Nature Shock - Tuesday February 5

nature shock
the zombie alligators (5/6)

The documentary series examining freak occurrences in the natural world continues. This programme focuses on a bizarre chain of events in Lake Griffin, Florida, which turned a once peaceful wilderness into a scene reminiscent of a horror film. Over a period of years, a number of Griffin’s resident alligators were turning up dead, but scientists were baffled as to the cause.

In May 1997, the bloated bodies of a number of adult alligators were discovered on the shoreline of Lake Griffin in central Florida. “There were times when I would go into the lake and find ten alligators within half a mile,” recalls local fisherman Skip Goerner. The reports of these strange deaths caught the attention of the Florida state’s Fish and Wildlife Conservation Commission (FWC), who sent a team to look into the mystery. Leading the investigation was wildlife biologist Allan Woodward who immediately suspected the work of poachers. However, the corpses told a different story –they bore no signs of attack by man and, most shockingly of all, some of the motionless animals were not even dead.

In order to discover the cause of these events, the FWC team began to study the behaviour of the alligators before they died. What the scientists found was that the animals were struggling to move properly and keep their heads above water, with many alligators spending much of their time floating listlessly in the lake or lying motionless on the banks. “We noticed alligators that showed poor equilibrium,” says Woodward. But why would these amphibious creatures who have survived for millions of years suddenly be unable to survive in their natural environment?

Pathologist Dr Scott Terrell conducted thorough autopsies on the alligators, but he could find no clues as to the cause of death. “What we were seeing were adult, healthy animals,” he recalls. “We weren’t finding much.”

Since the dead bodies were offering no evidence, the scientists returned to the lake and went in search of a living ‘zombie’ alligator. Soon, they had caught one such animal –an unusually easy manoeuvre since the alligator was incapable of putting up a fight. A sample of blood was taken from the animal and sent to Mark Merchant –a professor of biochemistry at McNeese State University. But Merchant could find no sign of any illnes. In fact, he attempted to infect the blood with a number of deadly viruses, including E. coli, salmonella and HIV, but each time the incredibly resistant blood fought off the infection.

Having drawn another blank, the scientists returned to their living specimen. “Some of the signs we saw did suggest some neurological problems,” says Woodward. “That became our next suspect.” Tests showed that the animal responded in a slow and unpredictable way to electrical stimulation, suggesting that the problem did lie somewhere in the nervous system –but it was still not clear where. Dr Terrell suspected that the key to the mystery lay in the alligator’s brain –an organ weighing just eight grammes. He sent tissue samples for tests and soon discovered that many of the neurons in the animal’s brain had died. “There were areas of the tissue that were almost ghost-like,” he says.

This brain damage explained all the symptoms common among the alligators, including disorientation, loss of balance, nerve damage and drowning –it seemed that for some reason, portions of these alligators’ brains were dying while they were still alive. However, despite their breakthrough, the scientists were still no closer to finding the culprit for the animal deaths.

The FWC suspected that man’s activites were responsible and began to focus on the change in water quality caused by increased agricultural activity on the banks of the river. However, it was not until a chance meeting with a man called Dr Dale Honeyfield at a scientific conference in Maryland that Woodward and his team would finally get to the bottom of the case. Could something as simple as a vitamin deficiency be responsible for such a strange turn of events?

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