Wild animals keep score differently than we do. A frog spends the winter frozen solid, a worm cannot survive a warm afternoon, and a ranch dog in Wyoming once carried home a species that science had given up for lost. These stories cover the savanna, the forest, the ice and the record books.
Every tile in a Wild Animals game carries one of these. Open one to read it now, or leave them for the board to hand you.
Savanna
nine stories
1The sound giraffes only make in the dark
On the tile: Giraffe Hum2015
Giraffes have a reputation for near silence, and for years nobody could say whether they had much of a voice at all. A team from the University of Vienna left microphones running overnight at zoos in Berlin, Vienna and Copenhagen. They collected 65 low, sustained hums with an average pitch around 92 hertz, deep but easily within human hearing. Every one came from a nocturnal session; not a single hum turned up during the day. What the giraffes are saying, and to whom, is still unknown.
The meerkat standing upright while the rest of the group digs looks like the selfless one, risking itself so the others can eat. A long study in the Kalahari led by Tim Clutton-Brock found something less noble. Sentinels take their turn only once their own bellies are full, and they guard from safe spots. Being first to spot a predator also means being first to get away from it. The team titled their 1999 report in Science "Selfish sentinels in cooperative mammals."
Explanations for zebra stripes have included camouflage, cooling and confusing predators. In 2019 Tim Caro and Martin How tried something simpler at a British horse farm, filming horse flies around captive zebras and plain-colored horses. Far fewer flies landed on the zebras. Then they dressed the same horses in striped coats, and the flies that had settled happily on solid cloth failed to land on the stripes, while the horses' bare heads were bothered exactly as before.
The Cincinnati Zoo laid out a straight course, put a lure on a line, and turned loose an eleven-year-old cheetah named Sarah. In 2012 she covered 100 meters in 5.95 seconds, with a top speed clocked at 61 miles an hour. She was breaking her own record: in 2009 Sarah had run the distance in 6.13 seconds, which had itself beaten the 6.19 of a South African cheetah named Nyana. Usain Bolt's best over the same ground is 9.58.
Before a hunt, African wild dogs gather in a noisy greeting ceremony that biologists call a rally. Watching 68 rallies across five packs in Botswana's Okavango Delta, researchers noticed the dogs sneezing, and the sneezes turned out to count. The more sneezes, the more likely the pack was to get up and go. When the dominant pair joined in, a few were enough. When the dominant pair stayed out of it, the pack needed about ten before anybody moved.
Naked mole-rats live in crowded tunnels under East Africa, in stale air with far less oxygen than the surface offers. In 2017 researchers found that when the oxygen is gone entirely, the animals drop into a kind of suspended animation and come back after 18 minutes with no apparent injury. The trick is fuel. Cut off from oxygen, a mole-rat stops burning glucose and starts burning fructose instead, which keeps energy flowing when the usual route is blocked.
The hump is not a canteen. It is a fat store, a pantry the camel draws on when food runs out, and it holds no water at all. The water talent is real but separate. A camel can survive losing 40 percent of its body weight, then drink as much as 32 gallons in a single session and walk away steady. An animal that can do that looks like it must be carrying a reservoir somewhere. The hump simply is not where any of it goes.
A hippo out of water appears to sweat blood. The film on its skin turns red, then brown, and it is neither blood nor sweat. Chemists isolated the pigments in 2004 and named them hipposudoric and norhipposudoric acid. Both absorb strongly in the ultraviolet, which makes the secretion a sunscreen, and the red one also holds back bacteria that cause infection. A hippo walks around wearing lotion and antiseptic at the same time.
The aardvark is the sole living species of Tubulidentata, an entire order of mammals down to one animal. The order's name points at its teeth, molars built from bundles of tiny dentine tubes with no enamel at all. Its Afrikaans name means earth pig, which suits the snout and the burrowing and is badly wrong about the family. DNA puts the aardvark's nearest relatives among elephants, hyraxes, sea cows and golden moles.
A mouse, a human, an elephant and a giraffe all carry exactly seven bones in the neck. So does an armadillo. Three-toed sloths break the pattern, with as many as ten ribless vertebrae above the shoulders. The catch, Cambridge researchers found, is that the extras are not true neck bones at all. They are rib-cage vertebrae that drifted forward during development, masquerading as neck bones, so the mammal rule bends without quite breaking.
Stories of a striped animal in the Congo forest reached Europe for years without convincing anyone. Harry Johnston went looking in 1899 and came away with two strips of striped hide. Working from that hide, Philip Sclater named the creature Equus johnstoni in 1901 and filed it with the horses. Later that year Johnston obtained a whole skin and two skulls, and the bones settled it. Ray Lankester saw a member of the giraffe family and renamed it Okapia johnstoni. The okapi remains the giraffe's only close living relative.
In 2017 an international team working in the Batang Toru forest of northern Sumatra announced that the orangutans living there were not Sumatran orangutans at all. Genetic and physical differences set them apart from both the Sumatran and the Bornean species, and they were named Pongo tapanuliensis. Fewer than 800 are thought to remain, so the newest great ape known to science was, from the day it was described, the rarest one alive.
In 2007 the Canadian researcher Jean Thie was going through satellite images of northern Alberta when a dark line in Wood Buffalo National Park caught his eye. It was a beaver dam, roughly half a mile of packed mud and branches, built by generations of beavers working since the mid-1970s. Guinness lists it at 850 meters; Parks Canada measures the dam front at about 775. Rangers photographed it from a helicopter in 2010, and Rob Mark became the first person to reach it on foot in 2014.
The binturong of Southeast Asia, also called the bearcat, is a shaggy tree-dweller with a smell that visitors recognize immediately: hot buttered popcorn. In 2016 a team led by Christine Drea at Duke ran binturong urine through a gas chromatograph and found 2-acetyl-1-pyrroline, the very compound that gives popcorn its aroma. In a popcorn machine the compound forms under high heat. No heat is involved here, and the researchers suspect bacteria do the work.
6The long wait to explain how bats fly in the dark
On the tile: Bat Sonar1790s to 1941
In the late 1700s Lazzaro Spallanzani found that blinded bats flew and dodged obstacles as well as ever. Louis Jurine then plugged bats' ears with wax and watched them blunder into things. Hearing, somehow, was doing the work of sight, and there the matter sat for well over a century, because nobody could detect the sounds. Then Donald Griffin and Robert Galambos borrowed a Harvard physicist's new ultrasonic instruments and reported in 1941 that bats dodge obstacles by hearing the echoes of their own cries. Griffin named it echolocation.
The aye-aye is a nocturnal lemur from Madagascar with an unnervingly long, thin middle finger. It uses the finger as a hammer, tapping along a branch and listening to the echoes. Where the wood sounds hollow, a grub is tunneling inside. The aye-aye gnaws through the bark and hooks the grub out with the same finger. Biologists call the method percussive foraging, and the aye-aye has built an entire way of eating out of it.
A black panther is not a species and never has been. The name covers unusually dark individuals of two cats: leopards in Africa and Asia, jaguars in the Americas. Extra melanin floods the coat, but the pattern underneath stays exactly where it was, and in the right light the rosettes show through like a watermark. The cat never really loses its spots. They only become harder to see.
A platypus dives with its eyes, ears and nostrils sealed, which leaves it blind, deaf and unable to smell for the whole hunt. The bill does the work. It carries receptors that read pressure and, unusually for a mammal, the faint electric fields thrown off by small prey moving in the mud. Males add another oddity: a sharp spur on each ankle, about 12 millimeters long, connected by a duct to a venom gland.
Polar bear hairs are transparent rather than pigmented, and the skin beneath them is black. For decades a tidy story circulated to explain the pairing: each hollow hair pipes sunlight down to that black skin like a fiber-optic cable, warming the bear for free. Daniel Koon and Reid Hutchins tested it with hairs from a zoo bear. Less than 0.001 percent of red light survived the length of a single inch-long hair. The warmth comes from insulation, not plumbing.
An Alaskan wood frog does not dig below the frost line. It settles into the leaf litter and lets the cold take it. Ice fills the spaces around its cells while glucose piles up inside them, balancing the salts that forming ice leaves behind. Don Larson and Brian Barnes of the University of Alaska Fairbanks found frogs frozen as low as minus 18 Celsius for as long as 218 days. Every one of them thawed out alive.
Behind a reindeer's retina sits a mirror, the tapetum lucidum, the layer that makes animal eyes shine at night. In Arctic reindeer that mirror changes color with the season: golden in summer, deep blue by midwinter. Pressure builds inside the eye through the months of darkness, squeezing the mirror's collagen fibers closer together, which shortens the wavelength they reflect. The blue setting scatters light through the retina instead of straight back out, and the animal sees better in the gloom.
When an arctic ground squirrel settles in for the Alaskan winter, its core temperature drops below the freezing point of water, the lowest body temperature ever measured in a mammal. Its blood still does not turn to ice. Biologists call the condition supercooling: a liquid kept clean and undisturbed can be chilled past zero without crystallizing. It does not hold all winter. Every two or three weeks, without waking, the squirrel shivers for 12 to 15 hours until it is back near 98 degrees Fahrenheit, then lets the cold take it again.
Lemmings do not throw themselves off cliffs. The belief comes almost entirely from White Wilderness, a Disney nature film of 1958 that showed a doomed migration ending in the sea. The sequence was staged. It was shot in landlocked Alberta, using lemmings brought in from Manitoba, a few dozen animals run on a snow-covered turntable to look like a horde and then driven off a cliff for the camera. A CBC producer, Brian Vallee, laid it out in 1983.
Every other backboned animal carries hemoglobin, the iron-rich protein that makes blood red and moves oxygen through the body. The Antarctic icefishes are the only known vertebrates without it. Their blood runs clear, and oxygen travels dissolved in the plasma alone, which works because their water, hovering near minus 1.9 Celsius, holds an extraordinary amount of oxygen. Even so, icefish blood carries less than a tenth of the oxygen a red-blooded relative's does, and the fish makes up the difference with an enormous heart that moves a thin cargo quickly.
Walrus tusks look like ornaments and work like tools. They are teeth, growing through the animal's life to as much as three feet, and a walrus hooks them over the lip of an ice floe to lever itself out of the water, the way a skier plants a pole. Naturalists noticed. The scientific name Odobenus rosmarus translates, roughly, as tooth-walking sea horse, which is a fair description of an animal climbing out of the Arctic on its own face.
A young female arctic fox left Spitsbergen, in Svalbard, on March 26, 2018, wearing a satellite collar. Seventy-six days later she was on Ellesmere Island in Nunavut, Canada, having covered 3,506 kilometers, about 2,180 miles, over sea ice and the Greenland ice sheet. She averaged 46 kilometers a day and once managed 155. No arctic fox had ever been tracked crossing between continents, and she did not stop at the shore; she settled into a new food web, one running on lemmings rather than on the sea.
Weddell seals range farther south than any other mammal that lives on the continent year-round, which means living under ice that keeps trying to seal shut above them. They keep their breathing holes open by rasping at the new ice with their canine and incisor teeth. With the door held open they can hunt below in the dark, staying under as long as 45 minutes and reaching 720 meters. The rasping grinds their teeth down, and a seal that can no longer open a hole cannot feed.
A blue whale is the largest animal that has ever lived, reaching 110 feet and more than 330,000 pounds. In 2019 a team reported the first recording of one's heartbeat, made with electrodes on suction cups pressed to the whale's side just behind the left flipper. Through the bottom of a foraging dive the heart held at four to eight beats a minute, and at its slowest two. At the surface afterward it reached 37. The biggest heart on Earth mostly idles.
The pronghorn of the American West sprints at 45 to 50 miles an hour, and nothing that hunts it today makes that necessary. The National Park Service gives the reason plainly: the speed is an adaptation to outrun an extinct cheetah. Pronghorn have been running on this continent for 20 million years, and somewhere in that stretch the cat that made them fast disappeared. The legs stayed. The animal is still fleeing a predator that is not there.
Old harpoon tips, some of stone and some of metal, have turned up inside bowhead whales landed in Alaska in the 1980s and 1990s, buried in blubber that had been growing over them since long before anyone now living was born. A second method agreed. Chemists dating the lens of a bowhead's eye put at least one animal past 200 years. NOAA says the bowhead has the longest lifespan of any marine mammal.
Cuvier's beaked whales feed in the dark far below the surface, and they hold the record for the deepest dive measured in a marine mammal, close to 3,000 meters. In 2020 a team from the Duke University Marine Laboratory reported something stranger still: one dive that lasted 222 minutes, three hours and 42 minutes, on a single breath. Of the 3,680 dives they tracked, most lasted about an hour, which makes the outlier hard to explain.
Ask which mammal is smallest and there are two correct answers. By mass it is the Etruscan shrew, 1.5 to 2.5 grams. By body length it is Kitti's hog-nosed bat of Thailand and Myanmar, the bumblebee bat, whose head and body run 29 to 33 millimeters against the shrew's 35 to 48. The shrew is the longer animal; the bat is the shorter one. Guinness keeps two records rather than pick a winner, which is the honest way to do it.
6The hardest bite ever measured on a living animal
On the tile: Crocodile Bite2012
Gregory Erickson's team spent years coaxing crocodilians onto a padded force meter, working through all 23 living species. One saltwater crocodile closed its jaws with 16,414 newtons, about 3,689 pounds, which the researchers reported as the highest bite force measured in any animal. Tooth pressures in the study reached as high as 1,344 megapascals. The number came from the animal itself rather than from a model, which is what makes it stand up.
In 1962 a rescue expedition went into the deserts of what is now Yemen and came back with three wild Arabian oryx, two males and a female. Zoos and private collections added a few more until nine animals in Phoenix formed what keepers called the World Herd. The last wild oryx was gone by 1972. Ten years after that, in 1982, ten of their descendants were released onto an Omani desert plateau, and in 2011 the species was downlisted from endangered to vulnerable.
Every horse most people ever see is a domestic animal or the descendant of one. Przewalski's horse, the takhi, is the exception, and it was last seen in the wild in the 1960s. What survived was in zoos. About 1,900 exist today, every one of them descended from 14 animals caught between 1910 and 1960, and monitored herds are back on the Mongolian steppe, where researchers watch them turn wild again.
By 1974 the black-footed ferret had vanished from the wild, and by 1980 the last one in human care had died. The species was written off. Then in 1981, on a ranch near Meeteetse, Wyoming, a dog named Shep brought home an animal John and Lucille Hogg did not recognize. It was a black-footed ferret, and a colony was living nearby. The last wild ferret was caught in 1987, leaving 18 animals, seven males and 11 females. Their descendants live across the American West now.