Timing of precipitation in an arid environment: Effects on population performance of a large herbivore

Abstract

Climate models predict that shifts in temperature and precipitation patterns are likely to occur across the globe. Changing climate will likely have strong effects on arid environments as a result of increased temperatures, increasing frequency and intensity of droughts, and less consistent pulses of rainfall. Therefore, understanding the link between patterns of precipitation, temperature, and population performance of species occupying these environments will continue to increase in importance as climatic shifts occur within these natural ecosystems. We sought to evaluate how individual, maternal, population, and environmental, particularly temperature and precipitation, level factors influence population performance of a large herbivore in an arid environment. We used mule deer (Odocoileus hemionus) as a representative species and quantified juvenile survival to test hypotheses about effects of environmental factors on population performance. Precipitation events occurring in mid‐ to late‐pregnancy (January–April) leading to spring green‐up, as indexed by normalized difference in vegetation index, had the strongest positive effect on juvenile survival and recruitment. In addition, larger neonates had an increased probability of survival. Our findings indicate that timing and amount of precipitation prior to parturition have strong influences on maternal nutritional condition, which was passed on to young. These results have important implications for understanding how animal populations may benefit from timing of precipitation during spring and prior to parturition, especially in arid environments.

Assessing future distribution, suitability of corridors and efficiency of protected areas to conserve vulnerable ungulates under climate change

“…For our mostly arid region, we estimated, on average, 66.5 ± 10.11% reduction in current distribution of the target ungulates by 2070, which is similar to the estimate calculated for Marco polo sheep ( O. ammon polii ) in Tajikistan (65.6% loss; Salas, Valdez, Michel, & Boykin, 2018), but higher than those obtained for large mammals in generally less arid regions like the Tibetan Plateau (30%–55% loss; Luo et al., 2015), the African continent (18% loss; Thuiller et al., 2006), in tropical forests of Asia (37% loss; Deb, Phinn, Butt, & McAlpine, 2019) and temperate Europe (30% loss; Levinsky, Skov, Svenning, & Rahbek, 2007) indicating that climate change could have generally larger impacts on species in arid regions (Heffelfinger et al., 2018), such as central Iran. Within central Iran, however, we obtained different estimates of climate change impact on the future distribution of the ungulates, which may be related to varying rates of climate change across their habitats.…”

Demographic performance of a large herbivore: effects of winter nutrition and weather

“…Our results suggest that enhanced winter nutrition provided adult females that were less fit to successfully rear offspring with capital to invest in reproduction despite the limitations imposed by harsh winters. Heffelfinger et al (2018) demonstrated the importance of high-quality forage during midpregnancy (January-April) for mule deer occupying an arid environment. The timing of latewinter and early-spring precipitation facilitated rapid green-up in that system during crucial periods of fetal development (Marshal et al 2005, Heffelfinger et al 2018.…”

“…Heffelfinger et al (2018) demonstrated the importance of high‐quality forage during mid‐pregnancy (January–April) for mule deer occupying an arid environment. The timing of late‐winter and early‐spring precipitation facilitated rapid green‐up in that system during crucial periods of fetal development (Marshal et al 2005, Heffelfinger et al 2018). Our findings also indicate the importance of nutritional resources during mid‐pregnancy in the Pacific Northwest.…”

Survival and cause‐specific mortality of desert bighorn sheep lambs

“…Neonate survival can be influenced by maternal body condition with young born to females in good nutritional condition typically having higher birth mass and post‐parturition growth rates. Neonates that are heavier at birth typically have higher survival rates that those born lighter (Thorne et al , Fairbanks , Keech et al , Cook et al , Heffelfinger et al ). Several studies have reported a positive relationship between fall lamb:adult female ratios in desert bighorn sheep and rainfall during the previous winter period (Douglas and Leslie , Wehausen et al , Douglas , Wehausen , Longshore et al ), suggesting a link between rainfall during late gestation and early post‐parturition, and juvenile recruitment.…”

“…During each year, we explored stage‐specific differences in survival rate using 7 a priori models of varying age intervals. Age intervals allow for survival rate estimation for specific biologically meaningful time intervals based on growth and development of young and have been examined with young grizzly bears ( Ursus arctos ; Schwartz et al ), elk ( Cervus canadensis ; Barber‐Meyer and Mech ), mule deer (Heffelfinger et al ), and white‐tailed deer ( Odocoileus virginianus ; Grovenburg et al ). We used stage‐specific intervals similar to those in Smith et al () in their survival estimation for Rocky Mountain bighorn sheep ( Ovis canadensis canadensis ) lambs in South Dakota, USA.…”