Drought reshuffles plant phenology and reduces the foraging benefit of green‐wave surfing for a migratory ungulate. (11th June 2020)

• Record Type: Journal Article
• Authors: Aikens, Ellen O.; Monteith, Kevin L.; Merkle, Jerod A.; Dwinnell, Samantha P. H.; Fralick, Gary L.; Kauffman, Matthew J.
• Is Part Of: Global change biology. Volume 26:Number 8(2020)
• Page Start: 4215
• Page End: 4225
• Publication Date: 2020-06-11
• Subjects: climate change -- migration -- mule deer -- normalized difference vegetation index -- Odocoileus hemionus -- the Green Wave Hypothesis -- trophic mismatch -- Wyoming; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15169
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: To increase resource gain, many herbivores pace their migration with the flush of nutritious plant green‐up that progresses across the landscape (termed "green‐wave surfing"). Despite concerns about the effects of climate change on migratory species and the critical role of plant phenology in mediating the ability of ungulates to surf, little is known about how drought shapes the green wave and influences the foraging benefits of migration. With a 19 year dataset on drought and plant phenology across 99 unique migratory routes of mule deer ( Odocoileus hemionus ) in western Wyoming, United States, we show that drought shortened the duration of spring green‐up by approximately twofold (2.5 weeks) and resulted in less sequential green‐up along migratory routes. We investigated the possibility that some routes were buffered from the effects of drought (i.e., routes that maintained long green‐up duration irrespective of drought intensity). We found no evidence of drought‐buffered routes. Instead, routes with the longest green‐up in non‐drought years also were the most affected by drought. Despite phenological changes along the migratory route, mule deer closely followed drought‐altered green waves during migration. Migrating deer did not experience a trophic mismatch with the green wave during drought. Instead, the shorter window of green‐up caused by drought reduced the opportunity to accumulate forage resources during rapid spring migrations. Our work highlights the synchronization of phenological events as an important mechanism by which climate change can negatively affect migratory species by reducing the temporal availability of key food resources. For migratory herbivores, climate change poses a new and growing threat by altering resource phenology and diminishing the foraging benefit of migration. Abstract : Many herbivores pace their spring migration with the progression of the "green wave" or the flush of nutritious plant green‐up that sweeps across the landscape. Little is known about how climate influences the dynamics of the green wave and the ability of animals to surf altered phenological gradients. Here, we show that drought compressed and reshuffled green waves that migratory ungulates exploit, resulting in an overall reduction in resource availability en‐route. Rather than being mismatched with resource phenology, our work draws attention to reduced resource availability due to shifting patterns of phenology as a key threat to migratory species.