An early morning mist weaves in and out of the brush lining the trails at La Purisima. This time is a quiet time, broken only by the rustle of a small animal and the occasional footsteps of a passing walker or jogger. Peaceful hours like this make La Purisima Mission a favored location for people seeking to be at one with nature.
But humans and nature don’t always mix well, and between the two, nature is the one that usually suffers.
Local animal rescue workers have been feeling that tension lately, particularly after a recent red-tape battle to trap and rehabilitate a bobcat with suspected rodenticide poisoning from the mission grounds.
Animal Rescue Team, based in Santa Ynez, tried to help the animal, but couldn’t interfere because Julia Di Sieno, executive director and co-founder of the group, couldn’t get the necessary permits from the California State Parks Department.
Unable to intervene, volunteers monitored the bobcat’s health daily for a month. Until one day the bobcat was gone.
Di Sieno still regrets not being able to help the sick bobcat, but acknowledges that there’s a bigger issue at play. Secondary and even tertiary rodenticide exposure is becoming a big threat to non-target predatory animals across the state, including many endangered animals.
“They say it’s the gift that keeps on giving; it never just kills the animal intended—it kills the predators,” Di Sieno said.
Letting nature take its course
Wolfie is one of several dogs living on the Animal Rescue Team property. He looks every bit the part-wolf he is. He followed Di Sieno around the yard on a recent afternoon, hamming it up for attention, rolling around at her feet, and nuzzling her hands for petting. Di Sieno clearly has a way with animals, a trait made even more evident as she walks around the wild animal pens.
Among the animals are a gray fox, turtles, and various birds. A beautiful bobcat starts to hiss, and Di Sieno tries to reassure it.
“It’s OK, Oscar, mommy’s right here,” she said, like a mother soothing a baby.
Oscar seemed to relax a bit, but remained on guard. Di Sieno explained that Oscar was abandoned as a baby and has a detached retina. He’s a permanent resident at the facility.
She said they don’t try to habituate the animals.
“As much as I talk to him and play with him, he’s pretty wild,” Di Sieno explained.
In a separate cage, a bobcat that had taken a bullet to the chest growled loudly. He would soon be released—and seemed ready. In yet another cage, two bobcats with mange huddled together. Di Sieno explained that yet another had succumbed to mange and that she and her team were doing what they can to rehabilitate the remaining pair.
Because second-generation anticoagulant rodenticides interfere with the synthesis of vitamin K-dependent clotting factors, causing hemorrhaging, rehabilitation consists of blood transfusions and vitamin K treatments. Animals that survive are set out in the wild usually within a two- to three-mile radius of where they were found. Those that succumb are sent off for testing to confirm that the death coincided with rodenticide poisoning. Most of them test positive for brodifacoum, the active ingredient in second-generation anticoagulant rodenticide.
How it works
One of the biggest—and probably the least understood—threats to predatory wildlife is the specific second-generation anticoagulant rodenticide. Such rodenticides act as blood thinners, causing internal hemorrhaging. Animals who ingest it immediately become lethargic and oftentimes thirsty, which leads them into backyards to find water. It’s a slow and miserable death. If the animal doesn’t die quickly, it becomes a slow-moving target for other predatory animals.
Because rodenticide can stay in tissue up to 100 days, any predator eating the sick rodent is also ingesting the toxin. Since the anticoagulant kills slowly, a rat might eat several doses, all of which could be passed on to predators.
When an owl, bobcat, or fox has died of exposure to rodenticide, it’s most often a secondary exposure—in other words, the predator ate a sick animal. There have, however, been cases of tertiary exposure, such as two mountain lions in the Ventura area that are thought to have become ill from eating a coyote sickened by eating a poisoned rodent.
And predatory animals aren’t the only ones at risk. Di Sieno said dogs and cats often get into poison when owners store it in the garage or other places to which domestic animals have access.
Wildlife-safe alternatives
One of the ironies in using rodenticides is that they’re killing off some of the target rodents’ natural predators. Wildlife advocates are urging the development of natural predators. For example, putting up owl boxes can draw the birds to nest near areas where people want to eliminate rodents, and then nature can take its course. There are also nontoxic pest control methods.
However, Di Sieno said, that isn’t what typically happens.
“Most of the time—I hate to say it—it’s property owners, horse owners
who want to eradicate … gophers, using the rodenticides,” she explained.
Property owners may be unaware or misled as to how the rodenticide works and believe it’s a quick way to eradicate pests. Di Sieno said people need to know the best option for pest control is a natural one.
“People should really do some research before they use it,” she said. “You’re not going to get rid of the problem; you’re going to make it worse. You’re killing off the apex predators.”
Widespread problem
Laurel Serieys, a Ph.D. candidate at UCLA who’s co-advised by the National Parks Service, has been steeped in studying the effects of second-generation anticoagulant rodenticide on bobcats. Her study area involves the Santa Monica Mountains, but it has ramifications for animals throughout the state.
On her website, urbancarnivores.com, Serieys details her
research on sublethal consequences of rodenticide exposure. She points out that there’s no direct causative link between bobcat mange and the rodenticide exposure, however there’s plenty of evidence to suggest bobcats that succumb to mange and other sources of mortality, in her study as well as outside the area, have also been exposed to the rodenticide.
Serieys has researched the topic for the last six years but has yet to determine whether a causative link between notoedric mange and anticoagulants exists. However, she said she’s never found a bobcat that died with this type of mange that hadn’t been exposed to anticoagulants. While performing necropsies on these animals, Serieys has regularly observed that individuals that die with mange have intestinal bleeding, likely associated with anticoagulant exposure. Further, bobcats exposed to anticoagulants are more than seven times more likely to die of notoedric mange, a disease that, until 2002, was never documented as causing population impacts in any species of wild cat globally, Serieys said. Although a causative link isn’t definitive, there are reasons that biologists like Serieys suspect anticoagulants are involved in the epidemic in bobcats observed in some regions of the state.
Adding to the confusion is that some animals are simply more susceptible to the rodenticide. While bobcats and other felines such as domestic cats and mountain lions have more of a tolerance, other predatory animals such as coyotes, gray foxes, and kit foxes and are known to be more susceptible.
“What we do know is that 95 percent of bobcats are being exposed to it in the Santa Monica Mountains. What we do not know are the consequences, though we believe it could affect bobcat disease susceptibility,” Serieys said.
To put this in perspective, a study examining animals’ deaths between 1997 and 2004 revealed that anticoagulant exposure was the No. 2 source of mortality in coyotes, next to getting hit by a car, Serieys said.
“I consider it a problem if animals are exposed,” she said. “In terms of exposure, it’s out there. It’s prevalent. It’s a huge problem, in my opinion.”
Manufacturers of the second-generation anticoagulant rodenticides containing brodifacoum, as well as bromadialone and difethialone, were required by the U.S. Environmental Protection Agency to take the products off the shelves of big-box retailers to limit their household use. They were also required to use bait stations for all outdoor, above-ground uses. While some manufacturers applied the safety measures, others didn’t, according to the California Department of Pesticide Regulation’s semi-annual report. That led EPA to initiate cancellation proceedings against the non-compliant products to remove them from the market. Meanwhile, the California Department of Fish and Game, which is in talks with EPA about wildlife exposure, requested that the Department of Pesticide Regulation reevaluate its approval of the products.
As part of the reevaluation, the Department of Pesticide Regulation is reviewing data on dead wildlife tested for rodenticides, and hopes to complete its data evaluation by the end of the year in order to make a decision on whether second-generation rodenticides should be restricted materials. Such materials require a permit from the agricultural commissioner in the county in which the product will be used, though the products can currently be purchased off the shelf, according to Lea Brooks, spokesperson for the Department of Pesticide Regulation.
The Department of Fish and Game has recommended that the Department of Pesticide Regulation make the second-generation anticoagulant rodenticides California Restricted Materials because of their widespread exposure to predators and scavengers in California.
“Based on monitoring studies of raptors, bobcats, mountain lions, fishers, Sacramento Valley red foxes, coyotes, and San Joaquin kit foxes, the majority of predatory and scavenging wildlife in California have been exposed to [second-generation anticoagulant rodenticides], presumably through consuming exposed prey,” said Stella McMillin, spokesperson for Department of Fish and Game, which is urging the EPA and Department of Pesticide Regulation to restrict public access to these materials in order to reduce exposure to non-target wildlife.
Arts Editor Shelly Cone can be contacted at scone@santamariasun.com.
This article appears in Mar 22-29, 2012.