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Understanding the relationships between animal population demography and the abiotic and biotic elements of the environments in which they live is a central objective in population ecology. For example, correlations between weather variables and the probability of survival in populations of temperate zone amphibians may be broadly applicable to several species if such correlations can be validated for multiple situations. This study focuses on the probability of survival and evaluates hypotheses based on six weather variables in three populations of Boreal Toads (Bufo boreas) from central Colorado over eight years. In addition to suggesting a relationship between some weather variables and survival probability in...
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The Society for the Study of Amphibians and Reptiles
ABSTRACT.-We studied egg production in two Californian populations of desert tortoises, (Gopherus agassizii) in 1992 and 1993. One population inhabited the Desert Tortoise Research Natural Area (DTNA) in the western Mojave Desert, where most of the rain falls in the winter. The second population lived near Goffs, in the eastern Mojave, where annual precipitation is divided more evenly between winter and summer. Due to El Niio conditions, heavy winter rains fell at both sites in both years (1991-1992 and 1992- 1993). Consequently, the biomass of spring annuals and annual egg production by tortoises were high in both years at both sites. There were no differences in reproductive output between years so we pooled data...
Stomach content analyses of 28 Leptotyphlops humilis humilis and 17 L. dulcis dulcis indicate that these snakes feed extensively on ants and termites which compromise 54-64 per cent of the total diet. L. d. dulcis appears to be more fossorial in its feeding activity than L. h. humilis which preys on a greater percentage of surface-dwelling arthropods. Presumably, this serves to reduce competition for the available food supply in geographical areas of sympatry. Both species show a definite preference for soft-bodied prey-types. In addition, several insect species which live as commensals in ant and termite nests are readily consumed along with their hosts. Published in Journal of Herpetology, volume 8, issue 2, on...
Activity patterns of nocturnal lizards are less well studied than those of diurnal species. Many diurnal species show a bimodal activity distribution in hot weather and a unimodal distribution in cooler weather (e.g., Tinkle, 1967; Pianka, 1973; Huey et al., 1977). Twelve species of nocturnal Australian geckos studied by Pianka and Pianka (1976) were active primarily during the first 3 h following sunset showing a unimodal pattern. Pianka and Pianka (1976) do point out however that their data may be biased due to a heavier sampling effort earlier in the evening. The eublepharine lizard Coleonyx variegatus of the western United States has long been known as a nocturnal species infrequently found to be diurnally active...
At 1000 on 26 April 1973 I found a male Bufo boreas (79 mm, 52 g) in amplexus with a female Rana aurora (96 mm, 102 g) at a beaver pond near Beaver Creek 5 mi E of Bellingham,Whatcom County, Washington (elevation, 120 m). The amplexing pair was in a group of several dozen males of B. boreas. After capturing the pair I noticed that the female had portions of the abdominal viscera protruding from an opening in the right lateral body wall (Fig. 1). Amplexus by the male toad was in the normal pectoral region, and except for the tear in the body wall there were no other signs of damage to the female frog. The duration of amplexus in this mismatched pair is not known. The normal breeding period of R. aurora at this pond...
ABSTRACT.-Wine vestigated the ability of Coleonyx variegatust o detect and identify integumentaryderived chemicals of a snake predator by using tail display, a predator-specific, behavioral bioassay of predator identification in geckos. We presented five stimulus conditions to geckos, including skin chemicals from a saurophagous snake (Phyllorhynchus decurtatus) and a nonsaurophagous snake (Chionactis occipitalis), and scored six responses, including attack, tail display, and flight. Skin chemicals from P. decurtatus elicited defensive attacks in 13% of the trials. Tail display occurred in 79% of the trials with skin chemicals from P. decurtatus, and only in response to these chemicals. Thirty-seven percent of the...
Ontogenetic diet shifts have been documented in many anurans (Smith and Bragg, 1949; Oplinger, 1967; Labanick, 1976; Christian, 1982; Donnelly, 1991; Lima and Moreira, 1993). These studies compared the diets of juveniles as a whole to those of adults (e.g., Livezey, 1961; Clarke, 1974a; Gittins, 1987). Diet patterns among juvenile size classes, however, have yet to be investigated. Bufonids exhibit high postmetamorphic growth rates early in ontogeny, as do other anurans (Clarke, 1974b). These differences in body size may be a means of avoiding overlap in resource use (Schoener, 1974; Toft, 1985). Hence, diet shifts associated with rapid growth during this relatively short period may be important for survival to...
ABSTRACT.- Hybridization between the Southwestern toad, B. microscaphus, and Woodhouse's toad, B. woodhousei, was investigated in central Arizona. Allopatric populations of these two taxa differed significantly in their morphology. Five regions of sympatry were identified, and morphological intermediates (hybrids) were present at three of these sites. Based on morphology and male advertisement calls, back-crossing may have occurred in at least one of the hybrid zones. Aquatic habitats have been altered by man in all zones of sympatry and B. woodhousei may have only recently arrived in these regions. It is suggested that Moore's (1977) 'ephemeral-zone' hypothesis may account for hybridization between these distinct...
ABSTRACT.-Survivaolf adult Desert Tortoises (Gopherusa gassizii) appears related to site-specific variation in precipitation and productivity of annual plants. We studied adult tortoise survival rates at two closely situated, but physiographically different, sites in the eastern Mojave Desert over a nine-year period (spring 1992 to spring 2001). Survival rates were initially derived from population surveys conducted over a threeyear period and by radio-telemetry monitoring over a seven-year period beginning in 1994. After a period of initial stability, survival rates on the two sites diverged over the study period, and seven-year survival rates estimated from radio-telemetry monitoring were 0.900 and 0.269, respectively....
ABSTRACT—Acquiring water is a challenge for desert animals, and organisms inhabiting arid regions have evolved morphological, physiological, and behavioral traits to maintain an appropriate water balance. On four occasions, I observed rain-harvesting or observed behaviors suggestive of rain harvesting in a population of speckled rattlesnakes (Crotalus mitchellii) in the Mojave Desert of southwestern North America. Snakes collected rainwater on the surface of their bodies and subsequently drank it. Speckled rattlesnakes also drank rainwater that accumulated in structural features of their habitat (e.g., surface of rocks). My observations suggest that C. mitchellii may engage in rain-harvesting when thermal conditions...
Early age classes of the Desert Tortoise (Gopherus agassizii) are particularly vulnerable to predation by several mammal and bird species. We studied tortoise survival at the Sand Hill Training Area of the Marine Corps Air Ground Combat Center, Twentynine Palms, California, from 1998 to 1999. We radiographed and thread-spooled 25 females to determine reproductive and nesting ecology. Predators consumed 11 of 42 monitored nests during the first 70 days of incubation. Ninety-one of 132 eggs in nests fenced after 70 days developed into healthy neonates. We recorded 0.84 and 0.91 neonate survival probability during dispersal in 1998 and 1999, respectively. Applying neonatal survival to egg success, we predict that 40%...
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