download

Artiodactyla Id code: amd142

Hippopotamidae

Hexaprotodon liberiensis

(Morton, 1849)

(Eng) Pigmy hippopotamus

(Fre) Hippopotame pigmée

Taxonomic notes

Formerly included in Choeropsis, it is currently regarded as the only living species of its genus (Wilson & Reeder, 1993), with two subspecies: H. l. liberiensis and H. l. heslopi (Oliver, 1993, 1995).

IUCN threat category

Critically Endangered (CR: criteria D1) as H. l. heslopi in Nigeria.

Available information

Literature available on the species’ ecology is very scarce. A study on the activity rhythms was conducted by Galat-Luong (1981) in the Tai National Park (Ivory Coast). Some data on its habitat and diet are available for Nigeria (Osemeobo, 1988). General information on the species’ ecology and distribution are found in Estes (1991), Kingdon (1997), and Stuart & Stuart (1997). Status, distribution and ecology are discussed in Oliver (1993).

Known extent of occurrence

Mainly confined to Liberia, the pygmy hippo may also survive in Nigeria and possibly Guinea Bissau, while its occurrence has been confirmed in Guinea, Ivory Coast and Sierra Leone (Oliver, 1993; Wilson & Reeder, 1993). Its distribution map was acquired from Oliver (1993); Dr. H. Klingel revised the map (31 January ‘97) (Fig. 8.2.1.a).

Categorical-discrete (CD) distribution model

The species is closely associated with water bodies in forested areas (Oliver, 1993; Nowak, 1991; Kingdon, 1997; Stuart & Stuart, 1997).

Based on these environmental preferences, the following scores were assigned (Fig. 8.2.1.b) (8.2.1.a):

Score

  

1

Forests occurring inside a 10-km buffer around permanent water

2

Forest mosaics occurring inside a 10-km buffer around permanent water

3

Croplands, savannas and their mosaics; all vegetation types occurring outside a 10-km buffer around permanent water

 

suitable

moderately suitable

unsuitable

Total

OCCURRENCE

km2

%

km2

%

km2

%

km2

%

certain

10 350

30

5 132

15

3 385

10

18 867

55

possible

8 911

26

4 715

14

1 536

5

15 162

45

Total

19 261

57

9 847

29

4 921

14

34 029

100

Tab 8.2.1.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

35

547

897

14.53

1.76

3.17

moderately suitable

70

142

422

11.26

1.31

3.04

Total AO

12

2 423

3 020

41.53

1.91

2.87

Tab 8.2.1.b: Area of Occupancy fragmentation indexes.

Probabilistic-continuous (PC) distribution model

The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 8.2.1.c.

Validation

No occurrence of the species within the four sample areas.

Comments and conservation issues

The species survives in a few pockets of forest in several west African countries: the small populations in Guinea Bissau and Nigeria, if still existent, are cut off from the main group of populations in Liberia, Sierra Leone and Ivory Coast. Within the areas of certain presence, the EO is largely suitable, confirming that the disappearance of the species is mainly due to hunting and not to habitat destruction. The total amount of suitable areas available within the three countries is about 15 000 km2, divided into at least 8 separate sub-areas with some further fragmentation due to the habitat suitability. Virtually none of the AO is included in any protected area and the species is correctly classified as Critically Endangered.

OCCURRENCE

SUITABILITY CLASS

inside

outside

Total

certain

suitable

0.01

30.41

30.42

moderately suitable

0

15.08

15.08

unsuitable

0.13

9.82

9.95

possible

suitable

0

26.19

26.19

moderately suitable

0

13.86

13.86

unsuitable

0

4.51

4.51

Total

0.14

99.86

100

Tab 8.2.1.c: Percent of environmental suitability classes within EO (as obtained from the categorical-discrete distribution model) inside and outside the protected areas.

References

Estes R.D. (1991). The Behaviour Guide to African Mammals. Including Hoofed Mammals, Carnivores, Primates. The University of California Press.

Galat-Luong A. (1981). Quelques observations sur un hippopotame pygmée nouveau-né (Choeropsis liberiensis) en foret de Tai, Côte d'Ivoire. Mammalia: 45(1), 39-41.

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

Nowak R.M. (1991). Walker's mammals of the World. Johns Hopkins University Press: Baltimore: 2 vols.

Oliver W.L.R. (Ed.) (1993). Pigs, Peccaries, and Hippos. Status Survey and Conservation Action Plan. IUCN/SSC Pigs and Peccaries Specialist Group & IUCN/SSC Hippo Specialist Group.

Oliver W.L.R. (1995). Taxonomy and conservation status of the suiformes - an overview. Ibex: 3, 3-5.

Osemeobo G.J. (1988). Animal wildlife conservation under multiple land-use systems in Nigeria. Environ. Conserv.: 15(3), 239-249.

Stuart C., Stuart T. (1997). Field guide to the larger mammals of Africa. Struik Publishers.

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.