Document xzRm9XmXkd2MVB4YvQxdEQpgg

ARCTIC REFUGE COASTALfPLAIN ffERRESTRIALfWILDLIFE RESEARCH fUMMARIESf 29f caribou during calving (June) were greater than expectedf beyond 4 km from roads and pipelines (Cameron et al.f I992).f Central .Arctic herd caribou may make substantial usef of fareas ifn tfhe fvicinity fof foil field ifnfrastructures fduringf periods of moderate fo high fnsect abundance fluring post-f calving in July (Pollard et al. 1994). That observation isf not relevant, however, to the distribution of the Centralf Arctic herd during calving ifn June nor to the assessmentf of Porcupine flaribou herd distribution during flalving fnf relation to potential oil development Caribou of thef Porcupine herd generally depart the calving groundf during fearly Jfuly.f Historically, 2 zones of concentrated calving of thef Central .Arctic herd have been fecognized (Murphy andf Lawhead 2000). The zones were physically divided by thef Sagavanirktok River find the trans-Alaska oil pipeline.f There was an eastern ReferenceZzone where developmentf infrastructure was historically fibsent through 1995, find fif western developedhzone that included fhe Prudhoe fiay,f Milne Point, and Muparuk petroleum development areas.f In f996, fhe developed versus reference Zone fitudyf design was compromised by the completion of pipelinesf leading fo fhe Badami petroleum development firea, fiastf of fhe trans-Alaska dil pipeline find fnto fhe referencef zone.f During the late 1980s, concentrated calving in thef developed zone shifted from fhe vicinity of the Muparuk-f Milne Point petroleum development areas to undevelopedf areas tfo fthe fsouth-southwest fof tfhe foil fields f(Lawhead fetf al. 1993, Murphy and Lawhead 2000). Low densityf calving continued to occur in these petroleumf development areas while concentrated calving shifted.f That shift was completed by approximately 1987 whenf the Oliktok Point and Milne Point roads were completedf and substantial fhfrastructure was fn place.fThe fini-f directional shift in concentrated calving in the developedf zone, f980-1995, has Subsequently been confirmed (PhQf 0.002, Wolfe 2000). During fhe same years, however, fhef concentrated calving area in the reference area showed nof uni-directional shift (Ph=f0.14, Wolfe 2000) (see also Fig.h 4.7).f ince 1996 the bulk of high density calving in thef developed fzone fhas fremained fsouth fof froads fand fpipelinesf although a small zone of high density calving occurred inf the Muparuk-Milne Point firea fn 1996 (Lawhead findf Prichard 2001). The shift fhfcalving distribution fn fhef developed fzone foccurred feven tfhough tfhe fMilne fPoint fandf Muparuk petroleum development areas includedf substantial improvements in field design and layout (e.g.,f elevated pipes, reduced road density) that should have facilitated caribou passage compared with the design of the older Prudhoe Bay Complex.f No other concentrated calving area of .Alaska barren-f ground herds has demonstrated a statistically significantf uni-directional shift during fhe past 2 decades.f Melleyhouse (2001) showed no fini-directional shift fnf concentrated Calving for fhe Western .Arctic herd, 1987-f 2000, but was finable fo Assess shifts fn fhe fioncentratedf calving areas of the Tf eshekpuk Lake herd due to anf inadequate number fif years for fhe fest. As notedf previously, directional shifts of concentrated calving areasf of the Porcupine caribou herd have not dif ered fromf randomness, f983-2001.f Forage during peak factation (NDVI_621) fn fhef concentrated calving area in the fdeveloped zone of thef Central Af rctic herd declined as the concentrated calvingf area shifted south-southwest, 1980-1995 (Wolfe 2000).f During this shift, forage during peak lactation remainedf highest in the area used for concentrated calving duringf 1980-1982 (Wolfe 2000). There was, however, no declinef in forage Availability fin June 21 fNDVI_621) fn fhef concentrated calving fireas fn fhe reference zone fif fhef Central .Arctic herd during 1980-1995 (Wolfe 2000). Nof clear biological evidence explained tfhe shift of concentrated calving in the developed fzone to an area of reduced forage availability for lactating females. Thus,f petroleum development was implicated as a cause of thef southerly shift in concentrated calving in the developedf zone fif the Central .Arctic herd, f980-1995.f Since fthe first fcensus fof tfhe fCentral Af rctic fherd finf 1978, the herd size has increased from approximatelyf 5,000 to approximately 27,000 animals fn 2000 (E. A.f Lenart, Af laska fDepartment fof fFish fand fGame, fpersonalf communication. Bee also Fig 4.2). There was a sharpf decline (from 23,000 fo 18,000) fn fhe herd from 1992-f 1995 and a subsequent recovery. ft fs Unknown whetherf the Central Af rctic herd would have increased at a higherf rate than observed had the concentrated calving area inf the developed zone not shifted fo the south-southwest byf 1987.f The fobservation fof feither fan ifncrease for fdecrease fof any magnitude in the size of the Central Af rctic herd orf any other herd is not, by itself, sufficient evidence tof conclude tfhat tfhere fhas fbeen fan feffect fof fdevelopment forf lack thereof fin herd size. For Cxample, had the 1002 Areaf been developed fn 1989, fhe subsequent natural decline fif the Porcupine caribou herd (Fig. 3.8) would not havef constituted evidence fif fin effect fif development.f Tofassess potential effects fif development fin thef growth fcurve fof tfhe fCentral Af rctic herd, we needed tof make comparisons with fin ecologically similar herd. Thef Porcupine caribou herd does not constitute fi goodf ecological comparison and neither does the Westernf Arctic herd. The Teshekpuk Lake herd (Fig. 3.9) is thef most ecologically comparable herd fo fhe Central Arcticf herd in Alaska.f The Central Af rctic herd and Tf eshekpuk Lake herd aref certainly not identical, however 1) both herds aref relatively small in size and the frajectories of their growthf 3 Of BIOLOGICALfSCIENCE REPORTfUSGS/BRD 002-0001 f curves suggest exponential growth, 2) both herds havef relatively high bull: cow fatios f~80 : 100), 3) Calvingf ground habitats of both herds showed similar climatef trends (Kelleyhouse 2001, Wolfe 2000), 4) both herdsf exhibited the same dip in herd size during the mid-1990sf (Fig. 3.9), 5) neither herd has consistently demonstratedf the long distance migrations exhibited by the Wf esternf Arctic herd find Porcupine Caribou herd, find 6) beforef 1987, both components Cf fhe Central Arctic herd fis Wellf as the Teshekpuk Lake herd calved in wet coastal habitatsf with relatively fate fnowmelt.f The apparent divergence in the relative sizes of thef Central .Arctic herd and adjacent Teshekpuk Lake herdf after 1987 (Fig. 3.9) suggests that fhe growth rate of thef Central Af rctic herd may have slowed after roads andf pipelines expanded fn the developed Zone find thef concentrated calving area in the fdeveloped zone shiftedf south-southwest. The felative trajectories of fhe 2 herds'f growth curves were parallel through the mid- fo fate-f 1980s when both herds were slightly less than 4 times asf large fis when first fiensused. Thereafter, fheir frajectoriesf diverged slightly. By fhe fate f990s fhe Teshekpuk Lakef herd was about 7 times farger fhan when first fensusedf while the Central .Arctic herd was only about 5.4 times asf large fis when first Cbserved. Cronin fit fil. (1998) notedf that exponential growth rate of the Teshekpuk Lake herdf was approximately twice as great as the exponentialf growth rate estimated for the Central .Arctic herd (0.152f vs. 0.077, respectively) rom the mid-1970s through thef mid-1990s.f Several ecological factors may have diluted orf obscured finy population consequences hf fivoidance Cf petroleum development areas by the Central Af rctic herdf during calving. First, only the half o the herd that usedf the developed Zone was potentially fiffected. Reduction fnf available food for lactating females during peak lactationf was demonstrated only for tfhe females that used thef developed fzone fconcentrated fcalving afrea (fapproximatelyf 25% df fill females fn fhe Central .Arctic herd; Wolfef 2000).f Second, the Central Af rctic fherd fremained fon tfhef coastal plain when it shifted its concentrated calving areasf in the developed zone. The parturient females and calvesf were not displaced fo fhe fidjacent foothills wheref predator densities were assumed to be greatest. Thus, thef shift may have incurred fittle ff finy additional fhortalityf due fo predation.f Third, development of the complex of petroleumf development areas from Prudhoe Bay to Muparuk hasf occurred during a period of relatively favorablef environmental conditionsf(Maxwell 1996). The resiliencef of herds fo fibiotic, biotic, dr anthropogenic challengesf would be expected to be greatest during favorablef environmental conditions.f Fourth, because the Central .Arctic herd obtained fif relatively small proportion of its annual nitrogen budget from its calving ground compared with other herds (Fig.f 3.22), the Central .Arctic herd calving ground may havef had less relative value to herd performance than thef calving grounds of other herds.f Fifth, calving ground density of the Central Arcticf herd has been, and remains, quite low (approximatelyf one-fifth the effective density of the Porcupine caribouf herd; Whitten find Cameron 1985). Thus, even fhough females of fhe Central .Arctic herd fn fhe developed Zonef shifted their concentrated calving to an area with reducedf total forage, fhe fimount remaining per caribou may havef been suf icient to accommodate nutritional requirements.f Because fecological fconditions for fthe fPorcupinef caribou herd fire substantially different fhan for fhef Central .Arctic herd, ft fs Unlikely fhat fill fhesef ameliorating factors will apply to the response of thef Porcupine caribou herd to development within its calvingf ground. fNevertheless, the fivoidance of oil field foadsf and pipelines by parturient females of the Central .Arcticf herd during the calving season ifs transferable tof Porcupine caribou herd because sensitivity fo disturbancef by parturient caribou has been repeatedly noted elsewheref (Wolfe fit fil. 2000).f Tofassess fhe potential effects of petroleumf development fn fhe 1002 .Area on the Porcupine caribouf herd, we fissumed fhat displacement of Porcupine caribouf herd's concentrated calving grounds would occur, similarf to the shift observed or the concentrated calving area inf the developed Zone of fhe Central .Arctic herd (Lawheadf et al. 1993, Wolfe 2000). Wefthen used empirical habitat-f demography relationships developed in the Porcupinef caribou herd studies fo fissess fhe implications of fhisf hypothetical displacement on calf survival during June forf the Porcupine caribou herd.f Wefbased our predictions on an empirical modelf relating calf survival to orage in the annual calvingf ground on 21 June find fo the proportion of calves born fnf low predation risk (Fig. 3.27). This empirical model wasf Percent June Calf Survival I f-0.0396 > (2.0989 f fnedianf NDVI_621 fn the finnual calving ground) > (0.00283 ff proportion of calves born fn fow predation risk)] f 100,f (r2 i 0.70; PZQ 0.001). The spatially explicit nature of thisf intermediate-scale model subsumed fhe effects of temporal and spatial caribou density on individual calf survival.f First, we used the empirical model to predict calf survival in each of the 17 observed annual calvingf grounds of fhe Porcupine caribou herd, 1985-2001 (Fig.f 3.13). Then each concentrated calving firea was displacedf the fminimum fdistance nfecessary tfo fprovide 4f kfmf clearance from fhe boundary of each of Efhypothetical 6ilf development scenarios for fhe 1002 .Area presented fnf Tussing find Haley (1999; scenarios 2-5) find for fhef