It’s a frog-eat-frog world

LIFE SPIRALS An emaciated female frog at Moorehall, utterly spent and near starving after the rigours of spawning. Pic: Michael Kingdon

From frog monsters to Fibonacci spirals, nature keeps us fascinated


Country Sights and Sounds
Michael Kingdon

In a drain where water tends to lie, where green fields edge into the bog, lies a new cluster of translucent pearls. Each one has a dark eye, a developing, comma-shaped embryo, the signature of life and the same basic shape as I find in an unfurling frond of fern, in the centre of an early-opening daisy and built within the shell of the green-tinted banded snail at my feet.
Even an unfolding galaxy and the parts of our inner ear are perfectly based on this spiral pattern, the so-called Golden Ratio or Golden Angle, which was discovered by Italian mathematician Leonardo Bigollo Pisano, better known as Fibonacci.
But look, within each pearl-bound embryo is another eye. Can it already see? What does it make of me, an intruding giant probing gently, seeking knowledge?
The frog that birthed this thousand was a late arrival to the drain. The rest of the females had departed soon after spawning, leaving just a few hopeful males behind. The other, older frogspawn is well on its way to hatching; a week of warm weather will hasten the process and for a while there will be food for all.
It is well that tadpoles are many, for every which way they turn they are eaten.
Water scorpions drift imperceptibly, their front legs disproportionately long and strong. These strangely angular limbs snap closed on contact with any potential snack as if loaded with elastic. They grasp and hook into their prey, and bring it within reach of those hideous, hypodermic mouthparts that are the mark of all true bugs.
Inch-long larvae of giant water beetles hang from the water surface, their breathing filaments protruding through the meniscus. There again is Fibonacci, that exquisite, almost balletic curve well described, this time in deadly pose. Legs are held apart, hollow, needle-pointed, scimitar jaws are wide and waiting to close on any passing innocent, such as we imagine our tadpoles to be.
In almost any permanent body of water there will be fishes. Sticklebacks inhabit small drains and streams, even those unconnected to other waters, forcing us to question how it was they came to be there. The stickleback is a picker, worrying at any blemish in the tadpole’s skin until flesh or organs are exposed. Pick, pick pick, go the little fishes lips, picking morsels until the wonder of life is undone.
In the farm pond it is perch that eat tadpoles. In the stream it might be trout, in the river pike, and at every step along the way something else. Herons peck them up as if they were ants. Kingfishers eat them by the score. Blackbirds come to dine as the water falls away, leaving myriad little forms squirming in the mud to watch with reflected eye as a golden beak dips and dips again.
We feel pangs of angst, as if our own pets were besieged. Who will save our little froglets?
Let’s go back to their beginning.
Frogspawn. Special secretions allow the developing tadpole to absorb nutrients from the jelly of its own egg.
On hatching, our tadpole turns his attention to algae and other plant material, rasping with increasingly bony jaws at almost anything that happens to be within reach. When the algae is gone any other green thing is fair game. An insect falls upon the water, and drowns. He, too, is promptly consumed, and when the stickleback dies revenge is readily taken.
There comes a time when food can no longer be found, and it is then that the true nature of the tadpole is revealed. He falls upon his brother, only to find his neighbour chewing at his tail. Cannibalism becomes widespread, infecting the entire tribe.
For a while it is frog-eat-frog, until such time as limbs are developed enough to carry our little frog-monsters away from their home and into the wide world.
At this stage they are barely half an inch long and likely have residual tails. Even a grassy field must be like a jungle to them. They scramble and climb past dangers unknown, eating and hoping to remain uneaten.
They might, by chance, meet their mother. She put all but her very life into making them. Now, exhausted and near starving, anything that moves will be eyed greedily. She never knew her offspring, apart from one short, fleeting moment when her eggs were passed. Now if she finds them she will eat them, and in doing so ready herself for winter sleep and another thousand births to come.
What a strange world, filled with mathematical art and terrible beauty.

Michael Kingdon formerly wrote these columns under the pseudonym John Shelley. A naturalist and keen fisherman, he lives close to the shores of Lough Carra.