wildlife DURING THE HIGH TEMPERATURES OF A SUMMER DAY, WHERE HAVE THE GARDEN SNAILS GONE AND WHAT ARE THEY DOING?
H
ere in France we normally expect a good, hot summer, with temperatures well into the 30°C bracket (that is mid-70°F and above in old money). Does this have any effect upon the wildlife that shares the summer with us? It can have a very strange effect upon humans that are unfamiliar with it. It produces a response which involves stripping off almost all protective clothing and spreading the now unshielded skin under the pitiless sun for a few hours. This, of course, allows ultra-violet radiation to penetrate that skin and by evening gives an effect rather as if a flame-thrower had been passed over the body. I worked in Exeter during the Great Heatwave of 1976. Few people in the UK had ever experienced sunshine on that scale. During the holiday period the easiest day to go shopping in the city was Monday, when all the newly-arrived vacationers headed for the beaches. The day when it was fun to go shopping was Tuesday, when one could watch the same folk walk slowly along the High Street, wriggling red-raw shoulders under the lightest shirt they could bear, and whimpering. Social distancing was strictly observed!
pile in the middle of the lawn. Amazingly, a few hours later, just before dawn, a scan with a fluorescent lamp showed that the snails had, for the most part, sorted themselves back into the appropriate areas of the garden. What took everyone by surprise was that the Cornish snails, a hundred miles from home, all set off in a south-westerly direction, where lay Cornwall. Even at full speed, travelling day and night, it would take at least 6 months to get there!
By M ik
e Geo r ge
Mike George is our regular contributor on wildlife and the countryside in France. He is a geologist and naturalist, living in the Jurassic area of the Charente
On a hot afternoon, of course, a snail will be seriously dehydrated before it has crossed your garden path. This is the reason that it goes quiet on the snail-front in summer in this region. You have spent the spring stepping on earlymorning snails or fighting to keep them off your lettuce-bed; now suddenly they have vanished. They have in fact aestivated. This is not some form of migration; it is the summer equivalent of hibernating. If you look carefully in the cooler, shaded areas of your garden, you will find hordes of snails dozing peacefully, their shell openings sealed with a membrane of dried mucous, conserving moisture. They often push their way behind things for extra protection.
Not many animals use this technique, No other creature would behave that way. mainly because the summer is the time of A “cold-blooded” maximum activity for vertebrate will bask You have spent the spring stepping them, and because they in the sun if its have other mechanisms body temperature on early-morning snails or fighting to cope with the needs to be raised, to keep them off your lettuce-bed; situation. One of the but will go about its now suddenly they have vanished most dedicated business when it aestivators is the lunghas reached a good fish, which seems to working temperature. Most mammals are have got all its choices wrong. It lives in covered with fur and enough natural mud-wallows because, having lungs, it, a pigment to protect them, though cats with fish, is better off breathing air. The mud, white ears may need watching if they of course, tends to dry out, and the spend time in hot sun. lungfish copes with this by burying itself in the mud at the last minute, surrounding There are a lot of creatures, of course, that itself with mucous to conserve moisture, are not equipped to avoid or deal with and waiting until the rains come. A rather strong sunlight. One such is the Garden risky strategy. Snail Cornu aspersum. The snail is famously slow-moving (maximum speed Plants also react to the hot weather, but for it is hard to discover, since each their requirements for water are rather authority quotes it in different units, but it more urgent. They cannot go looking for seems to be 50 metres/hr). it, nor can they hide away from the heat. As all gardeners and farmers know, it is Its slow speed does not mean that the snail down to us to provide the water for them, has no ambition. Recently an informal and woe betide any plant that test was tried whereby snails from all four gets forgotten. sides of an ordinary suburban Midland garden were collected. They were painted Some do have coping strategies. The with a different colour of fluorescent paint Tumbleweed plant so familiar to us from depending on where they had been old Western films is able to wither down to collected (north, south, east or west a ball of apparently dry sticks if it loses its section of the garden), mixed with some source of water, and allows itself to be control snails brought from far-distant picked up by the wind and carried vast Cornwall, painted yet a different colour distances. When it chances upon again, and all released by tipping them in a moisture, it will send out roots to anchor
itself and take advantage of the new-found life-giver. While it is bowling along, of course, it is scattering its seeds in quantity. These will lie in the soil until moisture arrives. Incidentally, the plant is not of American origin, but Russian, and was accidentally introduced in 1877 by Ukrainian immigrant farmers among flax seeds. It found the plains of the US ideal to its lifestyle, and also lacking in its natural predators. Any tumbleweed that you see blowing about in a Western dated any earlier than the late 19th century is definitely out-of-place. When “The Sons of the Pioneers” intoned their mournful ditty about “The Tumblin’ Tumbleweed” in the 1940s, it had been a problem for less than 70 years. Some trees have developed the technique of storing water in their tissues during the wet season for use in the dry months. These trees are enormously useful to knowledgeable travellers, who can tap the water for use at need. Finally, there is a frog in Australia that fills its stomach with water when it feels a drought coming on, and buries itself to live off this store. The Aboriginal Australians, who have a very welldeveloped sense of nature, can find these at need and squeeze out the frog to gain the water for their own survival. They do this sparingly, of course, because the result is fatal to the frog.
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