DOI: 10.5061/dryad.qt5bd
title: Data from: Maternal winter body mass and not spring phenology determine annual calf production in an Arctic herbivore

description: Warming of the Arctic has resulted in earlier snowmelt and green-up of
 plants in spring, potentially disrupting the synchrony between plant
 phenology and breeding phenology in herbivores. A negative relationship
 between offspring survival in West-Greenland caribou and the timing of
 vegetation emergence was the first finding of such a mismatch in Arctic
 mammals. However, other studies indicate that the energy for foetal growth
 and early lactation is predominantly drawn from stored energy reserves
 typical of ‘capital’ breeders, suggesting that conditions well before
 spring influence calf production more than the timing of spring onset.
 Here we use 20 years of observations of marked Svalbard reindeer to
 evaluate determinants of annual recruitment, as measured by the presence
 of a calf at foot in mid-summer. Spring temperatures and the Enhanced
 Vegetation Index were used as proxies for spring onset, while data on body
 mass and pregnancy rates in late winter allowed us to determine maternal
 condition and the reproductive status before spring. Pregnancy rate,
 offspring survival and annual recruitment were all strongly correlated
 with average late winter adult female body mass (r = 0.87; r = 0.83; r =
 0.92, respectively). Contrary to the findings in West Greenland, neither
 early calf survival nor annual recruitment were correlated with the two
 measures of annual variation in spring phenology (r= – 0.07, p = 0.8 and r
 = – 0.15, p = 0.6, respectively). We also revisit the Greenland data and
 reveal that the pattern of covariance between early and late measures of
 fecundity, as well as between early measures of fecundity and offspring
 survival, correspond with the results from Svalbard. Our results emphasize
 that conditions affecting maternal body mass during winter explain close
 to all the variation in recruitment, questioning the importance of the
 role of a mismatch between plant phenology and calving date.
description: Annual body mass,
 reproduction and spring datesAnnual estimates of the
 variables used in the analyses of the Svalbard and West Greenland reindeer
 data. Column description Svalbard data: bm = mean adult female body mass
 (kg), SE_bm = standard error of bm, pp = proportion of marked adult
 females pregnant in April, N_pp = the sample size pp is based upon, pc =
 proportion of adult females observed with a calf at foot in summer, N_ pc
 = the sample size pc is based upon, so = Offspring survival from April
 till summer, N_so = the sample size so is based upon, T50 and EVI-spring =
 The date of spring onset based on each respective proxy. Column
 description West Greenland data: PCmax = Maximum estimate of calf
 production before significant early calf mortality. PCfinal = Final
 estimate of calf production after early calf mortality, M = Early calf
 mortality ([PCmax – PCfinal]/PCmax), pcmax = proportion of females with a
 calf just after calving and before significant early calf mortality,
 pcfinal = proportion of females with a calf after early calf mortality, sc
 = offspring survival.Veiberg_et_al_data_for_dryad.xlsx