Sousa teuszii (Kükenthal,
English: Atlantic humpback dolphin, Cameroon dolphin
Spanish: Delfín jorobado del Atlántico
French: Dauphin du Cameroun
Sousa teuszii © Würtz-Artescienza (see
Humpback dolphins are medium sized and robust. Their melon is slightly
depressed and slopes gradually to an indistinct junction with the
long, narrow beak. The broad flippers are rounded at the tip and
the flukes are broad and full, with a deep median caudal notch.
The dorsal fin emerges from a hump or ridge of connective tissue
on the back. Body length reaches 2.8m and body mass 284 kg. Colour
is somewhat variable with slate gray on the back and light gray-whitish
below. Some animals have dark spots on the tail stock and near the
base of the fin (Jefferson et al. 2008).
Recent morphological as well as genetic research confirms that S.
teuszii is in fact a separate species of the genus Sousa (Jeffersson
and Van Waerebeek, 2004; Frere et al., 2008).
Sousa teuszii ranges on the coast of West Africa from Dakhla Bay
(23°54'N) in Western Sahara south to Tombua (15°47'S), southern
Angola. A total of six contemporary management stocks are provisionally
discerned: Dakhla Bay (Western Sahara), Banc d'Arguin (Mauritania),
Saloum-Niumi (Senegal), Canal do Gêba-Bijagos (Guinea-Bissau),
South Guinea and Angola. Two stocks are historical (now extirpated):
Cameroon and Gabon Estuary (Van Waerebeek et al. 2004).
Distribution of Sousa teuszii: coastal
waters of tropical West Africa
(Reeves et al. 2008; © IUCN; enlarge
The species remains unrecorded in Ghana and neighbouring
nations despite apparently suitable coastal habitat (Van Waerebeek
et al. 2009).
3. Population size
S. teuszii seems to be particularly common in southern Senegal
and northwestern Mauritania (Carwardine,1995). However, there are
no rigourous population estimates for any of the regions where the
species might exist (Van Waerebeek et al., 2004). From north to
south, the Dakhla Bay and the Banc d'Arguin stocks appear to be
very small (Van Waerebeek et al., 2004). Rough population estimates
for the Saloum delta, Senegal were 100 animals (Ross et al. 1994,
Reyes, 1991 and refs. therein). The high number of opportunistic
sightings suggests that the still relatively undisturbed waters
of Guinea-Bissau, enclosing extensive mangrove forest habitat, may
support one of the largest known populations of S. teuszii: the
Canal do Gêba-Bijagos stock. The status of the South Guinea,
Cameroon and Gaboon Estuaries management stocks is unknown, although
the latter two are likely extinct. The Angola stock is presumably
very small (Van Waerebeek et al. 2004), but its existence was recently
confirmed (Weir, 2007).
4. Biology and Behaviour
Habitat: This species prefers coastal and estuarine waters
less than 20m deep and occurs in the surf zone on more open coasts.
There are no reports of its presence in offshore waters. The preferred
habitat is near sandbanks and mangrove areas, in turbid waters with
temperatures ranging between 17°C and 28°C (Maigret, 1982,
in Ross et al. 1994). It has been recorded up to 33 miles up the
Saloum River and is known to enter the Niger and Bandiala Rivers,
and possibly others, though it rarely travels far upstream and usually
remains within the tidal range (Carwardine, 1995).
Photo: Jaap van der Toorn @ Jaap's Marine Mammal
Pages (see "links").
Schooling: Humpback dolphins form small schools throughout
their distribution, ranging from one to about 25 dolphins off West
Africa (Ross et al., 1994 and refs. therein).
Reproduction: Breeding has been reported in March and April,
but the season may be more protracted (Jefferson et al., 1993).
Food: Schooling fish e.g. mullet (Jefferson et al., 1993).
Stomachs contained pomadasyid, clupeid and mugilid fish (Ross et
al. 1994 and references therein). There is no evidence for herbivory
as suggested by Kükenthal (1892) (Jefferson et al. 1993).
Busnel (1973; in Ross, 1994) described a remarkable example of a
symbiotic relationship between fishermen and groups of bottlenose
dolphins on the Mauritanian coast around Cap Timiris, north of Nouakchott.
The fishermen wait for migrating shoals of mullet to appear close
to shore, and then apparently summon the dolphins by slapping sticks
on the water surface. The dolphins effectively contain the mullet
on their seaward edge while feeding, enabling the fishermen to deploy
their nets around the fish more easily. Humpback dolphins also take
part in the cooperative harvest, though perhaps fortuitously, since
the method probably requires a larger number of dolphins than the
usual humpback school size.
There are signs of a probable north-south migration, and there
is a potential exchange of individuals between known population
or subpopulation distribution centres (from north to south): Dakhla
Bay (Western Sahara), Banc d'Arguin (Mauritania), Langue de Barbarie
(Senegal), Sine Saloum delta (Senegal), NW bank of the Gambia River
outer estuary (The Gambia) and Guinea-Bissau archipelago (Van Waerebeek
et al. 2000).
Regular cross-border movements between the Saloum Delta (Senegal)
and Niumi National Park (The Gambia) technically qualifies S.
teuszii as a "migratory species" under the Conservation
of Migratory Species (CMS) Convention (Van Waerebeek et al., 2004).
They have been recorded in the Saloum Estuary from January to April,
with very few observations in subsequent months. However, catch
data show that the species was taken north of the estuary from June
to August (Reyes, 1991 and ref. therein, confirmed by Ross, 2002).
Daily movements observed off Senegal show that humpback dolphins
move onshore with the rising tide to feed in the mangrove channels
of the Saloum Delta, returning towards the sea with the ebb tide
(Maigret, 1981 in Ross et al. 1994).
Maigret (1982, in Reyes, 1991) recorded sightings of this species
in the Banc d' Arguin (Mauritania) between May and January, with
a peak in August and September.
Direct catch: A few Atlantic humpback dolphins have reportedly
been taken along the range. No recent information is available,
but direct catches still may occur (Reyes, 1991; Van Waerebeek et
Incidental catch: There are reports of incidental catches
in beach seines and shark nets in Senegal. Past and present levels
of these captures remain unknown (Reyes, 1991 and refs. therein).
The most recent interaction in Senegal was recorded in November
1996, when three animals were found together, each with a piece
of netting tied around the tailstock, on a beach of Sangomar Island
in the Saloum delta, probably an abandoned take. In Guinea-Bissau,
a 190-cm male was by-caught in a fishing trap at Canhabaque Island,
Bijagós in March 1989 (van Waerebeek et al. 2000 and refs.
Habitat degradation: In Senegal there has been a permanent
reduction of mangrove areas for extension of rice culture and exploitation
of forest, especially in the Fathala area. Excessive fishing of
prey species may reduce food availability and increase the risk
of incidental catch. Pollution may also be a source of habitat destruction,
since the species inhabits areas with high population growth subject
to agricultural and industrial development (Reyes, 1991 and refs.
therein). The possible fracturing of the species' habitat range,
resulting in reproductively isolated groups, due to coastal development
should be monitored (van Waerebeek et al. 2000).
Range states (Reeves et al. 2008) :
Angola; Cameroon; Congo; Côte d'Ivoire; Gabon; Gambia; Guinea;
Guinea-Bissau; Liberia; Mauritania; Nigeria; Senegal; Western Sahara.
Sousa teuszii is listed in Appendix I&II of CMS. The
World Wide Fund for Nature (WWF) considers S. teuszii as
one of the most endangered small cetaceans world-wide (WWF, 2009).
Sousa sp. is listed in Appendix I of CITES. The species is
categorized as "Vulnerable" by the IUCN (Reeves et al.
2008). This is based on the fact that the current population size
is below 10,000 with local populations smaller than 1,000 animals.
There is an inferred or suspected continuing decline in population
size with ongoing threats (see above).
There is a need to obtain baseline abundance data and establish
seasonal patterns of distribution for S. teuszii in northwestern
Africa, as well as investigate the level of genetic interchange
among different dolphin communities. At least two boat surveys,
one each in the rainy and dry season, would need to be conducted
in the estuarine and larger creek systems, and the coastal shelf
waters of southern Senegal and The Gambia. Similar surveys of inshore
and coastal waters are needed in Dakhla Bay and other parts of the
Western Saharan and Moroccan coasts known or suspected to have humpback
dolphins (Reeves et al 2003).
· Carwardine M (1995) Whales, Dolphins and Porpoises. Dorling
Kindersley, London, UK, 257 pp.
· Frere CH, Hale PT, Porter L, Cockcroft VG, Dalebout ML
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of humpback dolphin (Sousa spp.) taxonomy is needed. Mar
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identification guide. Marine mammals of the world. UNEP/FAO, Rome,
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· Reyes JC (1991) The conservation of small cetaceans: a
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the Conservation of Migratory Species of Wild Animals. UNEP/CMS
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S. plumbea, and S. teuszii. In: Encyclopedia of marine
mammals (Perrin WF, Würsig B, Thewissen JGM, eds.) Academic
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· Van Waerebeek K, Ndiaye E, Djiba A, Diallo M, Murphy P,
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Secretariat, Bonn, Germany,. 80 pp. PDF-copy of full report: (www.wcmc.org.uk/cms/reports/WAFCET/
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© Boris Culik (2010) Odontocetes.
The toothed whales: "Souza teuszii". UNEP/CMS Secretariat,
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.