Yellow-tipped gopher tortoise
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Yellow-tipped gopher tortoise ( Gopherus flavomarginatus ) |
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| Gopherus flavomarginatus | ||||||||||||
| Legler , 1959 |
The yellow-tipped gopher tortoise ( Gopherus flavomarginatus ), also known as the Mexican gopher tortoise , is a rare species of tortoise that only occurs in a small area of the Chihuahua Desert in Mexico . It was only discovered in 1958 and described by herpetologist John Marshall Legler in 1959 . It owes its German-language name, which is based on the scientific name, to the yellowish pigmentation of the side shields of the back armor.
description
The yellow-tipped gopher tortoise is the largest of the four North American species of gopher tortoise . The carapace can be up to 40 cm long. This back armor is flattened at the top and arched relatively low. It becomes wider towards the rear and reaches its greatest expansion a little behind the center. The neck shield is about as wide as it is long and has no notches. The plastron's throat shields are relatively wide and not forked. The vertebral shields are wider than they are long, the first is the narrowest, the third the widest.
The color of the armor varies from light green-yellow or lemon-yellow to straw-colored or brown. The areoles in the center of each shield are dark brown or black. The edge shields (marginalia) are always paler than the rest of the back armor, the side edge shields are often pigmented yellow. This trait is most pronounced in the population in the Mexican state of Durango .
On the two rear extremities, they have two large spurs with black tips on each thigh. The front extremities are broad, covered with large, overlapping scales in seven to eight rows. They are used for digging.
Gender differences
The sexual dimorphism is only weak. The males are usually slightly smaller than the females. They have a slightly more inwardly arched belly armor with more protruding throat shields and slightly longer and thicker tails. In the population in the Mexican state of Durango, however, this dimorphism in the curvature of the belly, which is supposed to facilitate copulation, is less pronounced than in specimens from other parts of the range.
Differentiation from other types
The shape of the back armor distinguishes the yellow-tipped gopher tortoise from other North American species. The California gopher tortoise ( Gopherus agassizii ) has an elongated, highly domed shell that does not widen towards the rear. The Texas gopher tortoise ( Gopherus berlandieri ) has a broad back armor and two pointed, fork-like branched throat shields. The Georgia gopher tortoise ( Gopherus polyphemus ), to which the yellow-edged gopher tortoise was sometimes placed as a subspecies, has an oval, elongated back armor that is hardly widened towards the rear. Morafkas tortoise ( Gopherus morafkai ), has an almost hemispherical bulging armor and a less broad head than the Bolson tortoise.
distribution
It is endemic to the Bolsón de Mapimí, which was declared a Biosphere Reserve by UNESCO in 1976 . This area extends over the southwest of the Mexican state of Coahuila , the southeast of the state of Chihuahua and the northeast of the state of Durango . It is a dry pool at an altitude of 1000 to 1300 meters.
During the last glacial period , these turtles were distributed from the Great Plains west of Arizona to southern Mexico. However, changes in the landscape and the climate ensured that they were isolated in a small basin in the Mexican desert and split into about 6 populations in the current range. However, the genetic variation between these populations is small. Under natural desert conditions, about one animal inhabits one hectare.
Some specimens were exported to the United States for offspring for conservation purposes . A reintroduction in areas of North America where they were found until the end of the Pleistocene is rejected by environmentalists.
Way of life
Yellow-tipped gopher tortoises live in colonies of up to 100 animals and only become really active at dawn or dusk. They are not sexually mature until they are 12–15 years old, but can reach an age of 80–100 years. In the wet season, the turtles dig burrows 10 meters long and 1.5 to 2.5 meters deep into the ground. These buildings only have one entrance. Here they survive both the dry periods of summer and cold winter days.
Reproduction
The mating season is from April to August. Nests are created near the structures between April and September. The eggs are laid outside of the burrow in holes about eight inches deep. A clutch contains 5 to 6 (in rare cases 3 to 9) eggs. Although eggs can be laid by a female up to three times a year, seven out of eight clutches are destroyed by predators. As a result, a pair of turtles produces an average of only 3.4 offspring in eight years. These are also in danger of not reaching sexual maturity. In addition to humans, their enemies include coyotes , hawks , racing cuckoos , badgers , skunks and ravens .
nutrition
Like other gopher turtles, the yellow-tipped gopher turtles are herbivores . 21 plant species serve them for food, mainly grasses that make up 64 percent of their food. The most important grasses are Bouteloua barbata (22.7%), Hilaria mutica (15.2%), Tridens pulchellus (14.9%) and Sida leporosa (13.6%). Bouteloua barbata is the main source of food in summer, while Hilaria mutica and Sida leporosa are mainly used for the rest of the year.
Danger
Around 1973 people feared that this species would become extinct , as it mainly feeds on a type of grass that has been displaced by grazing cattle herds. In addition, their eggs and meat were considered a delicacy by the residents. Thanks to the educational work of Mexican conservationists and the protective regulations , their population was able to recover. Since then it has only been classified as endangered by the IUCN .
Individual evidence
- ^ John Marshall Legler: A new tortoise, genus Gopherus, from North-Central Mexico. Univ. Kansas Publ. Museum of Natural History, 11, 5, pp. 335–343, 1959 (first description)
- ↑ a b c d e Roger W. Barbour & Carl H. Ernst: Turtles of the World. Smithsonian Institution Scholarly Press, 1992 ISBN 978-1-5609-8212-8 ( Online ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. )
- ^ A b c David J. Morafka: The status and distribution of the Bolson tortoise (Gopherus flavomarginatus). US Fish and Wildlife Service Research Report, 12, pp. 71-94, 1982
- ↑ a b c d Gopherus flavomarginatus in the endangered Red List species the IUCN 2008. Posted by: Tortoise & Freshwater Turtle Specialist Group, 2007. Accessed on May, 2014.
- ↑ Cinthya Alejandra Ureña-Aranda1 & Alejandro Espinosa de los Monteros: The genetic crisis of the Mexican Bolson Tortoise (Gopherus flavomarginatus: Testudinidae). Amphibia-Reptilia, 33, 1, pp. 45-53, 2012 doi : 10.1163 / 156853811X621508
- ↑ Eric Jaffe: Brave Old World. The debate over rewilding North America with ancient animals. , Science News, Magazine of the Society for Science and the Public, November 11, 2006
- ↑ a b David J. Morafka, G. Aguirre & GA Adest: Gopherus flavomarginatus. Bolson tortoise. In: IR Swingland & MW Klemens (eds.): The Conservation Biology of Tortoises , pp. 10-13, Occ. Pap.IUCN / SSC 5, Tortoise and Freshwater Specialists Group, 1988
literature
- John Marshall Legler: A new tortoise, genus Gopherus, from North-Central Mexico. University of Kansas Publications, Museum of Natural History, 11, 5, pp. 335–343, 1959 (first description)
- David J. Morafka & CJ McCoy: The ecogeography of the Mexican Bolson tortoise (Gopherus flavomarginatus): derivation of its endangered status and recommendations for its conservation. Annales of the Carnegie Museum, 57, pp. 1-72, 1988
- David C. Rostal, Earl D. McCoy & Henry R. Mushinsky: Biology and Conservation of North American Tortoises. Johns Hopkins University Press, 2014 ISBN 1-4214-1377-9
