Sawed flat turtle

Sawed flat turtle
	Sawed flat turtle ( Homopus signatus )
Systematics
Order :	Turtles (Testudinata)
Subordination :	Halsberger tortoises (Cryptodira)
Family :	Tortoises (Testudinidae)
Subfamily :	Testudininae
Genre :	Flat turtles ( Homopus )
Type :	Sawed flat turtle
Scientific name
	Homopus signatus
	( Gmelin , 1789)

The sawn flat turtle Homopus signatus ( Gmelin , 1789) is a tortoise belonging to the genus of flat turtles . It is considered to be the smallest recent species of turtle. The German name refers to their flat back armor, which is particularly jagged at the rear edge of the nominate shape. Their habitat is rocky semi-deserts in western South Africa. The sawn flat turtle is particularly endangered by its spatial limitation to a relatively small distribution area, which is increasingly threatened by climate change and the lack of rainfall.

features

Homopus signatus is a remarkably small turtle with an unusually flat shell for tortoises, an adaptation to the way of life in narrow crevices. The spine shields look partially depressed in the middle and are jagged at the rear edge. The animals have a sand-colored, brownish to orange-red basic color, with darker speckles, some of which are arranged in rays. The carapace length in males of the nominate form is on average 7–8 centimeters (at least 5 cm), in females 8–9 centimeters (maximum 11 cm). The species shows a pronounced sexual dimorphism . In addition to the smaller size or the different color, pattern and shape of the back armor, sexually mature males can be recognized by the concave belly armor and the longer tail, which is thicker at the base.

Taxonomy

Original name: Testudo signata
Origin of name: Homo (gr) equal, pous (gr) foot, signatus (lat) drawn
First description : Gmelin, JF (1789): Caroli a Linné, Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Editio Decima Tertia, Aucta, Reformata. Tomus I. Pars III. Lipsiae [Leipzig]: GE Beer, Ed. 13, 1 (3): 1033-1516

Hofmeyer et. al proposed in 2016 to place homopus species with five toes on the front legs ( H. signatus , H. boulengeri and H. solus ) in a separate genus, Chersobius .

Local forms

No independent subspecies are currently recognized in Homopus signatus, but there are significant morphological differences between northern and southern populations:

Spring in the habitat of Homopus signatus

Northern form , formerly Homopus signatus signatus (Gmelin, 1789). The back armor of the northern animals shows deep furrows between the shields, with partially sunken areoles . The basic color of the shell is beige to brownish with large dark spots.

Biotope : semi- arid , rocky areas with hot, dry summers and irregular, low rainfall in winter, predominantly succulent vegetation ( Succulent Karoo ).
Habitat : Namaqualand in northwestern South Africa, from the Orange River on the border with Namibia in the north to Bitterfontein in the south and from the Atlantic coast in the west to Calvinia in the east, occurrences from sea level up to approx. 1000 m.
Terra typica : Area around Springbok , Cape Province, South Africa

Southern form , formerly Homopus signatus cafer ( Daudin , 1801). This subspecies is slightly larger than the northern form, but above all it can be distinguished from Homopus signatus signatus by its reddish base color and the finer, mostly radial, black drawing elements . In addition, it has a smoother shell and less serrated edge shields. It populates areas with slightly higher amounts of precipitation than the nominate form.

Biotope: sandstone hill (Koppies)
Habitat: southern Cape Province , from Piketberg to Klawer
Terra typica: catchment area of the Olifants River, Cape Province, South Africa

Way of life

Homopus signatus prefers to live near rock formations, in whose crevices the animals retreat to protect themselves from extreme temperatures and predators. Due to their coloring and drawing, they are very well camouflaged. Oxalis spp., Leysera tenella, and Crassula thunbergiana minutiflora are the main food crops for a population of sawn flat turtles near Springbok .

Reproduction

Sawed flat turtles, like other turtles, become sexually mature depending on their growth when they have reached around 70% of their final size. In nature this usually takes 10–12 years, under extreme conditions even longer. In captivity, however, the first egg-laying was reported at around 3.5 years of age. The eggs are laid in late winter and spring. A sun-protected location under vegetation is preferred for the construction of the nest box. The clutch of the sawed flat turtle consists of only one egg, which is about 4 cm covered with earth. On average, the egg makes up 8%, in extreme cases even up to 11% of the female's body volume. Although the eggs are hard-shelled and inflexible, they are larger in diameter than the pelvic canal. This must therefore be expanded under the influence of hormones for successful oviposition, a process that is unusual for turtles. Laying individual, large eggs is probably an adaptation to the sparse and very irregular rainfall in the biotope. With several 1-egg clutches per season, the females increase their chance of reproduction compared to a single clutch with several small eggs, because it is assumed that large hatchlings have a decisive advantage in their semi-arid environment. The maturation time of the eggs is only known from artificial incubation and is given as 101 to 145 days.

Endangerment and protection status

Homopus signatus is listed in Appendix II of the Washington Convention on Endangered Species and Appendix B of the European Species Protection Guidelines, i.e. H. Export from the country of origin and import into the European Community require a permit; Keeping and breeding must be reported to the responsible state authority. Penalties are imposed if you violate this rule. The species was still relatively stable within its range until the IUCN Red List of Threatened Species was last updated . It is therefore only listed there as low risk. In the South African Red Data Book, however, the subspecies H. s applies in particular. cafer as endangered. In addition to the usual anthropogenic influence, overgrazing and destruction of the landscape, the limitation of the sawn flat turtle to a small area of distribution and their specialization in a certain type of biotope prove to be problematic, because semi-deserts are particularly affected by climate change and the resulting decline the amount of precipitation are threatened.

attitude

Homopus signatus is seldom held in private hands in Europe, as the Republic of South Africa rarely issues export licenses. An exception is the private Homopus Research Foundation , which has been running a studbook for this species under the umbrella of the European Studbook Foundation under its director, Victor Loehr, since 1995 . In 2010 it shows a live population of 78 sawed flat turtles of the nominate form including six new offspring. The animals are kept by zoos and private breeders in various European countries or have been registered in the stud book by committed keepers for breeding purposes.

Individual evidence

↑ ^a ^b ^c Loehr, VJT: The ecology of the world's smallest tortoise, Homopus signatus signatus: effects of rainfall. Dissertation, University of the Western Cape, South Africa 2008.

↑ Hofmeyer et al. (2016): Tortoise (Reptilia, Testudinidae) radiations in Southern Africa from the Eocene to the present

^ Website of the Homopus Research Foundation

↑ ^a ^b Bour, R. (1988): Taxonomic and nomenclatural status of Homopus signatus (Gmelin, 1789). J. Herpetolog. Assoc. Afr., 35, 1-6.

↑ MD Hofmeyr, BT Henen, and VJT Loehr (2005): Overcoming environmental and morphological constraints: egg size and pelvic kinesis in the smallest tortoise, Homopus signatus. Can. J. Zool. Vol. 83.

↑ Loehr V. (2008): Homopus signatus signatus (Gmelin, 1789) Namaqualand speckled padloper NATURAL OVIPOSITION AND INCUBATION. African Herp News, 9-10.

↑ Loehr, V. (2010): Homopus signatus Studbook 2010. ( 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. (PDF; 16 kB) Homopus Research Foundation.@1@ 2Template: dead link / home.concepts.nl

literature

Boycott, Richard C. and Ortwin Bourquin: The southern African Tortoise Book: A guide to southern African Tortoises, Terrapins and Turtles. O. Bourquin, KwaZulu-Natal, South Africa 2000, ISBN 0-620-26536-1 .
Loehr, VJT: The ecology of the world's smallest tortoise, Homopus signatus signatus: effects of rainfall. Dissertation, University of the Western Cape, South Africa 2008.
Manfred Rogner: Tortoises - biology, keeping, reproduction. Eugen Ulmer KG, Stuttgart 2008, ISBN 978-3-8001-5440-1 .