Nature 2016 February

The animated punctuation mark that does not eat shoots and leaves*

* With grateful acknowledgement to Lynne Truss, who coined the original

We are conditioned to expect most wildlife to behave in a predictable way. The dawn chorus is an example of a behavioural pattern which repeats on a daily basis. At longer timescales we revel in noting the recurrence of annual happenings. For example, recording when we hear the first cuckoo, in these parts around the third week of April, or the appearance in the chalk streams for just a single day of the year the ephemeral mayfly.

There are other cycles which follow longer periods, such as the cockchafer. Also known as a maybug, it usually takes between three and five years to complete its metamorphosis from grub (larva) to adult (imago). But there are longer cycles still. The European eel which, typically is born in the Sargasso Sea, takes around 300 days to migrate back to European waters. It seeks freshwater inlets and moves inland to lakes and rivers where the eel stays for between five and twenty years before making the return journey to his original birthplace in order to reproduce.

But this time period is not even close to some of the longest lifecycles. An interesting example is illustrated by some wood-boring beetles which infest ultra-slow-growing trees in highland Scotland.  Though they had been observed frequently in the wild, little was known about the habits of such beetles. This was largely due to the extraordinary length of the beetle’s lifecycle. Until recently it had defeated even the most dedicated of entomologists. Eventually this mystery was resolved by some smart detective work following the discovery of the beetles emerging from rustic furniture made from these temperature-stunted trees. By surveying he timber taken from a 40 year-old birch bookcase, out of which the beetles had emerged, it was found from counting the number of tree rings, the section of wood examined can be matched with a particular year range. In this case the larva had hatched from eggs 11 years before the timber was harvested. So the lifecycle of this particular wood-boring beetle took 51 (40+11) years.

Occasionally the behaviour of animals can confound our normal expectations. Take this example which I was lucky enough to observe. On a much warmer than usual Christmas Day just after midday, I saw what at first looked like a medium-sized garden bird flying in a haphazard manner round and round the garden. It was not a bird but quite a large bat, possibly a Natterer’s bat or one of the varieties of long-eared bats. Bats are one of three UK mammals that hibernate, the others being the hedgehog and the dormouse. Like the other two, bats are nocturnal in habit. Hibernation is an adaptive behavioural wired into the genetic make-up to enable survival during periods of harsh weather when food is in shorter supply. So what accounts for these counter-intuitive observations?

Well, it turns out that a zoologist carried out research on this phenomenon in 1985. He reported that although daylight flying during winter months is very unusual, it is a pattern of activity which has been observed under very specific climatic and ecological conditions. Firstly, emergence of bats in daytime only occurs on very warm days, which also creates a population explosion of small insects. Under these conditions the bats wake from their normal state of torpor. Once awake they need to feed to survive and as the gain of energy derived from feeding on the insects during the warmest part of the day outweighs the expenditure of energy needed for their foraging expedition, this has become an inbuilt response when such climatic conditions occur. This inbuilt response may have lain dormant in bats’ genetic makeup since the much warmer climatic conditions which persisted before the last Ice Age, over 100,000 years ago, when bats were not confined to night-time flying. Perhaps now the earth is subject to warmer winter temperatures within a period of climate change, this time driven by human activity, more unusual events will be observed, which echo a previous time when the planet’s climate was warmer.

Most of the time, in order to experience ‘nature in the raw’, at least a modicum of risk-taking is required venturing out into the unkempt local wilderness which we know as the Chilterns. Back in October 2004 I penned a Nature Notes for Hilltop News on the topic of Whose House is it Anyway? This explored how your house and its contents provide an ideal habitat for a whole variety of creatures which seek out a niche in which to thrive. Since 2004 there has been a technological revolution in domestic equipment and services, not least driven by the availability of broadband. No mention was made in the earlier article concerning creatures invading one’s technology, so the opportunity was laid on a plate for me to rectify this following an interesting discovery shown to me by my daughter recently. Whilst reading an article on her iPad, she suddenly noticed that what appeared to be a comma was slowly edging across the screen. Closer examination revealed the comma had legs and was in fact a miniscule creature.

The insect was a thrip or thunderbug. Normally these gregarious animals can resemble a cluster of iron filings. They are typically found beneath leaves feeding from the sap of a plant or inhabiting flowers, feeding on pollen. Others are predatory and voraciously hunt out even smaller creatures. The tablet, or under the face of it, provides a warm, dry and therefore attractive place for thrips and presumably several other minute arthropods to find refuge. For them it’s no different from any other crevice in which to hold up temporarily. For the benefit of anyone encountering thrips in their tablet or phone, the following might be helpful. The advice, according to several contributions found on iPad users forum pages, if your tablet is invaded, is to resist the urge to squash the bugs. Instead, remain calm and observe the thrips to see if they migrate off the screen area. If not, open as many applications as possible, as this sets the internal fans to maximise a cooling effect, which should encourage the thrips to move away from the screen.

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