Behavioral and environmental factors in the spatial distribution and population dynamics of a yellow—bellied marmot (Marmota flaviventris) population were studied in 1971 and 1972 in Gunnison Co., Colorado. Yellow—bellied marmots are generally considered to be colonial; however, this is not their on

It is concluded that either temporal differences or size differences of copepodids and adults would allow coexistence and that extreme size differences are probably unimportant compared to morphological differences of feeding appendages and perhaps behavioral differences.

Twelve 42—liter plankton cages were used in an alpine Colorado pond to test a size—efficiency hypothesis: to determine why small herbivorous zooplankton species tend not to coexist with large species. The size—efficiency hypothesis, that large species exclude the smaller ones through competition for

The distributions of pocket gopher species in Colorado are contiguously allopatric. The pattern has been attributed to competitive exclusion, perhaps due to aggression toward the broad—niche species by more narrow—niche species. This study tested for differences in aggressiveness between the narrow—

Five populations of marmots were studied in Colorado from 1962 through 1972. Males are classified by age as yearlings, two‐year olds, and adults. Socially, marmots are colonial, peripheral, or transient. Each population was divided into four age‐sex classes, male yearlings, female yearlings, male ad