JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. INTRODUCTION In this paper we present an analysis of the demography of the lizard Uta stansburiana in southern Nevada, based primarily on observations between 1966 and 1968. The work is part of a larger long-range study of the effects of low but continuous levels of gamma radiation on natural populations of plants and animals (e.g. see French 1964; French, Maza & Aschwanden 1966, 1967; Turner, Hoddenbach & Lannom 1965; Turner et al. 1967; Turner & Lannom 1968; Turner et al. 1969a, b). Our paper is a descriptive review of time changes in the abundance of Uta over a 21-year period, with suggestions as to the immediate causes of these changes. We also review five previous studies of lizard populations and discuss specific problems associated with such research. METHODS The field work was carried out between 15 February 1966 and 15 July 1968-in Rock Valley, Nye County, Nevada, in the south-western portion of the U.S. Atomic Energy Commission's Nevada Test Site. In Rock Valley there are four 20-ac (8.1 ha) areas, one of which is exposed to gamma radiations from a centrally located '37Cs source for about 300 days a year. The irradiated area and two of the three control areas are fenced. A more detailed description is given by French (1964). Most of the work was done in plots 1-4, one within each of the 20-ac areas. In an earlier paper we compared the age distribution and sex ratio of the irradiated population with corresponding attributes of the three control populations (Turner et al. 1969b). We also reported on density changes in these populations between 1966 and 1968. Although the densities of these populations differed, their composition and patterns of annual change were essentially identical. Hence, data from all four areas have been combined in the present study. In 1966 our sampling extended over four 2i0 ha quadrants. In 1967 and 1968 sampling was restricted to four 1*44 ha areas. Other observations were made in plot 5 (1.13 ha), about 1 mile (1 6 km) north-east of the experimental area. Female lizards were collected from various places with Rock Valley during the spring of 1966, 1967 and 1968, and seasonal changes in clutch size were inferred from counts of follicles, eggs and corpora lutea (see Hoddenbach & Turner 1968). Density of Uta Absolute densities of Uta in plots 1-4 were determined each spring by attempting to count completely all resident individuals. Each plot was worked by two or three people * Present address: P.O. Box 236, Zion National Park, Springdale, Utah 84767, U.S.A. 506 Demography of the lizard Uta stansburiana during 1 week of eac...

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Ovarian cycles and individual reproductive potentials of Cnemidophorus tigris in Colorado and Texaswere studied by counts and measurements of yolked ovarian follicles, corpora lutea, and oviducal eggs. Colorado lizards lay one clutch averaging 3.4 eggs annually between May and August; Texas lizards average two clutches, each averaging 2.2 eggs, between April and mid-August.Geographic variation in reproductive activity has been recognized, mainly by inference, in North American lizards of several families. In species with extensive latitudinal ranges, several clutches of eggs may be produced annually in the southern part of the range; only a single clutch in the northern part (1). There is also evidence that the average number of eggs in each clutch is greater in the northern part of the range of a species (2). The relation of these two variables in a single species has not been established, nor has the importance of this variation in the adaptation of populations of a species been generally recognized. Our studies reveal significant geographic variation both in number of clutches per season and in average number of eggs per clutch within the range of Cnemidophorus tigris (3). Cnemidophorus tigris ranges from southeastern Oregon well into northern Mexico, occurring in all the major deserts of North America. One of us (C.J.M.) studied populations of C. t. septentrionalis in Colorado National Monument, Mesa County, Colorado (4); the other (G.A.H.) studied C. t. marmoratus near Kermit, Winkler County, Texas (5). These study areas are about 950 km apart, near the northeastern and southeastern limits of the range of the species. Each of us took weekly samples of female lizards through two complete activity seasons (1962-63in Colorado; 1963-64 in Texas) and determined ovarian cycles, clutch size, and reproductive potential from counts and measurements of yolkfilled ovarian follicles (Fig. 1), oviducal eggs, and corpora lutea (178 in Colorado; 257 in Texas ) in reproductive lizards.In Colorado, C. tigris leaves hibernation around 1 May, and mature females are active for 75 to 90 days each sum- 30 DECEMBER 1966 mer. Enlarged ovarian follicles (3 to 4 mm in diameter) are visible at emergence; 20 to 25 days later the enlarged follicles begin vitellogenesis and are ready for ovulation within 20 days, when 11.5 to 12.0 mm in diameter. After fertilization and shell deposition the oviducal eggs are laid-all within 2 weeks of ovulation. The median date of egg-laying in 1962 was 21 June. The corpora lutea disappear immediately after ovoposition, and the ovaries remain inactive (all follicles less than 2 mm in diameter) for the remainder of the season.In Texas, the season of major activity starts in early April, although a few individuals may be active in February and March. Mature females become fully active before the end of April, remaining so until mid-August. Newly emerged females have enlarged ovarian follicles which start yolk deposition immediately and reach ovulatory (maximum average) size by 21 May. After ovulation, a...

We conducted a pilot study to evaluate the efficacy of rodent proofing continuously occupied homes as a method for lowering the risk for hantavirus pulmonary syndrome (HPS) among residents of a Native American community in northwestern New Mexico. Rodent proofing of dwellings was paired with culturally appropriate health education. Seventy homes were randomly assigned to treatment or control categories. Treatment homes were rodent-proofed by sealing openings around foundations, doors, roofs, and pipes and repairing screens and windows. Repairs to each dwelling were limited to $500 US. After repairs were completed, 15-20 snap traps were placed in each treatment and control home and checked approximately every 2 days for an average of 3-4 weeks. During 23,373 trap nights, one house mouse (Mus musculus) was captured in one treatment home, and 20 mice (16 deer mice, Peromyscus maniculatus, two Pinyon mice, Peromyscus truei, and two unidentified mice) were captured in five control homes (one house had 14 captures, two had two captures, and two had one capture). Trap success was 0.01% in treatment homes and 0.15% in controls. Intensity of infestation (mean number of mice captured per infested home) was 1 in treatment homes and 4 in controls. Observations of evidence of infestation (feces, nesting material, gnaw marks, or reports of infestation by occupant) per 100 days of observation were 1.2 in treatment homes and 3.1 in controls. Statistical power of the experiment was limited because it coincided with a period of low rodent abundance (August-November 2000). Nevertheless, these results suggest that inexpensive rodent proofing of occupied rural homes can decrease the frequency and intensity of rodent intrusion, thereby reducing the risk of HPS among rural residents in the southwestern United States.