Browsers and Grazers Drive the Dynamics of Ecosystems

Abstract

Large mammalian herbivores and the ecosystems in which they live are intimately connected through the food choices the animals make. Herbivores eat plants and plants have evolved mechanisms to defend themselves from being eaten. This arms race between plants and vertebrate herbivores continues to this day. The outcomes of this arms race are seen in the morphological, physiological and behavioural adaptations of large mammalian herbivores. The ways in which herbivores exploit plants affect not only plants, and the assemblages in which they exist but also the “dynamics” of whole ecosystems. The paleoecological work demonstrates that the consequences of large herbivore community and population dynamics at some point in history ripples through time and can be seen in the dynamics of ecosystems today. The Quaternary extinctions of many species of large mammalian herbivores changed systems as fire became the major consumer of vegetation in the absence of ungulates. Fundamental to the understanding of the role of herbivores in ecosystem dynamics is the concept of “niche”, however, “browsing” and “grazing” species of large mammalian herbivore are extremely flexible in their diet composition depending on the circumstances in which they find themselves. Whilst body size has also been used as an explanatory variable in understanding large mammalian herbivore ecology (including feeding and vital rates in population studies), there are many “exceptions to the rule”, which, as with the browser vs. grazer dichotomy, deserves further investigation and potentially also changes in ecological theory. There are rich seams of information and data from historical studies and literature that should be made freely available for such analyses, much more often than is presently the norm. Whilst ungulate ecologists should look to the literature on livestock for insights into, particularly digestive physiology and the increasing understanding of the important of the fermentation microbiome, studies on the various species of wild large mammalian herbivore (including those that are not foregut or hindgut fermenters) are needed to provide insights into dietary adaptations. So, what of the future? Climate change looms large in the picture for large mammalian herbivores; they may have flexibility in order to cope with variation but movement, to take advantage of nutritional opportunities, is key, and populations in, for example, semi-arid areas are increasingly unable to exploit spatial variation because of the massive impact of humans on land use. Let us not forget that currently about 37% of the total land area of the globe is agricultural land and 60% of this is grazing land for livestock. These proportions will only increase as the world’s human population grows in size and wealth. The foregoing Chapters in the Ecology of Browsing and Grazing II provide a wealth of information on the past and current ecology of large mammalian herbivores, but the book is also a call for future generations of researchers to seek to better understand the whats, whys and the wherefores of the interactions between herbivores and the ecosystems in which they live. Given the vital importance of mammalian herbivores to those ecosystems, and also the role they play in providing ecosystem services to humanity, researchers must seek partnership with policy and management practitioners in delivering evidence-based solutions for the future management and conservation of these amazing creatures, in a world that is changing before our eyes. But researchers should not forget that these ungulates are made of flesh and blood, that they graze and browse in real landscapes, and that there is a profound need for hard-core ungulate ecologists with a broad set of skills and deep understanding of ‘their’ animals. As a bonus, we, and all other ungulate ecologists, get to see, feel and understand some of the most beautiful creatures that share our planet.