- Pseudotsuga taxifolia—douglas fir
- Pinus Ponderosa—Ponderosa pine
- Mahonia Berberis aquifoliam—Oregon grape
- Arctosaphylos uva-ursi—kinnikinick
- Rubus occidentalis—blackberry
- Rubus stigosus—raspberry
- Populus tremuloides—quaking aspen
These distinctive plants have invaded from the prairie fringe:
- Stipa cometa—needle grass
- Agropyron smithii—wheat grain
- Boutelorea grasilis—grama grass
- Boutelorea curtipendula—grama grass
- Poa fendleriana—bluegrass
- Sphaeralcea ceccinea—globe mallow
- Helianthus petiolaris—sunflower
- Chrysopsis rillosa—golden aster
- Muhlenbergia montana—muhly
- Yucca glauca—yucca
- understory of sedges and broad-leaf herbs
The nature of the faunal belt characteristic of the Transition Zone is varied. Both boreal and austral mammals are represented. Only six species appear restricted to it, two squirrels of the Sciurus aberti group, three pocket gophers of genus Thomomys and a small brown bat. The following mammals are not restricted to the Transition Zone but are characteristic of it in the eastern foothills:
- Eutamias quadrivitratus—Say chipmunk
- Peromyscus nastus—Estes Park cliffmouse
- Neotoma fallax—Gale wood rat
- Lepus campestris—White-tailed jack rabbit
- Sylvilagus nuttalli pinetis—Rocky Mountain cottontail
- Canis lestis—Mountain coyote
- Lynx uinta—Mountain wildcat
- Mephitis hudsonica—Northern plains skunk
Mammals common to the Transition and Upper Sonoran Zones include:
- Antilocapra americana—Antelope
- Odocoileus virginianus—Macrourus white-tailed deer
- Onychomys brevicaudus—Grasshopper mouse
- Castor canadensis frondator—broad-tailed beaver
- Canis Occidentalis—Grey wolf
- Spilogale tenuis—Rocky Mountain spotted skunk
- Eptesicus fuscus—Brown bat
The following are common to the Transition and Canadian (mountain) Zones:
- Cervus canadensis—Elk
- Callospermophilus lateralis—Say ground squirrel
- Eutamias amvenus operarius—Colorado chipmunk
- Erethiron epixanthum—Yellow haired porcupine
- Eutamias mihumus consobrinus—Least chipmunk
- Microtus nanas—dwarf field mouse
- Microtus pennsylvanicus—Saguache meadow mouse
- Zapus princeps—Rocky Mountain jumping mouse
- Vulpus macrourus—Western fox
- Ursus americanus—Black bear
Common to the Transition, Canadian and Upper Sonoran Zones are: