National Geographic Tales of the Weird

by David Braun

  When Crocs Attack

  As for whether the crocodile is the perpetrator of the attacks, it’s impossible to know unless the animal is killed and cut open, Barr said. Officials did induce the animal to vomit, which produced no human remains. “It’s great they didn’t kill it,” Barr said. “That’s commendable [and] very rare.”

  Barr noted that most crocodile attacks occur because people have depleted croc habitat or prey. In these cases “crocodiles are just turning to the next available food source, and sadly sometimes that happens to be human,” Barr said.

  Cases of mistaken identity are also possible, when a crocodile thinks a human is a typical prey species. There are also “rogue” animals that purposely kill people, although that’s much less common, Barr said. Overall, he said, the “crocodile’s not the villain.”

  A caregiver cleans the giant saltwater crocodile’s new home in captivity. (Photo Credit 3.20)

  Saltwater crocodiles are considered a species at low risk of extinction. About a thousand of the species roam the Philippines’ southern swamplands, where the new catch was found, Philippine wildlife official Glen Rebong told the Associated Press. Though the species isn’t under immediate threat, it is protected from hunting by law.

  Philippine Secretary of Environment and Natural Resources Ramon Paje told the AP that the crocodile was captured because it was a threat to the community. But he added that the presence of such reptiles is a reminder that the country’s remaining habitats need to be protected.

  TRUTH:

  THE AVERAGE LIFESPAN OF A SALTWATER CROCODILE IN THE WILD IS 70 YEARS.

  Bunawan mayor Elorde told the Associated Press that he had plans to make the captured crocodile “the biggest star” in an ecotourism park, which he said would improve people’s understanding of the notorious reptiles’ role in the environment.

  Barr called that “an awesome idea”: “These big crocs are a tremendous resource. Australia is a great example—they have a multimillion-dollar tourism industry based around crocodiles. If you do it right, especially for some of these lesser-developed countries … it’s a great idea.”

  AMAZING ADAPTATION

  Hibernating Bears Keep Weirdly Warm

  Hibernating black bears can dramatically lower their metabolism with only a moderate drop in body temperature, scientists found in 2011. And the science behind it may be helpful to humans.

  Black bears have a reputation for being marathon sleepers. The North American mammals generally slumber about five to seven months without eating, drinking, urinating, or defecating, and then they emerge from their dens in the spring none the worse for wear. Scientists have long known that to survive this lengthy fast, the bears drop their metabolism, the chemical process that converts food to energy.

  But it was thought that, like most animals, the bears would have to drop their body temperatures to put the brakes on metabolism—each 18-degree Fahrenheit (10-degree Celsius) drop in temperature should equal a 50 percent reduction in chemical activity.

  TRUTH:

  BLACK BEAR HAIR ISN’T JUST BLACK: THEIR FUR CAN BE BLUE-GRAY, BLUE-BLACK, BROWN, CINNAMON, OR (VERY RARELY) WHITE.

  Slow Down

  Not so, according to a 2011 study. A black bear in Alaska can lower its temperature—normally about 91 degrees Fahrenheit (33 degrees Celsius)—by only about 9 to 11 degrees Fahrenheit (5 or 6 degrees Celsius), yet bring its metabolism to an almost grinding halt, at 25 percent the normal rate.

  For the study, zoologists at the University of Alaska, Fairbanks, rescued four “nuisance” bears that had been recently captured by the Alaska Department of Fish and Game. Such bears, which live too close to people, are usually euthanized.

  The scientists fitted the bears with various devices to record their temperatures, heartbeats, and other factors before placing the animals into artificial dens. The dens were located in an undisturbed forest near Fairbanks that mimicked the animals’ natural habitats.

  Hibernating Hearts

  The scientists also recorded that the bears’ heart rates dropped from 55 to 9 beats a minute. During intervals when the bears were not breathing, there were also as many as 20 seconds between beats. That’s because when metabolism slows, so does the need for the heart to pump oxygen through the body.

  “If we had that kind of longer interval within our heartbeats, we would probably faint,” said study coauthor Øivind Tøien.

  Spirit Bears

  In the Great Bear Rainforest, a 250-mile-long region down Canada’s western coast, live most of the world’s spirit bears (also called Kermode bears). Technically, these are North American black bears, but their fur is white. These white black bears account for nearly 1 of every 40 to 100 bears in that region. Scientists believe the unique coloration occurs when both parents pass on a recessive mutation of the MClR gene (the same one associated with red hair in humans) to their offspring.

  Metabolism Mystery

  How the bears’ bodies can create the unexpected drop in metabolism is still poorly understood, but Tøien has a few theories. For instance, bears could be like marmots, a hibernating mammal that regulates metabolism by shrinking the mass of its digestive system and then bulking back up when spring comes.

  In general, the bear’s uncoupling of metabolism from temperature “is yet another amazing thing that black bears can do,” noted Bryan Rourke, a biologist at California State University, Long Beach, who has studied how bears’ hearts can withstand hibernation.

  Black bears are the most common bear in North America. (Photo Credit 3.21)

  Rourke also pointed to the new study’s finding that bears can regulate their temperatures to suit individual needs. For instance, a pregnant female black bear in the study did not allow her body temperature to fluctuate as much as other hibernating bears, presumably to protect the fetus.

  Helpful to Humans?

  Both scientists emphasized that the bear research—published in 2011 in the journal Science—could offer practical applications for humans. “A lot of what hibernating mammals can accomplish addresses ways that maybe we could treat things like muscle disease or heart disease,” Rourke said.

  For instance, understanding how bears can survive with such low amounts of oxygen may help stroke victims who temporarily lose oxygen flow to the brain. Or, unlocking how bears can control their metabolism without dropping their temperatures may provide clues to how people can lose weight.

  “Nearly every organ system in the hibernating mammal,” Rourke said, “demonstrates some fascinating but contrasting physiology to humans.”

  CHAPTER 4

  Creepy Crawlies

  (Photo Credit 4.1)

  Ants, worms, spiders, and other slimy, skittery critters aren’t the most attractive creatures in the world, but they are some of the weirdest. Scientists are learning that bugs have a whole slew of “superpowers” that are as impressive as they are strange. Wasps have great memories, male spiders give expert massages, snails can survive being eaten alive, and ants can turn into zombies. Read on … but you may want to keep that fly swatter handy.

  HERE’S LOOKIN’ AT YOU

  Wasps Can Recognize Faces

  Study Says

  Are you one of those people who never forgets a face? You’ve got some company in the animal kingdom—the wasp.

  Scientists have discovered that Polistes fuscatus paper wasps can recognize and remember one another’s faces with sharp accuracy, a new study has found.

  A variety of paper wasp faces (Photo Credit 4.2)

  In general, an individual in a species recognizes its kin by many different means. But faces are extremely important to species such as humans, said study co-author Michael Sheehan, a Ph.D. candidate at the University of Michigan in Ann Arbor. “Studies show that when you look at a face, your brain treats it in a totally different way than it does other images,” he said. “It’s just the way the brain processes the image of a face, and it turns out that these paper wasps do the same thing.”

  TRU
TH:

  ADULT YELLOW JACKET WASPS BRING FOOD TO THEIR HIVE-BOUND YOUNG, AND IN RETURN, THE YOUNG EMIT SWEET SECRETIONS THAT THE ADULTS CONSUME.

  Face-Learning Reaps Rewards

  For the study, Sheehan and adviser Elizabeth Tibbetts put wasps of P. fuscatus and P. metricus—a closely related species with a much less complex social structure—in the long stem of a T-shaped maze. Each wasp in the maze was shown two images of faces of other wasps in the same species—one image to the wasp’s left and another to its right. The images “acted like signposts, telling [the subjects] which way to go to get their reward, which in this case was a safety zone,” said Sheehan, whose study appeared in the journal Science.

  Though images and safety-zone locations were constantly changed, “one particular image—face A versus face B—was [always] associated with the safety zone,” Sheehan explained. “So they learned, ‘If I go to this face, that’s good, but the other face does nothing good for me.’ ”

  Repeating the maze experiments using simple shapes or other images instead of faces showed that the wasps learned far more slowly and not as well when faces weren’t involved—emphasizing the insects’ special response to face recognition.

  You Lookin’ at Me?

  The unique, distinct faces of P. fuscatus wasps, as well as the wasps’ ability to recognize and remember one another’s faces, are likely tied to the insects’ multicolony social structure, Sheehan added.

  I See Ewe

  Sheep, like paper wasps, have also been discovered to possess facial recognition ability. British scientists found that sheep are able to recognize individual faces of at least 50 sheep and can remember them for over two years. “If sheep have such sophisticated facial recognition skills,” says Keith Kendrick, author of the study, “they must have much greater social requirements than we thought.” Preliminary research also suggests that sheep are able to form mental images of other sheep in their absence. These observations on sheep, paper wasps, and other animals could eventually be useful in developing facial recognition software.

  “They have multiple queens and they all want to reproduce—they all want to be the most dominant. So being able to recognize each other helps them understand who’s already beaten whom, who has higher ranking in the hierarchy and this helps to keep the peace. When they aren’t able to recognize each other, [as] we’ve shown before, there was more aggression.”

  P. metricus wasps, on the other hand, live in single-queen colonies and “don’t need to be able to tell each other apart,” he said. Not surprisingly, P. metricus wasps look alike and do not show the same ability for face-learning, Sheehan said.

  Human-Wasp Parallels?

  Next, Sheehan hopes to find out how human face perception compares with the ability in wasps. Mammals and wasps have very different eyes, for one thing, and wasp brains are also much smaller and boast far fewer specialized regions.

  “We’ll be investigating the parallels between primates and wasps,” he said. “There are thousands of research papers on face-learning in people, but we’re really only beginning to learn about the wasps.”

  BEES LIKE IT HOT

  Bumblebee Seeks Warm Flowers

  for Heavy Pollination

  Scientists have found that bumblebees can be picky pollinators and gravitate toward plants with nice, warm nectar.

  A recent study has shown that bumblebees prefer their food warm and learn to locate hotter flowers using color as a cue, scientists say. These findings may have broad implications for the evolution of flowering plants.

  Secrets of Attraction

  To attract insect pollinators, flowers offer a nutritious reward of nectar and pollen. Now biologists say many flowers may encourage visits by offering a “heat reward” as well. By consuming warmer nectar, bees may save energy they would otherwise have to spend maintaining their own body temperature.

  TRUTH:

  BEES CAN BE GREEN, BLUE, OR RED.

  “Bees can raise their body temperature to above 37 degrees Celsius [98.6 degrees Fahrenheit], even if it is just a few degrees above zero outside,” said Lars Chittka of Queen Mary College, University of London. “But this is costly so collecting warm nectar is a clever idea.”

  Many flowering plants have features that allow them to increase the temperature of their flowers. The scientists suggest that providing hot meals might be a shrewd evolutionary adaptation for plants, whose own reproduction depends on attracting pollinators.

  To Bee or Not to Bee

  According to a new study on bee diversity, bees and the flowers they pollinate are disappearing, which raises concerns about food crops and plant communities that count on animal pollinators to reproduce. Scientists compared a million records on bees from hundreds of sites in the United Kingdom and the Netherlands before and after 1980, and found that bee diversity has decreased at almost 80 percent of the sites. The team also found that plant diversity had suffered a decline, which they believe suggests that the decline in bee and plant diversity is somehow linked.

  Heat Seekers

  Previous work has shown that some insects are attracted to warmer plants. In tropical rain forests, for example, scarab beetles spend much of their time deep inside flowers capable of generating heat through chemical reactions.

  But scientists didn’t know if flower temperature is important to more active and widespread pollinators such as bees, which visit each blossom for only a short time. Chittka and his colleagues designed a set of experiments to test the effects of flower temperature on the behavior of pollinating bumblebees.

  They laid out a range of flower-shaped feeders holding equal concentrations of sugar solution that varied in temperature. The bees gravitated toward the feeders offering the warmest nectar. The researchers then placed food solutions in pink or purple feeders.

  The bees quickly learned to distinguish between colors and concentrated their foraging on the warmer nectar source. The results suggest that the bees learned to use color as a signal of temperature and utilized this information in choosing which flowers to visit.

  University of Arizona biologist Daniel Papaj says the study is intriguing. But it remains to be seen whether bees in nature commonly use sensory cues to identify warmer flowers, he notes. If bees do this, Papaj said, “one might expect such behavior to have demographic consequences. For instance, flowers in sunnier microhabitats would be more likely to be pollinated.”

  TRUTH:

  UNLIKE HONEYBEES, BUMBLEBEES CAN STING MORE THAN ONCE BECAUSE THEIR STINGERS ARE SMOOTH AND DO NOT GET CAUGHT IN THE SKIN WHEN THEY FLY AWAY.

  Bag of Tricks

  The fact that pollinating insects may be choosy about temperature suggests a new explanation for a number of features that help plants keep their flowers warmer than the surrounding environment.

  A small number of plant species generate heat through metabolic processes similarly to that of animals. Many others use more passive means to gather and retain warmth. The shape of many flowers—and the ability to track the sun’s movements—helps make them efficient collectors of solar energy. Some species even have cone-shaped cells in their petals that focus sunlight, increasing the temperature of the flower.

  “Many of these features had been previously thought to only enhance the color of the flower, or else warm the flower itself up to help its seed develop faster,” said study co-author Heather Whitney of the University of Cambridge in England. “Now we know that warming structures could be part of the bag of tricks that flowers have evolved to attract pollinators.”

  LIQUEFIED!

  Virus Brainwashes Caterpillars

  Just one gene is all it takes for a deadly virus to take over the brains and bodies of caterpillars before it turns them to goo.

  Scientists have identified a single gene that allows a caterpillar-brainwashing virus to do its dirty work, a new study says. The virus forces the “zombie” caterpillars to climb trees, where the invader eventually liquefies its hosts’ bodies into a dripping goo.

&
nbsp; Altered Behavior

  “When gypsy moth caterpillars are healthy and happy, they go up into the trees at night to feed on leaves, and then climb back down in the morning to hide [in bark crevices or soil] from predators during the day,” said study co-author Kelli Hoover, an entomologist at Penn State University.

  But caterpillars infected with a baculovirus—a type of virus that infects invertebrates—are driven to the treetops and reprogrammed to stay there until they meet a doom worthy of a horror film. “When they are infected, as they get sicker they stay up in the trees and die up there,” Hoover explained.

  The virus “ends up using just about all of the caterpillar to make more virus, and there are other genes in the virus that then make the caterpillar melt. So it becomes a pool of millions of virus particles that end up dropping onto the foliage below where it can infect other moths that eat those leaves.

  TRUTH:

  A CATERPILLAR HAS MORE MUSCLES THAN A HUMAN.

  Master Manipulators

  Though such zombie-making viruses were previously known, their genetics have been a mystery. So Hoover and colleagues infected gypsy moth caterpillars with half a dozen different types of baculovirus and placed the bugs in tall bottles with food on the bottom. Viruses that the scientists had determined carried a specific gene, called egt, drove caterpillars to climb to the top of the container and stay there to die.