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Trionyx triunguis 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Testudines Trionychidae

Scientific Name: Trionyx triunguis (Forskål, 1775)
Infra-specific Taxa Assessed:
Regional Assessments:
Common Name(s):
English African Softshell Turtle, Nile Softshell Turtle
French Trionyx du Nil
Synonym(s):
Aspidonectes aspilus Cope, 1865
Fordia africana Gray, 1869
Testudo triunguis Forskål, 1775
Trionyx aegyptiacus Geoffroy Saint-Hilaire, 1809
Trionyx egyptiacus Geoffroy Saint-Hilaire, 1809
Trionyx labiatus Bell, 1835
Trionyx mortoni Hallowell, 1844
Trionyx niloticus Gray, 1831
Trionyx triunguis ssp. rudolfianus Deraniyagala, 1948
Taxonomic Source(s): Fritz, U. and Havas, P. 2007. Checklist of chelonians of the world. Vertebrate Zoology 57(2): 149-368.
Taxonomic Notes:

Trionyx triunguis has been considered a single widespread, relatively uniform species for decades, with no subspecies or other taxonomic units recognized or proposed in recent years. Phylogeographic studies of regional variation have demonstrated different, partly conflicting results, but were based on generally limited sets of specimens and genetic markers (Gidis et al., 2011; Guclu et al., 2011, 2015; Shanas et al., 2012). However, there is still uncertainty as to whether Mediterranean and African populations may in fact represent genetically definable separate Management Units (O. Türkozan unpubl. data).

Assessment Information [top]

Red List Category & Criteria: Vulnerable A4bcd ver 3.1
Year Published: 2017
Date Assessed: 2016-06-21
Assessor(s): van Dijk, P.P., Diagne, T., Luiselli, L., Baker, P.J., Turkozan, O. & Taskavak, E.
Reviewer(s): Rhodin, A.G.J., Horne, B.D. & Branch, W.R.
Contributor(s): Baha El Din, S., Chirio, L., Gbeintor, E., Iverson, J.B., Ngwava, J.M., Pauwels, O.S.G., Petrozzi, F., Segniagbeto, G., Trape, J.-F. & Werner, Y.L.
Facilitator/Compiler(s): Rhodin, A.G.J., van Dijk, P.P.
Justification:

Populations in West Africa, representing about one-third of the overall historic range, have been in severe decline in recent decades with anecdotal indications that catch per unit effort has declined by 98% over the past two generations (estimated generation length of 20-30 years), and this trend is expected to continue. Its populations in Israel are small and fragmented, and considered Critically Endangered (under criterion C2a). In Egypt, the species has disappeared from the Nile below Lake Nasser. Populations in Central Africa are indicated to be in mild decline, while populations in northeastern Africa are understood to be stable. The Turkish population is expanding its range and is locally common; it may be threatened in Turkey but more information is needed. Overall, on balance this species has likely experienced well over 30% total population decline over its past two generations as a result of targeted exploitation and habitat degradation, and this trend is likely to continue, qualifying the species as Vulnerable based on criteria A4bcd. The West African populations likely warrant regional listing as Critically Endangered.

Trionyx triunguis was previously (1996) listed as Least Concern globally in view of its wide distribution, presumed large population, and because it was considered unlikely to be declining fast enough to qualify for listing in a more threatened category. It has long been recognized as a threatened species in the Mediterranean region; the Mediterranean population (Israel, Lebanon, Syria?, Turkey) was assessed as Critically Endangered under criterion C2a in 1996 by the IUCN SSC European Reptile and Amphibian Specialist Group. 

Geographic Range [top]

Range Description:

Trionyx triunguis ranges widely in Africa and the eastern Mediterranean. It occurs in the coastal regions of southern Turkey from Dalyan to Asi River, and in the Mediterranean coastal area of Israel from Tel Aviv northwards (Werner 2016). Records from Lebanon are known but current occurrence is uncertain. It has not been recorded from Syria, although vagrants probably occur there. Vagrants have been recorded from the Mediterranean coast as far north and west as Kos, Greece (Taskavak et al. 1999, Taskavak and Akçınar 2007). Trionyx triunguis has been successfully introduced into the Jordan River system in the north of Israel, including the remaining wetlands of Hula Lake (Werner 2016).  In Africa, Trionyx occurs in the Nile River basin from Egypt upstream, in river basins in Eritrea, Ethiopia, Sudan, South Sudan, Somalia, and northern Kenya, and in coastal and inland river systems from the Senegal (Mauritania-Senegal) River throughout the Guinean forest zone of southern West Africa, including the Gambia, Guinea-Bissau, Mali, and Lake Chad, and with records extending from southern Central African Republic to the Cunene River on the Angola-Namibia border, including many localities in Gabon and some in Republic of Congo (Iverson 1992; Branch 1988, 2008; Boycott and Bourquin 2000; Spawls et al. 2002; Trape et al. 2012). Insufficient survey data are available to conclude whether the species is continuously distributed across these regions or occurs primarily in particular, restricted and fragmented areas only; the range is not connected between Lake Turkana and Somalia, but there is a possible record from the Somalia border region of Kenya. This species also has a scattered distribution along the southern coasts of West Africa (G. Segniagbeto and L. Luiselli et al. unpubl. data). Historically, Trionyx was known from the lower Nile below the Aswan Dam, but it is considered to be extinct there now (Spawls et al. 2002).

Countries occurrence:
Native:
Angola; Benin; Cameroon; Chad; Congo; Congo, The Democratic Republic of the; Côte d'Ivoire; Egypt (Egypt (African part)); Equatorial Guinea; Eritrea; Ethiopia; Gabon; Gambia; Ghana; Guinea; Guinea-Bissau; Israel; Kenya; Liberia; Namibia; Niger; Nigeria; Senegal; Sierra Leone; Somalia; South Sudan; Sudan; Togo; Turkey (Turkey-in-Asia); Uganda
Vagrant:
Greece
Additional data:
Upper elevation limit (metres):1500Lower depth limit (metres):55
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:

Limited population data are available through most of the range of Trionyx triunguis.

In Turkey the species occurs in two main areas: the Cukurova delta (Seyhan River mouth) in the south and Dalyan and the Dalaman area in the southwest. In addition, reproduction occurs at seven more sites (Aksu/Acisu, Anamur, Goksu, Berdan River, Tuzla Drainage Channel, Karatas Drainage Channel, and at least formerly, Ceyhan River); recent records indicate that small populations may exist at a few more sites (Patara, Fethiye, Kopru Cayi/Acisu, Bozyazi, Orontes (Asi) River) (Gramentz 2005). All populations are under serious threat, but the one at Cukurova faces the highest pressure, especially from fisheries activity.

A previous nesting record from Lebanon (Demirayak et al. 2002) suggests that nesting may still occur there.

In Israel a robust population is known from the Alexander River. Introduced individuals are known from seven tributaries in the Hula Basin (part of the inland Jordan River system), with reproduction taking place occasionally and hatchlings being captured and moved to the native, coastal rivers (Werner 2016).

The recent status of Egyptian populations is unknown; it is considered to have disappeared downstream of the Aswan Dam, representing most of the historical Egyptian range. A survey of the Nile Delta and its lagoons suggested that it might now be extirpated there (with the possible exception of Bardawill Lake) (Nada 2002). South of the Aswan dam it is fairly common in Lake Nasser with large specimens frequently caught (Baha El Din pers. comm.).

The species is considered fairly common in Sudan, while no population data are available for South Sudan. The species is occasionally caught by fishermen and adults and eggs may be consumed locally; turtles were not seen at the fish landings or in markets in Bor or Juba (P. Baker pers. obs.). Waterfalls and strong rapids may be a barrier to its distribution in the Upper Nile. In Ethiopia, the species does not appear to occur in Lake Tana (the source of the Blue Nile) for this reason, although specimens from there have previously been reported, possibly representing traded or introduced animals.

The species is considered fairly common in Sudan in the main stem of the Nile and in its major tributaries. No current population data are available for South Sudan; however, habitats in its historic range are largely intact. The species is occasionally caught by fishermen, and adults and eggs may be consumed locally; turtles were not seen at the fish landings or in markets in Bor or Juba (P. Baker pers. obs.).  In Ethiopia, Trionyx have been observed in the Tekeze River and the Blue Nile, but does not appear to occur in Lake Tana (elevation = 1788 m), although specimens from there have previously been reported, possibly representing traded or introduced animals, as the ca. 40 m high Blue Nile Falls likely poses a barrier to natural migration to the lake.  Disjunct populations of Trionyx may be found in rivers that flow into Kenya (Omo River) and Somalia (Shabelle River).

The situation in East Africa is unclear and more information is needed, although the species is understood not to be exploited where it occurs and available habitat is good. In Uganda, Trionyx are known from Lake Albert and possibly Lake Edward; however, waterfalls (e.g., Murchison Falls) and strong rapids may be a barrier to its distribution in the Upper Nile. This species has not been observed in Lake Victoria.

In Kenya, Trionyx triunguis is restricted to Lake Turkana and possibly Turkwel River; oil exploration occurs in that region and the desert environment poses a challenge for management of the water resources on which the species depends. Hydroelectric dams on the major rivers that enter Lake Turkana may impact water levels in the lake and further isolate populations. No population is known in Tanzania.

West African populations from Senegal to Nigeria are considered to be rare and threatened; likely the species was never common in the past, when, in some regularly monitored sites, 2-4 specimens/month were reported, now only one is recorded approximately every three years. These populations need urgent assessments for status and demography analyses.

In Senegal, only three records are known; it is hard to find evidence of the species.

In Liberia the species was uncommon in the past and is now very difficult to find.

The species is confirmed from Niamey in the Niger River basin and probably occurs throughout the river basin. Occurrence in the transboundary Parc W, in the Niger basin, is confirmed. Fishermen of the Bozo tribe recognize two kinds of softshells, said to have been very common once upon a time, now very rare, but still present (L. Chirio pers. comm.).

In Togo, this species was first recorded by Matschie (1893) and Tornier (1901). However, these authors reported for its presence the locality of Kété Kratchi, which is currently situated in Ghana. Recently, this species was found in Sokodé area, and another specimen reportedly originating from Togo was observed at a reptile farm located in Lomé (Segniagbeto et al. 2014).

In Nigeria, the species is rare, and inhabits only brackish water rivers with mangroves along the banks (Rivers and Bayelsa States; Stubbs Creek Reserve in Akwa-Ibom State), and enters freshwater tracts along the Cross River. It has also been recorded in Cross River National Park (E. Eniang and L. Luiselli unpubl. data). In Nigeria, it generally occurs at the wide mouth of big rivers and in wide lakes, lagoons and waterbodies.

In Gabon Trionyx triunguis is considered quite common. It is known from Akanda, Ivindo, Loango, Mayumba, Minkebe, and Moukalaba national parks (Vande weghe et al. 2016).

In Angola and Namibia, the southern limit of the species is reached in the mouth of the Cunene River, between Namibia and Angola.  It was first recorded from Namibia by Penrith (1971); Griffin (2003) noted that the species nests at Foz du Cunene, perhaps accounting for reports of Green Turtles (Chelonia mydas) nesting there (Hughes et al. 1973). A single specimen is known from Olushandja dam, but this animal was possibly imported from Angola (C. Eyre pers. comm.). Trionyx is common at the Cunene River mouth and is frequently hooked by fisheries biologists. Animals are occasionally seen in the adjacent sea, but their occurrence and distribution upstream and along the coast is unknown. Besides the Olushandja specimen, only two other Namibian specimens exist (Penrith 1971), and a specimen in the Möwe Bay Museum from Torra Bay. This species also occurs in the Skeleton Coast Park.

Few recent records for Angola include specimens from “the mouth of the river Cunene and its surroundings, in the Cuio region near the mouth of the Coporolo River, on the river Cuanza where I saw nests about 100 km upstream of the mouth, and in the bay of Luanda where a few dozen animals feed. Additionally I have a record of a dead male in the Palmeirinhas region” (Michel Morais, in litt. to WR Branch).  Another large dead adult was recorded on the beach at Soyo, on the southern bank of the Congo River Mouth (W. Klein in litt. to W.R. Branch).

On balance, while the populations and trends in the Mediterranean are relatively well known and offer cause for concern, populations in West Africa and as far south as Angola are poorly known. Large rivers and suitable habitat are few (rapids on the Congo River preclude occupation of the Congo Basin) and populations in the rivers of West Africa are all subject to human population growth and habitat degradation. There is no justification for considering that the remnant West African populations meaningfully protect the species globally.

Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:No
Continuing decline in subpopulations:Yes
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:

Trionyx triunguis inhabits fairly deep water in permanent lakes, rivers, estuaries, coastal lagoons and coastal waters, down to 80 m depth. It is highly tolerant of full seawater conditions for some time (Branch 1988, Baran and Atatur 1998, Taşkavak and Akçınar 2009). In Nigeria, it occurs in brackish water creeks and rivers, with mangroves (Luiselli et al. 2000). May use hot springs in Turkey. In Israel the quality of the habitat, and availability of nesting sites, varies with river fluctuations. It ranges from below sea-level to over 1,500 m (in Africa). In West Africa it is found in both savanna and forested zones (Trape et al. 2012). It is found along the seashore in Angola and at the mouths of larger rivers.

Trionyx feeds on a variety of animal prey (molluscs, insects, crustaceans, frogs, fish), carrion, and vegetarian items (palm nuts, fruits) (Branch 1988, Gramentz 1993, Boycott and Bourquin 2000, Akani et al. 2001).

Large Trionyx triunguis have been recorded at 83 cm SCL and 33 kg weight (Gramentz 2005), 96 cm in Gabon (Pauwels et al. 2017), and a specimen with 108 cm SCL was caught in a bottom trawl in the ocean at 55 m depth at Iskenderun Bay, Turkey (Taskavak and Akçınar 2009). Females produce clutches averaging about 30–40 eggs (but exceptionally up to 60–90 eggs) in exposed sandbanks and banks with heavier soil along rivers (Branch 1988, Spawls et al. 2002, Gramentz 2005, Türkozan unpubl. data) and marine beaches (Türkozan et al. 2006). The SCL of hatchlings is about 45 mm with a mass of 11.6 g (Türkozan et al. 2006). Age at maturity and clutch frequency are unreported (Gramentz 2005). Captive animals have reached over 50 years of age (Branch 2008). For purposes of this assessment, generation time was estimated as at least 20 years.

Systems:Terrestrial; Freshwater; Marine
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):20
Movement patterns:Unknown

Use and Trade [top]

Use and Trade:

Trionyx triunguis is widely collected for consumption in the Sub-Saharan part of its distribution, mainly at local subsistence level (Branch 1988, Spawls et al. 2002). It is also hunted by fishermen for the bushmeat trade in West Africa (for instance, in southern Nigeria; Akani et al. 2001), but the trade level remains low because this species is very rarely encountered in the field. Nonetheless, the meat is highly valued, and the prices are considerable (G.C. Akani, E.A. Eniang, L. Luiselli unpubl. data). Large parts of the range are in areas predominantly occupied by Muslim communities, for whom this species is unsuitable for consumption.

Hatchlings are occasionally sold as pets. Trade data: 1987-2010: 1544 traded. 70% declared as wild-captured exported from Ghana and Togo, imported mainly by EU countries, United States and Japan. Peak declared trade volume was 400-500 animals 1992, in most years about 100, some 200 in 2009.

Threats [top]

Major Threat(s):

Trionyx triunguis is widely collected for consumption in the Sub-Saharan part of its distribution, mainly at local subsistence level (Branch 1988, Spawls et al. 2002). It is also hunted by fishermen for the bushmeat trade in West Africa (for instance, in southern Nigeria: Akani et al. 2001), but the trade level remains low because this species is very rarely encountered in the field. Nonetheless, the meat is highly valued, and the prices are considerable (G.C. Akani, E.A. Eniang, L. Luiselli, unpubl. data).

Animals caught by fishermen may be killed, and nests destroyed, as perceived competitors (e.g., in Turkey: Gramentz (1990), Baran and Atatur (1998)). Bycatch mortality in trawlers off the Çukurova delta (Seyhan, Ceyhan and Berdan rivers) on the coast of Turkey has been reported (Oruc et al. 1997). Boat traffic and water pollution, especially in Dalyan region, has impacted the rate of reproduction and increased the probability of boat collisions; fox predation is the main threat in the main breeding areas, and there is a slightly decreasing trend in nest numbers (O. Türkozan unpubl. data).

Habitat destruction, in particular for tourist and residential developments, is considered a significant threat in at least the Mediterranean part of the species’ range. While construction of dams has been detrimental to Rafetus euphraticus softshells in Turkey, dam construction has been beneficial to T. triunguis in Egypt (Baha El Din pers. comm.). In the Niger Delta of southern Nigeria, this species is locally threatened by oil spills, and tends to completely disappear when its natural habitat is being polluted (Luiselli and Akani 2003, Luiselli et al. 2006). 

Conservation Actions [top]

Conservation Actions:

Trionyx triunguis was listed on Appendix II by CITES in 2016, in addition to all other African softshells; the population in Ghana was also included in CITES Appendix III from 1976 to 2007. As far as can be ascertained, T. triunguis is fully protected from exploitation under the national wildlife laws of Congo, Cote D’Ivoire, Guinea-Bissau, Israel, Mali, Niger, Senegal, Sierra Leone, and Turkey, as well as being under partial protection in Chad (collection under permit only) and Ghana (trade is prohibited); legislative protective status for other countries could not be determined.

The Dalyan (Turkey) population is a tourist attraction, where marine turtle protection measures assist Trionyx. Livelihood alternatives in the form of turtle tourism is in place in Dalyan, and the practices merit expansion to other areas. There have been ongoing reproductive ecology study since 2006 in Seyhan River and Dalyan in Turkey. The species is actively managed and maintained in the wild in Israel. Trionyx triunguis has been recorded from at least three protected areas in Egypt (Baha El Din pers. comm.). Awareness of the species' ecology may help counteract wanton killing by fishermen.

In Turkey a conservation management plan needs to be developed and implemented. In West Africa, urgent conservation measures are needed. Conservation measures will likely need to be focused on maintaining all significant populations, defined by geography / river basin as well as any lineages recovered through molecular phylogeny. Better data on distribution, population status and trends, and information on threats and conservation actions, are required from across the range of the species.


 


Citation: van Dijk, P.P., Diagne, T., Luiselli, L., Baker, P.J., Turkozan, O. & Taskavak, E. 2017. Trionyx triunguis. The IUCN Red List of Threatened Species 2017: e.T62256A96894956. . Downloaded on 21 May 2018.
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