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Effects of Radiation on a Fenced Population of Horned Lizards (Phrynosoma platyrhinos) in Southern Nevada
Philip A. Medica, Frederick B. Turner and Donald D. Smith
Journal of Herpetology
Vol. 7, No. 2 (May 7, 1973), pp. 79-85
Published by: Society for the Study of Amphibians and Reptiles
Stable URL: http://www.jstor.org/stable/1563204
Page Count: 7
You can always find the topics here!Topics: Lizards, Horned lizards, Female animals, Species, Eggs, Age, Life span, Animals, Population ecology, Demography
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Between 1964 and 1966 minimum spring densities of horned lizards ranged from 1.0-2.5/hectare (ha) in 3 8 ha enclosures in Rock Valley, Nevada. Minimal survival of hatchling horned lizards to the age of 8 months was about 26-38 per cent. Annual minimal survival of older lizards was 50-60 per cent. Female horned lizards usually laid one clutch of eggs per year, but multiple clutches were observed in 1969. Conversely, no reproduction was observed in 1970. The maximum life span of horned lizards is at least 94 months. One of the enclosures was subjected to continuous gamma irradiation from a centrally located source of 137Cs. Between 1964 and 1966 numbers of horned lizards declined in all 3 plots. Between 1967 and 1970 numbers of horned lizards increased in the two control areas, but continued to decline in the irradiated plot. Female sterility owing to regression of ovaries is judged to be the cause of the population decline. Similar radiation effects have previously been observed among leopard lizards (Crotaphytus wislizenii), whiptail lizards (Cnemidophorus tigris), and side-blotched lizards (Uta stansburiana).
Journal of Herpetology © 1973 Society for the Study of Amphibians and Reptiles