Are There Bullfrogs in Colorado?
Bullfrogs are found in Colorado but only in limited areas at lower elevations, particularly along the Front Range and eastern plains. These frogs were introduced through human activity and now persist in scattered water bodies. Most of Colorado's high elevations and mountains lack bullfrogs due to cold conditions.
By Tim, founder of Easy Street Markets. I maintain the wildlife database and verify every animal and source myself. Updated August 6, 2026.
Bullfrogs are found in Colorado but only in limited areas at lower elevations, particularly along the Front Range and eastern plains. These frogs were introduced through human activity and now persist in scattered water bodies. Most of Colorado's high elevations and mountains lack bullfrogs due to cold conditions.
Where Bullfrogs Are Found in Colorado
Bullfrogs in Colorado are restricted to specific lower-elevation locations, primarily along the Front Range and eastern plains. The South Platte River basin, particularly in the Denver metropolitan area and surrounding lower elevations, supports scattered bullfrog populations. Certain reservoirs and ponds in the Denver metro region host bullfrogs. The Arkansas River drainage in southern Colorado contains bullfrogs in the lower elevations near Pueblo and downstream. The Rio Grande Valley in southern Colorado may support isolated bullfrogs in warmest sections. Eastern plains water bodies including reservoirs and retention ponds host some bullfrogs, particularly in Colorado's warmest eastern counties. Bullfrogs are largely absent from Colorado's mountain regions above 7,000 feet elevation. The North Platte River system in northern Colorado contains few established bullfrog populations. Cold-water reservoirs and high-elevation lakes throughout the Colorado mountains lack bullfrogs entirely. Bullfrogs concentrate in the warmest, lowest elevation water bodies with the longest ice-free seasons. Seethe Bullfrog guide for Coloradofor more.
Season and Timing in Colorado
Bullfrogs in Colorado have a compressed breeding season due to the state's short summer and cool temperatures. Males begin calling in late May or early June when water temperatures finally exceed 60 degrees Fahrenheit. The primary calling and breeding activity occurs from June through July, with peak intensity in early to mid-July. Calling activity may extend into early August in the warmest Colorado locations. Tadpole development occurs at slower rates than in warmer states, with many Colorado tadpoles requiring extended development periods. Some tadpoles fail to complete metamorphosis before fall temperatures arrive, entering dormancy and overwintering in the tadpole stage. Activity gradually declines in August and September as water temperatures cool. By October, bullfrogs have largely ceased calling activity and shifted toward hibernation locations. Most Colorado bullfrogs enter torpor by November. Winter months find bullfrogs dormant in deep water or buried in bottom substrates. Spring warming in April and May triggers emergence from hibernation. Seethe Colorado wildlife guidefor more.
How to Identify a Bullfrog
Bullfrogs are North America's largest frog species and notably larger than any native Colorado frog. Adult bullfrogs measure four to six inches in length, with some individuals exceeding eight inches. Their useful bodies are colored in shades of olive green, brown, or yellowish green, with darker mottling and patterns on the dorsal surface. The head is disproportionately large and broad, with prominent circular tympanums visible as distinct ear discs behind each eye. Male bullfrogs display brighter yellow or golden coloration on the throat and undersides compared to females. A distinctive fold of skin extends backward from the eye region along the tympanum. The skin is smooth and moist, markedly different from the bumpy or warty texture of Colorado's true toads. The legs are powerfully built for jumping, with hind limbs extending well beyond the body when fully extended. The call is unmistakable: a deep, loud, resonant sound like "jug-o-rum" or "bottlejug," distinctly deeper than any native Colorado frog. No Colorado native frog approaches the bullfrog's size. Seethe national wildlife hubfor more.
Where Colorado Bullfrogs Concentrate
Bullfrogs in Colorado concentrate in warm-water habitats with sufficient vegetation and protection. Ornamental ponds and water features in Denver metropolitan area neighborhoods frequently host bullfrogs. Slow-moving sections of rivers where water temperatures remain warm and vegetation is abundant support bullfrogs. Shallow margins of reservoirs and impoundments in lower elevations provide bullfrog habitat. Farm ponds and retention basins with established vegetation in the eastern plains and metro areas host populations. Sheltered bays and backwater areas in reservoirs offer ideal bullfrog concentration areas. Water bodies with emergent vegetation like cattails and bulrushes attract and support bullfrog populations. Beaver ponds and associated wetlands in lower elevation regions support scattered bullfrogs. Bullfrogs avoid cold, fast-moving water and deep lakes lacking vegetation. They gravitate toward vegetated edges where submerged plants, logs, and undercut banks provide cover and hunting ambush positions. Bullfrogs in Colorado concentrate in the warmest, most protected water bodies with the longest frost-free seasons. Seethe Bullfrog guide for Coloradofor more.
Typical Bullfrog Behavior
Colorado bullfrogs are ambush predators spending most of their time concealed near the water's edge. They feed on insects, spiders, crawfish, smaller frogs, and occasionally small snakes and mammals. Bullfrogs in Colorado hunt native species including leopard frogs and other native frog species. Adults hunt primarily at night using excellent vision to detect prey in dim light. Males are territorial during the abbreviated Colorado breeding season, defending specific water areas through aggressive displays and calls. The calling serves to attract females and warn competing males away from territory. Bullfrogs can jump six feet or more horizontally when pursuing prey or escaping threats. They spend most of their adult lives in or immediately adjacent to water but can travel considerable distances overland during wet conditions. Tadpoles are herbivorous, feeding on algae and aquatic plant material. The extended tadpole stage in Colorado's cool waters means many tadpoles do not complete development until the following year. Seethe Colorado wildlife guidefor more.
Coexistence and Safety Notes
Bullfrogs in Colorado are considered invasive species by the Colorado Parks and Wildlife Department. They compete with and prey on native Colorado frogs, including the state's native leopard frogs and other endemic species. Bullfrog tadpoles consume vegetation that native amphibian species depend on for food and shelter. In Colorado's unique alpine and montane ecosystems, native frogs are adapted to specific thermal conditions that bullfrogs have disrupted in lower elevation areas. Bullfrogs present no direct threat to humans and do not bite or cause injury. Handling wild bullfrogs is permissible, though contact with frog skin may transmit pathogens. Bullfrogs are legal to harvest in Colorado during specified seasons under state hunting regulations. Capturing bullfrogs for food or sport is permitted in most of Colorado's warmer regions. Relocating captured bullfrogs is discouraged, as it may establish populations in new water bodies. Never releasing bullfrogs or other amphibians from captivity is essential for protecting Colorado's native species. Reporting bullfrog sightings helps wildlife managers track invasive population distributions.
Confusions and Similar Species
Several Colorado frog species might be confused with bullfrogs. The northern leopard frog, Colorado's most widespread native frog, is significantly smaller than any bullfrog. The chorus frog and spring peeper species are tiny compared to bullfrogs. The boreal chorus frog in northern Colorado is much smaller. The canyon tree frog in southwestern Colorado is smaller and arboreal. Colorado's native toads, including the Great Plains toad and Woodhouse's toad, might be confused with bullfrogs by unfamiliar observers, but toads display bumpy, warty skin distinctly different from smooth bullfrog skin. The spadefoot toads of Colorado are smaller and primarily terrestrial except during breeding. Any frog definitively identified as a bullfrog in Colorado represents an invasive individual or escaped pet rather than a native species. Size difference makes mature bullfrogs unmistakable compared to any native Colorado amphibian. Awareness of bullfrogs helps protect Colorado's unique native amphibian communities.
Frequently Asked Questions
Why are bullfrogs rare in Colorado? Colorado's cold winters and high elevations make most of the state unsuitable for bullfrogs. They require warm water for breeding and cannot survive freezing conditions that most Colorado water bodies experience. Are bullfrogs native to Colorado? No, bullfrogs are native to eastern North America and were introduced to Colorado through human release of captive animals. They are considered invasive in the state. Where can I find bullfrogs in Colorado? Bullfrogs in Colorado are restricted to lower-elevation areas, particularly in the Denver metro region and along lower sections of river valleys. Most of Colorado's mountains and high elevations lack bullfrogs entirely. Are bullfrogs a problem for Colorado? Yes, bullfrogs compete with and prey on native Colorado frog species. They represent a conservation concern in specific lower-elevation water bodies. Can I eat bullfrogs in Colorado? Yes, bullfrogs are legal to harvest in Colorado during specified seasons under state hunting and fishing regulations. Harvesting may help control invasive populations.
More places to see bullfrog
More wildlife in Colorado