Scientists and veterinarians are racing to prevent a wildlife disaster from getting worse in Tulare Lake, where hundreds of birds are dying from avian botulism in its stagnant waters.
The lake that reemerged in the San Joaquin Valley during winter flooding, which was partly brought on by snowmelt, after decades of dormancy has become a warm and stagnant breeding ground for toxins that cause paralysis and death. It’s common for avian botulism to strike water fowl when temperatures rise in summer and fall. But in 1983, the last time Tulare Lake emerged to such a large size after winter flooding, the disease killed more than 30,000 birds.
“We’re trying to prevent that this year,” said Steve Gonzalez, spokesman for the state Department of Fish and Wildlife.
Department staff have removed close to 1,700 dead and sick birds since early August. The numbers went up sharply in the past two weeks, when 50 to 100 have been pulled from the lake daily. But the lake could host millions of birds during fall migration, so there’s urgency to deal with the situation as quickly as possible, according to the wildlife department.
Danene Birtell, left, with the Oiled Wildlife Care Network and Jeanette Bates with International Bird Rescue treat birds sickened with avian botulism in Tulare Lake (Kings County).
Provided by California Department of Fish and WildlifeSick birds are being treated by the Oiled Wildlife Care Network, an emergency response group from UC Davis that usually focuses on oil spills. It’s the first time the organization has treated birds with avian botulism, said staff veterinarian Jamie Sherman.
“We were brought in because we have so much expertise in setting up animal hospitals and helping large numbers of patients in a short period of time,” said Sherman.
They’ve treated about 18 species of birds, mostly ducks like the Northern Shoveler along with a few types of egrets and some great blue herons.
Also called type C botulism, avian botulism is caused by a toxin produced by the Clostridium botulinum bacteria and is distinct from the types of botulism that sicken humans and from highly contagious forms of avian influenza, which has not shown up in tests of dead birds collected from the lake.
Christian Alderson, left, scientific aide and Evan King, environmental scientist at the California Department of Fish and Wildlife, remove birds sickened with avian botulism from Tulare Lake (Kings County).
Provided by California Department of Fish and WildlifeBirds can ingest the toxin or bacteria from the lake itself or by eating fly larvae from the carcasses of infected ones. That’s why wildlife officials are focusing efforts on both rescuing birds that could be treated and released, as well as on collecting dead ones.
“Flies and bugs lay their eggs on the carcass. Larvae spring up from that and the other birds eat the larvae,” said Gonzalez. “We’re trying to break that cycle.”
When birds are taken into the clinic, they’re assessed and then given hydration, food and rest. When untreated, the disease progressively makes the birds unable to stand, fly and eventually not even lift their heads or blink.
There’s no medicine that helps; the treatment is simply time.
“We’re actually waiting for that toxin to move its way out of their system,” said Sherman, who said that birds can improve within 24 hours of treatment.
Of the 232 birds the wildlife network has taken in since late August, 56 have been rehabilitated and released back to the wild while 72 have died or been euthanized.
Part of the problem is that Tulare Lake, which reached almost the size of Lake Tahoe by June, does not have natural inlets or outlets, Gonzalez said. In other areas where they see botulism show up, they can control the intake and outtake of water and contain it, he said.
He said that scientists are also concerned because the lake could stick around for another year or longer and cause similar problems.
But so far, their strategy seems to be working and temperatures have gotten cooler, Gonzalez said. They will know more in a couple of months.
“If we weren’t here those animals would have died out there,” Sherman said.
Reach Tara Duggan: [email protected]; Twitter: @taraduggan
