Variation in the daily activity, movement and refugia of Critically Endangered geometric tortoises, Psammobates geometricus, in autumn and spring

To help assess habitat requirements of Critically Endangered geometric tortoises, we used thread-trailing to measure daily activity, movements and refugia of adult Psammobates geometricus in autumn and spring 2002. We found strong differences between seasons, and effects of weather, individuals and sex. The high activity was consistent with mild weather during autumn and spring. However, daily temperatures limited female movements on cool autumn days and male movements on warm spring days, a pattern consistent with sexual size dimorphism (large females and small males). The long movements in autumn probably helped tortoises find food plants that grow quickly after autumn rains; both sexes recover body condition from autumn lows, and females begin egg production in late-autumn and winter. These movements may also help males mate with females before they ovulate. The high activity of females in spring should help them forage and sustain their vitellogenesis, egg production and nesting in spring. Male paths tended to be more linear than female paths in both seasons, so this sexual difference is likely not linked to food consumption. Males may move long, linear paths to engage females and avoid other males. Males may have been thermally-challenged in spring. Their movements decreased with increased ground temperatures (in the sun), they used denser refugia in spring than in autumn, and in spring used denser refugia than females used. Geometric tortoises typically used different refugia on consecutive nights, a type of predator avoidance mechanism

Population ecology of Psammobates oculifer in a semi-arid environment

We studied the ecology of Psammobates oculifer over 13 months near Kimberley, South Africa, to ascertain if the population’s life history traits conform to chelonian patterns in arid environments. Capture rates were highest in spring and lowest in winter when environmental conditions were respectively most and least favourable for tortoise activity. Body condition did not change from autumn to spring, but reached lower values during the summer drought. Capture effort averaged 5 hours/tortoise, which corresponds closely to that of species with low population densities in arid regions. Population size structure was skewed towards adults, indicative of low recruitment and/or low juvenile survivorship. Females were larger and heavier than males, confirming sexual dimorphism in this species. Body size of cohorts scaled to annuli counts, indicating a close correspondence between body size and age. Telemetered adults deposited one or no growth ring in the year of study; consequently, annuli counts could underestimate adult age. Regression analyses showed that male and female growth rates did not differ, but males matured at a smaller size and younger age than females. The smallest male showing reproductive behaviour had 12 annuli and a shell volume of 157 cm3, while similar measures for females were 14 annuli and 185 cm3. The sex ratio of the population did not differ from 1:1 but the bias towards males in spring, and towards females in autumn, indicates that studies limited to particular seasons can misrepresent life history traits of populations. We concluded that the life history of P. oculifer conforms to chelonian patterns in arid regions.Web of Scienc

Living with the genetic signature of Miocene induced change: Evidence from the phylogeographic structure of the endemic angulate tortoise Chersina angulata

The phylogeographic structure of the monotypic endemic southern African angulate tortoise Chersina angulata was investigated throughout its distribution with the use of partial sequences from three mtDNA loci (COI, cyt b and ND4). Phylogeographic and phylogenetic structuring obtained for the three mtDNA markers were highly congruent and suggested the presence of two genetically distinct, reciprocally monophyletic evolutionary lineages. Group one contained two subclades with haplotypes from the north-western Cape and south-western Cape, respectively, while haplotypes from the southern Cape comprised group two. The two major clades were separated by nine and eight mutational steps for COI and ND4, respectively. Of the three mtDNA gene regions examined, the ND4 partial sequence contained the most phylogenetic signal. Haplotype diversity was generally low and we recovered 34 haplotypes for the 125 animals sequenced for the ND4 subunit. Nested clade analyses performed on the variable ND4 partial sequences suggested the presence of two major refugial areas for this species. The demographic history of the taxon was characterised by range expansion and prolonged historical fragmentation. Divergence time estimates suggest that the temporal and spatial distribution of the taxon was sculpted by changes in temperature and rainfall patterns since the late Miocene. Corroborative evidence from other reptiles is also suggestive of a late Miocene divergence, indicating that this was a major epoch for cladogenesis in southern Africa. Apart from the genetic differences between the two major clades, we also note morphometric and behavioural differences, alluding to the presence of two putative taxa nested within C. angulata. © 2007 Elsevier Inc. All rights reserved.Articl

Parasites of domestic and wild animals in South Africa. XLVII. Ticks of tortoises and other reptiles

A total of 586 reptiles, belonging to 35 species and five subspecies, were examined in surveys aimed at determining the species spectrum and geographic distribution of ticks that infest them. Of these reptiles 509 were tortoises, 28 monitor or other lizards, and 49 snakes. Nine ixodid tick species, of which seven belonged to the genus Amblyomma, and one argasid tick, Ornithodoros compactus were recovered. Seven of the ten tick species are parasites of reptiles. Amongst these seven species Amblyomma marmoreum was most prevalent and numerous on leopard tortoises, Geochelone pardalis; Amblyomma nuttalli was present only on Bell's hinged tortoises, Kinixys belliana; and most Amblyomma sylvaticum were collected from angulate tortoises, Chersina angulata. Amblyomma exornatum (formerly Aponomma exornatum) was only recovered from monitor lizards, Varanus spp.; most Amblyomma latum (formerly Aponomma latum) were from snakes; and a single nymph of Amblyomma transversale (formerly Aponomma transversale) was collected from a southern African python, Python natalensis. All 30 Namaqualand speckled padloper tortoises, Homopus signatus signatus, examined were infested with O. compactus. The seasonal occurrence of A. sylvaticum and the geographic distribution of this tick and of A. marmoreum, A. nuttalli, A. exornatum, A. latum and O. compactus are illustrated