The Forage Maturation Hypothesis (FMH) states that energy intake for ungulates is maximized 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 the digestive system. Selection for proximity to surface water was stronger for equids relative to ruminants, regardless of body size. To be more generalizable, 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.

The SSF_dataset.csv represents coordinates and habitat covariates of used (denoted by column ‘case’ equal to TRUE) and available steps (denoted by column ‘case’ equal to FALSE) during growing seasons for the 30 populations of ruminants and equids detailed in Esmaeili et al. Within each study population, GPS coordinates are offset by a predetermined length and direction to protect the true locations of study populations. Habitat covariates associated with the true locations are available. The dataset is organized based on a step selection function framework, and can be analyzed using conditional logistic regression following the methods described in the associated publication. Column headings exactly match the variables described in the associated publication in Ecology Letters. 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.

Below is a description of the data contained in each column:

species: common name of the study population.

country: country (and region) of the study population.

animal_id: a unique identifier for each animal monitored in each study population.

step_id: a unique identifier for each step of each monitored animal at each study population.

case: determines if the step was used (TRUE) or available (FALSE).

step_length: length of each used and available step in meters.

MSAVI, IRG, and water: values of MSAVI (forage biomass), IRG (potential energy intake), and water extracted at end of each used and available step. Unitless and standardized values between 0 and 1.

X1_ and Y1_: offset coordinates of start of each step

X2_ and Y2_: offset coordinates of end of each step