Advancing the match-mismatch framework for large herbivores in the Arctic: Evaluating the evidence for a trophic mismatch in caribou

Abstract

Climate-induced shifts in plant phenology may adversely affect animals that cannot or do not shift the timing of their reproductive cycle. The realized effect of potential trophic “mismatches” between a consumer and its food varies with the degree to which species rely on dietary income and stored capital. Large Arctic herbivores rely heavily on maternal capital to reproduce and give birth near the onset of the growing season but are they vulnerable to trophic mismatch? We evaluated the long-term changes in the temperatures and characteristics of the growing seasons (1970–2013), and compared growing conditions and dynamics of forage quality for caribou at peak parturition, peak lactation, and peak forage biomass, and plant senescence between two distinct time periods over 36 years (1977 and 2011–13). Despite advanced thaw dates (7−12 days earlier), increased growing season lengths (15−21 days longer), and consistent parturition dates, we found no decline in forage quality and therefore no evidence within this dataset for a trophic mismatch at peak parturition or peak lactation from 1977 to 2011–13. In Arctic ungulates that use stored capital for reproduction, reproductive demands are largely met by body stores deposited in the previous summer and autumn, which reduces potential adverse effects of any mismatch between food availability and timing of parturition. Climate-induced effects on forages growing in the summer and autumn ranges, however, do correspond with the demands of female caribou and their offspring to gain mass for the next reproductive cycle and winter. Therefore, we suggest the window of time to examine the match-mismatch framework in Arctic ungulates is not at parturition but in late summer-autumn, where the multiplier effects of small changes in forage quality are amplified by forage abundance, peak forage intake, and resultant mass gains in mother-offspring pairs.

Normalized Difference Vegetation Index as an Estimator for Abundance and Quality of Avian Herbivore Forage in Arctic Alaska

“…Although previous studies have contrasted satellite and plot-scale NDVI as estimators of arctic vegetation biomass [2], we are unaware of other work that explicitly contrasts the predictive power of NDVI metrics for properties of vegetation across multiple scales. Given the current evidence for rapid changes in physical and environmental phenologyin the Arctic, conflicting consequences of a phenology mismatch between migratory herbivores and their food resources [69,70], and an interest in forecasting the future of plant forage quality and quantity for herbivores [6], there is a compelling need to improve monitoring of forage plant quantity and quality at high latitudes. Appendix A Table A1.…”

Observed and predicted effects of climate change on Arctic caribou and reindeer

“…Studies from Tveraa et al (2013), Veiberg et al (2016), and Gustine et al (2017) found no evidence of a trophic mismatch between the onset of spring vegetation and Rangifer reproductive success in reindeer populations in northern Norway, Svalbard, or Alaskan caribou, respectively. In fact, it is characteristic of Arctic Rangifer populations to calve before spring green-up occurs.…”

“…Reliance on maternal body stores for foetal development rather than dietary income may mitigate negative effects of changing phenologies (Stephens et al 2009;Veiberg et al 2016;Gustine et al 2017). As previously noted, it has been well documented that many Rangifer populations calve before the onset of vegetation growth, reinforcing the importance of maternal capital for reproduction (Barboza and Parker 2008) and in some ways curtailing the conceptual potential for spring phenological mismatches.…”

“…Tveraa et al (2013) noted that the reindeer they studied calved two to four weeks before the onset of spring. Gustine et al (2017) reported that growing season had not begun in 1977 or in 2011-2013 at the timing of parturition and that key forage species did not emerge until 4-11 days after parturition dates of the Central Arctic Herd. A number of other studies further corroborate the timing of parturition as occurring well before the emergence of vegetation (Fleck and Gunn 1982;Reimers et al 1983;Crête and Huot 1993;Veiberg et al 2016).…”

“…Both Veiberg et al (2016) and Gustine et al (2017) noted that because caribou and reindeer are capital breeders (Taillon et al 2013), it is expected that the influence of spring phenology should be less important than that of maternal winter body condition on reproductive success. Reliance on maternal body stores for foetal development rather than dietary income may mitigate negative effects of changing phenologies (Stephens et al 2009;Veiberg et al 2016;Gustine et al 2017).…”