Great Basin Naturalist Volume 59 Number 2 Article 16 4-30-1999 Full Issue, Vol. 59 No. 2 Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation (1999) "Full Issue, Vol. 59 No. 2," Great Basin Naturalist: Vol. 59 : No. 2 , Article 16. Available at: https://scholarsarchive.byu.edu/gbn/vol59/iss2/16 This Full Issue is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. T H E GREAT baslBASIBASIN naturalistNATURALI ST mot A VOLUME 59 NO 2 APRIL 1999 ML BEAN LIFE SCIENCE MUSEUM BRIGHAM YOUNG university GREAT BASIN naturalist httpwwwlibbyueduhttpwwwlibbyuedunmsamsnms FAX 8013783733801 378 3733 editor assistant editor richardwbaumannrighardRICHARD W BAUMANN NATHAN M SMITH 290 MLBM 190 MLBM PO box 20200 PO box 26879 brigham young university brigham young university provo UT 84602020084602 0200 provo UT 84602687984602 6879 8013785492801 378 5492 8013786688801 378 6688 emailE mail richarclbaumannbyuedurichardriehard baumannbyuedu emailE mail nathan smithbyuedu associate editors JAMES C CALLISON JR JERRY H SCRIVNER department of environmental technology department of biology utah valley state college ricks college orem UT 84058 redburgrexburgRexburg ID 83460110083460 1100 JEFFREY R JOHANSEN STANLEY D SMITH department of biology john carroll university department of biology university heights OH 44118 university of nevada las vegas vegas BORIS C kondratieff las NV 89154400489154 4004 department of entomology colorado state ROBERT C WHITMORE university fort collins CO 80523 division of forestry box 6125 west virginia morgantown PAUL C MARSH university Morgantown WV 26506612526506 6125 center for environmental studies arizona NEIL D WOFFINDEN state university tempe AZ 85287 department of biology of JOSEPH R MENDELSON 111 university pittsburgh ililiiIII johnstown department of biology utah state university PA 15904299015904 2990 logan UT 84322530584322 5305 editorial board richard A heckmann chair zoology john D bell zoology berranjerran T flinders botany and range science duke S rogers zoology bruce A roundy botany and range science richard R tolman zoology larry L st clair botany and range science H duane smith monte L bean life science museum all are at brigham young university ex officio editorial board members include steven L taylor college of biology and agriculture and richard W baumann editor great basin naturalist the great basin naturalist founded in 1939 is published quarterly by brigham young university unpublished manuscripts that further our biological understanding of the great basin and surrounding areas in western north america are accepted for publication subscriptions annual subscriptions to the great basin naturalist for 1999 are 25 for individual sub- scriscribersbers 30 outside the united states and 50 for institutions the price of single issues is 12 allalialtbackbaekback issues are in print and available for sale all matters pertaining to subscriptions back issues or other busi- ness should be directed to the editor great basin naturalist 290 MLBM PO box 20200 brigham young university provo UT 84602020084602 0200 scholarly exchanges libraries or other organizations interested in obtaining the great basin naturalist through a continuing exchange of scholarly publications should contact the exchange librarian 6385 HBLL PO box 26889 brigham young university provo UT 84602688984602 6889 editorial production staff joanne Y abel technical editor emailE mail jyaemailbyuedu copyright 0 1999 by brigham young university ISSN 001736140017 3614 official publication date 30 april 1999 4994 99 700 29403 the great basin naturalist PUBLISHED AT PROVO UTAH BY MLM L BEAN LIFE SCIENCE MUSEUM BRIGHAM YOUNG university ISSN 001736140017 3614 VOLUME 59 30 APRIL 1999 no 2 gleatgreat basin naturalist 592 019991999 appp 105 111 reproductive ECOLOGY OF BISON ON ANTELOPE ISLAND UTAH michael L wolfel milan P shipka2 and john FE Kimball 3 abstractABSTRACI autumn musters ofot bison bison bison on antelope island state park utah conducted annually since 1987 provided data on temporal and age specific reproductive patterns and a basis to evaluate the efficacy of manage- ment measures implemented to elevate reproductive performance in the heidheldherd pregnancy rates were vanablevariable and low xY 46246 2 in comparison to other free ranging noncommercial bison herds in north america cows inm the 3 and gyigylgyr6 yiyr age classes exhibited lower than expected pregnancy rates P 0050.05oos0 05 annual pregnancy rates showed a significant r 0640 64 P 004700.047047 linear decline of 252.52 5 per annum variance in distribution of fetal ages observed in 6 yr indicates sub- stantial temporal fluctuation longtermlong term reproductive performancepeipel firmanceformanceformaneemance of cohorts born prior to implementation of manage- ment measures did not differ from that of cohorts born subsequent to these changes key words bison bison bison nutrition reproduction utah antelope island A population of bison has existed on ante- reproductive anomalies may also exist alterna- lope island utah for over a century this herd tive hypotheses to explain the long calving per- originated from a very small n 12 founder iod are the absence of predation and a low qual population popov and low 1950 and its sub- ity and temporally unpredictable forage resource sequent population growth was punctuated by prior to 1981 antelope island state park reduction to very low levels ie 30 animals AISP encompassed only a small area at the on at least 2 occasions increasing the potential north end of the island in that year the utah of low levels of genetic variability and raising division of parks and recreation udp&r questions concerning possible demographic acquired the remainder of the island includ- effects of the small founder population and sub- ing the bison herd which was thought to sequent bottlenecks preliminary field observa- number 250 280 animals initially the popula- tions of reproductive patterns in the herd by tion was subject to minimal management with wolfe and kimball 1989 revealed an unusually the removal of only 3 male bison reported dur- protracted calving period for this herd other ing the following 6gyryr period department of fisheriesfisberiesandand wildlife utah state university logan UT 84322521084322 5210 department2department otof animal dairy and veterinary science utah stolestate university logan UT 84322481584322 4815 sutah division of wildlife resources 1594 west north temple salt lake city UT 84114 105 106 GREAT BASIN naturalist volume 59 in 1987 the udp&r initiated an active 327c while minimum winter dec feb bison management program featuring annual temperatures were 62c lower elevations musters selective culling inoculation of ani- on the island experience about 200 frost free mals artificial winter feeding of calves and days annually higher elevations about 150 limited hunting of adult males in 1987 graz- ing by approximately 1500 domestic cattle on METHODS the island was also terminated the annual roundups provided an opportunity to collect the udp&r has conducted an annual information on reproductive patterns in the roundup of the antelope island bison herd in population and test hypotheses regarding the the last week of october or first week of impact of these management changes on november since 1987 these gatherings employ reproductive patterns within the population helicoptershelicopters and ground support on horseback specifically we hypothesized that a presum- and in wheeled vehicles to haze the bison into ably improved nutritional plane resulting from large holding paddocks at the north end of the the management program would increase island all animals in the herd are captured in reproductive rates and synchrony of parturi- the roundup or are at least accounted for dur- tion shipka et al 1995 provided a prelimi- ing followupfollow up flights bison typically remain in nary analysis of the data obtained through the holding paddocks for approximately a 1992 this paper includes data collected sub- week prior to being processed through a set of sequently and more comprehensive analysis working chutes during the period 1987 1997 this operation typically commenced on julian STUDY AREA day 309 and lasted 3 4 d upon entering the squeeze chute adult antelope island has been described previ- animals are identified and weighed every ously by wolfe and kimball 1989 briefly it bison in the antelope island herd is perma- is the largest 104 km2 of several islands in nently identified by means of metal ear tags the great salt lake lying approximately 6 kmkni and calves are branded according to their birth from the mainland topographically the island year beginning in 1991 animals were also is characterized by a north south ridge maxi- identified by means of micromicrochipchip implants in mum elevation above lake level 600 in with their ears adult females were examined for steep west facing escarpments and generally pregnancy by rectal palpation in 1987 1988 1994 fetal more gentle east facing slopes 1990 1992 1993 and age was esti- annual grasses constitute the principal veg- mated during pregnancy palpation etation on the island with cheatcheatgrassgrass bromus during the 1987 roundup provisional ages tectoriumtectorumtectorum and threethreeawnawn aristida