The death of a 2-year-old mountain lion from rat poison was unusual and unsettling enough to capture attention and sink hearts, especially because P-34 had attracted more than her share of local fame last year by lounging under a Newbury Park mobile home. But, in fact, wildlife of all sorts die from rodenticides that were never intended for them, and most of the state's mountain lions have those poisons in their systems.
Of most concern is so-called second-generation rat poison, which is more toxic than previous versions and, when eaten by a rodent, stays in its body at high levels. Birds of prey, bobcats and other animals that eat rodent carcasses — or live rodents, which are often woozy from the poison and thus easier to catch — then build up the poison in their bodies. Thus it works its way up the food chain.
According to a 2013 article in Audubon magazine, more than three-fourths of California's mountain lions have these poisons in their systems, as do more than 90% of the owls, hawks and other birds of prey in San Diego County. The poison also threatens bobcats, foxes and pet dogs and cats. The problem is widespread because rodents don't stay tidily on the property where they ate the poison; they wander into wilderness areas and other backyards before they die. In some cases, the rodenticides leave affected animals disoriented and with weakened immune systems. They are more likely to be hit by cars, to be unable to find food or seek shelter, or to be afflicted with mange.
Last year, California banned the sale of second-generation rodenticide to the public, though farms and licensed exterminators may still use them, and the state also forbade their use in state parks. Yet the deaths continue. In late 2014, three bobcats were found dead at UC Santa Cruz, and Griffith Park's well-known mountain lion, P-22, developed a case of mange that biologists believed was the result of rodenticide. In September, the poisoned body of a gray fox was found in the Santa Monica Mountains.
California has been ahead of the rest of the country in restricting the use of rat poisons, but, according to state wildlife officials, the new rules aren't working. The problem appears to be the too-lavish use of second-generation products by exterminators with too little attempt to fix the cause of rat infestation. For example, state officials said, it is common to see overflowing trash bins surrounded by rat-bait stations. As long as the trash remains, so will the rats.
California must consider more aggressive restrictions on pesticide use. It could require exterminators to use nontoxic approaches — cleaning things up, sealing openings in buildings and replacing rat-attracting plants — and to rely on second-generation rat poison only when absolutely necessary.