mmsp_650_104.1

AMMALIAN

PECIES

No. 650, pp. 1–3, 2 figs.

Aonyx congicus.

By Serge Larivie`re

Published 23 January 2001 by the American Society of Mammalogists

. 1.

Dorsal, ventral, and lateral views of cranium and lat-

eral view of mandible of

Aonyx congicus

(adult, sex unknown, SMF

4636, locality: Molundu, Dja River, South Cameroon). Greatest
length of skull is 143.5 mm.

Aonyx congicus

(Lo

¨ nnberg, 1910)

Congo Clawless Otter

Paraonyx congicus

Lo¨nnberg, 1910:3. Type locality ‘‘Lower Con-

go.’’

Aonyx microdon

Pohle, 1919:145. Type locality ‘‘Nana-Fluss, bei

Dorf Bomse, Kamerun’’ (

Cameroon).

Paraonyx philippsi

Hinton, 1921:195. Type locality ‘‘British Ru-

anda [

Rwanda].’’

CONTEXT AND CONTENT.

Order Carnivora, family Mus-

telidae, subfamily Lutrinae, genus

Aonyx. Aonyx congicus

often

was placed in its own genus,

Paraonyx,

which would include all

clawless otters with small molariform teeth (Davis 1978). However,
the genus

Paraonyx

does not appear to be valid because tooth size

varies geographically (Davis 1978). Alternatively,

A. congicus

often

is considered either synonymous with

A. capensis

(Davis 1978) or

a subspecies of

A. capensis

(Lo¨nnberg 1910). However, van Zyll

de Jong (1972) and Wozencraft (1993) recognized

A. congicus

and

A. capensis

as separate species. Within

A. congicus,

Kingdon

(1997) recognized 4 subspecies:

A. c. congicus, A. c. microdon,

A. c. philippsi,

and

A. c. poensis.

However,

A. c. poensis

refers to

Lutra maculicollis

(Harris 1968; Lo¨nnberg 1910), and the small

geographic distribution of the species likely does not warrant sub-
specific designation. Thus, recent authorities consider the species
monotypic (Wozencraft 1993).

DIAGNOSIS.

The Congo clawless otter is very similar to the

Cape clawless otter (

A. capensis),

but the 2 species are only sym-

patric in Rwanda and Uganda. The Congo clawless otter has a more
slender neck and head and smaller and more deeply cusped molars
than does the Cape clawless otter (Kingdon 1997).

Aonyx congicus

also is sympatric with the spotted-neck otter

(

Lutra maculicollis

) and the water mongoose (

Atilax paludinosus

However,

Aonyx congicus

lacks foot webbing and the spotted mark-

ings on the neck and throat of

L. maculicollis

(Rowe-Rowe 1978).

The water mongoose has a darker pelage compared with the brown-
and-white coloration of the Congo clawless otter (Dorst and Dan-
delot 1970).

GENERAL CHARACTERS.

Pelage is dark brown with con-

spicuous silvery gloss on the anterior parts of the body due to white
tips on hairs. Vibrissae, sides of face, ears, nose, and upper parts
of the chest are grayish or white (Dorst and Dandelot 1970; Lo¨nn-
berg 1910). A distinct marking of black fur exists between the eyes
and nostrils (Kingdon 1977).

Front feet lack claws and webbing. Hind feet are partially

webbed, and small claws are present on digits 2, 3, and 4 (Lo¨nn-
berg 1910).

Mean (range) length of head and body (sex and sample size

unknown) is 85 cm (79–97 cm), and length of tail is 50 cm (41–
56 cm—Kingdon 1977, 1997; Lo¨nnberg 1910). Body mass of adults
ranges from 14 to 34 kg (Kingdon 1977, 1997).

Skull (Fig. 1) is massive. Teeth are smaller and sharper than

those of

A. capensis

(Lo¨nnberg 1910; Rowe-Rowe and Somers

1998). No skull measurements have been published.

DISTRIBUTION.

The Congo clawless otter occurs in the

rainforest of the Congo River basin (Rahm 1966; Rahm and Chis-
tiaensen 1966), extending eastward to the forests and wetlands of
Rwanda, Burundi, and Uganda (Fig. 2). It is common in Central
African Republic and Zaire, rare in Angola, Congo, Gabon, Rwan-
da, and Uganda, and very rare in Cameroon (Crawford-Cabral 1989;
Rowe-Rowe 1990a, 1990b, 1995). The species may occur in Bu-
rundi and Nigeria, although its status in these countries is unknown
(Rowe-Rowe 1990a, 1990b).

FOSSIL RECORD.

The Lutrinae reached Africa in the Plio-

cene, but most ancestral forms cannot be linked to current forms
(van Zyll de Jong 1972).

Aonyx

is first genus recorded from the

late Pleistocene at Swartklip and Florisbab in South Africa and at

MAMMALIAN SPECIES 650

. 2.

Distribution of

Aonyx congicus

in Africa (modified

from Davis 1978; Rowe-Rowe 1990a; Rowe-Rowe and Somers
1998).

Gamble’s sites in Kenya (Hopwood and Hollyfield 1954; Savage
1978), but no information is available on the specific fossil record
of

Aonyx congicus

(Savage 1978).

FORM AND FUNCTION.

The structure of the toes suggests

that the Congo clawless otter may be more terrestrial than the Cape
clawless otter (Dorst and Dandelot 1970; Lo¨nnberg 1910). The de-
velopment of sensitive, clawless fingers is an adaptation for finding
food by feel in muddy and cloudy water (Lo¨nnberg 1910; Kingdon
1997). Molars and premolars are sharper than those of

A. capensis,

and the skull is slightly smaller (Harris 1968). This weaker den-
tition may be useful for cutting fish (Dorst and Dandelot 1970;
Rowe-Rowe and Somers 1998).

ECOLOGY.

Nothing is known of the reproduction of

A. con-

gicus,

and very little is known about its biology in general (Mason

1990; Rowe-Rowe 1986, 1995; Rowe-Rowe and Somers 1998).
Congo clawless otters occur mostly in rain forests and lowland
swamp forests, but they also may inhabit forested rivers and streams
(Rowe-Rowe 1990b; Rowe-Rowe and Somers 1998). Congo claw-
less otters consume mostly fish and crabs, but they opportunistically
eat giant worms, frogs, clawed toads (

Xenopus

), lizards, insects, and

aquatic birds (Baranga 1995; Carpaneto and Germi 1989). Only 1
parasite has been reported, the nematode

Microfilaria aonycis

(Round 1968).

Aonyx congicus

is sympatric with the water mongoose, spot-

ted-necked otter, and Cape clawless otter. Most likely, segregation
in diet allows those species to coexist (Rowe-Rowe and Somers
1998).

Potential predators of Congo clawless otters include crocodiles

(

Crocodilus

), leopards (

Panthera pardus

), pythons (

Python

), and

large raptors (Carpaneto and Germi 1989; Kingdon 1997). Congo
clawless otters are hunted for fur, may be captured in fish nets or
fish traps accidentally, and may be killed by fishermen who regard
them as competitors or because they damage fish traps (Kingdon
1977, 1997; Rowe-Rowe 1990b). Most regions in which

A. con-

gicus

occurs are sparsely inhabited by humans, but on the fringes,

deforestation, drainage of wetlands, and agriculture may alter or
destroy natural habitats of the Congo clawless otter (Rowe-Rowe
1990b). Mbuti pygmies in northeastern Zaire use the skins of Congo
clawless otters to make hats (Carpaneto and Germi 1989). The con-
servation status of

A. congicus

is unknown in many countries

(Rowe-Rowe 1990a, 1990b).

BEHAVIOR.

Congo clawless otters are mostly nocturnal and

solitary. They are excellent swimmers and often explore the shores
of rivers and swamps when foraging (Kingdon 1997). During the
day, they sleep in natural cavities along rivers (Carpaneto and Ger-
mi 1989).

GENETICS.

Aonyx congicus

has 2n

38 chromosomes (van

Zyll de Jong 1987).

REMARKS.

Similarities in morphology, ecology, and behav-

ior have contributed to the recurring placement of

A. congicus

un-

der

A. capensis.

Thus, unknown biological characteristics of this

species may be inferred from the better known

A. capensis.

Other

vernacular names for

A. congicus

include Zaire clawless otter,

swamp otter, loutre a` joues blanches du Congo (French), and Kongo
weisswangen-otter (German). The etymological origin of

Aonyx

from the Greek

meaning ‘‘without’’ and

onyx

meaning ‘‘claw or

nail’’ (Borror 1960). The specific epithet

congicus

is from the Latin

suffix

icus

meaning ‘‘to belong to’’ and refers to the original type

locality (

Congo).

D. Dyck, M. Mierau, and C. Moore helped with the map. K.

Fuhrmann helped in locating a suitable skull, and Dr. G. Storch of
the Senckenberg Forschungsinstitut und Museum, Germany kindly
provided skull photographs. D. T. Rowe-Rowe and M. J. Somers
reviewed an earlier draft of this manuscript.

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Editors of this account were E

LAINE

NDERSON

and L

ESLIE

N. C

RAWAY

. Managing editor was V

IRGINIA

AYSSEN

S. L

ARIVIE

` RE

, D

EPARTMENT OF

IOLOGY

, U

NIVERSITY OF

ASKATCH

EWAN

, 112 S

CIENCE

LACE

, S

ASKATOON

, S

ASKATCHEWAN

S7N 5E2,

ANADA

AND

NSTITUTE FOR

ETLAND AND

ATERFOWL

, D

UCKS

NLIMITED

, O

ATERFOWL

, M

EMPHIS

, T

NESSEE

38120-2351.