<p>The ecological roles, or niches, filled by the nearly 5000 mammal species are quite diverse. There are predators and prey, carnivores, omnivores, and herbivores, species that create or greatly modify their habitat and thus the habitat and structure of their communities [e.g., <span class="taxon">Castoridae</span> damming streams, large populations of ungulates (<span class="taxon">Artiodactyla</span> and <span class="taxon">Perissodactyla</span>) grazing in grasslands, <span class="taxon">Talpidae</span> digging in the earth]. In part because of their high metabolic rates, mammals often play an ecological role that is disproportionately large compared to their numerical abundance. Thus, many mammals may be keystone predators in their communities or play important roles in seed dispersal or pollination. The ecosystem roles that mammals play are so diverse that it is difficult to generalize across the group. Despite their low species diversity, compared to other animal groups, mammals have a substantial impact on global biodiversity.<span> (Reichholf, 1990a; Vaughan, Ryan, and Czaplewski, 2000)</span></p>  <p><strong>Ecosystem Impact: </strong>Disperses seeds; Pollinates; Creates habitat; Biodegradation; Soil aeration; Keystone species</p>