Squirrel specimens at Museum of Natural History. Shelly Meyers at Kahoots Feed Store in Ramona says that they can't keep enough squirrel poison in stock.
During the past few years, San Diego's rural tree squirrel population has nearly reached extinction. Their population is apparently coming back, even though few people seem to know exactly why they died off in the first place.
Scott Treemore, 37, is a research assistant at the Natural History Museum in Balboa Park. He has been studying squirrels for the last four years and monitoring local squirrel populations. "You'll find arboreal [tree] squirrels mostly in the coniferous forests in the backcountry and some of the local inland areas, particularly at higher elevations. It's the western gray squirrel and it's the common squirrel that people see that lives in the trees. Their populations don't normally fluctuate, but they were hit with a virus three years ago, and their population crashed. Now they're slowly coming back. I don't think it's a boom. They reproduce quickly, but it's going to take a while for them to move into new areas. I can't give you a number for the population -- you would have to do relative densities, and the relative density has increased over the last six months, but it's a very slow increase. It will take several years for them to get back to normal, about as long as it took for them to crash. The plague is mostly associated with ground squirrels."
Treemore opens a locker in a corridor on the third floor of the museum. He pulls open a drawer that has several stiff, dead squirrels laid out as scientific specimens. He explains how the gray squirrel likes to eat nuts and fruit, which can cause problems for local farmers and orchard owners. (Two Julian orchards were contacted, and both said that the tree squirrels never gave them any problems.)
"It's mostly the fruit trees out in that area. They are nut-and-seed eaters too. But I think that, legally, on your own property, you can trap them. Some people use the 'have-a-heart' traps, where they can trap them and relocate them somewhere else."
Laura Itogawa is the supervising ranger for Cuyamaca Rancho State Park and a Julian resident. Itogawa says that the squirrels are just beginning to reappear. "There was a virus that nearly killed them all off. It was an upper-respiratory infection that pretty much took out all the gray tree squirrels and rabbits. I lost two bunnies to it. About three years ago, I began to start seeing gray squirrels again up at the [Stonewall] mine, maybe two or three. I saw one at Green Valley last year, but that's about as far back as I've seen them. They're trying to make a comeback. Before, they were all over Julian, and I used to see them in my yard, but I still haven't seen one there since the infection came through. It was more than 90 percent that died. We went from having them everywhere to having none. The way I understand it, it was airborne, because my rabbits were in a cage."
Bill Goddard, a volunteer ranger at the Mount Laguna station, says that the tree squirrels were infected with a disease called snuffles. "I haven't seen any for quite some time." His wife, Phyllis, agrees. "Every so many years, they get the plague or something, and we don't have them around for quite a while. Then they gradually come back. I think last year I only saw a couple of the gray tree squirrels. We have ground squirrels aplenty!"
Another ranger at William Heise County Park, near Julian (who asked not to be named), said that there has been a tremendous drop in the population of tree and ground squirrels. "I'd heard that there was a disease that was particular to them, kind of like AIDS. I've seen one or two tree squirrels recently, and I'm glad to see them coming back. They're so beautiful."
Chris Wiersema is the squirrel team leader for Project Wildlife, a nonprofit group located on Sherman Street, near the Humane Society, devoted to rescuing and releasing endangered wildlife. "We've been seeing them sporadically over the last couple of years here and there, but no great numbers. I've heard that they are on the rebound. But we only see the ones who are injured or orphans, not the healthy animals. We see very few tree squirrels at all. The population is even down in Balboa Park. I know they've seen a few more in the mountains. The few we've caught down here we've released in the Julian-Cuyamaca area, hoping they would build. I know they've been seeing them out at the lake."
Dr. Jim Lang, the senior vector ecologist for San Diego County Vector Control, says that there has never been any virus. "I know that it's been a lot warmer the last couple of years and the plague hit some animals, but we've never had a die-off of squirrels caused by plague in the mountains. Tree squirrels are not affected by plague at all. I know that they're affected by mites, which can cause dermatitis and kill them that way. Sometimes these gray squirrels can get into garbage cans and get infected with salmonella, and that can kill them also. There was a big die-off of gray squirrels about five years ago in the Palomar and Pine Hills area near Julian, but I don't know what caused it. Perhaps the county veterinarian has had some squirrels come in that had died and examined them."
Dr. Al Guajarda is a public health veterinarian for the County of San Diego. "There hasn't been any virus diagnosed in any squirrels. I know that vector control will go out and tranquilize squirrels and test them to see if they have any exposure to plague by checking for antibodies. I do remember that in Alpine some squirrels had a bacterial infection called pasteurella, and it seemed like it was affecting the respiratory infection. It also affected their skin. We never knew why they caught this infection, and it did affect a certain amount of squirrels about four or five years ago. I don't think it went to wiping out most of the population.
"We rely on samples brought in by rangers and wildlife rehab groups, but we don't take our own samples, so just because we don't see something doesn't mean it doesn't exist out there. Our primary function is infectious/contagious diseases like rabies and salmonella. As far as the tree squirrels, I just remember the die-off in Alpine, and we did determine it was an infection of pasteurella. But I don't recall anything about other areas of the county."
Clint Powell, a Julian naturalist, seems to know more about the tree squirrel population than anyone. "In 1995, we started noticing a terrible decline in the species. They had an infection where they would drop to the ground and get hit by cars -- a very abnormal condition. Many people took the dead western gray squirrels to Vector Control or the county veterinarian. A lot of the reports said it was stress. Now, what would stress a western gray squirrel? I was told that what they died of was a bacteria that's common to domestic rabbits. The necropsies said that it was a disease called 'snuffles,' which is common for domestic rabbits and highly contagious among western gray squirrels. Interestingly, it doesn't affect the ground squirrel or the chipmunk, just the western gray squirrel, and that squirrel is the signature animal of the mountains. People here put out feeders specifically for the western gray squirrels instead of bird feeders. They'll put peanuts in them, because that's what the squirrels like. In this county, they're not considered a game mammal, so the Fish and Game people don't take any statistics on them. I've just heard on the phone that they are increasing. We're seeing babies, specifically at Lake Cuyamaca, so they are coming back. Back in 1962 or '63, they were just about wiped out and came back then too."
Pasteurella multocida, or snuffles, is always terminal for rabbits and tree squirrels, but Powell has never heard of any rabbits being infected. "We tested rabbits in the Pine Hills area up here, and it was not found. The veterinarians will only say what the animals died from in their necropsies, but [the squirrels] are coming back."
Contrary to Treemore's assertion, Powell says that the western gray squirrel poses no problem for growers and orchard owners. "There's 37 species of birds and mammals that feed on the horticultural community of Julian, and the western gray squirrel is not on that list. They are not high on any list as a public nuisance. The ground squirrel is, and the county has a problem with fleas and mange and things like that. But the western gray squirrel is not a threat to anyone in the community in Julian. People love them, and they're wonderful to have around the yard. They're very mobile and jump around. They're beautiful, and when you see western gray squirrels, you know you're in the mountains. They're a very important mammal to this community."
The ground squirrel population, on the other hand, is multiplying so fast that some local residents are beside themselves trying to contain the problem, especially in Ramona. Shelly Meyers at Kahoots Feed Store in Ramona says that they can't keep enough squirrel poison in stock. "The squirrels outnumber us two to one! At our own house, we've got four acres, and everywhere you turn the ground squirrels have a new hole going. I think it's just the dry weather and the lack of food. I've had them getting into my horse's feed barrel. They've eaten the grapes off of our grapevines. Our distributors haven't been able to supply us with one of our best-selling products, Gopher Getter. It's a poison used for gophers and ground squirrels. It could be that the FDA wanted to do some more testing, but that's my own speculation. The rest of the state is having the same problem we're having down here, and our distributor is having trouble keeping it in stock. It's bad. I've had customers come in and tell me that they think the poison is a delicacy for ground squirrels, because they eat it and nothing happens. They'll get into any kind of plants, trees, or shrubbery and destroy them. Rose bushes, trees. They eat plants, roots, any ground cover, cat food, dog food. You walk along and it's nothing to keep stepping into one of their holes. They can't kill them fast enough. Our customers are all talking about the ground squirrels."
Down the street at the Nutrena Feed Store, Allen Linstroth says the drought had caused the ground squirrel population to get more aggressive. "They are tunneling everywhere, looking for anything moist -- be it roots or vegetation -- and there just isn't any out there. I've heard this is the worst drought since 1947, and it couldn't be worse. I've been selling lots of baits, traps, and poisons, and a lot of live traps. Some people try to relocate them, but that really doesn't solve the problem."