Comparative Dynamics of Introduced Tule Elk Populations

Abstract

Growth rates in 2 re-established populations of tule elk (Cervus elaphus nannodes) were followed 6 and 7 years beyond the time of introduction. The elk population at Grizzly Island, California, grew at the maximum potential rate, whereas that at Point Reyes, California, grew at half the theoretical potential. The lower rate of growth at Point Reyes was attributed to an initial pulse of adult mortality, low calving rates, and high subadult mortality. J. WILDL. MANAGE. 51(1):20-27 Studies of introduced ungulate populations immediately following release are limited. The paucity of such information has led to experimental manipulation of populations to duplicate growth from low numbers (McCullough 1979, 1982). We report growth rates for 2 reintroductions of tule elk at Point Reyes and Grizzly Island, California. Both areas supported tule elk, at least seasonally, in pristine times but not since the 1860's (McCullough 1969). Reintroductions of elk began in 1977. Ten adult elk (2 males and 8 females) were transported in March 1978 from San Luis National Wildlife Refuge, Merced County, to a holding pen on a 1,030ha fenced portion of Point Reyes. Nine calves (1978 cohort) were born while the animals were confined within the pen (Ray 1981). Ten adults and 7 surviving calves (4 males and 3 females) were released to the entire range in September 1978. Three adult males from the Owens Valley, Inyo County, were reintroduced in December 1981. They were sighted occasionally in January and February 1982, but subsequently disappeared, and are not considered further. Seven adult elk (4 males and 3 females) were relocated to Grizzly Island from the Tule Elk State Reserve, Tupman, Kern County in February 1977. The animals were restricted to a holding pen until released, on site, in May. A yearling female, originally from Owens Valley, was released at Grizzly Island later that year. In May 1978, an adult female from Owens ValThis content downloaded from 153.90.6.19 on Wed, 25 Jun 2014 13:23:08 PM All use subject to JSTOR Terms and Conditions J. Wildl. Manage. 51(1):1987 INTRODUCED ELK POPULATIONS * Gogan and Barrett 21 ley joined the herd. One of the original 4 adult males was moved to another release site. An adult male was poached in November 1979, and a male seriously injured in the rut was sacrificed in September 1982. In 1978, both populations numbered 17 elk. We thank W. H. Sohrweide for sharing his observations of tule elk at Grizzly Island with us. Thanks are due J. J. Aho, Jr., T. S. Biller, W. J. Pierce, and R. T. Lesko of Point Reyes Natl. Seashore and D. A. Jessup and B. E. Curtis of the Calif. Dep. Fish and Game (CDFG) for assistance and encouragement during this study. We thank D. B. Houston, R. A. Lancia, and D. R. McCullough for reviewing earlier drafts of this manuscript, and L. M. Merkle for typing the final and earlier drafts. Research was funded by the Natl. Park Serv. under Contract CX 800-9-0029 and Calif. Agric. Exp. Stn. Proj. 3501-MS. The senior author was a Rob and Bessie Welder Wildl. Found. Fellow and this manuscript is Welder Wildl. Found. Contrib. 209.