Body size and digestive system shape resource selection by ungulates: A cross-taxa test of the forage maturation hypothesis

Saeideh Esmaeili, Brett R. Jesmer, Shannon E. Albeke, Ellen O. Aikens, Kathryn A. Schoenecker, Sarah R.B. King, Briana Abrahms, Bayarbaatar Buuveibaatar, Jeffrey L. Beck, Randall B. Boone, Francesca Cagnacci, Simon Chamaillé-Jammes, Buyanaa Chimeddorj, Paul C. Cross, Nandintsetseg Dejid, Jagdag Enkhbyar, Ilya R. Fischhoff, Adam T. Ford, Kate Jenks, Mahmoud Reza HemamiJacob D. Hennig, Takehiko Y. Ito, Petra Kaczensky, Matthew J. Kauffman, John D.C. Linnell, Badamjav Lkhagvasuren, John F. McEvoy, Joerg Melzheimer, Jerod A. Merkle, Thomas Mueller, Jeff Muntifering, Atle Mysterud, Kirk A. Olson, Manuela Panzacchi, John C. Payne, Luca Pedrotti, Geir R. Rauset, Daniel I. Rubenstein, Hall Sawyer, John D. Scasta, Johannes Signer, Melissa Songer, Jared A. Stabach, Seth Stapleton, Olav Strand, Siva R. Sundaresan, Dorj Usukhjargal, Ganbold Uuganbayar, John M. Fryxell, Jacob R. Goheen

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


The forage maturation hypothesis (FMH) states that energy intake for ungulates is maximised when forage biomass is at intermediate levels. Nevertheless, metabolic allometry and different digestive systems suggest that resource selection should vary across ungulate species. By combining GPS relocations with remotely sensed data on forage characteristics and surface water, we quantified the effect of body size and digestive system in determining movements of 30 populations of hindgut fermenters (equids) and ruminants across biomes. Selection for intermediate forage biomass was negatively related to body size, regardless of digestive system. Selection for proximity to surface water was stronger for equids relative to ruminants, regardless of body size. To be more generalisable, we suggest that the FMH explicitly incorporate contingencies in body size and digestive system, with small-bodied ruminants selecting more strongly for potential energy intake, and hindgut fermenters selecting more strongly for surface water.

Original languageEnglish (US)
Pages (from-to)2178-2191
Number of pages14
JournalEcology letters
Issue number10
StatePublished - Oct 2021

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics


  • Equidae
  • forage biomass
  • hindgut fermentation
  • macroecology
  • ruminant
  • step-selection function
  • water requirements


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