Technical Abstract: This chapter addresses the direct and indirect effects of animals on ecosystem processes and/or their effects on ecosystem properties. This has been the primary focus of animal studies on the Jornada Experimental Range (JER) and the Chihuahuan Desert Rangeland Research Center (CDRRC) during the twentieth century. Early studies dealt with animal species that were thought to reduce the amount of primary production that was available to support livestock. With the establishment of the International Biological Programme (IBP) in the late 1960s and its premise that ecosystems could be modeled based on the energy flow conceptual model, animal studies were designed to measure energy flow through consumer populations. Those studies yielded estimates of consumption of live plant biomass between 1 and 10% of the annual net primary production. It was concluded that, in most ecosystems, consumers process only a small fraction of the net primary production as live plant material and consumers play important roles in ecosystems as regulators of ecosystem processes and a less important role in energy flow. This hypothesis has been the focus of animal studies in the Jornada Basin for nearly 30 years. Studies of animals as regulators of ecosystem processes led to the expansion of this hypothesis to include the effects of animals on ecosystem properties. Expanding the spatial scale of studies from the patch to the watershed and landscape engendered hypotheses that animals have an effect on processes at those scales because of animal activities that affect redistribution of soil and organic matter.