Document pBqz3Ed5DpJZmL3EqknE5NkkX

ARCTIC REFUGE COASTALfPLAIN TERRESTRIALfWILDLIFE RESEARCH fUMMARIESf 25f segments of fhe Herd often follow fhe Coastline whilef moving along the coastal plain of the .Arctic Refuge inf July (F.fJ. Mauer, U.S. Fish and Wildlife fervice,f personal communication).f Individual radio-collared caribou showed at leastf partial fidelity (i.e., caribou repeatedly returned tof specific areas) fo Cither fhe coastal plain, foothills, brf mountain zones during the fnsect harassment season inf dif erent years (Walsh et al. 1992). The negative energeticf consequences 6f fnsect harassment (Helle and Tarvainenf 1984) suggest that free access fo insect relief habitat isf important to caribou (Walsh et al. 1992), but in somef herds the energetic cost of insect harassment may be lowf (Toupin et al. 1996).f Calf Performance in Relation to Habitat Usey Mean calf weights within 1-2 days of birth weref remarkably similar among years. On average, femalef calves caught during 1992-94 when the herd wasf declining weighed 6.2 kg, Slightly fess fPbif0.003) fhanf <2-day-old female calves caught during 1983-85 (6.7 kg,f Whitten et al. 1992) when the herd was increasing.f The fncrease/decrease classification, however,f explained only about 9% of fhe variance in calf weights.f The fiifference fn female calf weights between fhef increase find decrease phases 6f fhe herd was due Colelyf to a cohort of heavy calves in 1985 (7.2 kg). Femalef calves caught in 1983-84 weighed an average of 6.3 kgf (Whitten et al. 1992).f There was a significant interaction among years andf between periods (0-3 weeks and 4-5 weeks after birth) (Pb < 0.001) in daily weight-gain of female calves, 1992-94f (Fig. f .23). Daily gain was particularly fow during fhe fourth find fifth weeks 6f Efe for calves born fn 1993 (Fig.f 3.23).f Daily weight-gain of calves did not dif er betweenf calves born in the concentrated calving areas and in thef peripheral calving areas (Pb 0.214). Much higher relativef densities 6f caribou f7x on average) fn fhe fioncentratedf calving areas compared fo peripheral calving areas fnayf have reduced forage available to individual lactating females.f Even though concentrated calving areas had a greaterf proportion 6f area with high plant biomass (bothf NDVI_calving find NDVI_621) fhan Aid fhe annualf calving fgrounds, tfhe fdifferential ifn forage fabundance fwasf evidently not suf icient to overcome the higher densitiesf of caribou in the fconcentrated calving areas and tof enhance the weight-gain of calves born there.f Patterns of habitat use by calves varied significantlyf (P < 0.01) between periods and among years, 1992-1994f (Fig. 3.24a-c), but were generally similar to use of sites for calving (Fig. 3.21). Weight-gain of calves duringf calving ground use was not fassociated with the percent of Figure 3.23. Daily gain (kg) of caribou calves of the Porcupine herd,z 1992-1994, during 2 periods (0-3 weeks post-birth and 4-5 weeks post-z birth). Gain was estimated from sequential weights of recaptured radio-z collared animals. Means are listed above the appropriate bars.z time fhat calves spent fn any particular vegetation fype orf in any class of forage at calving (NDVI_calving), rate of increase fn forage during factation (NDVI_rate), foragef available fit fhe peak of factation (NDVI_621), orf snowcover (Pb 0.05).f Although individual calf weight-gain was notf explained by within-annual-calving-ground habitat fise,f several characteristics of parturient females and calvesf were related to habitat conditions in the annual calvingf grounds, 1992-1994. The fank firders 6f 1) NDVI_621 fnf the annual calving ground, 2) average parturient femalef weights (Fig. 3.25),f3) parturient female body conditionf score, and 4) average calf weights, all at 3-weeks post-f calving, were all the same (1993 > 1994 > 1992).f Lack of correlation between individual calf weight-f gain and use of annual calving ground habitat suggestsf that the location of annual calving grounds may havef maximized calf weight-gain, given fhe conditions of thef annual habitat available within the extent of calving. Oncef the annual calving ground was located in an area thatf provided a high proportion of easily digestible foragef (high NDVI_rate), then variation in caribou density and forage biomass (NDVI_calving, NDVI_621) may havef interacted to reduce variation in performance among thef individual study animals.f Factors Associated with Calf Survival on they Calving Groundy During 1983-1985, average mortality of calves duringf June was 29% (Whitten et al. 1992), slightly higher thanf the 1983-2001 average of 25%. In those early years, aboutf 61% of mortality on the calving ground was due tof predation and the remainder (39%) was due to nutritionalf 26f BIOLOGICALfSCIENCE REPORTfUSGS/BRD 2002-000if or physical characteristics of calves (Whitten et al. I992,f Rof e f993). The fnteraction Between nutritional Status Of the calves and predation foortality was not known.f 1992 Wsedge Msedge HerbTT ShrubTT Vegetation Type Available Use - Weeks 0-3 Alpine Riparian Use - Weeks 4-5 993 Wsedge Msedge HerbTT ShrubTT Vegetation Type Available Use - Weeks 0-3 Alpine Riparian Use - Weeks 4-5 994 Predation occurred further South and fit higher filevationsf near fhe foothills during f983-1985 (Whitten fit al. f992).f During 1983-1985, golden eaglesfcaused tnostf predation mortality of calves on the annual calvingf grounds f~60%), grizzly Bears fanked second (~24%),f and wolves ranked third (~16%) (Whitten et al. 1992).f Young and McCaBe (1997) estimated that Bears killedf aBout 2% of calves during 1994, a year with relativelyf high overall calf survival (Fig. 3.10f).f Immature golden eagles ranged fhroughout the coastalf plain and foothills (Clough fit al. 1987), while goldenf eagle nests and wolf dens were primarily restricted to the foothills (see Fig. 6.1). Grizzly Bear densities weref moderate and their distriButions were concentrated in the foothills (Young find McCaBe 1997). Bn fate summerf through winter, fhe source and distriBution of predationf mortality of calves were unknown, But wolves weref proBaBly the dominant predator.f Wefused multiple scales to analyze factors associatedf with calf survival during June : 1) fate of individual calvesf within the population of fialves; and 2) the proportion of the annual population of calves tfhat survived until the endf of June in relation to a) haBitat characteristics within thef extent of calving and B) haBitat characteristics within eachf annual calving ground. Tf hese latter 2 classifications aref conceptually equivalent to the fifth and sixth order haBitatf selection afnalyses.f everal factors were Associated with finhancedf survival of individual calves, 1983-1994 (nb= 345 calves).f urvival was greater (10.8%, fPb 0.004) if the calf wasf Born in a high density concentrated calving area ratherf than in the low density peripheral portion of the calvingf ground; greater (11.0%, PbF 0.008) if Born near thef median calving date rather fhan Being Born early or late inf the calving season; greater (11.2%,fPb= 0.006) if Born onf Wsedge Msedge HerbTT ShrubTT Vegetation Type Available Use - Weeks 0-3 Alpine Riparian Use - Weeks 4-5 Figure 3.24. Azailability of 6 zegetation types in the aggregate zrtentz of calving for the Porcupine caribou herd and use by radio-collaredz calves during 2 periods (0-3 weeks post-birth and 4-5 weeks post-birth)z for a) 1992, b) 1993, and z) 1994. Vzgetation types: Wsedge = wetz sedge; Msedge = moist sedge; HerbTT = herbaceous tussock tundra;z ShrubTT = shrub tussock tundra, Alpine, and Riparian.z Figure 3.2S. Median Normalized Difference Vzgetation Index on 21z June (NDVI_621) within the annual calving grounds of the Porcupinez caribou herd and weights of parturient female caribou when capturedz within the annual calving ground on 21 June, 1992-1994.z