The quoted number of black bears, like nearly all the estimated animal numbers except possibly the number of bighorn sheep, is quite uncertain since no regular census is conducted counting these animals. Since 1983, the California Department of Fish and Game has estimated a population of 400-500 bears. When asked by the press, the spokesman for the DFG, Patrick Moore, has given the lower number in "low production" years, and the higher number in "high production" years. Thus, for example, the number given in PSN on 5/27/99 was "about 500" black bears.
A "recent survey" of ANF personnel yielded estimates of 150-200 up to 400-500 bears "depending upon the biologist contacted".
Source: email from Patrick Moore, 8/23/99.
In addition, the number of black bears changes as a function of time.
- Prior to 1933, most authorities agree that there were no black bears in the ANF! "Eleven black bears were introduced into the San Gabriel Mountains 'near Crystal Lake' in November 1933 from the Sierra Nevada (Burghduff, 1935)." in Mammals of the San Gabriels by Terry A. Vaughn. (However, Seims references evidence for black bears in the ANF prior to this time in his book Mt. Lowe: Railway in the Clouds. But everyone agrees that there were grizzly bears here before they were exterminated by humans by ~1900.)
- Dr. Glenn Stewart of Cal Poly, Pomona, and his students conducted several black bear surveys in the late 1970s, yielding an estimated 150-200 bears in the ANF and 300-350 in the San Bernardinos.
- Dr. Stewart estimates that the population has increased at a 5 percent rate since the late 1970s, which gives a very rough estimate of 400-450 adult bears at present in the ANF and 600-700 bears in the San Bernardinos.
Source for Dr. Stewart's estimates: Patrick Moore email, 9/6/99.
The population estimates from various editions of TOTA are:
At a class taught in 1988, Pat Sullivan, director of the Eaton Canyon Nature Center, who is also a fish and game warden, gave the number as 40-50, which may have come from the same source used by Robinson.
- 1971, 1976 and 1979: "Rarely seen in the San Gabriels is the black bear; naturalists estimate that fifty are left, and the number is decreasing."
- 1984: "Rarely seen in the San Gabriels is the black bear; naturalists estimate that 40 are left, and the number is decreasing."
- 1990 and 1998: "Rarely seen in the San Gabriels is the black bear; naturalists estimate that 150 are left, and the number is decreasing."
Despite Robinson's comments about "the number is decreasing", even in the face of an increase in his reported numbers with time, there seems little doubt that the numbers are in fact larger in 1998 than they have ever been, as reflected in the current estimates by ANF biologists.
A "recent study" found that 50 bears have a home range that includes Mt. Wilson, which is only a small portion of the SGM. (LAT 12/10/01, B10R, which didn't give the reference for the study)
For comparison, the same Yosemite bear stock introduced into the San Bernardino Mountains at the same time has expanded from 16 bears in 1933 to 300-350 bears in the late 1970s to "over 300" in 1989. (The Natural History of California)
Other supporting evidence for an increase in the black bear population is the increased frequency of bears seen in the urban areas near the SGM:
The incidents came from a search of the the L.A. Times archive covering back to 1990. The dates are the date of article, usually a day or two after the actual incident.
- 12 May 1999: Azusa Pacific University
- 1 September 1997: Canyon Country
- 18 June 1995: La Canada Flintridge
- 19 August 1994: Arcadia
- 21 May 1994: Azusa
- 15 September 1993: Quartz Hill, Antelope Valley
The number of black bears in the San Gabriels probably leveled off by ~1991, as shown from the number of bears killed by hunters in L.A. County. Hunters killed 51 bears in L.A. County in 1991-1995, and 46 bears in 1996-2000. These numbers are highly consistent with an average of 9.7 bears killed per year, reflecting an approximately constant population. Since bears produce an average of ~0.5 offspring per bear per year, a population needs to measure in the hundreds in order to be stable against that loss and other mortality sources. Other mortality sources include cars and being killed by authorities after being labeled a problem bear for interactions with people. Jim Davis, a wildlife biologist with the California DFG says:I think it's fair to say we are probably losing more bears to road kill than to what hunters are taking.
The overall number of bears killed by hunters per year in Southern California has grown significantly in Ventura, Riverside and Santa Barbara counties:
County 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 Los Angeles 3 5 11 16 7 12 9 5 6 13 13 San Bernardino 16 23 22 19 21 24 19 18 17 17 14 Ventura 9 10 8 8 5 13 29 22 24 20 27 Riverside 2 0 2 0 2 2 3 6 2 2 4 Santa Barbara 2 4 4 8 6 8 19 23 20 18 14
Numbers are from the California Department of Fish and Game, reported in the LAT 12/10/01, p. B10R. Hunting beings in late summer, and ends when a quota of 1500 bears in the entire state is reached, typically in late fall.
Other estimates of the black bear population are:
- ~70-200, using an estimate of 5-15 sq. miles for the average habitat needs of a bear;
- ~250, derived from the estimate of ~700 in Yellowstone National Park, which is 3 times bigger in area, and assuming that the population scales with area. Since there are also about 250 Grizzly Bears in Yellowstone, the scaled ANF number would be ~300 from the total bear population in Yellowstone; and
- 500-700, derived from the estimate of 500-700 black bears in the Great Smoky Mountain National Park, which is comparable in size to the San Gabriel Mountains.
One has to be cautious in scaling the numbers from other areas, for a variety of reasons, including different densities of food supplies leading to different requirements on the average size of habitat needed, different number and types of animals also sharing the same food sources, different degrees of human influence (providing food sources, removing "problem bears", etc.) and so on. However, in the absence of highly reliable data, such estimates provide a sanity check on quoted numbers.
Hence we have chosen to simply quote the entire range of recent estimates, 150-500, made for the SGM. A number in that range seems reasonable compared to the other estimates.
For intellectual curiosity, to get more accurate numbers, there are at least two methodologies:
See Grizzly Bear And Black Bear Ecology . Both methods require some effort and considerable expense, so more than intellectual curiosity needs to be at stake to devote the resources to a count.
- Traditional studies entail intensive trapping with baiting, drugging, collaring, ear tagging, and frequent aerial radio tracking, which is clearly a very invasive way to conduct a count.
- DNA identification of "bear sign" could be used to give a reasonably accurate number.
For the sources quoted here, and estimates of other animal populations in the SGM, consult SGM: The Numbers.
Copyright © 1999-2001 by Tom Chester and Jane Strong.
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Updated 17 January 2001.