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

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.DATA AVAILABILITY STATEMENT : The dataset used in our analyses is available via Dryad repository (https://doi.org/10.5061/dryad.jsxksn09f) following a year-long embargo from publication of the manuscript. The coordinates associated with mountain zebra data are not provided in an effort to protect critically endangered black rhino (Diceros bicornis) locations. Interested researchers can contact the data owner (Minnesota Zoo) directly for inquiries.https://wileyonlinelibrary.com/journal/elehj2022Mammal Research InstituteZoology and Entomolog

Microtopographical Characteristics of Forest Dieback in a Semi-Arid Region Retrieved from Ground and Satellite Data

Various factors have been cited for forest dieback including global warming and dryness, overgrazing damage by wild animals, forest fires, and damage by insects. Hustai National Park (HNP) of Mongolia, which is 506 square kilometers (km 2 ) in size, encompasses high mountains, hills and valleys. The land cover of HNP, includes stepe land, mountain steppe and forest steppe. In recent years, HNP forests started to dry out significantly and the entire landscape has changed from forest steppe to mountain steppe. Currently, in HNP forests cover only 13.1 km 2 of the park. The dominate tree species are Betula platyphylla Sukaczev (Siberian silver birch) and Populus tremula (Eurasian aspen). Siberian silver birch is drought sensitive, frost resistant and able to grow well under different environmental conditions. Siberian silver birch is distributed only on the north-facing slopes of the mountains because evapotranspiration is much higher than precipitation in Mongolia. In this study, we conducted field surveys at three sites in the park over a five-year period and sampled 1130 points. We apply a tree measurement (TM) survey to examine living and dead (dieback) trees, as well as obtain a Diameter at Breast Height (DBH) measurement. Using the DBH and height of the trees we clarify the factors that influence white birch forest. Extraction of fallen and dieback tree pixels using time series Landsat satellite data, including an analysis of microgeomorphology characteristics (slope and solar radiation) of dieback trees using 30m SRTM DEM data were employed. Results show the DBH of the birch tree with dieback was around 10–15 cm and the tree height was 2–3 m. It was found that many of the dead trees have a negative correlation with the curvature of microtopography and a positive correlation with the amount of solar radiation

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

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.acceptedVersio