He knows where the carcasses are buried
The author of The Hidden Life of Trees and The Inner Life of Animals, completes his trilogy with his new book. This passage is not for the squeamish — or prudish.
So far, we’ve passed over a particularly tasty treat for many species: the carcasses of large mammals. Fascinating things happen around these dead bodies. Do you find that disgusting? That’s understandable; however, strictly speaking, we’re surrounded by the dead bodies of animals all the time, and unless we are vegetarians, we interact with them (albeit briefly) almost daily — on our plates. The main difference between our meals and the many dead wild boar, roe deer and red deer out in the wild is that the process of decomposition has barely started, which allows us to enjoy our meals safely.
Many animals tolerate or even require various stages of putrefaction in their food and are perfectly happy devouring servings of meat that stink to high heav- en as far as we’re concerned. And there are a lot of these servings of meat to be consumed. Every year in Central Europe alone, millions of roe deer, red deer, and wild boar die a violent death. And although in Germany, for instance, a lot of wild game is shot (about 1.8 million of the three aforementioned species, according to the German Hunting Association), many more die a natural death.
What happens to their bodies? Off the top of your head, you’d say: they decay.
That is to say, they rot and eventually, after smelling awful for a while, they become humus. But who facilitates this process?
Let’s start with the larger facilitators: bears. They have extremely sensitive noses and can smell a side of meat from many miles away. Together with other large predators, such as wolves, they can consume most of the meat off a dead animal within a few days. What they can’t consume, they bury, so they have a hidden supply of food.
Birds are early responders, as well. Whereas vultures circle over fresh carcasses in the African savanna, noisily laying claim to them, in northern latitudes, ravens take their place. Ravens are the vultures of the North, and they, too, patrol their territory from above to see where a deer or wild boar might have met its end.
Dead animals are often the cause of fights, and wolves lose out when brown bears turn up. Then it’s best for the pack to head for the hills, particularly if they have pups, which a bruin could easily scarf down as a snack. Ravens have a role to play here: they spot bears from afar and help wolves by alerting the pack to approaching danger.
In return, wolves allow ravens to help themselves to a share of the booty — something the birds wouldn’t be able to do without the wolves’ permission. Wolves would have no difficulty making a meal of ravens, but they teach their offspring that these birds are their friends. Wolf pups have been observed playing with their black companions; the young wolves imprint on the smell of the ravens and come to regard the birds as members of their community.
Wolves and ravens might live peaceably with one another, but other species fight over food resources. Apart from the black birds, there are other feathered parties, such as bald eagles or kites that would love to haul away a portion of the booty. With all the commotion and clamour as animals wait their turn, the ground around the carcass gets torn up. The plants are shuffled, because seeds that would otherwise have been stifled in the matted grass now have their moment in the sun.
Things also change for vegetation that is not disturbed. Rotting flesh serves as fertilizer — for the plants, deer carcasses are simply overgrown salmon. The more robust growth and greener colour of the grass and nonwoody plants for about three feet around the carcass are evidence of the nutrient boost.
And what happens with all the bones? After the flesh has been eaten or has rotted away, there should be huge numbers of bones lying around in field and forest, bleaching in the sun. But no, even I on my daily rounds as a forester have never come across a dead animal’s final resting place, and only very occasionally do I come across a skull.
There are two forces at work here. Sick or weak animals separate themselves from others of their kind to hide in the undergrowth, or on hot summer days they wander near or into small streams to cool any wounds they might have. Here, they wait for death. That makes sense, because this way they don’t endanger their kin — weak animals attract the attention of predators. Also, in a secluded spot there’s no one to disturb them in their final hours.
Usually, it is our sense of smell that leads us to dead animals in places like this; bones lie quietly hidden from sight under bushes. Because bones basically don’t break down, and because every now and then animals certainly die away from the protective cover of vegetation, over time you’d expect to find bones scattered all over the place. But that is not the case, because there are plenty of takers for the dead animals’ final remains.
There are mice, for example. They seem to love bones, and they gnaw away at them until there’s nothing left. Calcium and other minerals are mostly what they’re after; bones are for mice what salt licks are for cattle (or salted pretzels are for us). If the bones are still fresh, bears eagerly crack them open for the fatty marrow inside — a delicacy that no one will fight the bruins for, not even wolves. Although some dogs like to chew on bones, the grey-coated hunters clearly don’t think much of this tedious detail-oriented task, but it is an important one, especially for other species. Just how important this task is becomes clear everywhere bears have been eradicated, including in Germany, because it is only when the hard outer coating has been cracked that daintier creatures get their turn.
Take the bone skipper, which disappeared without a trace until it was rediscovered in 2009. This bizarre insect with its tiny orangey-red head looks like a creature from a fantasy world, and it doesn’t behave like other flies, either. The bone skipper likes it nice and cold. It is out and about mostly on winter nights, on the lookout for dead animals and cracked bones. Here, it feasts and lays its eggs.
By the nineteenth century, however, there were no longer any carcasses out in the open in Central Europe — thanks to stricter rules about hygiene. At the same time, bears were driven out, and so things became grim for the bone skip- pers, and in 1840, they were declared extinct. In 2009, however, the Spanish photographer Juli Verdu took a picture of what he thought must be a fly that had flown in from the tropics. Researchers at the University of Madrid recognized it as the long-lost insect, which could then be crossed off the list of extinct animals.
We spoke earlier of ravens as the vultures of the North, but we should also mention vultures themselves. Griffon vultures searching for dead animals regularly fly over Germany. On the website Club300, amateur ornithologists report sightings of these unusual visitors every year. If there were something for them to eat, several of them might once again make their home here, but as it is, all they do is make flying visits that pass unnoticed by most of us. Griffon vultures, like bone skippers, have been declared locally extinct in many places in the world.
Until now, we’ve been concentrating on the carcasses of large animals. These are usually fastidiously disposed of, but below a certain size, this cleanup no longer happens. There are numerous remains of small mammals out there, and they vastly outnumber the large ones. Take mice, for example. Up to 250,000 of these little rodents scurry around per square mile, living on average just four and a half months. Young mice are sexually mature by two weeks, and after another two weeks, about 10 babies are born.
Let’s assume that during one growing season, there are five generations of 10 mice each for every mouse pair. In particularly fruitful years, that would mean the 250,000 animals (or 125,000 pairs) per square mile would lead to 6.5 million mice scampering around — not all at the same time, of course, because most of them would have died from disease or been eaten as the season progressed. Over the course of the season, then, there could be up to 6.5 million dead mice lying around. If each weighs an average of 1 ounce, the total weight of these dead bodies would be 200 tons, the same as about12,000 roe deer. That’s way too much mouse meat to be carried off by buzzards, foxes or cats, which leaves plenty for others to exploit.
One of these others is a pretty blackand-orange striped beetle appropriately called the sexton or burying beetle. I encounter it frequently on my walks through the forest — it’s so striking that it’s hard to miss. Even though the adults hunt insects, they can’t resist the delectable scent of fresh carrion.
For sexton beetles, a mouse carcass is attractive not only as a hearty meal but also as a good place for their offspring to get their start in life. It’s often the males who first occupy the prize. They triumphantly raise their rear ends and discharge a scent message to attract females. Their goal is clear: sex. Rivals, however, also get the message and fly on over. Fierce struggles ensue, and the losing beetle has to beat a hasty retreat. When a female turns up, the work begins.
The beetles dig tirelessly underneath the mouse, dragging it down by its fur. In the process, a lot of the fur gets bitten off and the carcass gets coated with generous quantities of saliva. That doesn’t sound very appetizing, but it makes the mouse more slippery. And so the dead animal gradually descends farther down into the soil, until it eventually disappears completely — safely beyond reach of other carrion eaters.
The beetles take frequent breaks to have sex. After all the work is over, the mouse doesn’t look much like a mouse anymore. All that pulling and pushing has transformed the carcass into an elongated pellet. The female now lays her eggs alongside it. Unlike many other insect parents, sexton beetles stick around after their larvae hatch. The youngsters’ mouth parts are not strong enough to chew meat, and so the mother feeds her little ones, which lift their heads and beg for food like baby birds in a nest.
As researchers at Ulm University discovered, something else happens to the beetle mother: she loses interest in mating. Not only that, even if the male were to get lucky, it wouldn’t do any good, because his beloved is now completely infertile — at least as long as she still has her full complement of babies. As soon as a couple of the little ones go missing (perhaps because they died or were eaten by some animal), her desire for sex returns.
The male immediately gets wind of the change and goes berserk. The scientists observed up to 300 copulations — more than when the male initially laid claim to the carcass. The female quickly lays new eggs to replace her loss. If, in this flurry of activity, she ends up with too many babies, she soon fixes things by killing the extras.