ‘FROG!’ nearby.  Testing that theory is what leads me out into the wilderness on damp still nights, shouting in the dark.  That and finding out just how healthy the local population is, but I am still not a compulsive frogger.

My little toadlet lives in some two hundred pockets of land around Sydney.  In all likelihood, each population carries different genes, but there is no flow of genes between the different localities.  Each group is an isolated remnant.  If any group dies, it will not be replaced by new colonists moving in, for they cannot swim over the salt water of the harbour.  There is no bridge for them to use, and pioneers cannot hop over the 5 kilometres of settled ground to get here from the next pocket.

The toadlet's distinctive  underbelly.
By Tnarg 12345 at the English language Wikipedia, CC BY-SA
3.0, https://commons.wikimedia.org/w/index.php?curid=2652554

If any isolated group dies out, its small part of the genetic diversity dies with it.  The special genes that they alone may have are no longer available to the population as a whole.

It is a simple enough principle: even the ancient Romans understood it, when they coined the phrase ‘Divide et impera’ — divide and rule.  It is a cold implacable logical law, and its operation may one day wipe out all of the toadlets.

But why should we worry about one little frog, when there are hundreds of other species in Australia?  Many years ago, Paul Ehrlich taught us that we should think of an ecosystem as rather like an aeroplane which can lose a few bits and still fly.

I prefer to see an ecosystem as a steel bridge.  You can take one rivet away from a bridge, and nothing will happen.  You can remove another rivet, and the bridge will be as steady as ever.  You may even take some more, and still do no harm.  But somewhere along the way, you will take out one rivet too many, and the bridge will come tumbling down.  Ecosystems are robust, they can manage without some of the key species, but sooner or later, they start falling apart.

Biodiversity in a species works the same way.  Eliminate a few unusual genes, and no harm will arise, not yet.  Take a few more rare genes away, and there will still be no problem.  Sooner or later, though, some other change will mean that one of those eliminated genes will be needed.  By then, it won't be there, because the gene's minders have died, and the gene has died with them.  All over Australia, the frogs and toads are reminding us, calling ‘rivet, rivet’, but nobody cares, for the frogs' bridge is still standing.  It sags a bit, it may sway perilously from time to time, but it is still there.

It is a warm and moonless Saturday night.  It is raining, the cloud is down so low on the headland that it qualifies legally and scientifically as mist, and I am wandering around in the dark through dense heathland, half a kilometre from home, with the rain soaking through my broad-brimmed hat, and running down my neck.  Every so often, I stop and shout ‘FROG!’ as loudly as I can.  Then I raise my dripping hat to hear if anything answers.

I know now why I am there in the dripping mist.  I am still not a compulsive frogger, but I think I understand them now.