Gopher Tortoise Response to Habitat Management by Prescribed Burning

ABSTRACT As quality of forested habitat declines from altered fire regimes, gopher tortoises (Gopherus polyphemus) often move into ruderal areas to the detriment of the animal and land manager. We evaluated effects of a dormant-and-growing-season prescribed fire on habitat and gopher tortoise use of degraded longleaf pine (Pinus palustris) forests surrounding military training areas. We burned 4 of 8 sites in winter 2001–2002 and again in April 2003. Changes in vegetation measured during 2001–2004 indicated that burn treatments did not increase herbaceous vegetation. Similarly, movement patterns, burrow usage, and home range of tortoises radiotracked from 2002–2004 did not differ between treatments. Woody cover initially was reduced in the forests postburn, and we found more new burrows in burned forest sites. Once shrub cover was reduced, tortoises started using forested habitat that had become overgrown. However, shrub reduction may be temporary, as woody stem densities increased postburn. Thus, the one-time use of fire to manage tortoise habitat may not rapidly restore the open canopy, sparse woody midstory, and abundant herbaceous vegetation that this species requires. Repeated prescribed fires or additional management techniques may be needed for complete restoration.     

Long-Term Retention of a Relocated Population of Gopher Tortoises

Abstract: Relocations of gopher tortoises (Gopherus polyphemus) in Florida, USA, are frequently employed as mitigation tools when tortoises occupy land desired for development. Here we present information about retention and health of a relocated population of gopher tortoises 17 years after relocation. We combine our 17-year postrelocation data with earlier surveys 1 year and 2 years postrelocation to examine whether retention rates change over time. We also evaluate whether retention rates vary by age and gender. Of 74 gopher tortoises relocated in 1985, 31 were present in 2002. We found a 1-year retention rate of 42%, with retention rates of 100% each year thereafter, when we used the percentage of relocated individuals captured at each survey. We found a 1-year retention rate of 73%, a retention rate of 92% from year 1 to year 2, and an overall retention rate of 98.5% from year 2 through year 17, based on the assumption that all individuals present in later surveys were present in earlier surveys. We found no significant difference in retention rate over the 17-year period for adults and juveniles and for adult males and females. Relocated gopher tortoises showed natural growth patterns, indicating good health, but 35% of these gopher tortoises had ≥1 symptom of upper respiratory tract disease, a disease associated elsewhere with population declines of tortoises. Thus, retention rates of relocated gopher tortoises change over time, with relatively low retention during the first year postrelocation but nearly 100% retention in subsequent years. In general, our study shows that relocations can successfully lead to long-term retention of gopher tortoises, but we predict that without management (e.g., fire management and predator control) this relocated population is not viable.     

Growth and carapacial colour variation of the leopard tortoise, Geochelone pardalis babcocki, in northern Tanzania

Observations were made of growth rate and variation in colour pattern of the leopard tortoise ( Geochelone pardalis babcocki ) in northern Tanzania between October 1993 and June 1996. Growth rate differed significantly between tortoises, with immature animals (6.9 ± 1.4 mm month⁻¹) and females (5.7 ± 1.3 mm month⁻¹) exhibiting higher rates of growth than adult animals (2.9 ± 0.8 mm month⁻¹) and males (3.2 ± 1.1 mm month⁻¹), respectively. The faster growth rate in immature animals suggested that growth rate declined with age. The difference in growth rates between the sexes was ascribed to sexual dimorphism, adult females being larger and therefore growing faster than males.
The carapacial colour pattern observed in the northern Tanzanian tortoises was generally similar to that described elsewhere in the species' range. The colour pattern varied between Arusha and Serengeti District tortoises. Animals at the Arusha sites tended to be sparsely coloured (55.6%) compared to the Serengeti tortoises, which had a buff colouration with radiating spots (89.3%).; The sparse colouration provides effective camouflage in the drier Arusha habitats, as does the buff colouration with black spots in the wetter, darker habitats in the Serengeti.     

Persistence of distinctive morphotypes in the native range of the CITES‐listed Aldabra giant tortoise

Understanding the extent of morphological variation in the wild population of Aldabra giant tortoises is important for conservation, as morphological variation in captive populations has been interpreted as evidence for lingering genes from extinct tortoise lineages. If true, this could impact reintroduction programmes in the region. The population of giant tortoises on Aldabra Atoll is subdivided and distributed around several islands. Although pronounced morphological variation was recorded in the late 1960s, it was thought to be a temporary phenomenon. Early researchers also raised concerns over the future of the population, which was perceived to have exceeded its carrying capacity. We analyzed monthly monitoring data from 12 transects spanning a recent 15‐year period (1998–2012) during which animals from four subpopulations were counted, measured, and sexed. In addition, we analyzed survival data from individuals first tagged during the early 1970s. The population is stable with no sign of significant decline. Subpopulations differ in density, but these differences are mostly due to differences in the prevailing vegetation type. However, subpopulations differ greatly in both the size of animals and the degree of sexual dimorphism. Comparisons with historical data reveal that phenotypic differences among the subpopulations of tortoises on Aldabra have been apparent for the last 50 years with no sign of diminishing. We conclude that the giant tortoise population on Aldabra is subject to varying ecological selection pressures, giving rise to stable morphotypes in discrete subpopulations. We suggest therefore that (1) the presence of morphological differences among captive Aldabra tortoises does not alone provide convincing evidence of genes from other extinct species; and (2) Aldabra serves as an important example of how conservation and management in situ can add to the scientific value of populations and perhaps enable them to better adapt to future ecological pressures.     

The origin of Indian Star tortoises (Geochelone elegans) based on nuclear and mitochondrial DNA analysis: A story of rescue and repatriation

The Indian Star tortoise (Geochelone elegans) belongs to the family Testunidae and is distributed in southwest India and Sri Lanka. In addition to facing loss of its natural habitat, the species is also illegally traded as food and as an exotic pet internationally. Here we report DNA-based analyses for identification and repatriation of these tortoises into their natural habitat. We have attempted to establish the geographical origin of these tortoises rescued from smugglers, by comparing the microsatellite and mitochondrial markers of rescued animals with animals of known provenance. Star tortoises exhibited strong genetic structure in India. The populations from western India were genetically distinct at microsatellite and mitochondrial loci from southern populations. The rescued individuals had similar multilocus genotypes and mitochondrial DNA haplotypes as the reference individuals from south India. However, the precise geographic origin of many of the rescued samples remains unresolved, because we could not assign them to southern populations and the Neighbor-Joining cluster analysis indicated that some of rescued tortoises formed distinct clusters. These data strongly suggest that the rescued group of tortoises is composed of a mix of individuals from differentiated source populations that are probably located in southern India and possibly Sri Lanka. Our study provides valuable information based on molecular markers for the assessment of genetic diversity in Indian Star tortoises.     

Waif Gopher Tortoise Survival and Site Fidelity Following Translocation

Gopher tortoises (Gopherus polyphemus) are among the most commonly translocated reptiles. Waif tortoises are animals frequently of unknown origin that have been displaced from the wild and often held in human possession for various reasons and durations. Although there are risks associated with any translocation, waif tortoises are generally excluded from translocation projects because of heightened concerns of introducing pathogens and uncertainty about the post-release survival of these individuals. If these risks could be managed, waif tortoises could have conservation value because they can provide the needed numbers to stabilize populations. In the early 1990s, the discovery of an isolated population of gopher tortoises (≤15 individuals) near Aiken, South Carolina, USA, prioritized establishment of the Aiken Gopher Tortoise Heritage Preserve (AGTHP). Because of the population's need for augmentation and the site's isolation from other tortoise populations, the AGTHP provided the opportunity to evaluate the post-release survival of translocated waif tortoises without compromising a viable population. Since 2006, >260 waif tortoises have been introduced to the preserve. Using a Cormack-Jolly-Seber modeling framework to analyze release records and capture histories from trapping efforts in 2017 and 2018, we estimated the long-term apparent survival and site fidelity of this population composed largely of waif tortoises. We estimated annual apparent survival probabilities to be high (≥0.90) for subadult, adult male, and adult female tortoises, and these rates were similar to those reported for wild-to-wild translocated gopher tortoises and those from unmanipulated populations. Of the tortoises recaptured within the boundaries of the preserve, 75% were located within 400 m of their release location. These results suggest that waif tortoises could be an important resource in reducing the extirpation risk of isolated populations. © 2021 The Wildlife Society.     

Differentiation of the epidermis of scutes in embryos and juveniles of the tortoise Testudo hermanni with emphasis on beta-keratinization

The sequence of differentiation of the epidermis of scutes during embryogenesis in the tortoise Testudo hermanni was studied using autoradiography, electron microscopy and immunocytochemistry. The study was mainly conducted on the epidermis of the carapace, plastron and nail. Epidermal differentiation resembles that described for other reptiles, and the embryonic epidermis is composed of numerous cell layers. In the early stages of differentiation of the carapacial ridge, cytoplasmic blebs of epidermal cells are in direct contact with the extracellular matrix and mesenchymal cells. The influence of the dermis on the formation of the beta‐layer is discussed. The dermis becomes rich in collagen bundles at later stages of development. The embryonic epidermis is formed by a flat periderm and four to six layers of subperidermal cells, storing 40–70‐nm‐thick coarse filaments that may represent interkeratin or matrix material. Beta‐keratin is associated with the coarse filaments, suggesting that the protein may be polymerized on their surface. The presence of beta‐keratin in embryonic epidermis suggests that this keratin might have been produced at the beginning of chelonian evolution. The embryonic epidermis of the scutes is lost around hatching and leaves underneath the definitive corneous beta‐layer. Beneath the embryonic epidermis, cells that accumulate typical large bundles of beta‐keratin appear at stage 23 and at hatching a compact beta‐layer is present. The differentiation of these cells shows the progressive replacement of alpha‐keratin bundles with bundles immunolabelled for beta‐keratin. The nucleus is degraded and electron‐dense nuclear material mixes with beta‐keratin. In general, changes in tortoise skin when approaching terrestrial life resemble those of other reptiles. Lepidosaurian reptiles form an embryonic shedding layer and crocodilians have a thin embryonic epidermis that is rapidly lost near hacthing. Chelonians have a thicker embryonic epidermis that accumulates beta‐keratin, a protein later used to make a thick corneous layer.