Michael McCarthy: A shock to the ancient rhythms of the natural world

Animals that hibernate in winter abandoning hibernation: yet another signal that something momentous is happening to the rhythms of the natural world, in the way in which we have always understood them.

Consider what a significant disruption of a life pattern this is. Hibernation has evolved for the same reason most animal behaviour has evolved: as a strategy to maximise survival. Some creatures that need a lot of energy to get around have learnt to shut themselves down in the winter months, when the food to provide that energy is simply not available (or too much energy would be expended in searching for it). Zoologists have realised in recent decades that many species have an instinctive and finely tuned way of weighing up the balance between how much effort needs to be expended to acquire a certain food item, and how much energy is available, in return, in the item acquired. The general law is: if the second is less than the first, don't do it. This has been christened "optimal foraging".

Hibernation could be seen as a version of this: if the food search is going to be hopeless, it makes sense to stop foraging altogether. Instead, fatten yourself up before the hopeless time, then sleep it out. This is a strategy that has evolved - in bears, hedgehogs, bats and other species - over millions of years and it has persisted as a piece of behaviour because it has been successful.

If some European brown bears in the Cantabrian mountains are now stopping hibernation, we can draw two conclusions. First, something quite enormous is happening in the world around them, and if you want to hazard a guess that that something is global warming, you would have as good a theory as any other.

Second, they are abandoning a survival strategy - which has been successful - for the unknown. What if they give up hibernation because of rising winter temperatures, but then when they are active in winter, are unable to find enough food?

We are already witnessing what a problem such disruption of natural cycles can cause for other creatures. In Britain, insects are hatching earlier in the spring, but migratory birds that depend on the "flush" of caterpillars to feed their young are coming back at the same time as they have always done, and thus may be starting to miss out on the feast: this may be one of the reasons why many of our woodland birds are now in sharp decline.

Climate change is perceived as a terrible problem for human society, and rightly so; but we should not lose sight of the fact that, to the natural world and its inhabitants, the warming also presents a mortal predicament.