Rafetus euphraticus (Daudin 1801) – Euphrates Softshell Turtle

Abstract

The Euphrates Softshell Turtle, Rafetus euphraticus (Family Trionychidae), is a medium-sized (maximum recorded carapace length 680 mm), freshwater turtle thought to be most closely related to the eastern Asian species Rafetus swinhoei. The species inhabits diverse habitats, including rivers, streams, ponds, lakes, reservoirs, marshlands, and artificial canals. It is found only in the Euphrates and Tigris rivers and their tributaries in Turkey, Syria, Iraq, and southwestern Iran. It occurs in relatively shallow, calm waters, typically adjacent to deeper, fast-flowing water. The home range size averages 47.5 ha (minimum convex polygon) with a mean 95% kernel density of 21.8 ha. Knowledge of the species' distribution in the Tigris system lacks detail, due in part to political disturbance. Populations of the species are threatened by ongoing habitat fragmentation, alteration, and destruction throughout its range. Construction of several large dams has drastically changed the habitat of this turtle, especially in the Turkish part of the Euphrates watershed. This serious threat endangers the future of this species. No conservation measures are being taken in southeastern Anatolia (Turkey), Syria or Iraq. A participatory conservation project is underway in Khuzestan Province, Iran. Population studies, strengthened national and international protection, and regional cooperation will be required for the long-term survival of Rafetus euphraticus. distribution. -Iran, Iraq, Syria, Turkey. Restricted to the Euphrates and Tigris River basins. synonyMy. -Testudo euphratica Daudin 1801, Trionyx euphraticus, Gymnopus euphraticus, Rafetus euphraticus, Pelodiscus euphraticus, Amyda euphratica, Tyrse euphratica, Testudo rafcht Olivier 1807, Testudo rascht Gray 1830 (nomen novum), Tyrse rafeht Gray 1844 (nomen novum), Trionyx rafeht. subsPEciEs. -None recognized. status. -IUCN 2015 Red List: Endangered (EN A1ac+2c; assessed 1996); TFTSG Draft Red List: Endangered (EN, assessed 2011); CITES: Appendix II, as Rafetus spp. Taxonomy. -The Euphrates Softshell Turtle was described by Daudin (1801) as Testudo euphratica, based on a description provided by G.A. Olivier of a specimen from the Euphrates River, which was cited as the type locality. Olivier (1807) later applied the name Testudo rafcht to a specimen of this species from the Tigris. Geoffroy Saint-Hilaire (1809a,b), after establishing the generic name Trionyx, coined the new combination Trionyx euphraticus. Noting distinctive characteristics of the alveolar surface, Gray (1844) named a new genus and species, Tyrse rafeht. Later, Gray (1856) renamed this form Trionyx rafeht. Still later, Gray (1864Gray ( , 1869Gray ( , 1870Gray ( , 1873a claimed that the species was intermediate between Trionyx and Potamochelys, both in palatal features and in having just two plastral callosities, and he proposed a new genus, Rafetus.Boulenger (1889) reverted to Geoffroy Saint-Hilaire's (1809b) Trionyx euphraticus, which remained in common use until the work of Meylan (1987). Taking into considerat...

Determining home range, changes in habitat use with time, and the threats to an endangered freshwater turtle (Rafetus euphraticus) in Turkey

“…The construction of large dams on the Euphrates River strongly affected the water level fluctuations and decreased the temperature; thus, the growth of aquatic vegetation eliminated turtle basking spots while the rising water level submerged potential nesting sites (Gramentz, 1993; Taşkavak & Atatür, 1995; Taşkavak & Atatür, 1998). The construction of dams for many years has undoubtedly caused many potential habitats and nesting sites of R. euphraticus to be submerged, destroyed and fragmented (Taskavak et al, 2016). Reservoir sedimentation dramatically reduces the volume of sand that can be transported downstream, causing the progressive disappearance of river beaches and sandy islands.…”

“…Based on published literature and field observations on preferred habitat types, we suggest that if these shorelines are transformed into vegetated shorelines in the years to come, suitable habitats for turtles are likely to increase. However, Taskavak et al (2016) stated that even if suitable substrates are found for basking and nesting in the recently constructed reservoir areas, fluctuations in the water level are likely to make survivorship of nests extremely low.…”

“…The effects of pollutants on the local turtles, and their cascading effects across trophic levels (Mills, 2012), should be further studied as there are no data yet available. The Tigris River is probably exposed to higher pollution levels than the Euphrates owing to the slow current and the high rate of urbanization over many decades (Taskavak et al, 2016). This might have affected turtle populations as well.…”

“…Observations in Turkey suggest that the northern limit of R. euphraticus in the Euphrates is the junction of a small stream around the Çermik/Diyarbakir, which lies 50–60 km north of Zengecur Creek (Taşkavak & Atatür, 1996; Taşkavak & Atatür, 1998). In the Tigris River, the northern limit has been reported as a small stream 4–5 km east of Devegeçidi Dam (Taşkavak & Atatür, 1996; Taşkavak & Atatür, 1998; Taskavak et al, 2016). The territories below 800 m above sea level that are included in the species' distribution in Turkey were clipped, a 100‐m peripheral buffer zone was created, and the areas with a slope of more than 20% were extracted for the Euphrates and Tigris rivers given the known nest characteristics of trionchid turtles that are available in the literature (Fitch & Plummer, 1975; Biricik & Turğa, 2011; Ghaffari et al, 2013; Candan, 2018).…”

“…In Turkey, R. euphraticus was discovered by Ainsworth (1842) in Anatolia, but its ecology has remained poorly investigated although threats are mentioned in the available literature (Atatür & Üçüncü, 1986; Taşkavak & Atatür, 1995; Taşkavak & Atatür, 1998; Taşkavak, 1999), and Ihlow et al (2014) investigated the genetic diversity and the habitat suitability for the species in its entire distribution area. The only data on population status are derived from investigations carried out in south‐eastern Anatolia in Turkey nearly 3 decades ago (Taşkavak, 1992; but see Taskavak et al, 2016, for a review).…”