Variation in Tortoise Life History: Demography of Gopherus berlandieri

Abstract

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Population ecology ofPsammobates oculiferin a semi-arid environment

“…The population of P. oculifer at Benfontein was skewed towards adults, which is similar to that recorded for many other testudinid populations (for example see Van Heezik et al 1994;Hellgren et al 2000;Lagarde et al 2001). A high predation rate of juveniles and a low probability of finding them were both considered plausible reasons for low juvenile catches of Stigmochelys pardalis and Chersina angulata in the Eastern Cape (Mason et al 2000).…”

“…The dearth of males in older cohorts may indicate that the smaller body size of males makes them more predation prone. In a population of Gopherus berlandieri, Hellgren et al (2000) found that females, which mature earlier and are smaller than males, predominate in younger cohorts with the bias switching to males in older generations. The authors gave differential predation rates as one of the possible causes of fewer females in older generations.…”

“…Differential growth rates and early maturity in one sex may have wider implications on the population's demography. It leads to sexual size dimorphism (Gibbons & Lovich 1990;Lefebvre et al 2011) and the smaller body size may influence mortality, which in turn can skew the sex ratio of a population (Hellgren et al 2000). Data on species' demography are integral to conservation assessments and hence management strategies, particularly in view of climate change (Heppell 1998;Scott et al 2012).…”

“…Body mass and SV were used to calculate body condition as a ratio of mass to shell volume (Loehr et al 2004) and as mass scaled to shell volume (Loehr et al 2007a). Because scute ring counts often provide a reliable estimate of age in chelonians (Germano 1994;Germano & Bury 1998;Hellgren et al 2000), we used a hand lens to count scute rings (annuli) on the dorsal and ventral sides of all individuals. We also took digital photographs of dorsal and ventral surfaces, which helped to verify annuli counts made in the field.…”

Ultrasonographic and radiographic determination of egg development of jurarás (Kinosternon scorpioides) in captivity

“…However, there have been few evidences for this characteristic in reptil species, according to Iverson (1979), Iverson et al (1991), Redrobe & Scudamore (2000) and Hellgren et al (2000).…”