Читать книгу The Inner Life of Animals - Peter Wohlleben - Страница 11

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PIG SMARTS

DOMESTIC PIGS ARE descended from wild boar, which were prized by our ancestors as a source of meat. About ten thousand years ago, wild boar were tamed to ensure the delicious animals were available at short notice without us having to go out on dangerous hunts to get them, and they were then bred to better satisfy our requirements. Despite this interference, modern domestic pigs have retained wild boar’s behavioral repertoire and, above all, their intelligence.

First, let’s look at how wild boar behave. (Feral hogs or swine in the US are descended from pigs that escaped domesticity and share behaviors with European wild boar.)¹⁸ For example, wild boar know exactly which other boar they are related to, even if the connection is a distant one. Researchers from Dresden University of Technology determined this indirectly when they were investigating the home ranges of family groups (known as sounders). As part of this research, 152 wild boar were caught in traps or stunned with tranquilizer guns, fitted with transmitters, and then set free again so the researchers could see where these nocturnal roamers hung out. The researchers discovered that there is normally not much overlap between neighboring sounder territories, and, on average, territories range from 1½ to 2 square miles in size, which is much smaller than previously thought.¹⁹

Wild boar rub against trees to mark their territorial boundaries. After wallowing in mud, they cover these “rubbing trees” with their scent. Scent markings, however, are not permanent, which means that boundaries between territories remain somewhat fluid, and so it’s little wonder that every once in a while, boar intrude where they don’t belong. As meeting up with strangers usually leads to altercations that even boar prefer to avoid, border violations by unrelated sounders are fairly rare, but if the home ranges of two related groups are side by side, their territories may overlap by as much as 50 percent. Clearly, wild boar are more kindly disposed to family members than they are to strangers and, most importantly, they can obviously tell the difference.

Family dispersal starts when the previous year’s piglets, the yearlings, are driven off as the birth of the next litter approaches. The sow has no extra time to look after older piglets, which are pretty independent by then. Wild boar are highly social and love to engage in mutual grooming or simply to lie snuggled closely together, and the siblings join up to form yearling sounders so they can continue living in a group. If the yearling sounders run into their extended families with their new piglets later in the year, the meeting will be a friendly one. Everyone knows everyone else and they all still get along well.

Thinking about our domestic animals, I’ve often wondered whether our goats and rabbits are capable of picking their grown-up children out of the group and recognizing them as relations. After observing them for a long time, I believe I can now answer this question with a resounding yes. With one proviso: that the animals are not separated from one another. If they are kept in separate enclosures for more than a few days, they end up treating each other as strangers. Perhaps their long-term memory is not configured for storing information about family relationships. It is clearly different for wild boar, and therefore also probably for domestic pigs, because they have long memories for who belongs to whom. This is of little use to domestic pigs, of course, because unfortunately for them, they are separated from their parents and raised in groups of other pigs their own age, and as a rule, they don’t make it past their first year.

These days, most people are aware that pigs are extremely clean animals. They prefer to use some kind of a toilet—a designated place where they do their business—be it big or small. This toilet is never in their sleeping hollow. After all, who would want to sleep in a stinky bed? This goes for both wild and domestic pigs. When you see photographs of tiny stalls in factory farm barns (11 square feet per animal) and pigs covered in muck, you can imagine how uncomfortable the animals must be. In the wild, boar adapt their sleeping quarters according to the weather and time of year. Because they select their resting places with care, they prefer to use the same spot all the time; however, when storms blow and rains soak their slumbers, they will move to wooded areas where they can sleep protected from the wind and stay relatively dry. In summer, the bare earth is sufficient as a place to lay their head, because at that time of year wild boar are usually too warm anyway. In winter, however, they plan their nightly repose especially carefully. A snug little nest under a thick windbreak of blackberry bushes with only two or three tunnel-like entrances is ideal. They bring in dried grass and leaves, moss, and other soft materials, which they pile up carefully to make a cozy bed.

Did I say “nightly repose”? Although they would probably love to sleep as we do when we lie dreaming in our beds, these smart animals have adjusted their circadian rhythms. Every year in Germany, hunters shoot as many as 650,000 wild boar,²⁰ and to do that they need daylight. In order to avoid their pursuers, the boar go about their business under the cover of darkness. Normally, that would be protection enough, because in Germany it is illegal to shoot animals after dark; however, an exception has been made for wild boar to try to control their burgeoning populations. Because night-vision devices are still prohibited, hunters have to wait for a full moon and clear skies so they can see more than just vague shadows in woodland clearings. They attract the wild boar with small amounts of feed corn, which the boar are particularly partial to. The goal: dispatch the boar with a deadly shot while they are feeding. But it’s not that simple to outwit the canny animals, which simply put off feeding until the wee hours of the morning. But the hunting industry has a solution at the ready for this, as well: game clocks. These are clocks that stop when they are disturbed. When hunters put these clocks in among the corn, they show the time when the wild boar come to feed. Now hunters can climb up into their blinds at just this time, and they don’t have long to wait until their prey appear.

In the final tally, however, it is the wild boar that seem to have come out ahead. In some cases, they rely on the bait as their main source of food, and they multiply quickly despite the hunting pressure—so much so that reducing populations has become a lost cause in many places. In the US, feral hogs are generally diurnal if left undisturbed, but they react like their European counterparts and intensive human activity or hunting during the day can drive them to be active at night.

There have been many particularly touching discoveries made about domestic pigs, if only because a number of research facilities are working to improve factory farming. When the newspaper Die Welt asked Professor Johannes Baumgartner at the University of Veterinary Medicine in Vienna if there had been any notable characters among the pigs he had studied, he told them about one old sow. Over the course of her life, she gave birth to 160 piglets. She taught all of them how to build a nest out of straw, and when her daughters grew up, the old sow assumed the role of midwife and helped them prepare for the births of their own babies.²¹

The question then becomes, if researchers know so much about the intelligence of pigs, why isn’t the image of the smart pig publicized more? I suspect it has to do with eating pork. If people knew what kind of an animal they had on their plate, many would completely lose their appetite. We already know this from primates: could any of us eat an ape?