Location of OBA film 4:3
The Tagant, Mauritania and Senegal River
(mouse-over for view of the Tagant)
THE QUEST SPECIES
The most familiar and widespread crocodile in Africa, the ‘Nile crocodile’ (Crocodylus niloticus) was once much more widely distributed with prehistoric records from Sicily and the Mediterranean, possibly even southern France. The main conduit into the Mediterranean was probably the Nile delta, which housed a sizeable population of crocodiles until the late 18th century and also facilitated their movement into the rivers of what are now Syria, Israel and Jordan.
After two centuries of persecution the crocodile has been extirpated from the lower reaches of the very river that provided its name, and now only occurs in the Nile above Aswan, in southern Egypt and Sudan. During the 19th or early 20th century it was extirpated from Israel, Jordan, Syria, Libya, and Comoros, the result being that today the Nile crocodile is primarily associated with sub-Saharan tropical Africa and Madagascar. The concept of water-loving crocodiles living in the Sahara Desert is alien.
However, in the past the Sahara Desert was also much smaller than it is today. Currently going through a period of expansion, the desert is spreading into the semi-arid Sahel with the result that the Sahel is encroaching into the more vegetated areas at its southern boundaries. Much of what is now arid desert or semi-arid Sahel was once well-watered grassland or woodland. Crocodile populations from those earlier times have persisted for centuries in isolated aquatic refugia, often in upland areas or mountain ranges, surrounded by otherwise inhospitable arid lowland habitats. During the 19th and early 20th centuries, small crocodile populations were reported from southern Morocco/western Algeria (Oued Drâa), southern Algeria (Tassili n’Ajjer and Haggar Mts), central Tunisia (Chott el Djerid), northwestern Chad (Tibesti Mts), northeastern Chad (Ennedi Plateau), and southern Mauritania (Tagant, Assaba, Hodh El Gharbi and Hodh Ech Chargui Provinces). However, human persecution and environmental pressures, in the form of extreme droughts, are believed to have caused the 20th century demise of most of these populations, only the Chadian Ennedi population being confirmed extant with two individuals being sighted in a guelta* (Tubiana 1995).
|Desert crocodile populations known during the 20th century.
By the 1990s the southern Mauritanian population was believed to have gone extinct, prompting the Crocodile Specialist Group (CSG) of the IUCN (International Union for the Conservation of Nature) to declare the Nile crocodile extirpated from Mauritania (Thorbjarnarson, 1992). This action was premature, as in 1993 five gueltas in the 400m Tagent (Matmâta, Ederoum, Amzouzef, Rh Zembou and Laout) were subsequently found to still contain crocodiles, discovered by three French students with no previous crocodilian background, (Behra, 1994) but researchers visiting the area in 1996 determined that the populations were be too small and too isolated to ensure their continued survival (De Smet, 1999) and extinction was virtually inevitable.
A more recent and optimistic report (Shine et al 2001) suggested that southern Mauritanian crocodiles might be more numerous and more widely distributed than previously thought. Locals reported that as many as 28 wetland areas still contained crocodiles in the Tagent, Assaba, Hodh El Gharbi and Hodh Ech Chargui Provinces. A lack of interest in hunting crocodiles amongst Mauritanians may have contributed to their survival, but Malians, who did hunt crocodiles and had extirpated their own populations, were now encroaching into these remote areas in search of crocodiles.
Surviving populations of desert crocodiles, which were noticably smaller than crocodiles from East and southern Africa, were now known to exist in two countries: southern Mauritania and northeastern Chad. This was the scenario that triggered the film “Crocodile Canyon” in 2003.
At the same time as the expedition put into the field, there was another question that required answering. Were these desert crocodiles simply isolated dwarf Nile crocodiles (C.niloticus) or did they belong to a separate species?
A paper appearing in mid 2003 definitively answered this question. Not only were the desert crocodiles of the Sahara, from Mauritania to Chad, a separate species from C.niloticus of Eastern and Southern Africa, and Madagascar, but all West African crocodiles warranted specific recognition since they were genetically closer to the Australian freshwater crocodile (C.johnstoni) than the Nile crocodile.
The name C.suchus, coined by Geoffroy (1807) with the type locality as the Niger River, was available for the Northwest African crocodile.
Three of the authors of the molecular paper, Tara Shine, Hemmo Nickel and Wolfgang Böhme, had been intimately involved in the survey and conservation work on the desert crocodiles (Anon. 2000), and one Hemmo Nickel, was the contributor on the film “Crocodile Canyon”.
* Hassaniyan Arabic terms are used to describe important habitats in the Tagent and four are relevant for crocodiles:
Gaat = open wetland or plain exploited for agriculture
Guelta = small temporary or permanent pools, often in rocky areas and fed by springs
a seasonal river or wadi that either disappears in the dry season or shrinks to a chain of small stagnant pools
Tamourt = shallow lake area
on a clay soil, often fringed by Acacia
Anon. 2000 Remnant crocs found in Sahara. Science 18 February 2000 287(5456):1199.
Behra, O. 1994 Crocodiles on the desert's doorstep. Crocodile Specialist Group Newsletter 13(1):4-5.
De Smet, K. 1999 Status of the Nile crocodile in the Sahara desert. Hydrobiologia. 391:81-86.
Shine, T., W.Böhme, H.Nickel, D.F.Thies & T.Wilms 2001 Rediscovery of relict populations of the Nile crocodile Crocodylus niloticus in south-eastern Mauritania, with observations on their natural history. Oryx 35(3):260-262.
Schmitz, A., P.Mausfeld, E.Hekkala, T.Shine, H.Nickel, G.Amato & W.Böhme 2003 Molecular evidence for species level divergence in African Nile Crocodiles Crocodylus niloticus (Laurenti, 1786). Compus Rendus Palevolution 2:703-712.
Thorbjarnarson, J. 1992 Crocodiles: An Action Plan for the Conservation. IUCN/SSC Crocodile Specialist Group. vii+136.
Tubiana, J. 1995 Les crocodiles d'Archi. Courier de la Nature 153:26-29.
Northwest African crocodile, Crocodylus suchus
in Djoudj Wildlife Reserve, Senegal
South-central Mauritania with the Tagant Province outlined, elevated Tagant Plateau in the southwest, and main towns and Lake Gabou indicated.
(click on map for enlarged view)
Facts about the Tagant
(sources Wikipedia and others)
The Tagant is a province in southern Mauritania, named for the elevated rocky Tagant Plateau which rises 400m above the sandy desert. The provincial capital of Tagant Province is Tidjikdja on the plateau itself, but most other towns, such as Moudjéria and Tîckît, lie at the feet of the escarpments.
This elevated region was once an agriculturally rich area with cereal crops being grown in the soils that covered the now bare black rocks of the escarpments. Stone grain stores still stand as testiment to former, better times.
The Sahelian gueltas and oueds (see above) on the Tagant Plateau contain some of the last remaining desert crocodiles but also supports some 40,000 nomadic herdsmen and their livestock. This 700km hydrological network feeds into Gabou Lake in the northwest of the Gabou Basin on the edge of the Tagant (Tellería et al 2008), some fewer than 10kms from similar water-courses that feed into the Senegal River further south.
Crocodiles are also know to occur further southeast in the provinces of
Assaba, Hodh El Gharbi and Hodh Ech Chargui (Cooper et al 2006; Padial 2006) so not all the Mauritanian crocodile eggs are in one basket.
Cooper, A., T.Shine, T.McCann & D.A.Tidane 2006 An ecological basis for sustainable land use of Eastern Mauritanian wetlands. Journal of Arid Environments 67:116-141.
Padial, J.M. 2006 Commented distributional lit of the reptiles of Mauritania (West Africa). Graellsia 62(2):159-178.
Tellería, J.L., H. El Mamy Ghaillani, J.M.Fernández-Palacios, J.Bartolomé & E.Montiano 2008 Crocodiles Crocodylus niloticus as a focal species for conserving water resources in Mauritanian Sahara. Oryx 42(2):292-295.
The Film Crew and Expedition Participants
From the UK:
Jon Stephens (Director)
Amy Lansdown-Nasson (Associate Producer)
Mark O'Shea (Presenter)
Mark Stokes (Camera)
Terry Meadowcroft (Sound recordist)
Jon Pinkney (Second camera)
Hemmo Nickel (Contributer and crocodile biologist)
Mouloud (fixer and guide, Surmi Voyages)
|The crew (L-R) Jon Pinkney (second camera), nomadic arab,
nomadic arab, Mark O'Shea, nomadic arab, Mark Stokes (camera), Terry Meadowcroft (sound recordist).
|Mark and German herpetologist and desert crocodile specialist
Hemmo Nickel from Zoologisches Forschungsinstitut und Museum Alexander Koenig.
Due first two days of the expedition, after arrival in the Mauritanean capital Nouakchott, were sent in Senegal the spent in the Djoudj Wildlife Reserve on the Senegalese side of the Senegal River delta.
Subsequently the expedition decamped to the Mauritanean Sahara, setting up camp first on the dunes before Moudjéria and then transferring to the Oued le Glat leading to Matmâta on the southern Tagant Plateau.
From the camp in Oued le Glat the expedition made trips up the gorge to Matmâta, over the plateau to beyond the Matmâta waterfall and south to Lake Bouraga and Husseiniya.
The quest was confined to the southern portion of the Tagant Plateau and the Senegal River delta.
Main localities indicated on map.
(click on map for enlarged view)
The locations in Senegal and Mauritania in 2003 were:
a) Djoudj Wildlife Reserve
a) Nouakchott to Moudjéria
b) Matmâta camp
c) Oued El Glat & Hartéga Guelta
d) Tagant Plateau
e) Lim Sherba
f) Oued Bourâgga & El Housseînîya
g) Ayoun El Atrous
h) Back to Nouakchott
Filming schedule & itinerary:
Friday 14th March - Journey out and arrive Nouakchott
Saturday 15th March - Djoudj Reserve, Senegal River
Sunday 16th March - Djoudj Reserve, Senegal River, then return Nouakchott
Monday 17th March -Nouakchott to Moudjéria
Tuesday 18th March - Moudjéria to Matmâta
Wednesday 19th March - Matmâta
Thursday 20th March - Matmâta, Oued El Glat, Hartéga Guelta & Tagent Plateau
Friday 21st March - Tagent Plateau & Lim Sherba
Saturday 22nd March - Matmâta & Lim Sherba
Sunday 23rd March - Matmâta & Lim Sherba
Monday 24th March - Matmâta, Oued Bourâgga
Tuesday 25th March - Matmâta, Oued Bourâgga & Housseînîya
Wednesday 26th March - Matmâta & Lim Sherba
Thursday 27th March - Matmâta & Lim Sherba
Friday 28th March - Matmâta & Lim Sherba
Saturday 29th March - Moudjéria
Sunday 30th March - Depart Nouakchott, arrive home
Expedition Results include a full life-list for the 2003 expedition to Mauritania and Senegal.