Brookfield
Zoo’s
loss of 16
stingrays
in the overheated pool of a temporary exhibit Monday was the latest in a string of similar
stingray
deaths at
zoos
in recent months.
At least three other
zoos
had fatal accidents decimating their exhibits in the past year. In May, 41 of 43 cownose
stingrays
in a new exhibit at the Calgary
Zoo
in Alberta, Canada, died of undetermined causes over a few days. The Dallas
Zoo
lost 19
stingrays
in two weeks in mid-June after the city water department routinely added chlorine to the water supply in a volume fatal to the rays. The Fresno Chaffee
Zoo
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in California lost 18 of 19
stingrays
last summer because of power outages and equipment failures.
Brookfield
Zoo
officials said the incidents at the other three institutions were unrelated to the deaths in their touch tank, and once the
zoo
can pinpoint the exact cause for the die-off here, it still plans to reopen the exhibit.
Though the causes of the four incidents differed, some
stingray
researchers Thursday wondered whether the deaths indicate that special precautions need to be taken to care for
stingrays
in the shallow touch tanks, generally only about 18 inches deep to allow
zoo
visitors to touch them.
“These exhibits obviously need to be more carefully monitored than they have been,” said John McEachran, an emeritus biologist at Texas A&M University and one of the world’s top
stingray
authorities.
“Where you have a low volume of water, as you do in these shallow touch pools, you have to be careful because water temperatures can go up much more quickly than in deeper pools, and there is no place for the fish to escape.”
Chris Lowe, a marine biologist and
stingray
specialist at California State University Long Beach, is a fan of the touch pools but expressed worry that the deaths might have implications for wild
stingray
populations.
“It is surprising to see all these recent deaths,” he said. “Most of the
zoo
stingrays
were caught in the wild, so I suppose it forces you also to ask the question of whether or not they are coming in from the wild in a weakened condition for reasons we don’t know. Are they canaries in the coal mine that we haven’t figured out, with some sort of coastal pollutants that we haven’t detected that affect the health of wild populations?”
Stingrays
have long been a staple of exhibits in public aquariums — Shedd Aquarium has housed and displayed them since opening in 1930 — and are not particularly tricky to care for in captivity, experts say, particularly the two species involved in the
zoo
deaths: cownose and southern
stingrays
.
“I think these exhibits have done a lot of good, helping to stop the demonization of sharks and rays so prevalent in the public,” Lowe said.
At
Brookfield
, Fresno and Dallas, the fatal incidents were in temporary exhibits owned and operated by Living Exhibits, a San Diego company founded by two highly regarded ex-
zoo
administrators, Mike Yeakle and Brian Joseph.
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The deaths at
Brookfield
were due to a power fluctuation in the Commonwealth Edison system Monday morning, Joseph said Thursday. A sudden drop in voltage created havoc with built-in heating and cooling equipment, which allowed the water to warm “to 90 degrees, 8 degrees higher than normal,” he said.
Zoo
officials have not confirmed a power fluctuation was the cause.
In Dallas, the city “pulsed” chlorine into its water supply that “overwhelmed our precautions,” he said. The company and the
zoo
have since changed its monitoring system to protect the rays from chlorine.
In Fresno, Joseph said the city suffered two power blackouts last summer that cut all electricity at the
zoo
, causing equipment failures that had cascading effects on the
stingrays
, killing them over several weeks.
“The exhibit is running fine now, the fish are healthy, and the exhibit is one of the most popular attractions we have,” said Fresno
zoo
Executive Director Lewis Greene.
Kim Smith,
Brookfield
Zoo’s
vice president for animal programs, said visitors loved the touch tank, and officials want to reopen it when their internal investigation is complete.
“Of course if [the exhibit] is not safe, we will not reopen. The welfare of the animals is always our priority.”