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... ".-:1" # '2.S4 '-',:C,. fi:::t:\:;,:-..."- :.:, ' "-.,.: 1' '.:10. DA'S SHEEP yman Nihls, Jr. Wildlife ilgist Alaska l)epartment ffish and ame Cper anding, Alaska k: D ;i; :..,:;,};,'-:.'.-'S :",'1:'''. 2'1;' :,J:'.;..., ':- 71i : -ii "I \. :I;iI..': lj,.. E \.1 i " '',Ah}.', "', ",,-... '....\ ' :,,, E,, Y". \5;i..;;"' - ' _",,,'-:f!0 '": The thinhrn grup f Nrth Amerian 'sheep inludes bth 'the Dall's and Stne's sheep, fund in Alaska and nrthwestern Canada. th are wilderness animals residing fr the mst part in spetaular alpine,and subalpine muntain habitat. They are 'nsidered amng the best f Nrth Ameria's trphy speies; their hrns and meat are highly prized by hunters. eause.tht!se sheep are highly visible in their white ats against the treeless green ftheir sum ;Iller alpine envirnment, Dall's sheep in Partiular are favred subjets f amateur and prfessinal phtgraphers alike. In $rne partiularly aessible areas, Dall's eep are valued abve all else fr viewing d phtgraphy. There is sme debate amng taxnmists ether Amerian thinhrn sheep atually separate speies r, in fat, are speies f Siberian snw sheep, whih very similar in size and appearane t ne's sheep CCherniavski 1962, Cwan 0, Raush 1961). Arguments tend t r the Amerian thinhrn sheep as a disnet speies, Ovis dazzi.,at present, tw subspeies f Amerian,. 'Mrn sheep are regnized. One is the "true" Dall's sheep ro.d. mnly referred t as the sheep. It is fund in Alask Nrthwest Territries, a nrthwestern part f ritis ther is Stne's sheep nrthern ritish Clumbia part fthe Yukn Territry were named after persns A.J. Stne, respetively. C mmn names shuld be used in pssessive frms frequently used but inr sheep" and "Stne sheep." sin, further referene in Dall's sheep will indiate that name and differentia sheep. Readers shuld kee ever, that bth Dall's sh sheep subspeies are f speies. Tw ther subspeies regnized, the white s naiensis) f the Kenai P (uehner 1960a), and the bak Fannin's sheep ro.d between the main range Stne's sheep. The frmer idential t ther Dall's she is regnized as n mre th tin between the white Stne's sheep.
ig ame fnrth Ameria D u DESCRIPTION The pelage f Dall's sheep nsists f pithy, rinkled guard hairs with an underat f fine wl. It may be mre than 5.1 entimeters (2 inhes) thik in winter. The at is typially all-white in lr, althugh a few blak hairs n the tail are nt unmmn. Sme newbrn lambs have a nsiderable amunt f brwn in their ats with a dark middrsal line and dark hairs n the brisket, tail surfae and elsewhere. These nenatal ats are lst r vergrwn shrtly after birth. All lambs appear white within a week r tw. Dall's sheep ften appear yellwish r grayish due t staining ftheir white ats. Stne's sheep are typially dark brwn r blak with lighter-lred heads and white muzzles. They have white rump pathes, bellies and rear prtins f the legs. Hwever, they may vary greatly in lr, frm nearly white t blak. In bth the Mentasta Muntains and the muntains nrtheast f Eagle in eastern Alaska, asinal sheep are fund with gray r brwn markings. Suh lr variatins are mre mmn in the nrthwestern part fcanada between the ranges f the true Dall's and Stne's sheep. These are Stne's sheep, frmerly alled Fannin's sheep. The amber-brwn hrns f bth Dall's and Stne's sheep are lighter in nstutin than thse f the bighrn sheep. th sexes have hrns whih ntinue t grw thrughut the animals' lives (Figure 36). Hrns frams are massive at the bases and taper t relatively fine tips. They grw in a spiral frm as,;..t:i.....'''..,...",;; '.'..I.:,...,. './--," ',-;r ;.;..:. E 174 «:..!::.?...",,i'-...'-... '- j....') ;.: -Y._. 'J-,.1'-,\ \;:i...a.:,..;;"..., _ "".,F C.,,'>!'f! "'Sl...-4.. '....!. """... "--"""-,_I ''i.:. _, ;0:... 'Ja,.'.,..,_'. _ '.',,,,-..'.-." "t.j'"...1'".',......,. r.. { -:'. "..'...,..., "-"l'-";". ''''. M-' _,J"'. ". :..,:1'-"'" v..k _.J - _ '..,.',.. :tr:>"?;' Yung Dall's sheep ram (left) and mature ewe in winter pelage. Nte blak hairs in ram's tail and till, ness fat. Pht urtesy fthe Alaska Department ffish and ame.
Dall's Sheep the IT II. eir- in n> 9d " '- Mature Stne's sheep ram in late summerpelage. Pht by enard ee Rue III. 100 80 :0", ffi60 ii :::.. 20!.r' Jl-...-----... --*--*- 30,.--r... H,...<;, ", '0,rj. '",, " ''' fw' _ 0 0 2 4 6 8 10 12 AE IN YEARS '" w :t: 20 d' '" rl.,rur 36. Dall's sheep hrn grwth by age and. "t'x. Data urtesy f W. E. Heimer, Alaska Dep;lrtmnt ffish and ame.,,'". '-.,;0..-.: - viewed frm the side. Outside diameters f the urls f adult Dall's rams' hrns average abut 27 entimeters (10.5 inhes), and basal irumferenes average abut 36 entimeters (14 inhes). Exeptinally large hrns may have bases mre than 36 entimeters (14 inhes) in irumferene. The average length fa full-url ram's hrns in Alaska is abut 90.1 entimeters (35.5 inhes); the largest rerded hrns frm a Dall's ram measured 123.5 entimeters (48.6 inhes) in length. Mst Alaskan rams have hrns f three-quarter url by age six and reah full-url by abut eight t nine years f age. Mst rams attain abut 90 perent f their ptential hrn grwth (by vlume) by the time their hrns are full url. There is nsiderable variatin in hrn size amng Alaskan Dall's' sheep ppulatins. This is believed t be related t "ppulatin quality" whih, in turn, prbably is dependent upn ppulatin density (Heimer and Smith 1975)..-.. C 175
ig ame fnrth Ameria :. J b C t Mature Dail's sheep ram in summerpelage. Pht by en Rue, Jr. Similar data n hrn url and age are nt available fr Stne's sheep, but in a sample f six hrns frm eight-year ld rams, the average length was 90.5 entimeters (35.6 inhes) (eist 1971a). Measurements f the 50 tp-sring hrns (using nly right hrn measurements) fr bth subspeies as listed in the ne and Crkett Club's rerd bk shw an average length f 111.3 entimeters (43.8 inhes) fr Dall's sheep,and 111.5 entimeters (43.9 inhes) fr Stne's sheep (Nesbitt and Parker 1977). asal irumferenes.s:,'eraged 36.3 entimeters (14.3 inhes) and 37.1 entimeters (14.6 inhes), respetively, suggesting almst idential hrn grwth. The largest rerded set f hrns taken frm a Stne's ram measured 131.6 entimeters (51.8 inhes) in length. Ewes' hrns are muh shrter, slimmer and less urved than rams'. In rss setin, 176 female hrns frm a rather narrw val, whereas ram hrns are rughly triangular. A sample f 52 hrns frm female DaIsheep mre than six years ld averaged 2 l,;-, entimeters (9.7 inhes) lng (Heimer 197, Nihls 1971). Stne's sheep ewes prbably have hrns fabut the same length. Thinhrn sheep, like mst nrthern ungulates, are heaviest and fattest in late fall and are lightest in spring after rigrs f winter have taken their tll. A sample f 13 Dall'" ewes weighed in the fall averaged abu! 56 kilgrams (124 punds) (Nihls, l"l\ published), but exeptinally large nes m:i. reah 63.6 kilgrams (140 punds) r mu!", y later winter and early spring, avera:.:' weight in a sample f 45 ewes drpih',: t abut 48 kilgrams (105 punds), a 10,. f 18 perent f average fall bdy weil-!h! (Nihls 1971). Data n fall weights f Dalirams are santy, but estimates plae th,
6 8 average weight f adult rams frm 82-100 kilgrams (180-220 punds) with sme very large rams pssibly exeeding 114 kilgrams (250 punds). A spring sample f nine adult Dall's rams in Alaska shwed an average weight f 69.6 kilgrams (153 punds) (Heimer 1972). Average weight f adult Stne's rams is estimated t be smewhat heavier in the fall, frm 100-104 kilgrams (220-230 punds). Exeptinal individuals pssibly exeed 114 kilgrams (250 punds). Whether r nt a real weightsize differene exists amng the subspeies has nt yet been demnstrated. Mean height at the shulder fr nine Dall's rams mre than six years ld was 93.3 entimeters (36.8 inhes),.,and 84.4 entimeters (33.2 inhes) fr 62 ewes lder than six years. IFE HISTORY The life yle f thinhrn sheep begins with the rut, w}lih takes plae in early winter, generally extending frm mid-nvember t early Deember. Fr tw suessive years in Alaska's Kenai Muntains, the peak f rutting ativity in ne herd was fund t be Nvember 30 (Nihls, In press). ambing urs during late May and early June, fllwing a gestatin perid f abut 171 days. Chrnlgy f lambing appears t vary smewhat frm year t year and amng herds in Alaska. Whether it is a funtin f variatin in the rutting seasn is nt yet knwn. It may be merely an anmaly f data resulting frm variable mrtality at birth whih, in turn, affets the numbers f living newbrn lambs bserved. Single births are the rule fr bth subspeies, althugh twinning urs infrequently. ambs weigh abut 3.2-4.1 kilgrams (7 9 punds) at birth and grw rapidly during their first summer, reahing an average weight f abut 30.4 kilgrams (67 punds) by fall. Weaning usually takes plae by Otber even thugh mst lambs appear apable f fending fr themselves by tw t three mnths f age. ambs remain with Dall's Sheep their mthers during their first winter, and nursing asinally may be bserved during winter and even the fllwing summer. There is sme evidene n pr ranges in Alaska that many Dall's ewes nurse their lambs thrughut the winter and nly bear ne lamb every ther year (Heimer 1976). If these behavirs are general rules, they may funtin as adaptatins t redue the birth rate and inrease survival f lambs brn n depleted ranges. The sex rati at birth is prbably abut equal, althugh the few data available suggest a prepnderane f males (eist 1971a, Nihls, In press). Yearlings f bth sexes may be sexually mature by 18 mnths fage, althugh sme d nt mature until the fllwing fall. Maturity in dmesti sheep is related t physial nditin and weight rather than age alne, and this may apply t wild sheep as well. If s, well-fed, larger individuals tend t mature faster than smaller, less adequately nurished sheep. Male yearlings, even thugh physilgially apable f partiipating in reprdutive ativities, seldm d. Dminane rder amng males prevents mst rams frm breeding until they are abut seven years fage (eist 1971a). Ewes and rams prbably are apable freprduing thrughut their life-spans. In several seasns f bserving Dall's sheep during the rut, I saw n ld rams whih were nt ative partiipants. I lleted tw pregnant Dall's ewes whih, frm hrn annuli, were estimated t be mre than 13 years ld. I als fund ne l5-year ld ewe that died after giving birth. Anther ewe, 16 years ld when aptured and marked, was ampanied by a lamb. She was bserved fr three mre years, but withut lambs. During a study f a Dall's sheep herd in Alaska believed t h.ve reahed r exeeded the arrying apaity f its range, all 18 adult ewes taken were fund t be pregnant. Three f fur yearling (18-mnths ld) ewes lleted als were pregnant (Nihls, In press). Thus, even under nditins f envirnmental stress, Dall's sheep an have a pregnany rate f as high as 100 perent in adult ewes and, in this ase, 75 perent in 177
ig ame fnrth Ameria 8 u 'bj i yearling females. The effetive natality rate-the number f lambs that survive lng enugh t be bserved-nrmally is muh lwer than this, hwever. A rati f nly 20 lambs t 100 ewes was bserved in the abve herd the fllwing spring, refleting an apprximate 80 perent lss frm ptential reprdutive gains. Average prdutivity f Dall's sheep in Alaska was abut 37 lambs per 100 ewes ver a number f years and within a number f herds (sample = 57; standard errr f mean = 2.10). Hwever, great variability amng herds and years was nted-the range was 8-81 lambs per 100 ewes. ife-span f a wild sheep is believed t be limited primarily by teeth nditin and rrespnding feeding abilly. The ldest Dall's ram skull fund in a large series fnaturally urring mrtalities in an verrwded ppulatin was 12 years ld at death (Murie 1944). Ewes tend t live lnger than' rams. In additin t the afrementined Dall's ewe that was aptured and marked at age 16 and lived at least three mre years, eist (l971a) reprted a Stne's ewe that reahed 16 years fage. MORTAUTY AND UMITIN FACTORS Nutritin A number ffatrs an affet the prdutivity f thinhm sheep whih, in tum, is a majr determinant f herd status. In a herd with adequate winter frage, pregnant ewes reeive suffiient nutritin t maintain their wn physial nditin and allw grwth f fetuses t ptimum size. Healthy, wellnurished ewes give birth t well-develped lambs and are able t prvide them with ample milk, thereby assuring maximum prdutin and early survival f yung. Furthermre, these yung grw quikly during their first summer and have a better hane f surviving their first winter. Under these nditins, expeted mrtality f 178 adults wuld be lw and herd inrease prbably wuld ur. On the ther hand, in a herd that has reahed r exeeded its winter range's arrying apaity and thus faes a shrtage f winter feed beause f rwding and mpetitin, pregnant females are unable t btain suffiient nurishment t maintain their wn physial nditins r enable ptimum grwth f fetuses. As a result, the pregnant ewe may experiene fetal mrtality thrugh resrptin r abrtin t enhane her wn hane fsurvival. Nenatal mrtality, beause f weakness and nsequent hypthermia, and/r abandnment, als inreases-smetimes drastially. Furthermre, surviving lambs may be small and grw slwly beause f dams' inadequate milk supplies. They are prly,prepared t fae their first winter, during whih they may suumb in,large numbers. Density-dependent natality fatrs appear t be the mst imprtant limiting fatrs affeting thinhrn sheep. These sheep usually ur at near-maximum densities in relatively stable, limax habitats whih are subjet t harsh winters. The availability ffd in these habitats may be limited severely by deep snw ver. One a sheep herd reahes a ertain density n its winter range, natural ntrls limit reprdutin and survival, and its ppulatin bemes stable r begins t deline. During nrmal winters and when snw remains sft, sheep are able t dig feeding raters dwn t gd quality frage that is still green. Strng winds, prevalent in alpine winter ranges f thinhtn sheep. remve muh f the snw frm pen ridges and slpes, expsing frage. y late winter. hwever, snw may be wind paked and impenetrable. Sheep then are fred t depend n limited amunts fpr quality feed n the few, windsured ridges that remali1 snw free. At this time, sheep are in :I ptentially negative energy-balane situ,, tin; they may use mre energy than thl'' an take in feeding. Frm this time until spring, they depend heavily n stred bd.\ fat fr nutritinal needs. dy fat reserve
Dall's Sheep 6 (J A C 8 :. u E ' :', ",f. '. rj / '/;4-1:".. /J'::!;:;)tI!'..'.., -.;:,,4 'C'.Ii '::t'.; -;; /_. J 'tj.:.:. "-'r,( ;:','..i.f:.",._,' ' ---"',;.;,-.,:"",.,';"" - _' '*.-..' - '..,. -.'" t } /..: I.,t'-, l ".,'.., 't r--' -;::.....,.. t '\, 1.. J {. -,;,. ;.( "<.,.",.1,1) I t' h _,),I.,.r. r..".. ;-...,. J...--l./.i... l '.:;f'?",'ilr/ ifr ' w"'1a1':';,( -{:.v :... :.{..."":.: r-' i-- :;i;-. :.:t: #;/("'( "I.,) r',t "" r... ': -.l. -tj,j- I...... 1' ' \...,..{. -,/.....".:'., "'..,,"", 'i..'...4, '..10'-', Three Dall's sheep ewes feeding in pawed-ut snw raters in early winter, Pht urtesy f the Alaska Department ffish and ame. deline rapidly; the last t be atablized are thse stred in the bne marrw. th lambs and yearlings, with limitedfat reserves, suffer mre than adults d (Figure 37), Mrtality amng lambs surviving the initial rigrs f birth nrmally is very lw the r:rst summer but high during the first winter, reahing abut 40-50 perent r mre iii stable r delining herds. The winter f their send year is anther ritial perid in the lives fnrthern sheep, Muh f a yearling's summer nutrient intake supprts grwth rather than being stred as fat, and nutritin is nt supprted by mther's milk. Therefre, yearlings are "... A.../:!.. ;..- ity '1};,:... \ I. ", :. /;,,,'.I C',,. _. - -".'.. :. '!':"A1',,:.::',;''.r. /1.,.:.....-' mre vulnerable t nutritinal sarity in winter than are adults, Few data are available n mrtality rates f sheep in their send winters, but thse rates appear t apprah 15-20 perent. After sheep are tw years ld, mrtality rates derease, presumably beause their physilgial grwth rates deline and mre nutritin is available fr the prdutin f fat reserves needed during winter. eist (1971a) fund that bighrn sheep mrtality averaged abut 4 perent per year frm ages tw t seven, then inreased t 23 perent per year thereafter. Murie's (1944) data indiated a similar pattern fr Dall's sheep. 179
lj ig ame fnrth Ameria 6 b q,' 3 u 140 100... :I: el al..j60 20 100... 80 < 0 a:: a:: < :::E... z w (,J a:: w 40 '" Adult i 9 / I,,,, i,,,, I 8 9 10 11 12 1 2 3 4 5 6 MONTH 20 I,, i' i'" I 8 9 10 11 12 1 2 3 4 5 6 MONTH Figure 37. Changes in Dall's sheep weights and perentage fat in bne marrw by mnth and age lasses. east squares urves fitted t data frm a series f sheep lleted in the Kenai Muntains, Alaska (after Nihls, Unpublished). Winter weather At present, the main influene n thinhrn sheep numbers appears t be winter weather. Exeptinally severe winters may ause drasti "rashes" in sheep numbers regardless f ppulatin densities r range nditins. Suessiva severe winters urred in Munt MKinley Natinal Park, Alaska, between the late 1920s and the mid-1940s and prbably elsewhere in the state. Unusually deep and rusted snw resulted in high mrtality, and herds drpped t a fratin f their frmer abundane. Other, mre lalized delines have sine been dumented fllwing 60 40 20 el '" severe winters. These were nt winters f exeptinal ld, but f abve-nrmal temperatures and mre-than-usual preipitatin. During nrmal winters, snw remains light and fluffy and is blwn free f alpine feeding areas. Wet snws, r thaws and subsequent refreezing, fix snw in plae with a hard rust, preventing remval by wind r digging by sheep. Snw depth and hardness, maximum winter winds and temperatures the previus winter are rrelated inversely t lambing suess (Murphy 1974, Nihls 1976). The inferenes are that lambing suess is depressed by deep and hard snw, abvefreezing temperatures lead t rusting, and high winds alng with thawing temperatures pak snw t rk hardness. Dall's sheep are adapted t ntinuing ld, high winds and nrmally light snwfall f winters in nrthern interir muntain ranges. Disease andparasites Disease, suh as atinmysis, and parasites inluding lungwrms and gastrintestinal nematdes are present in nrthern sheep, but have nt been shwn t be main auses fany herd delines. Neilsen and Neiland (1974) suspeted, hwever, that gastrintestinal nematdes in partiular may ntribute signifiantly t spring mrtality beause f the inidental "spring rise" in internal parasite lads and weakened nditin f sheep at that time. It is prbable that parasite infestatins and disease exert mre influene n sheep survival during times f maximum ppulatin density and envirnmental stress than during ther times. Predatin Thinhrn sheep are apable muntaineers, able t negtiate rugged terrain with speed and grae. They depend n this terrain fr prtetin frm predatrs. Ex- 180
6 ellent eyesight and a well-develped sense f smell enable them t detet ptential threats befre mst predatrs beme dangers. The hearing f sheep appears t be very aute, but this sense may be heeded smewhat.less than thers beause sheep envirnments ften are disturbed by suh natural sunds as falling rks. Althugh ytes, wlverines, lynx, blak bears, grizzly bears and glden eagles asinally take adults and lambs, the nly serius predatr f thinhrn sheep is the wlf. Althugh wlves have been bserved apturing sheep bth in summer and winter, they d nt appear t exert any majr influene n sheep numbers exept in times f ppulatin verabundane,when sheep may be weakened r fred by mpetitin and fd sarity t feed.far frm esape terrain. Frm 1947-1961, when wlves were prteted and presumably abundant, the MKinley Natinal Park sheep herd inreased at an average annual rate f apprximately 11 perent (Murphy 1974). Average annual inrease rates f 11-14 perent were bserved in three Kenai Peninsula herds where n wlves were present (Figure 38). l r 200 I I 1,00 FinED POPUATION ROWTH CURVES, / THREE DA'S SHEEP HERDS / / Figure 38. Inrease patterns f three Dall's sheep herds in the Kenai Muntains, Alaska, tw f whih (Surprise Muntain and Cresent Mun in) were heavily hunted fr rams, while the third (SlaughterMuntain) was lsed t hunting (after Nihls 1976). I.,II //,/. CRESCENT MT.,/ /...,/ " "SAUHTER MT..," 7 '/ /',,," /.,',,,/'.,,;, /./ -,,0 1949 1953 /' "'--SURPRISE MT. 1958 1963 I 1968 1973 Aidents EHAVIOR Dal!'s Sheep Aidental falls take a small number f sheep, as d avalanhes and ther aidents. Nevertheless, it is winter weather whihby restriting bth fd supplies and mvements-exerts the nly knwn mrtality f signifiane t thinhrn sheep ppulatins at the presenttime. In general, sheep are diurnal, althugh sme mvement may ur at night. Summer daylight in the Nrth is lng, s sheep may be fund mving r feeding at almst any time. Majr feeding perids generally ur during early mrning and late afternn with asinal shrter perids f grazing ativity abut mid-day. Muh f the time between feeding is spent resting and ruminating. Preferred resting sites, partiularly at night, are n r very lse t liffs r large rk utrps whih serve as esape ver. Daily mvements generally nsist f mving ut f rugged t"!rrain t preferred feeding areas in the mrning, then drifting bak befre dark. During the shrt winter days, mrning and evening feeding perids are interrupted by a brief midday rest. Mst ruminatin prbably urs at night when feeding and mvement are relatively diffiult. During summer, thinhrn sheep may mve nsiderable distanes frm winter hme ranges t upy nearly all suitable alpine habitat in an area. y late summer, they begin t drift bak t wintering ranges, where they ngregate befre the rut begins. Winter range usually is a small part f the verall range and is limited by snw nditins t thse areas where snw-free feeding sites and esape terrain lie in lse prximity. In early spring, sheep usually mve lwer n slpes, ften int the upper limits f subalpine timber. They seek the first emergent green vegetatin when snw lines begin t reede. Sheep mve upward with the reeding snw line until they are free t leave their winter-spring ranges. 181
ig ame fnrth Ameria U fl.. ; fl IS Mid-day rests between mrning and evening feedings are mmn during shrt winter days. Pht by William E. Ruth. Where summer and winter ranges are ntiguus, annual mvements an be haraterized as dispersal ver all suitable habitat during summer, and withdrawal t smaller areas that prvide neessary winter habitat. Atual migratins may ur alng traditinal rutes in spring and fall where summer and winter hme ranges are separated by unsuitable habitat suh as frests r wide river valleys. Visits t mineral liks are an imprtant part f winter-t-summer range mvements f Dall's sheep. Sheep, espeially ewes with lambs, may linger in the viinity f liks fr days, M'eeks r even muh f the summer. Heimer (1974) and eist (1971a) reprted high inidene f individual adults returning t their previusly upied seasnal ranges year after year. Sheep siety enters abut tw basi grupings: maternal ewe, lamb and yearling grups whih ften merge int larger herds; and ram grups. As parturitin apprahes, 182 pregnant ewes leave their past year's lambs and seek islatin in the mst rugged terrain available, where births take plae. They remain there fr several days fllwing parturitin (Pitzman 1970). They then mve away frm lambing liffs; whih usually are merely part f the spring range, and jin ther ewes with new lambs. Meanwhile, abandned yearlings frequently frm small grups whih fllw ne r mre barren ewes. Frequently male yearlings begin t fllw lder rams. Nursery grups, nsisting f ewes with new lambs and asinal yearling females, persist fr a few weeks after parturitin, then gradually merge with grups f barren females and yearlings t frm lse herd assiatins that upy summer ranges. The basi unit f these grupings is a latating ewe, her lamb and frequently her yearling female. Hwever, sme male yearlings remain with ewe-lamb mbinatins.
....Ġ t Dalt's sheep ewe seeks slitude and rugged terrain just prir t parturitin in the spring. Pht urtesy f the Alaska Department f Fish and ame. Mter the rut, during whih all ages and sexes are intermixed, lder rams usually seek the mpany fther rams even thugh they may remain n the same winter range as the ewe grups. As sn as snw nditins permit in the spring, grups f rams whih have begun ngregating n spring range mve tward summer range, frequently assembling in large grups en rute. During these mvements, smaller rams fllw the largest ram in the grup. At this time, many yearling rams and mst twyear-ld rams leave the assiatin f ewes and fllw lder rams. Rams' summer range may verlap that f ewes' r may be gegraphially separate. Mst rams remain separate frm ewes even when upying the same areas. Sial behavir, like that f ther members f the genus Ovis, is well-de \'elped inthinhrn sheep. Ram behavir revlves abut the establishment and maintenane f a dminane hierarhy based n the size f hrns. Interatins amng rams, inluding hrn displays and the well-knwn lashing, may beme quite Dall's Sheep mpliated and ur thrughut the year exept during stress nditins f late winter. Sheep interatins are well-dumented by eist (1971a). Rams determine and maintain sial rders with limited nfusin and damage t individuals thrugh visual regnitin f eah ther's hrn size-dminane status. arge-hrned rams are sially dminant, treating all smaller individuals as "females," while small-hrned rams are aggressive tward dminant rams. Ewes are largely ignred by rams sine they reat passively exept during estrus perids. When in estrus, ewes behave smewhat like small males and enurage sial and sexual behavirs by adult males. During the rut, the established dminane pattern between rams may be disrupted temprarily when a ewe mes int estrus, with all nearby lasses fmature rams jstling and lashing fr pssessin f the ewe. Pssessin is established quikly by the largest ram, wh then remains with the ewe thrugh her apprximately ne-day estrus, defending her against ther rams and breeding her repeatedly. Rams neither maintain territries nr gather harems. Instead, they seek ut ne ewe at a time and eventually leave her at the end f her ne-day estrus fr anther. They travel widely amng ewe grups just befre and during the rut seeking reeptive females. Althugh sexually mature at 1.5 2.5 years f age, rams generally d nt beme behavirally mature and partiipate seriusly in reprdutin until the age f 7 (eist 1971a). Where mature rams are remved frm a herd thrugh hunting, yunger males beme sexually ative. In at least ne Alaskan herd f Dall's sheep, all rams with hrns f three-quarters url (abut six t seven years f age) and lder were remved by hunting fr a number f years (Nihls 1976). The remaining yung rams in the fur-t-six year age lasses arried ut all rutting ativity, behavir in whih they wuld nt nrmally be allwed t partiipate. The rates f inrease in this herd and anther nearby herd subjet t 183
C- igame fnrth Ameria ' D J 6 Clashing r hrn displays amng rams may ur at slightest prvatin during muh fthe year as well as during the rut. Ram n right prvked this shrt-lived lash t take ver a hllwed ut resting site. Pht by William E. Ruth. D similar hunting pressure and age struture were nearly the same as that f a third herd whih was nt hunted. The results infer little shrt-term effet n the rate f reprdutin by the remval flarge rams. Serius frmal lashes generally ur nly amng rams f nearly equal hrn size and wh are unable t identify eah ther's dminane status. Clashing and ther breeding and sial interatins appear t be less intense amng Stne's rams than amng bighrn rams, and even less intense amng Dall's rams than amng Stne's rams. This irumstane may be an adaptatin t nserve energy resures f speies faing lng and severe winters in nrthern latitudes. Ewe sial behavir is muh less apparent than that f rams. Exept during the estrus perid, it nsists f little mre than maternal treatment flambs and asinal ag- 184 gressive behavir twards thers fr spae r fd, as well as banding tgether lsely fr. mpaninship. ambs interat frequently in play, running and jumping, and in the learning press, they exhibit many fthe behavirisms fadults. On asin, adults will run and leap in play fr shrt perids. HAITAT Dall's sheep habitat is typially alpine: steep, pel:' grasslands interspersed with brken liffs and talus slpes n reently glaiated muntains. It usually lies almst entirely abve timberline whih, in Alaska. is variable in elevatin but averages abut 765 meters (2,500 feet) abve sea level. Winter snwfall is mparatively light, averaging 31.9 entimeters (12.5 inhes) ver a five-year perid n three Kenai Muntains
1] '1 k:l... 1..:i-t,.:19 0-.. '!. 1'... "". :. l...j:l... i- *... a.... :'.. j'f'1.:.....: l";;:\' Il< well 7g sitl', pa(. sely A.fr!'. 6nng. xhibit r.,a. fr llpine n. Vith tjnth IIm:'1 ( '3-;ka, lou t <!ivl. It. 'lvfjt'r;, Uun,.. sheep ranges (Nihls 1976). Temperatures nrmally remain belw freezing during the winter, and high winds sweep many ridges and slpes free fsnw. Vegetatin nsists largely f sedges, bunhgrasses, lw shrubs suh as blueberry, rwberry, dwarf willw, muntain avens, and msses and lihens. The lwer prtins f sheep habitat may have large stands f dwarfbirh interspersed with larger willws and dense alder and alpine hemlk thikets. In sme plaes where brken liffs extend suitable habitat belw timberlines, sheep utilize benhes supprting stands f. twisted ttnwd, aspen and asinal white sprue. Stne's sheep habitat is smewhat mre subalpine in nature, and in muntains less reently glaiated and with higher preipitatin than Dall's sheep habitat. There are fewer pen alpine grasslands, and muh f the higher slpes are vered with thikets fdwarfbirh and alpine fir. Aspen, Engelmann sprue and ldgeple pine are mmn. th subspecies are primarily grazing animals, althugh many frbs and brwse plants are eaten as well. A study f three.herds f Dall's sheep in Alaska fund that sedges and bunhgrasses made up the bulk f their diet, fllwed by lesser amunts f brwse (mainly dwarf willw), mss and lihens (Figure 39). During summer, frage f gd nutritinal quality and great diversity is available. Sheep eat a greater variety f plants in summer than in winter when the variety, quantity and quality f available frage are redued greatly. As indiated by amunts f rude prtein, grss energy and ttal available arbhydrates in their summer diets, Dall's sheep btain mre than adequate nutritin during that seasnwhih allws them t aumulate fat. y late winter, hwever, diet quality, as indiated by the relative amunts f the same mpnents, deterirates t a level belw that presumed neessary fr physial maintenane. - In additin t suitable limate, terrain and fd, mineral liks appear t be ne- Dall's Sheep Figure 39. Diet f Da's sheep in Alaska (after Nihls, Unpublished). essary mpnents f Dall's sheep habitat. iks are fund n mst f Alaska's sheep ranges. Use is highest in late spring and early summer, and diminishes by late summer. Sme liks are quite large; ne serves a ppulatin f abut 1,500 sheep that travels as muh as 19.3 kilmeters (12 miles) t the lik (Heimer 1974). Hebert (1967) fund that sdium was the element mst sught in natural liks by muntain gats. He suggested that lik use was the result f a high water intake n a lw sdium diet (initiated by feeding n suulent frage in the spring) rather than a winter dietary defiieny. eist C1971a) suggested that sheep use liks t replae skeletal minerals lst thrugh atablism during winter. MANAEMENT Distributin and status 'In Alaska, Dall's sheep upy suitable habitat in the rks Range, the Alaska Range frm the Canadian brder t ake Clark, the Wrangell Muntains, the Chugah Range, the Talkeetna Muntains and parts f the Kenai Muntains. Small 185
r: ig ame fnrth Ameria E J Q E u E islated herds are fund in the White Muntains and Tanana Hills nrth and east f Fairbanks (Figure 40). Estimates plae the state's ppulatin frm 30,000-50,000 sheep. Early market hunting and pssibly hunting by natives depleted a few lal herds whih appeared t rever by the 1920s. In respnse t a series f severe winters, a majr deline apparently urred in the 1930s and early 1940s, leaving many f Alaska's sheep ppulatins at very lw levels. Sine that time, herds have revered and nw appear t have stabilized in mst areas while delining gradually in a few thers (Nihls 1975). Management in Alaska mainly has nsisted f allwing nly the harvest t rams with hrns f three-quarter url r larger in annual August-September hunting seasns. Nnresident hunters are required t have a liensed guide. One ram is allwed per hunter eah year. Apprximately 1,000 1,200 rams are harvested annually (Figure 41). Reently initiated management praties inlude establishment f restrited aess areas and full-url ram-nly hunts as well as limited either-sex hunts. In the Yukn Territry, Dall's sheep are fund in all ranges between the Yukn River and the Alaska brder t the west and the ritish Clumbia brder t the suth. They ur nrth f the Yukn River in the Q daj/idahi 0 dll, stnel NORTHWEST TERRITORIES Figure 40. Current distributin f Dall's and Stne's sheep. 67 68 69 70 71 72 73 74 75 YEAR Figure 41. Dall's sheep harvest statistis in Alaska, 1967-1975. ritish, Rihardsn, Warneke, and Ogilvie muntains. An estimated 18,000 Dall's sheep ur in the Yukn Territry, and ppulatins are believed t be generally stable. Stne's sheep are fund in relit ppulatins in the Cassiar, Pelly and Selwyn muntains, and the Salmn Range; a few ur in the Ogilvie Muntains. There are sme 4,500 present, mstly in small and sattered bands. Ppulatins are thught t be relatively stable (Hefs 1975). th subspeies are hunted under the threequarter url regulatin, with ne ram per hunter per year allwed. uides are required fr nnresident hunters, and natives are allwed unrestrited hunting f bth sexes. The estimated annual harvest f thinhrn sheep in the Yukn Territry is abut 250 rams. Frm 3,000-8,000 DaIl's sheep are estimated t inhabit the MaKenzie Muntains in the Nrthwest Territries (Stelfx 1975). Ppulatins are stable. As elsewhere, nnresidents must hire a guide, and hunting by natives is unrestrited. Apprximately 150 rams are taken annually under the threequarter url restritin, with ne ram per nn-native hunter allwed eah year..'.."... 186
6 D Q E D Small herds f Dall's sheep ttaling abut 200 animals are fund in the nrthwest rner fritish Clumbia (Demarhi 1975). Stne's sheep ur n the Yukn and Stikine plateaus, and in the Skeena, Cassiar, Ominea and Rky muntains nrth fthe Peae River. Frm 9,000-15,000 Stne's sheep inhabit ritish Clumbia. Market hunting redued sme ppulatins in past years, but mst herds are thught t have revered and nw are relatively stable r pssibly delining slightly. Mst herds are harvested n the basis f the threequarter url, ram-nly regulatin, but a seven-eighths url law nw applies t rams f Rky Muntains ppulatins. Relatively heavy harvests have dereased the male segment f sme aessible herds. Als, predatr ntrl, primarily pisning f wlves, has been u.ndertaken in sme Stne's sheep ranges. In.general, management f thinhrn sheep in bth Alaska and Canada has had the primary bjetive ffurnishing trphies t hunters. Harvesting nly adult rams has nt been shwn t adversely influene thinhrn sheep ppulatins' apaity t re prdue, nr is it effetive t ntrl r redue herd numbers where desired. Intensive ram-nly hunting redues the number f available rams. Sme individuals ntend that if seletive ram-nly hunting is arried ut ver a lng enugh time, there may be a geneti effet in seleting fr the survival f small-hrned males. Hwever, this has nt yet been demnstrated. Aumulated evidene reprted earlier in the hapter shws breeding by yung rams and herd reprdutin are nt redued. Reent innvatins f ntrlling aess, limiting numbers f hunters harvp.sting frm selet herds, and inreasing the minimum size f rams t be harvested shuld have even less impat n ppulatins while inreasing pprtunities fr enjyment f rereatinal hunters. Cntrlled hunting f ewes will enable manipulatin and management f sheep herds by making pssible ntrl r redutin f ppulatins, alteratin f sex ratis in favr frams, and Dall's Sheep imprvement f reprdutin and survival rates in verrwded herds. In additin, need has been regnized in bth Canada and Alaska t set aside ertain sheep herds fr nnnsumptive uses, suh as viewing, phtgraphy and sientifi study. Estimatingppulatins eause f the size and ruggedness f sheep habitats, aerial surveys are the mst enmial and effiient way t evaluate ppulatin status. Thinhrn sheep an be lassified by sex and age lasses n the basis f hrn and bdy sizes and nfrmatins. Aerial surveys are appliable espeially t Dall's sheep, whih reside in treeless alpine regins and usually are highly visible in the summer. ight, fixed-wing airraft are relatively enmial and an prvide the means f determining distributins and ppulatin sizes with fairly high degrees f auray. Using fixed-wing airraft t determine sex and age lasses is pssible als, but requires nsiderable flying and bserving skills. Use f helipters allws fr mre aurate surveys, but generally is enmially impratial exept under speial irumstanes. Als, sheep reat mre t lw-flying helipters than t small airplanes-a harassment fatr that must be nsidered, espeially when yung lambs are present. Use fgrund surveys t examine samples f a herd, mbined with aerial surveys t estimate ttal herd size and distributin, generally is preferable t exlusive use f either aerial r grund surveys. eause rams usually are nt with the ewe bands after lambing, detailed sex-age lassifiatins are best nduted just prir t the lambing seasn. The bjetive is t btain the best ram-ewe and yearling-ewe ratis and ram size lass estimates befre the ram prtin fthe herd bemes segregated. During aerial surveys ndutedjust after lambing, the prprtin f new lambs (whih are readily visible frm the air) and ttal herd size may be estimated effetively. Ppula- 187
E E ig ame fnrth Ameria tin mdels then may be nstruted mathematially by mbining results f bth surveys; and ppulatin parameterssuh as reprdutin, survival, and herd mpsitin-may be estimated (Nihls 1970). Up lse, thinhrn rams may be aged aurately by their hrn annuli (eist 1966, Hemming 1969). These annuli, refleting a essatin f hrn grwth eah.fall, are readily visible t the trained eye. They may be used t estimate age f arasses r just hrn speimens t within abut ne mnth if the date fdeath is knwn. Ages fewes als may be estimated frm hrn annuli, but mre areful examinatin is required beause these annuli,are lser tgether and diffiult t distinguish in lder-aged speimens. THE FUTURE At present, Dall's sheep in Alaska and Canada have n serius man-related habitat prblems. They inhabit rugged and remte terrain, fr the mst part inhspitable t man. Hwever, the future may bring several types f human ativity that ()Uld ause habitat damage r redutin. The well-publiized trans-alaska il pipeline has already pushed a rad thrugh the heart f sheep habitat in the frmerly remte rks Range. The rad des n signifiant damage in itself, but undubtedly will pen the area t further 'mineral explratin and pssible develpment. Harassment f sheep by helipters during mineral explratin already is mmn in many ranges. Mineral develpment in sheep habitat may affet sheep ppulatins adversely by severely disturbing habitat and fring sheep t abandn vital ranges. One majr mineral lik already has been staked ut (but nt develped) as a mineral laim. A planned hydreletri prjet n Alaska's Susitna River, althugh prbably ding n damage t sheep habitat in itself, will pen heretfre remte sheep ranges t bat traffi and pssible further develpment. 188 The greatest danger faing Dall's sheep in Alaska is a plan nw being nsidered t pen large trats f sheep habitat t grazing by dmesti livestk, inluding dmesti sheep. Shuld this materialize, wild sheep ppulatins may be depleted as a result f mpetitin fr frage and diseases brught in by livestk. In Canada, Stne's sheep already are faed with lss f habitat t a large hydreletri prjet as well as t mineral develpments. A railrad has been nstruted thrugh the heart f sheep habitat and a highway is planned, bth f whih will pen sheep ranges t further explitatin. A ptential prblem faing bth Dall's and Stne's sheep in nrthern Canada is the inreasing mmerial value f their hrns and apes. Sine natives have n restritins n the number fsheep they an kill, there is a ptential fr whlesale destrutin f ppulatins. A management apprah is needed immediately t permit use f sheep ppulatins nly within bilgial limits. Althugh nt neessarily harmful t sheep, large trats fland will bl;) withdrawn sn frm unrestrited publi use under the Alaska Native Claims Settlement At. Inluded will be large blks f sheep habitat prbably set aside as natinal parks n whih all hunting will be restrited, and large areas t be under the ntrl f private, native rpratins, n whih the future f sheep hunting is unknwn as yet. These withdrawals nt nly will remve presently available sheep herds frm publi hunting, but will nentrate hunters n the remaining pen lands. This undubtedly will neessitate mre intensive management and restritive harvests. The mst imprtant future need f thinhrn sheep will be habitat prtetin. This will require Ii herd-by-herd inventry f ritial sites, inluding mineral liks, lambing and wintering areas, and migratin rutes. One knwn, these sites and the sheep that use them will need prtetin frm human develpment and undue harassment. Unless undertaken prmptly,
b A.J u suh habitat prtetin may me t late fr many sheep ppulatins. Cntinuing and lng-term researh is vital t understanding f thinhrn sheep elgy and management needs. Researh t date has been limited in spe, area and time. In partiular, mparative studies f sheep upying different habitats are Dall's Sheep needed. T make mre effiient use f the thinhrn sheep resure, management pliy makers will have t prvide mre mney and manpwer fr sheep management and researh, and managers will have t make better use f mdern management tehniques and researh findings. l 189