328 



liiU'/'lor VVcsV — Our Liviiti^ Rcstntrces 



Table. Threatened and endangered species of the Colorado Plateau. An X indicates that a 

 species is listed as threatened or endangered by particular states or by the U.S. Department of the 

 Interior. 



Common name 



Scientific name 



Threatened or endangered status 



AZ 



CO 



NM 



UT 



Federal 



Amphibians 



Jemez Mountains salamander 



Western toad 



Chiricahua leopard frog 



Relicl leopard Irog 



Spotted frog 



Plelhodon neomexicanus 



Bulo boreas 



Rana chiricahuensis 



Rana onca 



Rana pretiosa 



Reptiles 

 Desert tortoise 

 Chuckwalla 

 Gila monster 

 Narrow-headed garter snake 



Gopherus agassizii 

 Sauromalus obesus 

 Heloderma suspecturn 

 Thamnophis rutipunctalus 



For further information: 



Charles Drost 



National Biological Service 



Colorado Plateau Research Station 



PO Box 5614 



Flagstaft, AZ 86011 



Future Needs 



In the arid Southwest, plant and animal com- 

 munities depend on the same scarce water 

 resources as human populations, agriculture, 

 and industry. Amphibians and some reptiles, 

 such as garter snakes, are directly dependent on 

 free-flowing water and aquatic habitats. 

 Amphibians are of further concern because of 

 recent, unexplained losses in many areas 

 (Barinaga 1990; Blaustein and Wake 1990). A 

 thorough understanding of the present status, 

 population trends, and requirements of native 

 species is essential to avoid or lessen conflicts 

 among competing natural resource demands. 



This ongoing project provides an assessment of 

 our current knowledge, baseline information on 

 distribution, and a starting point for intensive 

 studies of rare and declining species. The devel- 

 opment of an adequate inventory, coupled with 

 long-term population studies of particular 

 species of concern, forms the basis for informed 

 protection and management of local natural 

 communities. 



References 



Barinaga, M. 1990. Where have all the froggies gone? 



Science 247:1033-1034. 

 Blaustein, A. R., and D,B. Wake. 1990. Declining amphibian 



populations: a global phenomenon? Trends m Ecology 



and Evolution 3(71:203-204. 

 Carey, C. 1993. Hypothesis concerning the causes of the 



disappearance of boreal toads from the mountains of 



Colorado. Conservation Biology 7(2):3?5-361. 

 Hayes, M.P., and M.R. Jennings. 1986. Decline of ranid 



frog species in western North America: are bullfrogs 



{Rami catesheiaiui) responsible? Journal of Herpetology 



20(4):490-509 

 Miller, D.M., R.A. Young, T.W. Gatlm, and J. A. 



Richiirdson. 1982. Amphibians and reptiles of the Grand 



Canyon National Park. Monograph 4, Grand Canyon 



Natural History Association. 144 pp. 

 Stohlgren.T.J., and J.F. Quinn. 1992. An assessment of biot- 



ic inventories in western U.S. National Parks. Natural 



Areas Journal 12(31:145-154. 

 Woodbury, A.M., ed. 1959. Ecological studies of the flora 



and fauna in Glen Canyon. Anthropological Papers. 



University of Utah. 229 pp. 



Wintering 

 Bald Eagles 

 Along the 

 Colorado 

 River 

 Corridor 



by 



Charles van Riper III 



Mark K. Sogge 



National Biological Service 



Timothy T. Titbits 

 U.S. Fish and Wildlife Ser^'ice 



The construction and operation of reservoirs 

 have had a dramatic influence on wintering 

 and migrant bald eagles {Haliaeetus leuco- 

 cephalus: Southern 1963; Spencer 1976; 

 Steenhof 1978; Stalmaster 1987). In contrast to 

 reservoir-induced destruction of riverine habitat 

 upon which many wintering bald eagles have 

 traditionally relied, reservoirs may harbor, in 

 some instances, new or alternative food sources 

 (Spencer 1976; Jenkins 1992). In addition to 

 hunting the shorelines and surface waters of 

 reservoirs, eagles congregate below some dams 

 in winter to feed on fish that are killed or 

 stunned while passing through the turbines or to 

 hunt in ice-free water (Steenhof 1978). 



Commercial river guides on the Colorado 

 River first noted winter bald eagle concentra- 

 tions on the southern Colorado Plateau below 

 Glen Canyon Dam at Nankoweap Creek in the 

 early 1980's (Fig. 1). Before this, bald eagles 

 were considered uncommon along the Colorado 

 River in Grand Canyon National Park (Brown et 

 al. 1987). A preliminary study by Brown et al. 

 ( 1989) concluded that wintering bald eagles had 

 increased in numbers, particularly below Glen 

 Canyon Dam, because of a combination of reg- 

 ulated discharge of cold water from the dam and 

 the introduction of rainbow trout 

 {Oncorhynchiis mykiss). Although trout were 

 introduced bv the National Park Service into 



tributaries of the Colorado River in the 1920's, 

 it was not until after the dam was completed 

 (1963) that trout numbers increased in the 

 Colorado River. By 1988 the mouth of 

 Nankoweap Creek had become a concentration 



Fig. 1. The Colorado Plateau. 



