Document 7RoOVNOkpyx5Ba7zzJdV3KMNE

ARCTIC REFUGE COASTALfPLAIN ffERRESTRIALfWILDLIFE RESEARCH fUMMARIESf Ilf this report and in the 1987 Final Legislativef constitutes scale-dependent selection (cf. Wiens 1989,f Environmental fmpact ftatement (Clough et l. 1987).f O'Neil and Ming 1998). Wefpursued this fssue of scalef dependency in habitat selection by the Porcupine caribouf Nutritional Importance pf the Calving Groundy herd at the larger scales of the annual calving grounds andf concentrated calving areas.f pring arrival on the calving ground is the time of Because fhe fnability fo meet factation flemands fnayf minimum body reserves for parturientfemalesZ(thosef lower the performanceUi.e., weight-gain, survival) of about fo give birth or accompanied by Very young Calves) calves, calving ground habitats may be fmportant. Theyf (Chan-McLeod et al. 1999). Thereafter, their energyfandf may be fmportant because fhey can contributef protein requirements reach the highest level of the yearf substantially to the female and calf protein budgets duringf during peak factation fn fhe first 3 weeks bf June (Whitef the calving season, when maternal protein reserves can bef and Luick f984, Parker Ft fil. f990). The females'f low (Gerhart et al. 1996, Chan-McLeod et al. 1999).f appetites are high and forage intake rates can matchf lactation demandfonly /here primary production fs Eighf Habitat Trends During the Study Periody (White et al. 1975, 1981). Small changes in nutritionalf content and digestibility of forage, however, can havef The climate of the .Arctic has been warming in bothf substantial multiplier ef ects on digestible energy andf protein intake (White 1983), and fhus may influencef summer and winter during recent decades (Chapman andf Walsh 1993, Groisman et al. 1994, Houghton et al. 1995).f nutritional performance of Porcupine caribou herd Temperature increases have been greatest in winter.fThef females on the calving ground.f warming has been heterogeneous across the Af rcticf Recent advances in identifying fhe basis of selectionf of food by ungulates demonstrate that forage intake is a (Chapman find Walsh 1993, Serreze 2000), but wasf evident in spring (Fig. 3.3a) and winter (Fig. 3.3f) function of Ungulate morphology, plant architecture, andf temperatures within the northern part of the annual rangef biomass Uf acceptable forage (White Ut al. 1975, Trudellf of the Porcupine caribou herd.f and White 1981, Spalinger ft al. 1988, Shipley andf An earlier greening and later senescence of greenf Spalinger 1992, Gross et al. 1993, Langvatn and Hanleyf plant biomass in areas north of 40N (Myneni et al. 1997,f 1993, Wilmshurst find Fryxell 1995). Because fingulatesf 1998; hou et al. 2001) have been fletected with NDVIf select forage With high fligestible energy and highf and associated with the warming trend. The earlierf digestible protein (Langvatn and Hanley 1993,f greening was evident focally within fhe extent of calvingf Wilmshurst and Fryxell 1995), these properties are thef (Fig. 5.2) 5f fhe Porcupine caribou herd fn fhe form of finf relevant measure of forage value of habitats at any spatialf increasing relative amount of green plant biomass on 21f scale (White et al. 1975, White find Trudell 1980a,b).f June (NDVI_621, f2 =fD.50,fP = 0.002) fluring 1985-1999f Thus, the forage currency for ungulates is primarily a (Fig. 3.4).f function Uf fligestibility 5f acceptable foods find fs notf A very low value for NDVI_621 was observed inf simply plant biomass or gross energy (Fryxell 1991).f 1992, fhe year that stratospheric aerosols from fhe 1991f The source 5f protein for fetal growth comes almostf eruption of Mount Pinatubo fn the Philippines reached fhef exclusively from body protein of female caribou enteringf Arctic fn spring (Minnis et al. 1993). Both 2001 find 2000f winter (Gerhart et al. 1996). Females with high bodyf were substantial hutliers (RSfudent = -2.49, -2.86,f protein fn fate Winter produce the largest calves (Allaye-f respectively) from the relationship between NDVI_621f Chan 1991). Early weaning of calves occurs when habitatf and year, 1985-1999 (Fig. 5.4). Both 2001 find 2000 hadf conditions flo not support a protein fntake sufficient fof exceptionally fate springs with high snowcover at calving.f meet a minimal fate of body protein deposition; milkf Wefdo not yet know if these outliers indicate a change inf synthesis fhen ceases (Russell and White 1998). Thef the trend observed fluring 1985-1999.f protein: energy ratio of forage consumed during lactationf The &rctic OscillationUFig. 3.5) is centered over thef increases tfhe fmilk fprotein ifntake fby cfalves (fChan-McLeodf high .Arctic and fs flne flf afnumber of correlated fndicesf et al.1994), the most important milk nutrient af ecting calf of large-scale atmospheric pressure flifferentials (e.g.,f growth rate at all calf ages (White 1992).f North Af tlantic fOscillation, fNorthern fHemispheric Af nnularf When forage biomass is lfow at calving, Porcupinef Mode) (Thompson find Wallace 1998, 2001). The .Arcticf caribou herd females might be expected to usef Oscillation is the height of fhe level of one-half microhabitats of highest biomass of acceptable foods findf atmosphere of pressure above fhe surface of the earth andf to select the most digestible forages from within them, asf is weakly correlated with surface temperaturesf has been flocumented for caribou 5f the Central Arcticf (Thompson Und Wallace 1998). The Arctic Oscillation hasf herd (White et al. 1975) and the Western .Arctic herdf a warm positive phase when surface pressures are fowf (White find Trudell 1980f).fThis change fn fhe basis of and warm North Af tlantic water enters the Af rctic Ocean,f selection, from forage biomass to forage digestibility,f 12f BIOLOGICALfSCIENCE REPORTfUSGS/BRD 2002-0001f Figure 3.S. Standardized values of the Arctic Oscillation (AO) forz winter (January, February, March) and population size of the Porcupinez caribou herd, 1958-2001. Mean value indicated by solid horizontal line.z | PDO is the Pacific Decadal Oscillation (Hare and Matuna, 2000).z Shingle Point, Yukon Territory, Canada) and 1 station within its winterz range (Old Crow, Yukon Territory) for a) June, and b) winter (January,z February, March), 1950-1995.z Figure 3.4. Median Normalized Difference Vzgetation Index (NDVI) onz 21 June within the aggregate extent of calving for the Porcupinez caribou herd, 1983-2001. Values for 2000 and 2001 were outliersz (RStudent = -2.49, -2.86, respectively) and excluded from thez displayed regression line, r 2 = 0.496, P = 0.002.z and fool fiegative phase /hen Surface pressures firef relatively high.f Initiation of increasing and decreasing trends in thef Arctic Oscillation has Been Coincident /ith phase shifts inf the Pacific Decadal Oscillation fn 1977 and 1989 pHaref and Matuna, 2000) (Fig. 8.5). Correlations Bet/een fhef closely related North .Atlantic Oscillation and a numBer of vegetative and Ungulate population characteristics havef Been feported for Northern Europe pPost ft fil. 1997, Postf and ftenseth 1999).f Median annual NDVI at calving fNDVI_calving) /ithin fhe extent of calving of fhe Porcupine cariBou herdf /as positively correlated /ith the .Arctic Oscillation fromf the /inter (January, FeBruary, March) of fhe previousf calendar year ,~15 month lag, f2 = 0.32, $ = 0.011) ,Fig.f 3.6). This suggested that early forage availaBility forf lactating females /as influenced By /eather patterns on af hemispheric scale.f Further, fthe fsuspected fphase fshift fin tfhe Af rcticf Oscillation at fhe end of the 1980s pFig. 3.5) /asf coincident /ith an increase in the frequency of dailyf temperature excursions aBove freezing fn Both the springf ,Fig. 3.7a) and fall (Fig. 3.7f) on the transitional rangesf of fhe Porcupine cariBou herd during the 1990s. There hasf Been a decrease fn fhe depth and extent of sno/cover fnf Northwestern Canada near fhe /intering grounds Bf fhef Porcupine cariBou herd during this fatter period as /ellf (Bro/n find Braaten 1998).f Thus, forage Biomass during peak lactation demandf (NDVI_621) increased during the period of study, 1985-f 1999 (Fig. 3.4), and this positive trend /as coincidentf /ith summer /arming on fhe calving ground fFig. 3.3a).f In addition, forage availaBility at calving fNDVI_calving) has Been positively correlated /ith hemispheric-scalef