Victor J. T. Loehr

REPRODUCTION OF THE SMALLEST TORTOISE, THE NAMAQUALAND SPECKLED PADLOPER, HOMOPUS SIGNATUS SIGNATUS

The smallest tortoise, Homopus signatus, is inadequately protected, and information on its reproductive ecology can facilitate effective conservation. We combined X-ray radiography and ultrasonography to assess the reproductive status of free-ranging female Homopus signatus signatus during August–September 2000 (n = 30) and September–October 2001 (n = 29). Females produced only single-egg clutches but can produce more than one clutch in a season. Most (ca. 75%) of the females were gravid each spring, so H. s. signatus probably has a seasonal pattern of egg production. This pattern may be related to the seasonal climate; summers are hot and dry, yet winter rainfall is moderately predictable. Females were gravid from August through October, but further analyses are necessary to characterize the entire reproductive season and quantify clutch frequency. Large females produced large eggs, compared to eggs of small females. The smallest gravid female had a straight-line carapace length of 84.1 mm while the largest female measured 110.0 mm. Compared to gravid females, nongravid females were in poorer body condition (body mass and mass relative to carapace length) only in 2000, when there was lower rainfall and plant availability than in 2001. The difference in body mass approximated the mass of one egg. The low clutch size and fecundity suggest that populations have low intrinsic rates of natural increase. This plus their limited range and specific habitat requirements make H. s. signatus vulnerable to anthropogenic impacts.

Diet of the Namaqualand speckled padloper, Homopus signatus signatus , in early spring : original article

Abstract A baseline determination of the early spring (August ‐ September) diet of the Namaqualand speckled padloper (Homopus signatus signatus) was accomplished using in situ observation and faecal analysis methods. I analysed 13 focal observations and 49 faecal samples. Tortoises fed on a broad variety of plant species, possibly supplemented with a few insects. Important food items appeared to be Oxalis spp., Leysera tenella, Grielum humifusum and Crassula thunbergiana minutiflora. Crassula t. minutiflora may be a potential source of water as it is a succulent. Flowers were present in 96% of the faecal samples and may be an effect of the study period. Almost all faecal samples contained nematodes and their eggs, sometimes in huge quantities, but the effect on the tortoise population is not known. Since only 50 ‐ 60% of the faecal volume could be identified, care must be taken in deriving conclusions from this study. I recommend that future dietary studies of H. s. signatus emphasise focal observations, include pollen analysis, and determine food availability in different seasons to identify preferences and temporal shifts.

Shell Characteristics and Sexual Dimorphism in the Namaqualand Speckled Padloper, Homopus signatus signatus

Abstract There is little quantitative information regarding the two subspecies of the worlds smallest tortoise, Homopus signatus. To help characterise the northern subspecies H. s. signatus and evaluate the development of shell size and colour patterns, we measured shell characteristics of wild juvenile, male and female H. s. signatus. When scaling shell dimensions on carapace length, male shell size represented an extension of juvenile shell size for shell height, width and volume, but not plastron length. The slope of plastron length scaled on carapace length was smaller for males than for juveniles or females, suggesting differential growth of the plastron. The smaller male plastron translates to large shell openings, perhaps to improve locomotion and to facilitate tail movement during copulation. Conversely, the slope of female shell height, width and volume (scaled) was larger than for juveniles or males, presumably providing more space to accommodate follicles and the large egg. Serration of the marginal scutes and shell colour changed with body size, and shell colour pattern differed between sexes. The carapace was darker at intermediate body sizes (large juveniles and small adults); the increase in dark appearance resulted primarily from widening of the dark pigment band around scute margins as growth laminae were added. Both the lighter shell colour and reduced serration of large adults may be due to shell wear; large adults may produce less dark pigment, and older laminae disappear due to flaking or peeling. Females had a darker overall colour, more rays and fewer speckles than did males. This dimorphism may relate to thermoregulation, gamete protection or intraspecific communication. Both male and female patterns may confer crypsis if the sexes use microhabitats differently.

Small and sensitive to drought : consequences of aridification to the conservation of Homopus signatus signatus : short communication

Abstract Several climate models predict that the western Succulent Karoo in South Africa will aridi-fy. This region includes the range of the smallest tortoise, Homopus signatus signatus. Although the effects of rainfall on the physiology and ecology of H. s. signatus received attention in recent years, the results of these studies have not been integrated to facilitate conservation planning. Here we evaluate the importance of body size and the responses of H. s. signatus to rainfall variation to make recommendations for the taxons conservation. The small body of H. s. signatus offers one solution to its habitat of low primary productivity and rocky slopes. Nevertheless, female fecundity and egg size increase with female size, and large eggs result in large hatchlings capable of surviving their harsh environment. Females accumulate nutrients in the rainfall season, winter, but also in the dry season, to enable the production of large eggs. Egg production decreases during drought, although some females continue to channel resources to reproduction, apparently at the cost of their own growth. Reduced fecundity and growth, a result of aridification, would likely lower the production of large eggs and hatchlings. Therefore, conservation measures that reduce the mortality of large females may aid population sus-tainability. Because egg and hatchling size might drop below a minimum viable size in an aridified environment, H. s. signatus conservation would benefit from the development of suitable habitat corridors to enable tortoise movements to regions that will receive sufficient rainfall in the future.

Reproductive Responses to Rainfall in the Namaqualand Speckled Tortoise

Abstract Although many tortoise species inhabit drought-prone regions with potentially limiting resources, these species have long, iteroparous lives. To assess reproductive responses to variation in rainfall, and to understand interactions among egg size, body size, body condition, and rainfall, we studied egg production in the Namaqualand Speckled Padloper, Homopus signatus signatus, in Springbok, South Africa, in five consecutive spring seasons. Annual rainfall was low and varied substantially (131–226 mm). The percentage of females that were gravid (36–75%) differed among years and correlated with the amount of rain in the months prior to nesting. Gravid females had a higher body condition than that of non-gravid females, presumably because individual variation in resource acquisition caused some females to forfeit reproduction. The body condition of gravid and non-gravid females differed among years and was lowest in the year of lowest rainfall. In most years, egg size correlated to female size, but neither female size nor egg size differed among years. Egg size did not significantly correlate to maternal body size in dry years, when other determinants, such as body condition, seemed to outweigh the effect of body size. Egg volume represented up to 11.9% of female shell volume. The adult shell is somewhat flexible dorso-ventrally, which may help females accommodate the large egg, as indicated by the larger shell height and volume of gravid compared to non-gravid females. Large eggs may be advantageous for H. s. signatus, as larger hatchlings may survive better in arid environments. Since the range of H. s. signatus is threatened with aridification, the effects of drought on egg production may seriously challenge the long-term survival of populations.

Growth of the Namaqualand speckled padloper, Homopus signatus signatus (Reptilia : Testudinidae) : short communication

Growth was calculated for the world’s smallest tor toise species, Homopus signatus signatus, by compar ing body size data gathered in spring 2000, 2001 and 2002. Sexual differences could not be identified, but mean growth was significantly lower in 2000/01 than in 2001/02, possibly due to higher winter rainfall preceding the second period. Variation in growth rates was highest in juveniles. Growth decreased with increasing straight carapace length, resulting in a preliminary estimate of 11 years for females to reach sexual maturity.

Tick infestations in the Namaqualand speckled padloper, Homopus signatus signatus (Gmelin, 1789)

ABSTRACT Many terrestrial chelonians are parasitized by ticks, but we have a poor understanding of what determines tick infestations on chelonian hosts. We counted ticks on Homopus signatus signatus during each spring in the years 2001–2004, and evaluated tick frequencies in relation to tortoise anatomy, climate and microhabitat. Tortoises hosted Ornithodoros compactus and O. savignyi, and ticks seemed to prefer the hindlimbs, avoid the shell, and use the forelimbs and neck in intermediate frequencies. The number of ticks on the neck and forelimbs did not differ among males, females and juveniles, but for the hindlimbs and all body parts, males and females usually had similar tick numbers and adults often had more ticks than juveniles. The number of ticks on the hindlimbs correlated with the body size of male and female tortoises, whereas the number of ticks on the forelimbs correlated with juvenile body size. Males and females had similar incidences of ticks despite sexual dimorphism in body size (female size > male size), and this may be due to the relatively large shell openings (soft skin exposure) of males compared to females. Body condition and microhabitat had no effect on the number of ticks. It is unclear why tick numbers on H. s. signatus increased in dry years. The adverse effects of drought on mammals may have caused ticks to switch from mammals to tortoises when preferred hosts were no longer available.

Wide variation in carapacial scute patterns in a natural population of speckled tortoises, Homopus signatus

Abstract The arrangement of scutes on the carapaces of extant chelonians is very similar among species, but intraspecific deviations from typical scute patterns are common. Because intraspecific variation may relate to inbreeding depression, unfavourable egg incubation conditions and the presence of environmental pollutants, investigations of carapacial scute patterns in natural populations can enhance insight into the ecologies and survival challenges of chelonians. A population of the tortoise Homopus signatus, inhabiting an arid range with substantial annual rainfall variation, was sampled to record carapacial scute patterns. The typical pattern of H. signatus consisted of five vertebral scutes, four pairs of costal scutes, a cervical and a supracaudal scute, and 12 pairs of marginal scutes. Although it was expected that size classes (i.e. representing tortoises born in different years) and sexes would have different percentages deviations from the typical scute pattern as a result of different egg incubation conditions, percentages were similar among size classes and sexes. A high percentage of 44% (25% if counts of the relatively variable marginal scutes were excluded) of all tortoises had deviant carapacial scute patterns. Since the study population was situated in a relatively pristine area and supernumerary carapacial scutes appear related to egg incubation conditions in other chelonians, the wide variation in carapacial scute patterns in wild H. signatus may be the result of frequently challenging incubation conditions in the species’ harsh environment.

Activity of the Greater Padloper, Homopus femoralis (Testudinidae), in Relation to Rainfall

The greater padloper, Homopus femoralis, is largely endemic to South Africa. Its ecology remains unstudied, yet the efficient planning of field research is complicated by lack of data on its activity patterns. I studied a population in spring, summer and autumn 2008–2011, and found that H. femoralis was active (i.e. basking, drinking, feeding or walking) only during brief intervals following rainfall or imminent rain, perhaps to avoid avian predators or physiological costs of water and food shortages. Future studies might locate active tortoises in the highest rainfall months, and use telemetry to identify activity patterns throughout the year.