Zoo Knoxville works to solve mystery of 32 reptiles' deaths

Zoo Knoxville officials Monday were listing what they did – and did not – know about the sudden deaths of 32 snakes and other reptiles, including several endangered species. But the deaths remained a mystery that doctors warn may never be solved.

The 32 reptiles died in an "environmental" event some time between 5 p.m. March 21 and 8 a.m. March 22 in one of the herpetology buildings at the park in East Knoxville. Thirty-one snakes and lizards, including a blue-tongued skink and Gila monster, were found dead when zookeepers arrived at 8 a.m. March 22.

A sau python died later despite efforts to revive it with oxygen.

After days of tests and pending results of the necropsies and blood work, zoo officials say they know the deaths happened because of a sudden, yet unknown, change in their environment. But what caused that change isn't known.

The dead animals were sent to the University of Tennessee College of Veterinary Medicine for necropsies, which are autopsies on animals. Blood was taken from the dead animals, the building's survivors and from snakes in other unaffected buildings. The results of the necropsies and blood work are pending and expected within one to two weeks.

The zoo has eliminated some potential causes but no reason has been found for the deaths. Zoo President and CEO Lisa New said veterinarians warned her "we may never know" the cause.

"The vets have told me to anticipate and prepare myself that we might never know because it happened so acutely and to so many at once, indicating it was such a fast event that it might not show up in their tissue levels," New said.

The dead reptiles included a forest cobra and albino Eastern diamondback rattlesnake, both popular with zoo visitors. Members of three critically endangered species – the Louisiana pine snake, Catalina Island rattlesnake and Aruba Island rattlesnake – died. The deaths of the endangered snakes sets back their breeding programs but the zoo does have other snakes of those species, Zoo Director of Animal Collections and Conservation Phil Colclough.

The 19 surviving animals included some other snakes, lizards, some poisonous tree frogs, a bog turtle and a baby radiated tortoise. It appears that tortoise eggs in incubators weren't harmed, New said.

Intiital reports listed 33 dead animals. But the 33rd – a tiny yellow-headed poisonous dart frog – was later found in his habitat.

The surviving animals were evacuated from the building that includes both small exhibit and off-exhibit areas. The 1,400-square-foot building, built in 1974 but maintained and up to standards, has been closed pending the investigation. Other buildings in the herpetology area on a zoo hill were not affected and remain open.

The reptiles didn't die from food problems, of disease or infection. No predators – human or otherwise – entered the building. Knoxville Utilities Board tests for gases, that included carbon monoxide, carbon dioxide and methane, were negative. Those tests were done the day the snakes were found and again two days later, zoo officials said. The building doesn't use gas in its operations. No signs were found of any leaks from nearby buildings that do use gas.

While there was a "giant" storm that evening with lightning and hail, there's no sign that the building lost power or had a power "blink or surge," New said. "There's no indication of a lighting strike but that doesn’t mean it couldn't have affected the equipment somehow," she said.

Alarms that would sound with building changes in temperature didn't go off. Zoo rangers checking the building at night reported no issues. When zookeepers arrived, the building didn't feel too warm or too cool, New said. 

Preliminary findings showed some – but not all – dead snakes had "moderately" red lung tissue. That might indicate an inhaled irritant, New said. Ten to 12 snakes had some soil from their habitats in their mouths, a possible sign they were "thrashing around," she said. Most – but not all – of the dead reptiles were housed more than 3 feet above the ground, Colclough said. Other dead reptiles included a lined flat-tail gecko, four Western African Gaboon vipers and several species of boas and pythons.

The zoo cares for some 400 reptiles and is known internationally for its successful breeding programs for some species of snakes and tortoises.The park's current reptile habitats are among its oldest.

Zoo officials have hoped to build a new reptile and amphibian building for some 30 years. A new $13 million complex is now in the park's current plans.