DEPARTMENTS  |
FEBRUARY 2008 – NO. 21 |
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Zoology
CHIMPANZEES (Pan troglodytes) kill one another as often as humans in hunter-gatherer or subsistence societies do. On average, 207 chimpanzees out of every 100,000 will be killed by one of their kind each year. Males are killed at a rate about twice those of infants and juveniles, with 977 to 1,421 males per 100,000 being killed each year compared to 476 to 736 infants and juveniles per 100,000 per year. In humans, rates of death from warfare among subsistence-society hunters and farmers are 164 and 595 per 100,000 per year, respectively.
ELEPHANTS (Loxodonta Africana) will pay particular attention to the remains of other dead elephants, spending more time investigating elephant skulls and ivory than natural objects or the skull of other large terrestrial mammals. However, they do not pay any particular regard to the remains of relatives compared to other elephants.
Apart from humans, WHALES are the only group of animals for which there is an official criterion of death. In humans, this may include the death of the whole brain, or of the brain stem. In whales, the criteria formulated to help to decide when a hunted whale is indeed dead include: a prerequisite that the hunted whale has stopped moving, defined as a relaxation of the lower jaw; or no flipper movement; or sinking without active movement.
One rat, nicknamed Razza, is famous for accomplishing the rodent equivalent of the great escape. Razza, a single male NORWEGIAN RAT (Rattus norvegicus), was fitted with a radio-tracking collar and released all alone on the uninhabited ten-hectare New Zealand island of Motuhoropapa near Auckland. The researchers wanted to see what happens when a single rat invades an island, as a way to understand better how pests invade new territories. However, Razza gave the researchers more than they bargained for. Surrounded by traps, tempted by chocolate and even tracked by dogs, he managed to evade capture for an astonishing four months. Eventually, Razza made one final dash for freedom and leapt into the sea, swimming 400 meters across open sea to a neighboring island, the longest documented sea crossing by a Norwegian rat. Razza's epic run-around finally came to an end when he took a rather misjudged bite out of a piece of penguin meat, which had been laid in a trap.
The longest continuous satellite tracking of an individual bird came to an end on March 5, 2005, when a WHITE STORK (Ciconia ciconia) known as Donna was electrocuted when flying into power lines. First tagged in 1999, Donna was tracked for 2,033 days.
Electrocution by power lines is the leading cause of death in STORKS. For instance, almost six out of ten storks that die while migrating across Israel are killed this way.
At least 30 percent of newly fledged SPANISH IMPERIAL EAGLES (Aquila adalberti) are electrocuted each year. Fewer than 200 pairs of the raptors survive.
Male nuptial GIFT-GIVING SPIDERS (Pisaura Mirabilis) will feign death to avoid being eaten by the female they are trying to mate with. Males offer gifts of food to attract a mate, but when a female approaches a gift-displaying male, she not only shows interest in the gift but will sometimes attack the male. At this moment, males often pretend to drop dead by collapsing and remaining completely motionless. When the female has eaten the gift, the male will miraculously come back to life and attempt to mate with her.
Horseracing is a dangerous sport and it is possible to determine the relative risk that a racehorse will die while running a race. Generally speaking, HORSES (Equus caballus) that run on flat races are at a lower risk of fatal injury than those running hurdle, chase or British National Hunt flat races. The longer the race, and the harder the racing surface, the greater the likelihood that a horse will be fatally injured, and novice races are also particularly susceptible, with risk of death decreasing the more the horse has run during the previous year, or the more often it has run a particular style of race. There also appears to be a seasonal effect on how many horses die while racing, with the risks being significantly higher between February and May. Male horses are also more likely to die during a race than females. Two-year-old horses running for the first time in the UK have a fatality rate of 1.29 per 1,000 starts. Three-year-olds have a fatality rate of 2.59, while four-year-olds and older have a rate of 5.32.
A MADAGASCAR FISH EAGLE (Haliaeetus vociferoides) managed to survive in the wild for at least seven years with only one foot. The feat is remarkable because raptors such as eagles and falcons not only need two legs to walk properly but rely on their talons to catch and carry food. The eagle, first spotted near Lake Nefotaka in 1996 and then again seven years later, walked on other birds, holding a dominant position within the local community of fish eagles. Only two other raptors are known to have survived in the wild after losing a foot, one an immature bald eagle that survived for two years, the other a one-legged adult EURASIAN KESTREL (Falco tinnunculus) that survived for one month before being struck and killed by a vehicle.
In 1996, a deaf and mute dolphin was discovered by marine researchers working at U.S. Naval Command Ocean Surveillance Center in San Diego, CA. The young female BOTTLENOSE DOLPHIN (Tursiops truncates), aged nine years old, was monitored for another seven years, during which she never whistled or made echolocation pulses or made burst pulse sounds as other dolphins do. Despite this handicap, the dolphin was well nourished and evidently had no problems feeding or looking after herself in the wild.
FIRE ANTS (Solenopsis invicta) have an unusual way of surviving floods. When water levels rise, huge numbers of the ants cling together forming large rafts that float on the water's surface. By building these life rafts a colony can survive until the flood recedes or higher ground is found.
From Fish that Fake Orgasms by Matt Walker. Copyright © 2007. Courtesy St. Martin's Press.
