Although overshadowed in the media by the struggle local cougars face in an increasingly urban Los Angeles metro area, the local bobcats,(lynx rufus), face their own enemies with poisons and autos remaining major threats.
in an email to Wild Animal News and Information, Joanne Moriarty , a biologist with the National Park Service (NPS) wrote generally of the battle the small size predators face. The NPS has been studying local cats since 1996 and has tracked over 300 0f the felines, Mostly from Westlake Village, Thousand Oaks and Agoura Hills. NPS says the length and size of the study makes it one of the most important studies of its kind. She cautions, however, that because the study is very local it is difficult to know exactly what is going on throughout the range. Bobcats are found throughout Southern California and indeed most of the US, Mexico and southern Canada.
In the early years of the study, local bobcat populations were stable and healthy but in 2002 mange began to sweep the population, killing many. Although the direct link isn’t clear according to NPS the problem seems to be caused by anti-coagulant rat poisons, related to warfarin. This in turn is part of our war against rats and our efforts to control human disease. Warfarin and other anti-coagulants inhibit Vitamin-K production leading to deficits in coagulation and internal bleeding. In humans it can be used as a blood thinner to help treat certain diseases in which blood thinning helps. It kills rats by causing internal bleeding, Rats are prolific breeders and if left alone can breed astronomically. Of course there are natural ways to get rid of rats, but as you see from the list found on the website of a landscaping company shows, many of them require considerable work. So it is little wonder many homeowners and institutions turn to poisons. California has instituted some controls on these poisons, but they remain widely available. As predators, including bobcats, kill and eat rats the poisons build up and begin to cause illness, Although Moriarty says rabbits are the mainstay of local bobcat diets they also eat rats, mice, squirrels, birds, reptiles and insects. They often consume sub-lethal doses of the anti-coagulants, which build up in the liver and then interfere with their immune systems apparently leading to mange, a severe skin and hair disease. and other fatal conditions.
The story of B-332 is an example. He was an adult cat in the study who contracted mange and died.
B-332 was first captured and tagged in 2015. NPS had this to say about his death in a press release
“California restricted the retail sale of second-generation anticoagulant rodenticides in 2014, but they are still available for use by licensed applicators. First-generation anticoagulant rodenticides are widely available for purchase. Both first- and second-generation compounds were detected in B-332’s liver.
B-332 died on December 19, 2016, in Simi Valley. Residents in a neighborhood flanking the Simi Hills reported a mangy bobcat hanging around. Local animal control picked him up, euthanized him, and, noting the research GPS collar, contacted and delivered the body to Moriarty, who estimated he would likely have died within a day.
The connection between exposure to anticoagulant rodenticide and mange, a parasitic disease of the hair and skin, is still not fully understood. Previous NPS research, however, has found that bobcats that have ingested rodenticide are much more likely to suffer from severe mange.
The prevalence of mange peaked between 2002 and 2006 in the Simi Hills area, during which time more than 50 percent of radio-collared bobcats died as a result of the condition, overtaking vehicular collisions as the leading cause of death among the local population. Although few cases were seen in the Simi Hills by 2008, until about 2013, unfortunately more cases have been seen again in recent years.”
Moriarty said in the email NPS has not done a recent survey regarding bobcats and mange but that anecdotal evidence does not indicate a change for the better. Perhaps predictably, the second biggest threat to bobcats is death by automobile. It is also a risk for mountain lions, who often die trying to cross busy roadways although there have been incidences of them successfully crossing freeways.
Bobcats also face other challenges. Mountain lions will kill them as wild cats do not generally tolerate other wildcats. As for coyotes, Moriarty said that the relationship is complicated. Bobcats are fierce and well armed and can defend themselves well but sometimes fall prey to coyotes, especially the young. She said there is no evidence they are inter breeding with local feral cats. The local bobcatscats top off around 20 pounds. In areas where they grow larger, as much as 30 pounds, she said they sometimes kill and eat deer. Locally, they have been observed feeding off a deer carcass but they have not been found to kill deer.
life goes on, however, and bobcats continue to deliver kittens even under trying circumstances as they demonstrate a strong will to survive.