Geography Reference
In-Depth Information
forest musk oxen (
Symbos cavifrons
); elegant Conclin's mountain pronghorn (
Tetra-
meryx conklingi
); large, stocky mountain deer (
Navahoceros fricki
); herds of fleet-
footed guanacos (
Hemiauchenia macrocephala
) and large camels (
Camelops
hesternus
); at least two species of native horses (
Equus occidentalis, E. conversidens,
and a large horse); as well as assorted large predators, such as the huge short-faced
bear (
Arctodus simus
); true lions (
Panthera leo atrox
) larger than the African variety;
big American cheetahs (
Miracinonyx trumani
); and dire-wolves (
Canis diurus
) as tall as,
but more massive than, today's gray wolves (
Canis lupus
). Missing from the assemblage
would be elk (
Cervus canadensis
), moose (
Alces alces
), grizzly bear (
Ursus arctos
), and
gray wolf, as these are post-Pleistocene Siberian immigrants that entered North Amer-
ica along with humans, following the massive collapse of the native megafauna (Ripple
and Valkenburgh 2010) that so impoverished North America's species diversity. In ad-
dition to the later Pleistocene extinction of large mammals, there was also a major ex-
tinction of birds (Steadman and Martin 1984; Tyrberg 1998). These included not only
several species of large vulture-like scavengers, but a broad spectrum of birds.
FIGURE 8.1
Schematic representation of the trophic web established among warm-blooded mammals
living for at least part of the year (summer) above timberline in the Beartooth Mountains,
Montana. (From Hoffman 1974: 515.)
For millions of years, the megafauna had conditioned the composition and structure
of the vegetation and molded the land surfaces to create unique habitats and shape the
evolution of many mammalian and avian species. Large mammals diversify the land-
scape on a micro scale, with traditional dung deposits, deep cutting trails, bedding
areas, sand-bathing, and feeding sites. These features can redirect and capture water,
cause colonizing plants to sprout, open up closed forests into highly productive savan-
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