A number of once common native plant and animal species on the Colorado Plateau have become increasingly rare, and some, particularly native freshwater fishes, have become extinct. Habitat destruction, degradation, and fragmentation, sometimes in combination with hunting and poisoning, has led to significant decreases in the overall populations of a number of species. The federal government has classified a few of these as endangered, meaning that the species is in danger of extinction throughout all or a significant portion of its range. Others, classified as threatened, may reach endangered status if habitats continue to be degraded and populations continue to fall.
For a complete list of threatened and endangered (T&E) species for Utah, Colorado, Arizona, and New Mexico click here. For a history of the California condor on the Colorado Plateau, click here. Below are brief descriptions and status of three T&E species on the Colorado Plateau.
Mexican Spotted Owl
Falling populations of the Mexican spotted owl (Strix occidentalis lucida) have been linked to the destruction of much of its preferred habitat. The owl uses late seral ("old-growth") forests and rocky canyonlands for nesting, roosting, and hunting prey (mostly small mammals). Harvest of old-growth timber stands, even-aged timber harvest systems, and catastrophic crown fires have contributed to loss of habitat.
The range of the Mexican spotted owl extends to western Texas and into the mountains of northern and central Mexico. On the Colorado Plateau most of the birds occur in steep canyons ranging from central Utah and southwestern Colorado south into New Mexico and Arizona. The US Fish and Wildlife Service estimates the total U.S. population at approximately 2,700 owls.
In March 1993, the United States Fish and Wildlife Service (USFWS) listed the "Mexican spotted owl" as a threatened subspecies (there are three subspecies in North America: the Mexican, California, and Northern Spotted Owls). In 1995, the USFWS published the "Recovery Plan for Mexican Spotted Owls", which provides a long term plan to monitor the owl's progress, preserve its habitat, and ultimately, de-list the owl from the Endangered Species List. Critical habitat designation of 13 million acres across Arizona, Utah, New Mexico and Colorado was proposed in 2000.
Dr. David Willey, who has studied Mexican spotted owls in the steep canyonlands of southern Utah, found that the rocky canyon habitat provided numerous rock cavities and ledges for roost and nest sites, and provided thermal and escape cover for both the adults and young. Willey found that during winter, when ambient temperatures decrease, spotted owls were observed roosting in more open habitats, and several moved up-slope into forested highlands. This suggests that the need for thermal cover could partially explain the strong association between spotted owls and steep canyon habitat, and that these areas should be conserved while the owl is listed as threatened.
Native to a small region of the southern Colorado Plateau in Arizona, Apache Trout are found only in lakes and streams of the White Mountains. The Apache trout formerly was found in the White and Black Rivers of the White Mountains, the headwaters of the Little Colorado River, and KP Creek, a tributary of the Blue River in the San Francisco River drainage. In all the fish inhabited approximately 600 river-miles. Presently, the Apache trout occupies fewer than 30 miles of small headwater streams and impoundments on the Fort Apache Indian Reservation and the Apache-Sitgreaves National Forest. The Apache trout was listed as endangered in 1969 under the precursor to the Endangered Species Act and then down-listed to threatened in 1974. The Apache trout is one of only two trout native to Arizona. This yellowish-gold fish can grow to be from 6 to 24 inches in length and weigh from 6 ounces to almost 6 pounds. They feed on aquatic and terrestrial insects.
The Apache trout is currently listed by the federal government as a threatened species as its population has dwindled. Its habitat, montane riparian areas, have been highly degraded in many areas of its range due to intensive grazing of livestock and timber-cutting operations. The Arizona Game and Fish Department is increasing its efforts in stocking Apache trout in upland streams, but without habitat restoration efforts the population will likely remain precarious.
Southwestern Willow Flycatcher
The Southwestern Willow Flycatcher (Empidonax traillii extimus) has declined during the last 100 years, primarily due to the loss, fragmentation, and modification of riparian habitats. Based on recent surveys coordinated by various state and federal agencies, fewer than 500 breeding pairs of the Southwestern Willow Flycatcher remain throughout its range. Surveys have also shown that the breeding sites are widely scattered and isolated, and most sites include fewer than five breeding pairs.
The breeding range includes southern California (from the Santa Ynez River south), Arizona, New Mexico, extreme southern portions of Nevada and Utah, extreme southwest Colorado, and western Texas. Another subspecies which is not endangered, E.t. adastus, breeds from Colorado west of the plains, to the west through the intermountain/Great Basin states, and into the eastern portions of California, Washington, and Oregon. On the Colorado Plateau, e.t. extimus has been detected in very small numbers along the San Juan River in southern Utah, and one or two pairs may nest along the Colorado River in Grand Canyon. They were common further upstream in Glen Canyon before the canyon was flooded to become Lake Powell after the completion of Glen Canyon Dam in 1963.
In 1993, the U.S. Fish and Wildlife Service formally proposed to list the flycatcher as a federal endangered species, and to designate critical habitat. In a 1995 ruling, the Service found that the flycatcher population was currently very low and faced a significant threat of extinction unless protected.
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