Nature Studies by Michael McCarthy: It's springtime for the swingers of suburbia One of the most fascinating things we have learned about life in the past 50 years is that the principle purpose of all living things, in so far as they have a purpose at all, is to reproduce. It's an insight from evolutionary biology (if you want to explore it further, pick up Richard Dawkins's bestseller, The Selfish Gene). And it certainly fits with what we can observe in the natural world, that reproduction is a pressing, not to say a frantic business, the most urgent of all activities, after escaping death at the hands of a predator. In myriad creatures, from dung flies to elephant seals, we see their urge to pass on genes into the next generation becoming so fierce that it invariably results, among males, in violence towards rivals. Whereas we humans, we have generally tamed the basic reproductive urge, have we not? Civilised it. At least, we have in my part of the world. That's south-west London suburbia. There, if you try to display your basic reproductive urge in all its primal power, you will probably be arrested. In the suburbs, reproduction is kept under wraps. Except for now. Right now at the bottom of our suburban garden, with its neat lawn and its lilac tree just coming into leaf, sex is rampant. Couples are coupling with abandon, and not just couples: there are threesomes, foursomes, maybe even fivesomes going on - maybe, but after a certain point it becomes impossible to disentangle the flesh, to separate out the ecstatic bodies and the grasping arms and legs. It's like a swingers' convention in Florida. If you filmed it for a documentary, you'd have to show it after the watershed. Good job it's only frogs. I reckon there are probably about 20 in the pond, maybe 30, maybe more. One spring, a few years back, in the most spectacular copulation carnival I ever did see, I stopped counting at 70, and the pond is no bigger than a circular dining table. That's the way frogs do it, the reproduction business - at least, that's the way our native species does it, the common frog, Rana temporaria: as soon as spring comes, they all assemble on the same watery dance floor, so to speak (sometimes travelling a fair distance to get there), and let desire take over. The zoological term is explosive breeding. It's explosive all right, and it's fascinating beyond words, one of the few examples of the reproductive behaviour of a wild creature most of us will ever be able to observe: at the height of their passion the frogs are so preoccupied, you can approach them closely. A male grasps a female in an embrace from behind known as amplexus, until she drops her eggs, at which point he fertilises them (when they become frogspawn) and lets go. However, males without females will try to dislodge the embracing males by clinging on to the couple themselves, and this can result in bundles of three or four or, indeed, even five desperate frogs forming a ball in the water like some bizarre stunt from a synchronised swimming gala. It's most definitely a reason to have a garden pond. I find it one of the most engaging episodes of the year in the natural world, perhaps because it seems so incongruous in its surroundings. The suburbs are respectable. I will have you know that our suburban garden is an entirely respectable garden. Our pond is a respectable pond. It is calm and tranquil and offers no more unruly behaviour than the blue flash of a departing damselfly. Apart, that is, for one wild week in March, when the celandines are out and the magnolias are blooming, for which we make allowances. Alas, poor Clement... Sad news for all those who have been following the remarkable odyssey of the five cuckoos - the birds fitted with satellite transmitters by the British Trust for Ornithology (BTO) last summer and tracked on their winter migration back to Africa. Clement, the first of the cuckoos to leave Britain, is dead. His last known position was in Cameroon, more than 300 miles north-west of his wintering area in Congo - meaning that, like his four fellow birds, he had begun his journey back to Britain. But after nearly a month of silence, his final transmission on February 25 has been reanalysed by the BTO, and it shows that his body temperature had dropped significantly - which means he is no longer alive. BTO scientists are keeping their fingers crossed that the other birds - Kasper, Lyster, Martin and Chris, currently in Ghana and the Ivory Coast - will make it back and be cuckooing in Britain a month from now. Twitter:@mjpmccarthy