INSECTIVORA

Insectivora Id code: amd028

Tenrecidae
Potamogale velox

(Du Chaillu, 1860)

(Eng) Giant otter-shrew

(Fre) Potamogale

Taxonomic notes

No significant taxonomic notes.

IUCN threat category

Endangered (EN: criteria B1+2c).

Available information

A study on the main aspects of the ecology of the species was carried out in the Makak District (central-south Cameroon) by Nicoll (1985); the author reports mainly on its density, feeding habits, activity patterns, and intraspecific relationships. Data on its presence in north-eastern Gabon are found Brosset (1988). General information on the species' ecology and distribution is found in Kingdon (1971-77, 1997). Status, threats, and distribution are discussed in Nicoll & Rathbun (1990); the authors also describe the habitat in which the species is found.

Known extent of occurrence

Ranging in tropical Africa, the giant otter-shrew is recorded from Nigeria (to the east of the Cross River) eastwards to Uganda, Rwanda, Burundi and Tanzania and southwards to north Zambia and Angola (to the north of the Cuanza River) (Wilson & Reeder, 1993; Nicoll & Rathbun, 1990; Kingdon, 1997). A separate population occurs to the east of Lake Victoria between Uganda and Kenya. Its distribution map was first obtained from Kingdon (1971-77), then updated using the more recent map in Kingdon (1997) and finally refined to match the river network. The result is shown in Fig. 1.1.3.a.

Categorical-discrete (CD) distribution model

This species occurs in rivers, streams and swamps in rain forest; it is also found in montane torrents (Nicoll & Rathbun, 1990; Kingdon, 1971-77).

Based on these environmental preferences, the following scores were assigned (Fig. 1.1.3.b) (Tab. 1.1.3.a):

Score
1	Forests occurring inside a 1-km buffer around permanent water.
2	Forest mosaics and montane vegetation occurring inside a 1-km buffer around permanent water.
3	Savannas; croplands; all vegetation types occurring outside a 1-km buffer around permanent water.

suitable		moderately suitable		unsuitable		Total
km²	%	km²	%	km²	%	km²	%
819 890	18	171 621	4	3 509 266	78	4 500 777	100

Tab 1.1.3.a: Cumulative size (km2) of areas pertaining to each environmental suitability class within the Extent of Occurrence.

	Number Patches (NP)	Mean Patch Size (MPS) km²	Patch Size SD (PSSD) km²	Largest Patch Index (LPI) %	Mean Shape Index (MSI)	Area-Weighted Mean Shape Index (AWMSI)
suitable	5 573	146	1 059	6.09	1.44	6.64
moderately suitable	2 844	60	106	0.18	1.19	1.82
Total AO	6 846	144	1 301	10.01	1.43	7.37

Tab 1.1.3.b: Area of Occupancy fragmentation indexes.

Probabilistic-continuous (PC) distribution model

The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 1.1.3.c.

Validation

% of EO in sample areas	Number of valid plots	Index of Accordance (%)
10.97	152	67.11

Tab 1.1.3.c: Categorical-discrete (CD) distribution Comments and conservation issues

The good percentage of EO (10.97%) included in the validation sample areas and the high Index of Accordance (67.11%) support the results of the CD model. In fact, despite the large EO covering most of the central forest block, the actual distribution of the species is restricted to permanent water bodies: 22% of the EO is thus suitable, along the network of rivers and lakes. The CD model shows this pattern and the PC model smoothes the suitability across the entire range. The isolated patch in Kenya and Uganda appears to be of lower suitability. Fragmentation is therefore very high, as shown by the number of patches, their MPS and their PSSD. The LPI (10.01%) confirm the extreme patchiness of the whole AO. For this main reason the species is classified as Endangered, while only 5% of its AO is included in existing protected areas.

SUITABILITY CLASS	inside	outside	Total
suitable	0.98	17.24	18.22
moderately suitable	0.13	3.69	3.81
unsuitable	4.47	73.50	77.97
Total	5.58	94.42	100

Tab 1.1.3.d: Percent of environmental suitability classes within EO (as obtained from the categorical-discrete distribution model) inside and outside the protected areas.

References

Brosset A. (1988). Le peuplement de mammifères insectivores des forets du nord-est du Gabon. Revue de Ecologie (La Terre et la Vie): 43, 23-46.

Kingdon J. (1971-77). East African Mammals. VOL I: primates, hyraces, pangolins, protoungulates, sirenians. VOL IIA: Insectivores and bats. VOL IIB: hares and rodents. VOL IIIA: carnivores. VOL IIIB: large mammals. VOL IIIC: bovids. VOL IIID: bovids. Academic Press, London and New York.

Kingdon J. (1997). The Kingdon field guide to African Mammals. Academic Press, London and New York: Natural World.

Nicoll M.E. (1985). The biology of the Giant otter-shrew Potamogale velox. Nat. Geo. Soc. Research Report s: 21, 331-337.

Nicoll M.E., Rathbun G.B. (Eds) (1990). African Insectivora and Elephant-Shrews. An Action Plan for their Conservation. IUCN/SSC Insectivore, Tree-Shrew and Elephant Shrew Specialist Group.

Wilson D.E., Reeder D.M. (Eds) (1993). Mammal Species of the World: A Taxonomic and Geographic Reference. Second edition. Smithsonian Institution Press, Washington D.C.