by Ted Dewan
More grown up human behaviour also finds its monkey equivalent. Monkeys plan ahead: Grey-cheeked mangabeys (Lophocebus albigena) make decisions based on the weather, remembering the location of particularly good fig trees and waiting for the sun to shine before setting out on fruit-picking expeditions. Vervet monkeys (Chlorocebus aethiops) display a very human attitude to booze. On the Caribbean island of St Kitts they have learnt to hang out near bars, and finish the cocktails people leave behind. The majority are social drinkers who imbibe in moderation with other monkeys. They prefer their alcohol to be diluted with fruit juice and never drink before lunch. Others refuse to drink at all, but 5 per cent are serious binge drinkers who consume as much hard liquor as they can, make a lot of noise, and start fights, before finally passing out.
Drunkenness is not the only vice we share. An experiment with rhesus macaques (Macaca mulatta) revealed that they would ‘pay’ to look at pictures of the faces and bottoms of high-ranking females by forfeiting their usual reward of a glass of cherry juice. With low-ranking females, however, the researchers had to bribe them with an even larger glass of juice before they’d pay any attention. Some species have even taken the law into their own hands. Pigtailed macaques (Macaca nemestrina) ‘elect’ senior monkeys to break up fights and keep order. Their authority rarely requires the backup of force, but as soon as the police monkeys are removed, cliques rapidly form and social cohesion breaks down.
For all the similarities there is a gulf between humans and monkeys that only our imaginations can fill. Macaques, smart as they are, know if we’re imitating them but can’t make the leap and imitate us back. A deep bond remains, nonetheless, and may even be hard-wired. A Canadian research team recently found that, up to the age of three months, newborn humans respond as positively to the calls of rhesus monkeys as they do to human speech.
FROM NOSE TO TAIL
Moose
Lippy northern stripper
Moose (Alces alces) are, by a wide margin, the largest living members of the deer family. A bull moose weighs three times as much as a red deer stag. The weight of his antlers alone would exceed the personal baggage allowance on international flights (50 lb), and are wide enough for a child to sling a hammock between them. Moose have grown big to cope with the cold: they are only found in the high latitudes of the northern hemisphere. Big is better for keeping warm (a lower surface-area-to-volume ratio helps prevent heat loss), which is why so many ice-age mammals grew so large.
Moose have a double layer of insulating fur, and long legs for wading through snow; even their newborn calves seem happy in temperatures of –30°C. More troubling is warm weather: they can’t sweat, and fermenting vegetation turns their stomach into a furnace. In winter, temperatures much above –5°C will set them panting or lying flat in the snow to cool down. During the summer they spend a lot of time wading in water for the same reason.
Moose antler is the fastest-growing animal tissue, sprouting an inch a day. Antlers are sensitive enough for the moose to feel a fly land on them.
WHY THE LONG FACE?
Moose are notoriously difficult to keep in captivity. Unlike most other deer, who can browse happily on twigs or graze grass, they are specialised feeders. An adult moose needs to eat the equivalent of a large straw bale of vegetation every day, chewing the cud like a cow to extract the maximum nutritional value. They eat leaves, bark and twigs during the autumn and winter for energy, and marsh plants, when they are in season during spring and early summer, for sodium. Commercial feed can’t match this balance, so captive moose tend to die quite quickly. The need for salt explains why you often see them licking roads during the summer. It’s also why moose spend so much time in the water; aquatic plants like water lilies and horsetails are sodium-rich and moose will completely submerge themselves to graze on the bottom of ponds. Reports of them ‘diving’ are usually exaggerations: they are the wrong shape and size for serious underwater swimming.
What they can do well is to strip trees with their large drooping upper lip (they have no upper front teeth) – the name ‘moose’ comes from the old Algonquian word mooswa, meaning ‘the animal that strips bark off trees’. Their eyes can move independently, enabling them to see behind while still looking forward and the long nose, full of soft cartilage and muscle, is a hypersensitive food-finder-cum-sex aid. This nasal succulence wasn’t lost on local Native American tribes. According to the eighteenth-century naturalist, Thomas Pennant, the moose’s nose was the ‘perfect marrow, and esteemed the greatest delicacy in all Canada’.
In Europe moose are called elks, from the Latin alces, and were first described by Julius Caesar in 50 BC. The elk became extinct in Britain in the Bronze Age but the name lived on and was used to describe any large deer. When English settlers reached America, the commonest deer, Cervus canadensis, reminded them of its British relative, the red deer (Cervus elaphus). As a result, it acquired the name ‘elk’ and the other huge and unfamiliar beast continued with its local name, ‘moose’.
Mouse
The furry weed
The histories of humans and house mice (Mus musculus) are inseparable. The original Mus had lived happily outdoors in northern India for millions of years but as soon as our hunter-gatherer ancestors started to farm in Mesopotamia 10,000 years ago, the mouse lifestyle was also transformed. Permanent houses and grain stores inadvertently provided reliable food and shelter and the small, swift, resourceful mouse needed no further encouragement. The very name ‘mouse’ (from Latin mus and Greek mys) ultimately derives from the Sanskrit root mush, which means mouse and also to steal. Hence wherever we went thereafter – on foot, in carts, or by ship – the little thief kept us company.
As a result, house mice can be found wherever there are settled populations of people (as well as many places where there are none). They live on all the continents; at altitudes as high as 15,600 feet; as far north as the Bering Sea; and as far south as the sub-Antarctic islands. They live in coal-mines, meat freezers, underground railway tunnels. This is partly because they can live on almost anything – seeds, roots, insects, larvae, food scraps – and if they need to drink at all, licking dew or condensation is enough. But the real source of their success is that they can rapidly adapt their behaviour to suit the environment they find themselves in. Most animals change slowly. Wherever we take them, mice not only survive: they find a way to thrive.
Their prodigious fertility helps. Mice are sexually mature at four weeks; a single pair of mice can produce 500 offspring in a year. It’s a competitive business and female mice are extremely promiscuous. The bigger the penis, the longer and more frequent the copulation; and the higher the volume of ejaculate, the more likely conception is to occur. A quarter of all litters are the product of more than one father, a strategy that not only ensures genetic diversity but also helps to prevent any new male partner eating a female’s offspring, just in case they are his. In extreme cases, she will even reabsorb the foetuses to prevent them being eaten.
Mouse sex is not without its romantic side. Male mice sing complex songs in ultrasound, both to attract mates and during the act itself. Slowed down, they sound disconcertingly like Clangers. Most murine communication is via urine, which they dab around continually. Age, sex, health and sexual status are all encoded in a mouse’s urine ‘signature’. Male scent is used territorially; female scent is to do with breeding, a kind of mousy ‘girl talk’. It’s one of the reasons mice dislike peppermint – it scrambles their communication network.
Sanskrit has forty words for ‘mouse’. Mushka is ‘little mouse’ but also means ‘testicle’. From this, we get ‘musk’ (from the scrotum-like gland of the musk deer) and ‘muscle’ (from its mouse/testicle-like movement under the skin).
What do we get out of the relationship? House mice now comprise 98 per cent of all animals used in genetics research. Amazingly, most of these derive from just two breeding strains (C57BL/6 and L/10) sold to a laboratory in 1921 by Massachusetts schoolteacher and ‘fancy mo
use’ breeder, Abbie Lathrop. Also, mice are what most carnivorous predators eat most of the time. This is a very good thing: if there weren’t any mice, they would be forced to eat our livestock. Indeed, without the little thief, it is unlikely that the ancient Egyptians would have bothered domesticating cats in the first place.
Naked Mole Rat
A termite with teeth
A strong contender for the planet’s ugliest animal, the Naked mole rat looks like a flaccid penis with teeth. It is also one of the least well named, being neither naked, a mole, nor a rat. Cousin to the porcupine and the guinea pig, it is a 3-inch long rodent, which uses its huge incisors to carve out tunnels in the hard desert soil. Although it looks completely bald, it does have whiskers on its face and tail which act as navigational sensors, and hairy toes which sweep soil behind it like a broom.
Naked mole rats feel no pain. They lack a neurotransmitter chemical called ‘Substance P’, which may be an adaptation helping them cope with the near poisonous levels of carbon dioxide in their stuffy burrows.
They are the only mammals to live in organised colonies, like termites and bees. Only one female breeds, serviced by a harem of three males and supported by as many as 300 ‘workers’ and ‘soldiers’, who divide the tunnelling, childcare, food collection and defence functions between them. This behaviour is called eusocial (eu-meaning ‘good’) and has evolved in response to the harsh conditions of their home territory in eastern Africa, where a lack of rain and food mean they need to cooperate to survive. A large colony gives them better odds of coming across the sparse underground vegetable tubers which cater for all their food and drink needs. By carefully boring into them, they can keep the tubers growing, providing a sustainable food source for years.
Naked mole rats (Heterocephalus glaber, the ‘odd-headed smooth one’) spend almost all their life underground. Their eyes have become so useless that they usually keep them closed. They can also close their lips behind their teeth, to keep their mouths free of soil while digging.
NAKED CHAIN GANG
Except for the queen and her harem, digging is what mole rats do. A quarter of their muscle is in the jaw, and a third of their brain is used to process information from their mouths. Colonies contain miles of tunnels; an individual worker can dig half a mile a month when the soil is softened by rain. That’s equivalent to a human digging the 12 miles from central London to Heathrow Airport. Mole rats are practically cold-blooded: when they’re not digging or eating, they sleep heaped together in communal chambers to keep warm.
As with other mammals, the newborns are suckled by the mother. The queen gives birth to between twenty and thirty ‘pups’ at a time, but only has twelve nipples – a unique mismatch for a mammal. Pups get their food by waiting patiently and taking turns.
Queen mole rats are fat bullies, nose-shoving the underlings when their work isn’t up to snuff. A combination of work stress and intimidation seems to be enough to suppress the sex hormones in both male and female workers, although the queen supplements this with a special chemical in her urine, the equivalent of bromide in a soldier’s tea. A ‘sterile’ worker that is removed from a colony becomes sexually active within a week.
A queen and her harem can live for twenty-five years, producing over a thousand offspring. When she dies, vicious fights break out between the largest remaining females to decide the next ‘queen’. Mole rat colonies are like large, in-bred, dysfunctional families. The lack of interbreeding with other colonies means that the workers are propagating some of their own genes by helping to raise a conveyor belt of siblings.
Octopus
Well-armed
To look at, octopuses are about as different from humans as it’s possible to imagine: no body to speak of, just a head sprouting eight arms (it’s very biologically incorrect to call them legs or tentacles). So it’s pleasing to discover that they have larger brains, relative to body weight, than any animals except birds and mammals, and that they get bored easily. If they are kept in environments enriched with natural features, they grow faster, learn faster and remember more of what they learn than if they are kept in bare tanks. They remember places where they might find food, and where they have already hunted. And although octopuses are mostly solitary, there is evidence that they can communicate and, if kept together, they establish hierarchies and avoid confrontations. For all these reasons, in the UK octopuses enjoy the same legal status in labs as vertebrates.
Octopuses are good mimics. Some imitate other dangerous animals like sea snakes and lionfish. Others pretend to be drifting clumps of algae or waterlogged coconuts.
What they are not so good at is recognising the sex of other octopuses (or octopodes, but never octopi: the word is derived from Greek, not Latin). Put two octopuses in a tank and they will start to copulate regardless of sex. Thirty seconds into a male-on-male encounter there’s usually an unembarrassed disentangling, although some of these gay clinches can last for days. In one case, the two males weren’t even from the same species. Despite Japanese artists’ persistent obsession with giant octopuses pleasuring women in eight erogenous zones simultaneously, octopus sex is a polite affair, carried out at arm’s length. One of the male’s eight arms is for mating and it differs from the others by having a groove on its underside and a grasping tip called a ligula which in some species inflates with blood, rather like a mammal’s penis. The arm carefully places a packet of sperm in a corresponding slot in the female’s mantle (the body/head). The ligula then breaks off and remains embedded in the female. The male dies within a few months of mating. Although octopuses can regenerate lost limbs, they can’t grow a new sex arm.
THE OCTOPUS ELBOW
The male blanket octopus takes sexual discretion to a new level. He is 40,000 times smaller than the female and his technique involves tearing off his mating arm, placing it somewhere on her body and then swimming off to die. Given that this is roughly equivalent to a herring nudging a blue whale, it’s unlikely that she’s even aware of him. Meanwhile his disengaged arm crawls into her gill slit, where it can live for as long as a month, until her eggs are mature. She then retrieves it, tears it open like a packet of café sugar and sprinkles the sperm over her eggs.
Octopuses are as dextrous as they are smart. They can open jam-jars, use stones as tools to open shells and wield snapped-off jellyfish tentacles as weapons. Some ‘walk’ on two arms, as if they were bipeds. They use their body muscles to squirt themselves forwards, reaching speeds of 25 mph. They can even ‘fly’ using this method – squirting themselves right out of the water to escape predators. As octopuses have no skeleton – the only hard part of an octopus is its parrot-like beak – they can squeeze through spaces as small as their eyeballs.
Owl
Dim and deadly
The large, slow-blinking eyes lend the owl’s face an expressive quality most birds lack and this has doubtless contributed to its reputation for wisdom. In fact, an owl is not overburdened with brain. Its eyeballs are almost as large as a human’s, even though its skull (without feathers) is barely the size of a golfball. This doesn’t leave a lot of room for problem-solving. Owls look as they do because they are supremely well adapted for the job of catching small prey at night. Their huge pupils capture a lot of light and the eyeball is shaped like a café salt-shaker rather than a sphere to allow space for the largest possible retina. The retina itself has many more light-sensitive rods than detail-focusing cones, enabling owls to see when the light level falls to almost nothing. A long-eared owl’s (Asio otus) eyes are so sensitive that it can locate a stationary mouse in light levels equivalent to a football stadium illuminated by a single candle. The downside of such big forward-facing eyes is that owls can’t move them. If they want to change their range of view, they have to swivel their head. If they want to judge an object’s position accurately, they bob their heads round, reading it from slightly different angles.
AVIAN IMAX
But eyes are only half the story. An owl’s e
ars are, in contrast, very sensitive. The flat feather-dishes on its face help to capture sound waves like a pair of satellite bowls, channelling them to its ears, which are huge vertical slits running down both sides of the skull. Sometimes these are cock-eyed (or, rather, cock-eared) on the head, with one higher than the other, or else the owl can manipulate its ear-flaps to create different-sized openings. This allows it to calculate the precise location of its prey by estimating the tiny span of time it takes for the rustling sound of a mouse to get to each of its ears. It is accurate enough for some species to hunt in total darkness.
As well as unusual sight and hearing, owls have evolved a unique system for silent flight. Their bodies and legs are covered with a great number of downy feathers, and even their flight feathers have unzipped, fringed ends to soften the flow of air over them. This makes them look a lot larger than they really are. The long-eared owl has a 3-foot wingspan but weighs less than an orange. To hide, it sucks in its feathers and manages a reasonable impression of a branch.