Читать книгу The Inner Life of Animals - Peter Wohlleben - Страница 14

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STOP, THIEF!

IF LYING IS widespread among animals, then what about thievery? A good place to start is by looking at socially oriented animals, because thievery, like lying, has a moral component, and it is judged to be negative only when it is socially relevant and when it adversely impacts other animals of the same species.

When it comes to thievery, the American gray squirrel is a sly one, but before delving into its behavior, let’s check out how it’s doing in Europe, where it has become a serious threat to native red squirrels (which can also be black in color). In 1876, a certain Mr. Brocklehurst from Cheshire, England, took pity on a pair of grays that were being held captive, and he released them. In the years that followed, many dozens of other animal lovers followed his example. The gray squirrels thanked their liberators by reproducing enthusiastically—so enthusiastically that they have now pushed their red European relatives almost to the brink of extinction. Gray squirrels are larger and more robust than their red cousins, and they adapt to any kind of woodland, whether deciduous or coniferous. Even more dangerous for native European squirrels, however, is a stowaway that hitched a ride along with the grays: squirrel poxvirus. Whereas American grays are generally immune to the virus, European red squirrels die in large numbers when they are infected. Unfortunately, not only were grays released in the UK, they were also released in northern Italy in 1948, and since then they have been advancing on the Alps. We don’t know if at some point they’ll manage to scale the mountains and march victorious into the German woods, as well.

Despite all this, I don’t want to characterize gray squirrels as vermin. After all, it’s not their fault they were brought to Europe, and their dominance is not due to their behavior, which brings us back to the topic of thievery. Squirrels sometimes get food by plundering the winter caches of other squirrels. In many cases, they must do this to survive, as the unsuccessful searches in the snow that I observe from my office window every winter attest. A squirrel that cannot remember the location of its caches will starve, and as a last resort, it may help itself to its neighbors’ loot. I don’t know whether European red squirrels have developed a counter-strategy, but researchers discovered that American grays have. A team from Wilkes University in Philadelphia observed gray squirrels digging empty caches. The squirrels did this in clear sight of others of their kind to lead them astray, but only when they thought they were being watched. When the eyes of other squirrels were on them, they dug around a bit in the dirt and pretended to bury something. According to the researchers, this is the first report of rodents using deceptive tactics. When lots of unfamiliar squirrels were watching, up to 20 percent of the caches were empty. As part of the experiment, the researchers then had students raid the caches that had food in them, and guess what happened? The squirrels reacted immediately and from then on used deceptive tactics in the presence of suspect humans, as well.²⁷

Thievery is also a big deal for Eurasian jays. These birds are fanatical about survival. In the fall, each bird caches up to eleven thousand acorns or beechnuts in the soft forest floor, even though they could survive the winter just fine with far less food. Not only do they rely on the oil-rich seeds as emergency rations until the next growing season, but they also feed them to their chicks in spring. Even allowing for this, the sly birds usually store way too many seeds. And what an amazing memory they have: jays find every one of their thousands of caches with a single stab of their beak. Small trees sprout from the unused seeds to ensure that future generations will have their own supply of nuts and acorns.

In the woodland I manage, we use the birds’ passion for collecting to plant young deciduous trees in the monocultures of old spruce plantations. This is how it works. We put seed trays on posts and fill them with acorns and beechnuts. Jays love to come and help themselves, and they distribute their booty in the soil hundreds of yards in every direction. It’s a win-win situation. We get precious new stands of deciduous trees in the woodland, and the jays get huge quantities of winter provisions with very little effort. Some years, however, the oaks and beeches do not set seed, and then things get tight for these colorful birds. Whereas the population increases in years of plenty, in lean years it shrinks. This ruthless natural cycle has been repeated over and over since time immemorial. But who wants to starve? Some of the birds fly south, while most try to survive in the woodlands they call home.

Just like the squirrels, in lean times jays watch other jays in late fall to see where they bury their treasures. And because no bird can keep watch over such a large number of hiding places, sneaky individuals can live well over the winter by profiting from the hard work of others. Scientists at the University of Cambridge have discovered that the birds are well aware of these shenanigans. They discovered this by putting trays filled with two different materials into the aviaries. Some trays contained sand; others contained gravel. Whereas sand doesn’t make any noise when you dig in it, gravel gives the game away by rattling. And the jays kept this in mind when they buried their caches.

If the jays were alone in their enclosures, it didn’t matter to them whether they hid the proffered peanuts in sand or in gravel. If the competition could see and hear them when they were digging, it also didn’t matter which material they were rummaging around in. In the first case, no other bird was around to witness where the precious booty was hidden. In the second, the birds realized that any bird watching them would know where the food was anyway. However, if the competition was out of sight but still within earshot, the jays opted for the quieter sand. Under those conditions, there was a much higher likelihood that the potential thief would have no idea anything had been hidden. And for their part, the thieves were also quieter. Whereas they normally called loudly when they saw other jays, when they were watching food being hidden, they were considerably less vocal, clearly to avoid betraying their presence.²⁸ This experiment clarified two things. First, the bird doing the hiding can put itself in the position of other jays and take into account what they can and cannot see. And second, the future thief was obviously planning its actions in advance, because it limited the sounds it made in order to increase its chances of later plundering the cache of peanuts undisturbed.

Of course, theft in the sense of the intentional seizure of assets that don’t belong to you doesn’t occur only within a species. Come winter, in many deciduous woods you can find traces of interspecies plundering. Sometimes you come across holes in the forest floor one to two feet deep, their edges strewn with big clumps of excavated earth. Wild boar are the only animals that root around like this, and they do it in so-called mast years. This technical term describes years when beeches and oaks go into overdrive to produce seeds. These years were once a blessing for farmers. A mast year meant they could drive their domestic pigs into the woods one last time to fatten them up before the winter slaughter. Farmers are not allowed to pasture their animals in woodlands any longer (at least, not in Central Europe), but the term “mast” (from the German mästen, “to fatten”) is still used.

Naturally, wild boar behave the same way as their domestic relatives in a mast year: they put on a nice thick layer of fat. But once the unexpected gift has been cleaned up and all the nuts lying on the ground have been scarfed down, rumbling stomachs demand a top-up. And snacks can still be found deep down in the soil. This is where mice have buried stores—pantries stocked with their portion of the harvest so they can make it safely through the winter. Even in times of hard frost, the ground doesn’t freeze more than a few inches below the insulating layer of leaf litter, and in the mouse’s quarters, it’s always at least 41 degrees Fahrenheit. Thanks to a cozy layer of leaves and moss and a completely draft-free location, a mouse can survive very well down here. That is, as long as no wild boar come calling.

The gray hustlers have extremely sensitive noses and can smell the mouse’s digs from yards away. From experience, they know that the little creatures diligently collect beechnuts and other seeds, and store them all together in one convenient spot. An enormous store that will last a mouse for months is a tiny snack that will tide a wild boar over until its next meal. However, since mice mostly live in large colonies, a number of small snacks can provide the calories a wild boar needs to make it through a cold winter’s day. And so the boar burrow along the underground tunnels, smashing storerooms and emptying them in a couple of gulps. The only option the mice have is to flee and face an uncertain future, for in winter there are very few sources of food for the homeless. If they can’t evade the wild boar underground, they are gobbled up along with their food stores; boar enjoy their veggies with meat on the side. At least the swallowed mice are spared a long, slow death from starvation.

And what does this behavior look like from an ethical point of view? The wild boar’s plundering of mouse assets isn’t really theft, because they are not deceiving other boar. They are perfectly aware they are raiding mouse provisions, but this is a completely normal way for them to get food, even if the proceedings look very different from the perspective of the mice.