by David Braun
5 Animals Deadliest to Humans
1. Mosquito: causes 2 million deaths annually
2. Asian cobra: causes majority of snakebite deaths in India
3. Australian box jellyfish: kills with one of world’s deadliest toxins
4. Australian saltwater crocodile: believed to cause 2,000 deaths per year
5. Hippos: kill more people in Africa than any other mammal
The crested rat, native to East Africa, uses poison bark for defense. (Photo Credit 3.7)
Paralyzing Poison
“For as long as colonials have been in Kenya, there have been tribes that specialize in hunting elephants using this poison, and now we’re seeing it being used in rhino poaching,” O’Brien said. Ouabain can cause paralysis and, at high enough doses, heart attacks.
“The dogs that we know of that have attacked the crested rat have suffered everything from temporary paralysis for a couple of weeks to death,” said O’Brien, who is also a researcher at the Mpala Research Centre in Kenya, where the experiment was conducted.
Other mammals are known to use toxins that they don’t produce themselves. For example, a hedgehog species applies a mild toxin from a toad to its fur, O’Brien said. Likewise, some capuchin monkeys rub an extract from millipedes onto their fur to repel insects. “But there are no other examples of an animal using [an external substance] that is actually a lethal toxin,” he said.
“What is quite clear in this animal is that it is hardwired to find the poison, it is hardwired to chew it and it is hardwired to apply it to the small area of hairs.”
Jonathan Kingdon
researcher at Oxford University
Why Is the Rat Immune?
While the new study solves one crested rat mystery, others remain. It’s unclear, for example, why the rodent itself doesn’t suffer from the poison. One idea is that its saliva subtly alters the poison, O’Brien said.
Scientists also don’t know how each young crested rat learns about ouabain. Is the chemistry lesson passed from parents to offspring? Does each animal discover the poison on its own? “No one knows,” he said. “We know the general outlines about this animal but none of the details.”
THEY KNOW WHERE YOU BLEED
Vampire Bats
Have Vein Sensors
Here’s a finding that might make your blood run cold—vampire bats have specially evolved nerves that can sense the heat of your veins.
The facial nerves of vampire bats tell them much more than we ever thought they could: They tell them where the veins are. Scientists already knew that vampire bats have snakelike pit organs in their faces that point the mammals to the juiciest parts of their prey—the veins. But it was unknown how the predators located those choice biting spots, until now.
The vampire bat’s facial nerves tell it the best places to bite. (Photo Credit 3.8)
Bloodsucker’s Senses
Now a study has shown that bats have evolved special facial nerves that can detect body temperatures as low as 89.6 degrees Fahrenheit (32 degrees Celsius). The vampire bat is “clearly adapted in a lot of unusual ways for a very unusual lifestyle—this is one more example,” said study co-author Nicholas Ingolia, a genomics researcher at the Carnegie Institution for Science in Baltimore, Maryland.
People have a similar heat-sensitive channel, but it’s only activated by painfully hot stimuli, such as touching a hot stove. The vampire bat, the study found, has two forms of heat-sensitive channels, one to sense painful heat—like us—and another to zero in on its prey’s veins.
Blood Thinner
An enzyme found in vampire bats’ saliva, desmoteplase, or DSPA, is being used in a new experimental drug treatment for stroke victims. DSPA helps thin blood and prevent clotting—a useful tool for vampire bats to get the most blood out of each bite. The current medication for dissolving blood clots that cause brain attacks, TPA (tissue plasminogen activator) must be used within three hours after the onset of symptoms, so most stroke victims don’t receive the treatment in time. On the other hand, DSPA can be used up to nine hours after the onset of symptoms and is easier to administer.
Bloody Nerve Cells
Such an evolutionary adaptation—known previously only in three snake species—is especially crucial for the vampire bat, which needs a blood meal every one or two days to stay alive. The vein-sensing ability is “an extreme version of an existing trait,” Ingolia said. Other bats have the gene for this hypersensitive channel, but only the bloodsuckers’ bodies appear to activate the gene.
In the study, Ingolia and colleagues isolated the nerve cells that travel to the pit organs in the bat’s face and compared them with the sensory nerve cells that go to the rest of the bat’s body. The nerve cells were anatomically different from the regular, pain-sensing nerve cells, which means the vein-sensing cells convey separate information, Ingolia said. The team also looked at vampire bat genes and found that the same heat-sensing gene is found throughout the body, but the gene results in a different type of nerve cell in the pit organs.
MOVIN’ ON UP
Goats Scale Dam Walls
Salt cravings drive goats to new heights—literally.
Using moves that would make any rock climber jealous, Alpine ibex scaled a near-vertical rock face of a northern Italian dam. In summer 2010, pictures of the goats were making the rounds online, particularly in emails falsely claiming the animals are bighorn sheep on Wyoming’s Buffalo Bill Dam (the rumor-quashing website snopes.com busted the hoax).
Crazy Salt Cravings
In truth, Adriano Migliorati snapped the pictures at the 160-foot-tall (49-meter-tall) Cingino Dam, the Italian hiker told National Geographic News via email. The goats are attracted to the dam’s salt-crusted stones, according to the U.K.-based Caters news agency. Grazing animals don’t get enough of the mineral in their vegetarian diets and scale the dam to get a fix.
It’s not far-fetched, though, to think such a scene could be photographed in the United States. For example, mountain goats could scale dams in the U.S. West, according to Jeff Opperman, senior adviser for sustainable hydropower at the U.S.-based nonprofit the Nature Conservancy.
TRUTH:
GOATS’ EYES HAVE RECTANGULAR PUPILS.
Opperman, who called the Cingino pictures “mind-boggling,” described a similar instance of a Montana mountain goat doing an “incredibly acrobatic stretching maneuver to lick salt … He is wedged up this sheer vertical cliff face, almost doing a yoga pose with four hooves splayed out there,” he said. “It’s the same concept [with the Italian goats]—these animals can overcome what looks like impossible topography to get what they want.”
To satisfy their salt cravings, several goats scale Cingino Dam in Italy. (Photo Credit 3.9)
Opperman cautioned, though, that the Italian dam is rare, in that its rough masonry provides gaps that act as toeholds. The more common, smooth-concrete dams—such as Buffalo Bill Dam—would give goats anywhere in the world trouble, he said.
Gravity-Defying Goats
Cingino Dam isn’t completely vertical, allowing ibex to gain some purchase. Adapted to their perilous environment, Alpine ibex have evolved a specialized split hoof, whose cleft is wider than on any other split-hooved species, according to Smithsonian magazine. The hoof also has a hard wall that can grab on to steep cliffs and a soft, rubbery inside that serves as a “stopper” when the animal is pushed forward by gravity, the magazine reported.
And because dams are usually built in steep canyons, Cingino’s steep rock face is likely nothing novel for the mountain-dwelling ibex, according to Opperman. The herbivores spend their lives scrambling the European Alps’ rocky and steep terrain.
By scaling Cingino Dam, salt-craving ibex are “showing ingenuity, taking advantage of this human-created thing in their environment,” the Nature Conservancy’s Opperman said.
Close Call
The alpine ibex nearly became extinct in the early 19th century; it was believed to have healing powers, which led
to overhunting. Today, the ibex is no longer endangered as a result of conservation and reintroduction of the species in Switzerland, Austria, and France.
MONSTER MOMS
Nature’s Four Worst Mothers
Who are the worst moms in the animal kingdom? Do they deserve our judgment, or should we cut them a break?
There are a number of outstanding moms in the animal kingdom, but many animal mothers are more Mommie Dearest than Mom of the Year—at least at first glance. Take the giant panda …
MOM 1
Giant Panda Mom: Playing Favorites, Fatally?
One of the good ones: A giant panda mom nuzzles her cub. (Photo Credit 3.10)
She’s a “bad” mom because … Panda mothers sometimes have two babies—but they rarely raise more than one. “Pandas have good press, but they [can be] bad moms,” said Scott Forbes, University of Winnipeg biologist and author of A Natural History of Families. Pandas’ second offspring, helpless and about the size of a stick of butter, are typically left to their fate in the wild.
Give Mom a break because … As the “favored” offspring gets bigger, he or she takes a lot of attention and eats a lot of bamboo. Mothers probably wouldn’t be able to provide for two offspring during the eight to nine months until they are fully weaned, Forbes said. “One robust offspring is probably better than two weak ones later on,” he said, “so the quality control occurs early on when it’s cheap—before you’ve invested lots of resources.”
MOM 2
Hamster Mom: She Could Just Eat Them Up
Nibble or nurture? A hamster mom approaches one of her offspring. (Photo Credit 3.11)
She’s a “bad” mom because … Despite their cuddly appearance, hamster moms can be cold-blooded killers—they often eat their own young.
Give Mom a break because … She was planning for the best, and now she’s just dealing with the rest. Forbes believes hamster moms practice “parental optimism” by creating broods bigger than they may be able to rear. “They don’t know how much food is going to be out there,” he said. “They create a litter with a few spare offspring to ensure high-quality young even if [food is scarce] or there are developmental defects in others.”
MOM 3
Rabbit Mom: Absentee Parent
Where’s Mom? Baby rabbits are often left alone in their burrows. (Photo Credit 3.12)
She’s a “bad” mom because … Rabbit mothers abandon their young in burrows immediately after birth and return to feed them for only about two minutes daily during their first 25 days. After this brief bout of “drive-by” parenting, young rabbits are left to fend for themselves.
Give Mom a break because … Rabbits are tasty and predators especially enjoy feasting on helpless newborns. Mothers likely avoid their young to keep their underground locations secret—and their precious progeny alive. Though mother-child “quality time” is limited, increased odds of survival may be the greatest gift of all—a little something to remember this Mother’s Day.
Brood for breakfast? Long-tailed skinks may eat their own eggs. (Photo Credit 3.13)
MOM 4
Long-Tailed Skink Mom: Self-Absorbed Pessimist?
She’s a “bad” mom because … Even though “Mother of the Year” candidates are scarce among reptiles, this lizard is a standout among callous moms. If the skink mother lays a clutch of eggs when there are lots of predators around, she’s likely to eat her brood before they hatch.
Give Mom a break because … The skink is probably saving her young from an inevitable fate while making herself stronger to ensure another chance to reproduce, Forbes said. “She may decide that because of all the predators, there is no chance of her eggs making it, so she’s going to eat them to recycle the nutrients.”
POLAR BEAR ODYSSEY
Longest Polar Bear Swim Recorded
A female polar bear has set the record for the longest consecutive swim—426 miles (687 kilometers) of water, equivalent to the distance between Washington, D.C., and Boston, a new study says.
A female polar bear swam for a record-breaking nine days straight, traveling 426 miles (687 kilometers). The predator made her epic journey in the Beaufort Sea, where sea ice is shrinking due to global warming, forcing mother bears to swim greater and greater distances to reach land—to the peril of their cubs.
TRUTH:
PARTIALLY WEBBED FRONT PAWS HELP POLAR BEARS SWIM. THE BEARS MAY USE THEIR BACK PAWS LIKE RUDDERS TO STEER.
Shrinking Ice
The cub of the record-setting bear, for instance, died at some point between starting the swim and when the researchers next observed the mother on land. She also lost 22 percent of her body weight.
“We’re pretty sure that these animals didn’t have to do these long swims before, because 687-kilometer stretches of open water didn’t occur very often in the evolutionary history of the polar bear,” said study co-author Steven Amstrup, chief scientist for the conservation group Polar Bears International. Amstrup is also the former project leader of polar bear research for the U.S. Geological Survey (USGS), which led the new study.
Polar bears are swimming greater distances because of shrinking sea ice. (Photo Credit 3.14)
Another female bear in the study swam for more than 12 days, but appears to have found places to rest during her journey.
Long Swims Deadly for Polar Bear Cubs
Biologists collared 68 female polar bears between 2004 and 2009 to study their movements. Thanks to what study co-author and World Wildlife Fund polar bear biologist Geoff York calls an “accident of technology and design,” the researchers noticed data gaps in the bears’ whereabouts. The researchers were later able to link the gaps to periods when the bears were at sea.
The scientists examined GPS data for more than 50 female polar bears’ long-distance swimming events, defined as swims longer than 30 miles (50 kilometers). This data was then correlated to rates of cub survival. “Bears that engaged in long-distance swimming were more likely to experience cub loss,” said study co-author George Durner, a USGS research zoologist in Anchorage, Alaska.
Five of the 11 mothers that had cubs before they began their lengthy swims lost their young by the time the researchers observed them again on land, according to the research, presented at the International Bear Association Conference in Ottawa, Canada.
Sea Ice Loss to Continue
Until 1995, summer sea ice usually remained along the continental shelf of the Beaufort Sea, a critical habitat for polar bears due to its rich seal population. Now the sea ice in the Beaufort and Chukchi Seas is retreating from the coast by hundreds of kilometers, Durner said.
In 2010, Arctic sea ice extent was the third lowest on record, part of a long-term trend of ice loss that will continue for decades to come, according to the National Snow and Ice Data Center in Boulder, Colorado.
It’s unknown whether the cubs are drowning at sea or whether the metabolically costly act of swimming long distances in nearly freezing water kills them after they reach land.
“So the sort of conditions that contribute to long-distance swimming are likely going to persist in the future, and if cub mortality is directly related to this, then it would have a negative impact on the population,” Durner said.
A New Food Source
Polar bears usually hunt for seals from blocks of ice when they’re out at sea, and they come back to shore when springtime temperatures melt the ice. However, due to climate changes, the ice is melting earlier each year, forcing the polar bears to come ashore sooner, without sufficient food. The bears’ early arrival coincides with the time that snow geese are incubating their eggs, and the bears have discovered that these eggs are quite delicious. A recent study on Canada’s Hudson Bay by biologist Robert Rockwell has shown that the snow goose population is in no danger of being wiped out, and their eggs may prove to be a valuable and nutritious alternative food source for the bears.
LOVE AND DEVOTION
Alligators Surprisingly Loyal to Old Flames
&nb
sp; Bringing new meaning to the phrase “see you later, alligator,” a new study suggests that female American alligators frequently return to their sexual partners.
In a study of wild alligators in Louisiana’s Rockefeller Wildlife Refuge, seven out of ten of the female reptiles studied in multiple years were found to have mated with the same males during the 1995 to 2005 mating seasons. Like females of other reptile species, alligators still couple with several males, according to study leader Stacey Lance of the Savannah River Ecology Laboratory in Georgia.
A female American alligator lances a hatchling on her nose. (Photo Credit 3.15)
But in an unusual twist, it seems the same female and male find each other during multiple mating seasons. Scientists aren’t sure whether the female chooses the male, or the male seeks out the female. Based on the sheer number of alligators in the park, it’s incredible “to think that the same two were getting together every year,” Lance said. Once the sex is over, however, the “males are out of the picture.”
