The National Park Service is facing a lot of pressure from local environmentalist groups who argue that the rat poison recently dropped on Anacapa Island killed more than just rats.
A recent report released by the National Park Service showed that at least 44 non-target migratory birds were killed during the December 2001 attempt to rid Anacapa of rats with poison bombings. The report led local environmentalists to question whether the extermination of rats was worth the loss of other species.
In early December, a coalition formed by the Channel Islands National Park Service, U.S. Fish and Wildlife Services, California Dept. of Fish and Game, and the National Oceanic and Atmospheric Administration dropped bait containing the poison brodifacoum on the eastern end of Anacapa in an attempt to exterminate the Black Rat (rattus rattus), a nonnative species.
The rat reportedly preys upon the eggs and hatchlings of the Xantus Murrelet, a small seabird classified as a species of special concern. However, the park service report said species of protected birds were found dead on the island after the bait was released.
Opponents of the project argue that the deaths of the birds, as well as other island species not targeted by the poison, were unnecessary and that they are currently working to prevent further droppings.
The project’s next phase, scheduled for November or December 2002 will simultaneously drop poison on the middle and western end of the island.
Paul Collins, who studied vertebrate life on Anacapa for a 1979 National Park Service study, said the short-term population losses in the ecosystem are reasonable costs given the predation of the rats.
“This is what I keep telling people: there are rats all over the world,” he said. “There aren’t these endemic species all over the world; they are only found on this small island biome. I think it makes more sense to protect these species over rats.”
The Poisoning’s Aftermath
Scarlet Newton, spokesperson for Channel Islands Animal Protection Association (CIAPA), said poison killed the entire Anacapa population of deer mice, an act she says was “uncalled for and threatens the genetic diversity of the deer mouse species.”
“The Anacapa Deer Mouse is listed as a species of special concern, the same status of the seabird the project is trying to protect,” she said. “Why is this necessary if the rat is not preying on a bird that is not declining?”
In an attempt to preserve the species on Anacapa, the park service took 175 deer mice from the eastern end of the island and placed them in captivity in a facility on the island. They have since been released from captivity and the park service said they have been repopulating rapidly in the absence of competition with Black Rats.
“Prior to their release, the mice were given a little physical in which they were weighed and given tags. In the last few days, the mice have been collected and re-weighed, some are pregnant and many, if not most, have gained weight, meaning they are healthy and thriving,” Channel Islands National Park Ranger Tom Dore said.
Opponents of the poison droppings are also asking if the Black Rat is actually a threat to the Xantus Murrelet. Newton said there is no substantial evidence that the bird population was declining on Anacapa in the first place.
Collins said his research was being misinterpreted, and that he has made no conclusions about the interaction between the rats and the birds.
“Nowhere in my study does it state that the Black Rat preys upon Xantus Murrelet nests, but that is not to say that it doesn’t happen,” he said. “To assume that just because I don’t state something it doesn’t happen – that is not science, no scientist would make that assumption.”
Poison in the Ocean
The Environmental Protection Agency classifies brodifacoum as highly toxic to aquatic organisms but there is still scientific disagreement persists about its effects on marine life.
Dore said due to the poison’s extremely low solubility in water and careful distribution on the island, it is assumed that not enough brodifacoum could have dissolved in the ocean water to endanger non-target animals. He said National Park Service divers determined that kelp forests and inter-tidal fish did not eat non-toxic test bait, so the poison drop did not harm them.
“All in all, there have been no effects on any population, it is a thriving healthy ecosystem,” Dore said.
Newton said the poison in the waters might be linked to the recent bloom of phytoplankton.
“I hypothesize that the poison brodifacoum, which EPA warns highly toxic to aquatic organisms, triggered a virulent bloom of the toxic plankton, which experts suspect is the cause of the vast numbers of dolphins, sea lions and seabirds that have been washing up dead and dying from Santa Barbara to Los Angeles,” she said.
Collins said there was little scientific merit to Newton’s claim.
“Absolutely not. That correlation is pretty shortsighted. These phytoplankton blooms occur regularly in the channel. There is no indication whatsoever that this poison would trigger the bloom,” he said.
The National Park Service will hold deer mice in captivity to prevent their deaths as a result of the poison.