Minimum Habitat Areas for Cougars in Southern California

From the Environmental Review Newsletter Volume One Number Nine, September 1994


In his paper, Determining Minimum Habitat Areas and Habitat Corridors for Cougars, Paul Beier studied a population of approximately twenty cougars (Felis concolor) in the Santa Ana Mountains of Southern California. Dr. Beier developed a computer simulation of population dynamics of cougars (the model) and compared its predictions to the real population of cougars. This population of cougars is likely to become extinct unless corridors of habitat are maintained to allow immigration from neighboring cougar populations.
     Dr. Beier received the M.S. and Ph.D. in Wildlife Ecology from the University of California Berkeley and is now at the Forestry Department of Northern Arizona University at Flagstaff.

ER: Dr. Beier where is the study area you used for your work with the cougars?

PB: It is 2070 square kilometers or 800 square miles about half way between Los Angeles and San Diego.

ER: What is the point of your paper?

PB: The questions I addressed are, How much more cougar habitat can we lose before we lose this population? And to what extent can loss of habitat area be compensated for by corridors that would allow immigration between areas?

ER: Is 800 square miles sufficient to keep a cougar population viable?

PB: Yes, probably. We are right at the borderline where the risk of extinction, according to the model, is about one or two percent. But it is important to remember that all models are wrong to some degree. I think this is a very good model but we have to realize that it is a only model, and a one or two percent risk could be very serious.

ER: How long has this population of cougars been studied?

PB: The study is over now, but it lasted for almost five years, 1988 through 1992.

ER: How did the population behave through that time? How did it compare to the model's predictions?

PB: For one year - 1988 - in a little over a third of the mountain range, there was no adult male mountain lion. So this indicates we were already having some problems with demographics. The population is small enough and isolated enough that we were able to have no breeding male on a third of the mountain range for twelve months. Not only we did not see any tracks of a male or any of their scrapes but also we had seven radio-tagged females who for one year were not pregnant or raising young.
     This supports the model. The model says that the habitat in the Santa Ana Mountains is about the smallest area that can support a cougar population. This is exactly where the model predicts you would start to see these temporary failures in reproduction.

ER: Can this cougar population recover?

PB: Yes. In April 1989, two males moved into that part of the mountain range and all the females except for one got pregnant right away and had babies. And so cougars do bounce back rather quickly in the youngest age classes.

Even then, the territories of some of the adult females that died in 1988-90, were not re-occupied by December 1992, so that some good habitat had no resident adult female. In contrast, there was a resident adult female pretty much every place we looked in 1988. It took two to three years for some of these vacancies to be re-occupied, so the adult age classes do not bounce back as quickly.

ER: Are the females territorial?

PB: No, they are pretty much solitary but their home ranges overlap quite a bit. The males were territorial. The adult males did not do a perfect job of defending their territory, but they had large core areas that they had pretty much exclusive use of. Male home ranges were about 200 square miles, each of which had well over 100 square miles of exclusive use area, or core area.

ER: So one male's territory overlaps with two or three other females? Is that how it works?

PB: Exactly. Usually a male home range would intersect with at least three to five females.

ER: Is your study area isolated from other mountain lion populations?

PB: There is one potential linkage to a larger mountain range (Palomar Range) off to the southeast. And I think the linkage does work. We did have one animal that used the corridor to disperse. And we had four road kills where the corridor is crossed by a freeway that is not heavily used at night. So I suspect that other animals do use the corridor successfully. I am not optimistic that we will have a linkage there in five or ten years, but right now we do.

ER: Why? Is that because of development?

PB: Yes. The rest of the mountain range, except for that area just south of Temecula is literally encircled by a band of tract homes at least one mile wide.

ER: A cougar was found in a city park in Seattle recently. They do wander.

PB: Yes, they do. And some of my study animals did wander. Generally though, they had some habitat corridor. One of my radio-tagged juveniles was shot in the city of Oceanside. He walked seven kilometers down the San Luis Rey River which is some very nice habitat, but very narrow with very dense urban areas on either side. He was downtown, two blocks from the ocean when he came out of the creek. This area was indeed a very improbable place to find a cougar. But there was a strip of habitat leading to this area and cougars are excellent explorers, especially during the juvenile dispersal.

ER: How do cougars use habitat corridors?

PB: To improve the viability of a population, corridors must be used during dispersal when an animal leaves its mother's home range to become a breeding adult. So the critical question is, how do dispersing juveniles use corridors? I am finishing a paper on this issue right now. In the Santa Ana Mountains, nine of our radio-tagged juveniles survived to disperse. And I examined their dispersal movements with respect to three corridors and several habitat peninsulas that jutted into urban areas. All of these habitat corridors and peninsulas were accidental byproducts of urban sprawl - none were designed as animal movement areas.
     We found that five of the nine dispersing animals used at least one of the corridors, that all nine explored habitat peninsulas that adult cougars avoided, and that all three corridors were used by at least one disperser. Two animals each used two of the corridors. So their ability to find these narrow habitat connections was pretty impressive, and I think this is an optimistic message for conservation. However, I would hate to see us deliberately make corridors as poor as these.

ER: They are very resourceful animals.

PB: Yes. They explore very hard. And if we give them a decent chance at having some habitat connection between major habitat blocks, they will find them.

ER: What was the habitat like in the corridors the cougars were using?

PB: In this study we had three corridors. One of them was Coal Canyon. It was only about a mile long but it was terrible cougar habitat. The corridor is crossed by an extremely busy eight-lane freeway and an approaching animal was forced to cross the wide and devegetated right of way on both sides of the freeway. And then past the freeway the animal would have to pass through a large horse stables area which at night is quiet but basically bare ground with many horses and a few eucalyptus trees. And then the animal would have to cross the Santa Anna River and walk through a golf course. All in a mile and a half. And two of these nine dispersers actually used this corridor.
     Another corridor was seven kilometers long and had far better habitat including an intermittent stream and oak-sycamore riparian forest. [Riparian means streamside. ed.] It was only 300 to 600 meters wide, very narrow but the stream was in an arroyo about thirty feet deep. These thirty foot cliffs buffered the corridor from the tract homes on top of the buffs on each side.

ER: So kids would go down and play in there?

PB: Yes. Kids and vagrants were down there frequently, and so were mountain lions. Three different dispersing cats traveled the entire length of that corridor and each of them discovered it independently, without help from their mothers.

ER: What constitutes good habitat for cougars in the Santa Ana?

PB: An oak-sycamore forest. Chapparal or most anything with natural woody vegetation and some deer for them to eat. [Chapparal is a community of shrubby plants adapted to dry summers and moist winters. ed.] They are not real fussy about type of habitat but they need lots of it, and well connected.

ER: Are cougars an endangered species?

PB: No. And throughout most of the West, they are doing quite well over the last twenty to thirty years since the end of the bounty period. But the Santa Ana population is defacto endangered, and I do not have great hope that it will be there in twenty or thirty years, but it is not listed.
     The Mountain Lion Foundation, a California based environmental group, has petitioned Fish and Wildlife Service to list this population. But that has been over a year now and the Fish and Wildlife Service is ignoring the ninety day response deadline.

ER: The Endangered Species Act is quite clear. This is a subpopulation and it is in danger of extinction, so it falls within the purview of the act.

PB: Yes. I would think so too.

ER: What could developers do to preserve this population? If you were able to sit down and say, we are going to have development in the Santa Anas, how can we do that so we do not wipe out this cougar population?

PB: The main message of the paper is that we can lose a lot of habitat as long as we keep the habitat blocks connected. So I think the main strategy is to keep these connections open. The most critical one would be the corridor connecting the Santa Anna Mountains with the Palomar Range.
     The paper identifies the two most critical corridors. I have provided this information to cities and counties contemplating developments, pointing out some of the other corridors too.  
     This would actually be good news for developers in that a very small amount of habitat preserved in corridors can ensure the stability of this population. This is much less restrictive to developers than a strategy that lacked corridors and required each parcel to be "big enough". But the developers do not want to accept any restrictions. And the politicians in Southern California are one hundred percent pro-development. Orange County has never disapproved of a large development, ever. And they won't on the basis of my report either.
     I do not even blame the developers. Nobody who owns a piece of property wants to be told they cannot become a millionaire off of it. It is the governments who are being irresponsible. And you can sympathize with them on one level, and that is because jurisdictions are so fragmented. Even that tiny Coal Canyon corridor - only a mile and a half long - straddles three counties and two cities!

ER: You have to deal with five governments to protect it.

PB: Yes. And each one of them says, "why should I deprive the developer in my city of his ability to make $20 million if the next jurisdiction over might trash the corridor"?  The city of Anaheim used this exact argument when they approved a project to destroy the Coal Canyon corridor. And the answer, of course, is we need to have some sort of regional planning.

ER: In your paper you referred to large animals like grizzlies and cougars as umbrella species. If you protect them, then you protect a lot of other species in the process.

PB: Yes. And that is an approach I believe in, with qualifications. I do not subscribe wholeheartedly to it because it is possible to provide for grizzly bears and mountain lions and still lose habitat specialists  like the California gnatcatcher. But the umbrella species approach is one of the intelligent strategies for conservation.

ER: Until the 1920s cougars and wolves were shot on sight as varmints in the Northwest.  

PB: Oh, until the 1960s! Absolutely. In every Western state, until the 1960s, you would get between $50 and $100 for every pelt you brought in.

ER: A woman in California was mauled by a cougar recently. Are people being unreasonable in resisting the reintroduction or recovery of large predatory animals?  

PB: There are two separate issues here: livestock depredation and danger to humans. With respect to livestock depredation, the public needs to decide whether we want to have public lands for wildlife, including cougars and grizzly bears, or whether we want them for mutton and beef. It is different on private land. We might need to make compensation to livestock owners if we do introduce grizzly bears or cougars that cause damage to livestock.

ER: Isn't there a program like that in effect around Yellowstone?

PB: Yes. And I think it is a good idea because we all benefit from the wildlife. On publc lands we can tell the rancher he has to eat the losses. But if a rancher is feeding our grizzly bears on his private land we should help pay for it.
     The human safety issue is a tough question. The only ways to get to zero risk are either to have zero humans or zero predators. Nobody wants either of those solutions. Bumperstickers notwithstanding, nobody wants to kick the U.S. out of North America and no rational person would want mountain lions and grizzly bears out of North American either.

ER: It was not a question thirty years ago.

PB: That is right. Thirty years ago the universal position was "grizzly bears out of North America, cougars out of North America."  We have certainly, I think, seen a big shift in public attitudes, and I think it is probably a permanent shift. We realize predators are part of ecosystems and we want to keep them as a part of ecosystems.
     That means we are going to have to learn to live with a certain level of danger - the same way we value the automobile as a part of our lifestyle to the point where we are willing to live with 50,000 highway deaths a year. So we now are valuing mountain lions as part of our environment and this will also involve a price in terms of risk. We can minimize the risk but it is never going to be zero. Each death is a tragedy, but that is part of learning to live with our new values for predators.

ER: People in Northwest Canada and in Alaska are living with grizzlies. They figure out how to do it. There are certain things you do not do around them.

PB: That is right. British Columbia has more mountain lion deaths than all of the U.S. And they do not have a lawsuit after each one like we do. Not that they are blasé about it. They change their lifestyle to minimize risk but they realize that they cannot prevent all injuries or deaths.

ER: We are talking about restoring a functioning ecosystem and puttin a top predator in it. Are the other components really there? If we try to recover a top predator like a grizzly or a mountain lion, is there space and the prey base - the other parts of the ecosystems - to  support these animals?

PB: For mountain lions certainly. Most suitable habitat in the West has mountain lions. Grizzly bear were present throughout most of the West until eighty years ago and the situation has not changed that much. There is still a prey base to support them.

ER: How long do cougars live in the wild?  About ten years, do you think?

PB: Yes. That is a reasonable estimate.

ER: So they actually have a pretty long duration for their memory of being hunted and shot at?

PB: Yes.

ER: Do cougars lose their fear of humans after living in a reserve for many years?

PB: We do not see that happening anywhere,  partly because very few if any cougars are truly protected within a reserve. Even if you take a large reserve like Yellowstone - most of the mountain lions probably spend much of their time outside the park.

ER: My experience with bears is they do lose their fear of humans.

PB: That is right. Bears have a much smaller home range than mountain lions. They are also carrion eaters which predisposes them to feed on picnic baskets and garbage.  It is well documented that a subset of the bear population habituates to humans.

ER: We don't see cougars breaking into cars.

PB: That is right. Not to say it could not happen - animals change behavior, sometimes unexpectedly.  But we have not seen it yet. After every cougar attack, somebody says that cougars lose their fear of humans. But most of the attacks have occurred in British Columbia and on Vancouver Island where those animals are hunted quite heavily. And in the U.S. most attacks occur in areas where hunting is allowed. There is no evidence that
cougars are becoming habituated to humans - not that it could not happen. Maybe it is happening now.

Copyright 1994 Environmental Review