Body size, digestive systems shape ungulate foraging

Date:
July 27, 2021
Source:
University of Wyoming
Summary:
Smaller-bodied ruminants forage primarily for the highest energy
intake, while equids -- which tend to be larger -- choose to
forage in areas close to surface water, with less attention to
forage condition.



FULL STORY ========================================================================== Research led by a University of Wyoming graduate student involving about
50 scientists from across the globe has provided new insights into the
behavior of ungulates (hoofed animals) as it relates to forage conditions
and water availability.


========================================================================== Saeideh Esmaeili, who graduated from UW's Program in Ecology in December
2020 and is now a postdoctoral assistant at Colorado State University,
is the lead author of a paper that appears in the journal Ecology
Letters. It explores the foraging behavior of 30 species of ungulates
across North America, Europe, Africa and the Middle East, ranging from
elk and mule deer in Wyoming to gazelles, impalas, reindeer, wildebeest,
wild asses and zebras.

"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 ungulates," Esmaeili says.

Other UW researchers who participated are Shannon Albeke, Jeff Beck,
Jake Goheen, Matt Kauffman and Jerod Merkle, along with Hall Sawyer, of Laramie- based Western EcoSystems Technology Inc. Goheen was Esmaeili's
Ph.D. adviser.

The research adds nuance to a long-held hypothesis that ungulates
choose to forage on grasses and other plants when the vegetation is at
an intermediate stage of growth, so as to maximize energy intake. This
is called the "forage maturation hypothesis." Plants are most digestible
at the beginning of the growing season; however, because they are small
during this time, biomass is low. As plants mature, they gain biomass,
but they become harder to digest.

The ungulates that were part of this study include both ruminants,
such as deer and elk, which acquire nutrients by fermenting plants in a specialized stomach prior to digestion; and equids, such as horses and
zebras, which don't have such specialized stomachs.

Most notably, the scientists found that smaller-bodied ruminants forage primarily for the highest energy intake, while equids -- which tend
to be larger -- choose to forage in areas close to surface water, with
less attention to forage condition. That's likely because equids don't
conserve water as efficiently as ruminants and proportionally excrete
more water. The research also confirmed that ruminants' ability to
process higher-biomass forage increases with the species' size.

A primary conclusion of the research is that, while the forage maturation hypothesis largely holds true, there is some variation based upon
ungulates' body size and digestive systems.

"The forage characteristics that influence population persistence of free- ranging ungulates should differ according to body size and digestive
system, such that access to a combination of resource gradients is key to maintaining viable populations of diverse free-ranging ungulates across
the globe," the scientists conclude.

Other institutions, organizations and agencies whose researchers
participated in the project include Virginia Tech University; Yale
University; the U.S.

Geological Survey; Colorado State University; the University of
Washington; the Wildlife Conservation Society; France's University of Montpellier; South Africa's University of Pretoria; Germany's Senckenberg Biodiversity and Climate Research Centre; Mongolia's Hustai National
Park Trust; the Cary Institute of Ecosystem Studies; the University
of British Columbia; the Minnesota Zoo; Iran's Isfahan University of Technology; Japan's Tottori University; the Norwegian Institute for
Nature Research; Austria's University of Veterinary Medicine; the Inland
Norway University of Applied Sciences; the Mongolian Academy of Sciences;
and the Smithsonian Conservation Biology Institute.

========================================================================== Story Source: Materials provided by University_of_Wyoming. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. 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 Chamaille'‐Jammes, Buyanaa
Chimeddorj, Paul C. Cross, Nandintsetseg Dejid, Jagdag Enkhbyar,
Ilya R. Fischhoff, Adam T. Ford, Kate Jenks, Mahmoud‐Reza
Hemami, Jacob 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. Body size and digestive system shape resource
selection by ungulates: A cross‐taxa test of the forage
maturation hypothesis.

Ecology Letters, 2021; DOI: 10.1111/ele.13848 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210727173718.htm

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