Using Geographic Profiling to Track Great White Shark Predation

Larger sharks are more successful in capturing seals than smaller sharks. (Photo credit: Corbis)

Geographic profiling is a method typically used by criminal investigators to track the movements of serial killers by tracing a connection between crime scenes. Researchers from the University of Miami, University of British Columbia, and Texas State University recently used this method to study the hunting habits of the great white shark off the coast of South Africa.

This research study was the first time geographic profiling was used in a marine environment. Previously, in addition to its use in crime investigations, this technique has been used to study the foraging habits of bats and bees and explore the spread of infectious diseases in Africa.

The hunting tactics of the great white sharks are difficult to observe under natural conditions, so up to now, not much was known about the sharks hunting behaviors. In their study, the scientists tracked the movements of great white sharks as they hunted Cape Fur seals at Seal Island in False Bay, South Africa.

Using geographic profiling, the scientists collected data on 340 natural predatory great white shark attacks on seals. In tracking the sharks movements, the scientists discovered that the sharks utilize a clearly-defined search base. The researchers found that the search base was not located where the chance of running into seals was the highest. Instead, it was based on a balance between three factors: prey detection, capture rate, and inter-shark competition.

Scientists are now using geographic profiling to track great white sharks as they hunt off the coast of South Africa. (Photo credit: Arco Images GmbH/Alamy)

The researchers determined that the spatial patterns of the sharks did not occur randomly. They also found that larger sharks were more successful in capturing their seal prey than smaller sharks. Smaller sharks in turn had a more dispersed search pattern and a lower kill rate than larger sharks. The scientists think one explanation for this occurrence may be that sharks perfect their search technique over time and must learn to center their hunting efforts in areas where hunting success is more likely. A second explanation proposed by the scientists is that larger sharks exclude the smaller sharks from their hunting areas.

The results of the scientists research were published in the Journal of Zoology. Scientists who contributed to this research include R. Aidan Martin of the University of British Columbia, Kim Rosso of Texas State University-San Marcos, and Neil Hammerschlag of the University of Miami.

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Outdoor Cats Significantly Impact Local Wildlife

The predator crouches in the grass, lying in wait. Tail gently swaying side to side, concentration remains on its prey, foraging unsuspectingly nearby. When the moment is right, the predator pounces and catches the prey by surprise, and with one lethal bite, struggle ceases.

Such a scene may evoke thoughts of the African savannah and its wildlife inhabitants. However, the animal depicted lives much closer to home and can be found in over 38 million American households. The animal in question is Felis domesticus or the domestic cat, and like its African relative, can have quite a significant effect on local wildlife populations when left to roam freely outside.

Pet cats that live outdoors can wreak havoc on native songbird populations. (Photo credit: Steve Vates/Alamy)

According to a study conducted by the American Pet Products Manufacturers Association (APPMA) in 2007, 34 percent of the United States population owns at least one cat. Cat ownership is highest in rural areas, where up to 60 percent of the population count cats among their household members. It is these rural populations of free-roaming cats that can have the most devastating impact on native wildlife species.

Cats, known to be skilled hunters, not only affect wildlife numbers directly by predation, but also indirectly by preying on the animals that serve as a food source for naturally occurring predators. In addition, cats can spread disease to other species. In a study published in the Journal of Wildlife Diseases in 1993, cats were listed as culprits in the spread of feline distemper and Feline Immunodeficiency Virus (FIV) to populations of the endangered Florida panther.

According to a study conducted by researchers at the University of Wisconsin, outdoor cats can be implicated in the killings of hundreds of millions of birds and perhaps a billion small mammals each year. Rural cats have the most impact, as 90 percent of their diet is dependent on wildlife.

Predation by cats has led to the extinction of several bird species, and is particularly devastating to nesting shorebirds and island seabird populations. Introduced onto islands as both a way to combat rats (also human-introduced, albeit inadvertently) and as pets, cats took to hunting the native bird species, which were not adapted to such predators. On the islands of New Zealand alone, cats were responsible for the extinction of eight bird species. Within the U.S., bird species considered to be particularly susceptible to cats include ground-nesting shorebirds whose populations are already in decline, and the endangered California Quail, a species known to be targeted by cats as prey.

In response to these impacts, several conservation organizations have become involved in education programs to encourage cat owners to keep their pets indoors. One such program is Cats Indoors!, developed by the American Bird Conservancy and promoted by the Audubon Society. The campaign has been in place for twelve years, and its tenets have been adopted by the states of Florida, Hawaii and Minnesota, as well as the Department of Defense and Outer Banks National Seashore.

Keeping cats indoors helps to ensure good health and protects small bird species that live in your neighborhood. (Photo credit: Mark Scheuern/Alamy)

Our citizen education program has thousands of activists across the country who are conducting education campaigns, getting local ordinances passes, trapping stray and feral cats themselves, and fighting efforts to legalize trap/neuter/release efforts in their communities, Cats Indoors! campaign director Linda Winter said.

Rural housecats and feral cats pose an even greater problem to wildlife due to their sheer numbers and their often complete reliance on wildlife for their diet. According to Dr. Jo Liska, director of educational programs for the Bloomington (Indiana) Animal Shelter, these cats potentially pose a danger to themselves and others around them.

“There is a prevalent mentality, especially in rural areas, that cats should be free to roam, and one doesn’t really care if they are not seen for awhile,” Liska said. “Generally, those cats are also intact, not vaccinated, and not tested for FIV/FeLV [Feline Leukemia Virus]. This endangers all cats who spend any time outdoors and unsupervised.”

Among the guidelines suggested by the Bloomington Animal Shelter include keeping cats indoors, spaying or neutering, keeping vaccinations complete and up to date, and testing for FIV/FeLV. Aside from preventing potentially devastating impacts on wildlife species, keeping cats indoors is also in the pets best interest.

“Indoor cats live an average of 15 years, while outdoor cats live a mere three to five,” Dr. Liska said. “The latter are subject to acts of cruelty, to predation by coyotes, dogs, skunk, et cetera, to vehicles, to disease, to starvation, and to inadvertent poisoning.”

Providing outdoor cats with food does little to decrease their impact on native species in the wild because their hunting instinct is not driven solely by hunger. The most effective solution is to prevent them from having the opportunity to hunt outdoors.

Outdoor cats take their share of wildlife, especially birds, even if they are well-fed, she said. They are natural predators simply doing what is hard-wired behavior.

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The Male Praying Mantis — Dying to Mate?

A female mantis chews off the head of a male.

Females of the praying mantis and Chinese mantis species are infamous for their habit of devouring male mantises before, during, or after mating with them. For years scientists have been arguing over how and why this gruesome relationship could have evolved. The female certainly benefits from having a large meal that essentially delivers itself to her spiny embrace. What can account for this suicidal form of insect chivalry on the part of the male?

In the evolutionary scheme of things, any organism that reproduces and passes on its genes is considered successful, even if it involves personal sacrifice. Have male mantises not evolved a way to avoid being eaten by females because their main objective passing on genes is achieved? Have females evolved in a way that leads to selecting males who cooperate in their own death? Do males who fight for their lives never get a chance to mate and pass on their genes? If you’re a female mantis, especially a hungry one, why choose a mate who’s going to put up a fuss when you try to bite his head off?

Some point out that the nutrition offered to females in the form of a male probably improves the odds that the sperm deposited in a female will end up resulting in a new generation of offspring. If a male simply mated with a female and walked away, as is the case in many animal species, then the female would have to fend for herself and the few hundred eggs she carries. A well-fed female should fare much better than a hungry female.

Despite these compelling, logical arguments, some scientists insist that a male who could mate with a female but also live to mate another day would be more successful in reproductive and evolutionary terms. So why hasn’t evolution lead to male mantises adapted to the female’s aggression? Is there no way to mate without losing your life?

William Brown of the State University of New York–Fredonia, decided to study Chinese mantises to see if males demonstrated any ability to avoid death at the hands of their mates. Brown and one of his undergraduate students, Jonathan Lelito, experimented with introducing male and female mantises to each other under different conditions.

“We predicted that if the male is complicit, he’s just going to march into her jaws,” Brown said. “But if the male does not want to become her meal, then he should avoid the risk of being eaten.” They placed some males in containers with females who had not eaten recently, and placed others with females who had already feasted on crickets. They also experimented with how the males approached the females. Did males fare better if they approached from behind?

The results of Brown’s experiments showed that males are quicker to approach females that are full. When presented with hungry females, males will jump onto them from a greater distance, possibly to avoid being grabbed and killed before getting a chance to mate. Males also tend to stay on hungry females for longer, perhaps to wait for the female’s hunger to pass. Males who approach females from behind are also less likely to be eaten.

“It’s clearly a case of sexual conflict,” Dr. Brown said. “Males are not willing partners.” While the work of Brown and Lelito shows that male mantises are not gung-ho about being cannibalized during sex, the fact that as much as 63% of a female mantis’s diet is composed of male mantises suggests that the urge to mate is stronger than the urge to live.

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