- Email: [email protected]
Feeding preferences of duiker (Cephalophus maxwelli, C. rufilatus, and C. niger) in Ivory Coast and Ghana
Mamm. biol. 68 (2003) 65±77 ã Urban & Fischer Verlag http://www.urbanfischer.de/journals/mammbiol
Mammalian Biology Zeitschrift fuÈr SaÈugetierkunde
Original investigation
Feeding preferences of duiker (Cephalophus maxwelli, C. rufilatus, and C. niger) in Ivory Coast and Ghana By T. HOFMANN and H. ROTH Receipt of Ms. 31. 05. 2001 Acceptance of Ms. 01. 07. 2002
Abstract Stomach contents of 139 Maxwell, 15 red-flanked and 57 black duiker were analysed with a view to investigating the range of food plants utilised by these animals and to determine their feeding preferences, seasonal and other influences on their diet and habitat dependency. Samples of stomach contents of Maxwell and red-flanked duiker were collected on the bushmeat market of Toumodi in Ivory Coast and those of black duiker at Kumasi in Ghana. The sampled animals originated from an area of about 25 respectively 50 km in radius around the markets. Whereas the sampling area in the Ivory Coast is characterised by a mosaic of Guinean semi-deciduous forest and moist savanna, the sampling area in Ghana is predominantly covered with mostly degraded secondary moist forest of the Celtis-Triplochiton-association. Fruits and dicotyle leaves constituted the most important food component in all three duiker species. Grasses were also found in all species but only in small quantities. Tubers and rhizomes were consumed regularly and in greater quantities mainly by the black duiker. Blossoms and fungi were also consumed by the three species, but had no quantitative importance. Animal matter was found only in Maxwell duikers in the form of ants. Duiker may thus be classified after HOFMANN and STEWARD (1972) as ªbrowsersº. The proportions of the essential food components to eachother varied seasonally very little. Types and numbers of fruits consumed fluctuated mostly with seasons which may, however, be related to their varying availability. Only some of the fruit species were evidently selectively utilised. Fruit consumption by Maxwell and red-flanked duiker was more similar to each other than to that of the black duiker. The food composition in the three duiker species studied showed that red-flanked duiker fed preferably in and around forest patches within the moist savanna, and black duiker frequented cultivations in and near moist forest. Maxwell duiker did not show a marked food-dependent habitat preference. The diversity of their food indicated that they utilise diverse habitats. None of the three duiker species is food dependent on primary forest and a large part of their food plants occurs also in secondary, to a varying degree degraded forest and savanna habitats. Duiker might contribute significantly to the distribution of some of the identified fruit-bearing plant species. Key words: Cephalophus, feeding preferences, Ivory Coast, Ghana 1616-5047/03/68/02-065 $ 15.00/0.
66
T. HOFMANN et al.
Introduction The aim of the present investigation into the feeding preferences of different duiker species was to enhance the knowledge of the selective use of different kinds of food plants by the 3 species of duiker quantitatively and qualitatively. This may have importance with a view to their dependence on specific habitats, their adaptability to anthropogenic modification of their environment and their possible role in the propagation of specific plant species. Sufficiently large numbers of stomach contents become available only on so-called ªbushmeatº markets which exist in many West and Central African countries. The present study was based on the bushmeat markets at Toumodi in the Ivory Coast and of Kumasi in Ghana and included Maxwell, red-flanked and black duiker (Cephalophus maxwelli, C. rufilatus and C. niger) under specific ecological conditions.
Material and methods A total of 154 stomach samples, 139 from Maxwell duikers (C. maxwelli) and 15 from the redflanked duiker (C. rufilatus), was collected at the Toumodi bushmeat market in the Ivory Coast, situated about 180 km north of Abidjan, and another 57 samples from the black duiker (C. niger) at the Kumasi bushmeat market in Ghana, located at about 250 km north of Accra. Whereas the Toumodi region is characterised by a mosaic of Guinean moist forests and savanna, the sampling area in Ghana is predominantly covered with mostly degraded, secondary Guinean moist forests of the Celtis-Triplochiton association. To cover seasonal variation, samples were collected in June/July, Oct./Nov. and Jan./ Feb. Total weights of the stomach contents were determined by first weighing the full stomach and then the empty one. Contents of each stomage were mixed and a sample of them taken at random. As the samples varied in volume and a certain pre-selection of hard and fibrous elements took place, a quantification of the different components of the contents was only possible to a limited degree. Such samples were then preserved in formalin for later botanical examination. The villages from which the duiker had originated were
marked on a map and overall ªsampling areasº could thus be determined. In these areas the vegetational conditions and human activities were studied by interpretation of aerial photographs. All collected samples were taken to the Centre Floristique National (National Herbarium) in Abidjan (Ivory Coast) for botanical analysis. They were washed and passed through a sieve of 1 mm mesh size and all water removed by centrifugation. The contents were then spread out on a large white enamel dish and the different elements macroscopically examined piece by piece with the aid of a tweezers and a magnifying glass. In order to determine at a later date the proportion of gramineae present a 10 ml vial was filled with contents from each sample and preserved in 90% alcohol. Qualitative analysis: All identified fruit, leaves and other plant particles were classified into families, genera and species. These were then broken down into plants predominantly found in the moist savanna, in the moist forest, or cultivated by man. Quantitative analysis: The quantitative representation of the samples was not sufficient since in all cases hard and fibrous elements were separated with bias from the remaining mostly liquid detritus of the contents. The quantification therefore could only be expressed as percentual frequency of any particular plant species and of the different food elements in the sample present in the laboratory. Cuticular analysis: To investigate to what extent duiker feed on grasses, microscopical examination of the cuticular pattern of epidermal particles was employed. This is fundamentally different in monocotyle grasses as opposed to those found in dicotyle plants and fruits (Barthlott and Martens 1979). Determination of utilisation indices for identified fruits: The intensity with which a plant species is utilised by an animal depends on the quantity of the particular species ingested by an animal and the frequency with which this is found in the samples of many individuals of the particular animal species. To determine the degree of utilisation of different fruits indices were calculated according to Dubost (1984) by multiplication of both factors: Pij ´ P'ij = index of utilisation (in percent). Pij is the weight of the fruit ªiº found in all stomachs of duiker species ªjº (in percent), and P'ij is the relative frequency of this plant species in all analysed stomach contents of the particular duiker species ªiº.
Feeding preferences of duiker
Results A total of 131 different plant species of 42 families was identified. Their listing with relevant botanical information may be obtained from the senior author. Consumption of fruits Fruits constitute the essential component of the food of all three duiker species (88 ± 100%). In table 1 (a±c) the types of fruit consumed by the different duiker species during the course of the year are broken down botanically. The number of different types of fruit found must be considered a minimum and fluctuated in each of the three examined duiker species between 0 and 8. On average Maxwell duiker samples (n = 139) contained 3, black duiker samples (n = 57) 2.5 and red-flanked duiker samples (n = 15) 2.9 different fruit species per sample. With 78 different types of fruits Maxwell duiker had the largest spectrum, followed by black duiker with 33 and redflanked with 21 (14.8% of the 88 different types of fruits identified were consumed by all three species of duiker.) 32% of the fruit species were consumed by two of the examined duiker species. Fruit species found exclusively in the diet of only one duiker species constituted 60% of the total number of fruit species found in Maxwell duiker, 24% in black duiker and 5% in red-flanked duiker. Feeding preferences In table 2 apparent preferences for different types of fruit are shown during the collection periods January/February and June/ July in terms of utilisation indices. Only 12 species of fruit-bearing plants had a utilisation index of > 5% of the total of all indices in one or several duiker species. These are defined as ªpreferredº species although it is not known whether they were actively sought or whether they were simply available in abundance due to seasonal factors. Comparing red-flanked and Maxwell duikers it can be seen that all three fruit spe-
67
cies preferred by the red-flanked duiker (Phoenix reclinata, Nauclea latifolia and Ficus capensis) were also preferably consumed by Maxwell duiker. These, however, fed preferably on five other species (Alchornea cordifolia, Blighia sapida, Griffonia simplicifolia, Spondias mombin and Canthium vulgare). The examined black duiker shared only one fruit species (Ficus capensis) with Maxwell and red-flanked duikers and another one (Alchornea cordifolia) with Maxwell duiker. Only four fruit species were found exclusively in the stomachs of the black duiker (Persea americana, Elaeis guineensis, Theobroma cacao and Ficus vallis-choudae). The overlap of fruit species between Maxwell and redflanked duiker was thus greater than between these two species and the black duiker. Only a rather small proportion of the leaves found in all stomach content samples could be botanically identified. Leaves of Manihot esculenta (cassava) were found in 53% of the samples of the black duiker (n = 57) showing the importance of this cultivar for their nutrition. In Maxwell and red-flanked duiker they were found only in 13 and 25%, respectively, of the samples. The leaves of Thonningia sanguinea are of greatest importance to Maxwell duikers (present in 23% of the samples), but were rarely found in black duiker samples and in none of the red-flanked duiker samples. Other leaf species of some importance were Canthium vulgare (present in 14.5% of Maxwell duiker samples) and Alchornea cordifolia (present in 17.5% of black duiker samples). Microscopic examination of epidermal particles showed that grasses were found only rarely and in small quantities, but in all three duiker species with little difference. Tubers and rhizomes consumed by the duikers pertained mainly to the Dioscoreaceae and Araceae and were found most often in the black duiker samples (19%). In Maxwell duiker only two of the above species were found (in 5% of the samples). Redflanked duiker samples contained no tubers or rhizomes.
68
T. HOFMANN et al.
Table 1. Types of fruits consumed by duikers during seasonally different sampling periods + = consumption of fruit with utilisation index < 5% ++ = consumption of fruit with utilisation index > 5% Plant family
Plant species
Habitat (1)
JUN
OCT
JAN/ FEB
JUN/ JUL
NOV
(a) Cephalophus maxwelli ANACARDIACEAE
Mangifera indica Spondias mombin ANNONACEAE Monathotaxis schweinfurthii Uvaria afzelli Uvaria chamae Xylopia sp. (1 art, n. i.) APOCYNACEAE Hunteria sp. Landolphia hirsuta Landolphia sp. (1 art, n. i.) Saba florida ARECACEAE Elaeis guineensis Phoenix reclinata ARISTOLOCHIACEAE Pararistolochia sp. (1 art, n. i.) CAESALPINIACEAE Griffonia simplicifolia Cassia sieberiana Dialium guinense Delonix regia Piliostigma thonningii CARICACEAE Carica papaya CECROPIACEAE Musanga cecropioides CONNARACEAE Byrsocarpus coccineus EUPHORBIACEAE Alchornea cordifolia Phyllanthus discoideus Ricinodendron heudelotii HIPPOCRATEACEAE Salacia elegans Salacia cornifolia Salacia sp. (1 art, n. i.) Reisantia sp. (1 art, n. i.) IRVINGIACEAE Irvingia gabonensis LAURACEAE Persea americana LINACEAE Hugonia planchonii LOGANIACEAE Anthocleista djalonensis Strychnos sp. (1 art, n. i.) MELIACEAE Carapa procera Trichilia prieureana Trichilia sp. (1 art, n. i.) MENISPERACEAE Dioscoreophyllum cumminsii MIMOSACEAE Dichrostachys cinera MORACEAE Ficus capensis Ficus mucuso Ficus vallis-choudae Antiaris africana Treculia africana MUSACEAE Musa paradisiaca OLACACEAE Olax gambecola
K S/F/K F S/F F F S/F S S/F/K S P F S S/F K S K F S/F S/F F F F F P K F S/F S/F S/F
++
+ + +
+ +
+
++ + ++ +
+ +
+ +
++
+ + + + +
+
+
+
+
+ +
+
++ +
+
+
+
+
+
+ + +
+ +
+ +
+ + + + ++
+ + ++ +
+
+ + +
+ + + ++
+
+ +
+ ++
+
++ + + +
+
F S S/F F S S/F P K P
++
++ +
+ ++ + + + +
+
++ + +
Feeding preferences of duiker
69
Table 1. Continue Plant family
Plant species
Habitat (1)
OLEACEAE OPILIACEAE PAPILIONACEAE
Schrebera arborea Opilia celtidifolia Arachis hypogea Mucuna pruriens Rhynchosia pycnostachya Vigna sinensis Canavalia ensiformis Millettia sp. (1 art, n. i.) Vigna sp. (div. arts. n. i.) Atroxima liberica Canthium vulgare Canthium multiflorum Canthium venosum Coffea canephora Dictyandra arborescens Gardenia sp. (1 art, n. i.) Morinda longiflora Morinda morindoides Nauclea latifolia Pavetta sp. (1 art, n. i.) Rytigynia canthioides Allophyllus africanus Blighia sapida Blighia unijugata Deinbollia pinnata Lecaniodiscus cupanioides Paullinia pinnata Chrysophyllum welwitschii Chrysophyllum sp. (1 art, n. i.) Malacantha alnifolia Solanum erianthum Solanum torvum Cola gigantea Sterculia tragacantha Theobroma cacao
F
POLYGALACEAE RUBIACEAE
SAPINDACEAE
SAPOTACEAE
SOLANACEAE STERCULIACEAE
K S/F/K F K K P S/F F S/F F/K
JUN
OCT
JUN/ JUL
+
+
+ + +
++
+
+ + + + ++ + +
F S F S/F S/F F F S/F S/F F F S/F S/F F S/F S/F K
++ + + + + + + + + +
+ ++ +
HIPPOCRATEACEAE LAURACEAE LOGANIACEAE MELIACEAE MORACEAE
Anchomanis difformis Elaeis guineensis Griffonia simplicifolia Carica papaya Musanga cecropioides Alchornea cordifolia Phyllanthus discoideus Ricinodendron heudelotii Salacia elegans Persea americana Strychnos sp. (1 art, n. i.) Carapa procera Ficus capensis Ficus mucuso
+ +
++ +
++
+ + +
++
++
+
+ +
++
+
+ +
+ + + +
+ + + +
(b) Cephalophus niger ARACEAE ARECACEAE CAESALPINIACEAE CARICACEAE CECROPIACEAE EUPHORBIACEAE
NOV
+
+ + + + + + ++ ++ + +
JAN/ FEB
F S/F/K F K F S/F S/F F F K
+ + + + + ++
S/F S/F F
+ ++ +
++
++
+ + + ++ + ++ +
+ + ++ +
70
T. HOFMANN et al.
Table 1. Continue Plant family
MUSACEAE OLACACEAE PAPILIONACEAE RUBIACEAE SAPINDACEAE SAPOTACEAE SOLANACEAE
STERCULIACEAE
Plant species
Habitat (1)
Ficus vallis-choudae Ficus sp. (1 art, n. i.) Antiaris africana Musa paradisiaca Ongogea gore Mucuna pruriens Vigna sp. (div. arts, n. i.) Morinda lucida Morinda morindoides Tricalysia sp. (1 art, n. i.) Blighia unijugata Blighia sapida Chrysophyllum pruniforme Chrysophyllum sp. (2 arts, n. i.) Physalis anguina Solanum erianthum Solanum torvum Solanum lycopersicum Cola gigantea Cola nitida Theobroma cacao
S S/F K F S/F/K S/F F F F S/F F F S/F S/F F K S/F F/K K
JUN
OCT
JAN/ FEB
JUN/ JUL
+ + + + + + +
+ +
+ + + +
+ + +
NOV
+ + + + + + + + + ++
(c) Cephalophus rufilatus ANACARDIACEAE ARECACEAE CAESALPINIACEAE CARICACEAE COMBRETACEAE EUPHORBIACEAE LOGANIACEAE MELIACEAE MORACEAE PAPILIONACEAE RUBIACEAE SAPINDACEAE SAPOTACEAE SOLANACEAE STERCULIACEAE
Mangifera indica Elaeis guineensis Phoenix reclinata Griffonia simplicifolia Carica papaya Combretum racemosum Alchornea cordifolia Phyllanthus discoideus Anthocleista djalonensis Carapa procera Antiaris africana Ficus capensis Ficus mucuso Mucuna pruriens Canthium vulgare Nauclea latifolia Blighia sapida Malacantha alnifolia Solanum erianthum Solanum torvum Theobroma cacao
K S/F/K S F K S/F S/F S/F S/F S/F S/F S/F F S/F/K S/F S S/F S/F S/F F K
+ ++ + + + + + + + ++ + + ++ + + + + ++
°
°
° ° °
°
° ° °
°
(1) F = plant species occurring in secondary as well as primary moist forest; P = typical plant species of the primary forest; K = cultivated plant species; S = plant species of the savanna; n. i. = not identified
Feeding preferences of duiker
71
Table 2. Overview of the types of fruit preferably consumed by the three examined duiker species during the collection periods January/February and June/July Number of examined stomach content samples
C. maxwelli
C. rufilatus
C. niger
n = 62
n = 12
n = 57
Plant species
Ni in % (1)
Plant species
Ni in % (1)
Plant species
Ni in % (1)
Nauclea latifolia Ficus capensis Canthium vulgare Blighia sapida Griffonia simplicifolia Alchornea cordifolia Phoenix reclinata Spondias mombin
17.8 15.5 14.1 8.0 7.7 7.5 6.4 6.3
Phoenix reclinata Nauclea latifolia Ficus capensis
30.7 26.5 20.8
Persea americana Alchornea cordifolia Ficus capensis Ficus vallis-choudae Elaeis guineensis Theobroma cacao
30.4 21.2 16.5 7.1 6.4 6.3
(1) Ni = proportion of utilisation index for the respective type of fruit against the total of all utilisation indices
Blossoms were found in all Maxwell samples, but had no quantitative significance. Fungi were found only in small quantities and could not be identified. Animal matter was present only in form of ants (Paltothyreus tarsatus and Oecophylla longinoda) and only in Maxwell duiker. Seasonal variation of the diets Table 3 shows the seasonal variation of the different fruit species in the diets of the three examined duiker species. Leaves predominated conspicuously over fruit during the rainy season. Tubers and rhizomes were mainly found during the dry season. Flowers were eaten in quantity only during the dry season, fungi during the whole year. In Maxwell duikers there was no significant seasonal change in the number of different types of fruit consumed, whereas in black duiker the number increased slightly in the dry season. In table 4 the consumption of fruits is compared with the periods of fructification of the respective plant species. It shows that some of the fruits are consumed also more than two months before or after the main period of fructification in the particular plant species. This would suggest that they are actively sought also when not present in abundance.
Age-dependent variation of the diets Weaned juvenile Maxwell duikers start feeding on leaves, fruit and tubers when they attain a body weight of about 3±4 kg, red-flanked duiker juveniles at a body weight of about 9 kg, and black duiker juveniles at about 12±14 kg. There was no significant difference between the diets of subadult and adult animals. Dependence of food selection on habitat In order to examine the correlation between food selection and habitat preference the identified food plants were broken down into habitats: (a) primary semi-deciduous moist Guinean forest; (b) both primary as well as secondary moist forest; (c) moist Guinean savanna; (d) both moist forest and savanna (ªmixed speciesº), and (e) cultivations. The percentual presence of fruit preferably consumed by the different duiker species broken down into habitat types is shown in figure 1. The diet of the Maxwell duiker contained the largest proportion of ªmixed speciesº (70.6%) and therefore there was no habitat dependency detectable as regards consumption of fruits. Typical moist forest and savanna species were found at a ratio of 11.2 : 12.1 and cultivated species ranged low (4.5%). Presence of fruits of
72
T. HOFMANN et al.
Table 3. Types of fruits preferably consumed by the examined duiker species broken down into dry and rainy season collection periods (i. e. January/February and June/July) C. maxwelli (n = 31) (1)
C. niger (n = 27) (1)
C. rufilatus (n = 10) (1)
type of fruit (2)
Ni in Fcl. % (3) (4)
type of fruit (2)
17.6 15.7 14.8 12.7 11.1 9.0 5.7
6±8 1±6 11±12 1, 12 2, 11 n. a. 2±4
Alchornea cordifilia 50.3 Ficus capensis 14.6 Persea americana 10.0 Ficus vallis-choudae 5.2
11±12 1±6 n. a. n. a.
57.9 16.0 6.6 5.0
n. a. n. a. 6±8 2±4
Persea americana Theobroma cacao Ficus capensis Elaeis guineensis
n. a. n. a. 1±6 n. a.
Ni in Fcl. % (3) (4)
type of fruit (2)
Ni in Fcl. % (3) (4)
Phoenix reclinata Nauclea latifolia Ficus capensis Theobroma cacao
36.8 22.8 19.7 5.3
Dry season Nauclea latifolia Ficus capensis Alchornea cordifolia Phoenix reclinata Griffonia simplicifolia Mangifera indica Blighia sapida
1.12 6±8 1±6 n. a.
Rainy season Canthium vulgare Spondias mombin Nauclea latifolia Blighia sapida
54.0 12.9 6.4 6.2
(1) Number of stomach content samples analysed (2) Included are only types of fruit with an utilisation index (Ni) > 5% (3) Utilisation index (4) Fructification cycle in months (indicated numerically: 1 = Jan., 2 = Feb., 3 = March etc.); n. a. = no information available (5) Due to the small number of samples collected from C. rufilatus during the period June/July (main rainy season) it was not possible to identify preferred types of fruit for this species Table 4. Fructification cycles of some ªpreferredº food plants in the diet of Cephalophus maxwelli. Collection periods in which respective types of fruit were found and which differed by more than 2 months from the fructification cycle (Fcl.) of the respective plant species are boxed Collection periods Plant species
JAN/FEB
Alchornea cordifolia Anthocleista djalonensis Blighia sapida Ficus capensis Griffonia simplicifolia Nauclea latifolia Phoenix reclinata
+ + + + + +
JUN/JUL
OCT
+ +
+ + +
+
+
NOV
Fcl. (1)
+
11±12 1 2±4 1±6 2, 11 6±8 1, 12
(1) See Table 5
typical primary forest species was also low (1.1%). Of these only Atroxima liberica could be rated ªpreferredº. Red-flanked duiker consumed mainly fruits of savanna species (53.5%) and cultivars (11.6%). Typical forest species constituted only a very small part of their diet (0.7%). The diet of black duiker contained also a high percent-
age of ªmixed speciesº (50.5%) but more forest species (2.3%) than in the other duiker species. Remarkable was the conspicuous use of cultivars (38.4%) which indicates that black duiker frequent cultivated lands for feeding and are not dependent on primary forest habitat with regard to their nutrition.
Feeding preferences of duiker
73
Fig. 1. Proportions of different fruits preferably consumed by C. maxwelli (n = 139), C. niger (n = 57) and C. rufilatus (n = 15) with the respective plant species broken down into different habitat types. The percentages refer to the proportion of the respective species within the total of utilisation indices.
Only leaves of Manihot esculenta and Thonningia sanguinea were identifiable in measurable quantities in the samples of all three duiker species. Normally, duiker do not utilise the tubers of Manihot esculenta i. e. cassava in abundance, but rather feed on its stems, sprouts and leaves. The tubers were, however, particularly important to black duiker. Thonningia sanguinea is a highly specialised parasite of the underbrush, preferably in savanna vegetation (Ake Assi 1984). Henle and Apfelbach (1984/85) have identified this species also as a food plant of the bay duiker (C. dorsalis). In this study it was found almost exclusively in the diet of the Maxwell duiker (27%). Only blossoms of Bombax buonopozense and Ceiba petandra were found in measurable quantities. Both species pertain to the habitat ªmoist forestº with a preference to the forest edges and secondary formations. They were consumed predominantly by Maxwell duiker (in 11% of samples).
Discussion
gestion. Such preference is methodologically difficult to determine as an overproportionate presence alone of any plant in the stomach contents of an animal does not necessarily indicate a ªfeeding preferenceª. It may be due to a greater abundance or easy accessibility. Therefore feeding preferences can reliably be only determined by careful quantitative comparison of the availability of feed plants to the animal and their occurrence in its stomach. This was not possible in the present study and therefore ªpreferenceª denotes only an evidently stronger utilisation of some plant species than others in all samples of one or different duiker species. This was shown by calculation of so-called ªutilisation indexesª. Also, the number of available samples of red-flanked duiker was not representative. Despite the limitations in this respect the qualitative findings are fully valid and allowed to compare feeding habits between the different duiker species and to correlate these to different habitats as the source of identified food components.
Methodology
Food spectrum and its utilisation
Feeding preference is the selective use of a food plant as opposed to casual arbitrary in-
The study has confirmed that duiker are true browsers, utilising grasses only very oc-
74
T. HOFMANN et al.
casionally and in very small quantities. Fruit constitutes the most important element in the nutrition of duiker and this was reported already by Aeschlimann (1963) for Maxwell duiker in the Ivory Coast. In Gabon Dubost (1984) and Feer (1989) calculated fruit to constitute 70±89% of the diet of six sympatric duiker species (C. monticola, C. leucogaster, C. nigrifrons, C. callipygus, C. dorsalis and C. sylvicultor). Such a high proportion of fruit in the diet is known for many other fruit-eating mammals (Gautier-Hion et al. 1980). The average number of fruit species found in Maxwell duiker per stomach content was 3.0, in black duiker 2.5, in red-flanked duiker 2.9. Dubost (1984) found an average of 4±9 and Feer (1989) even of 7.7±8.5 per stomach content of duiker in a largely primary rain forest habitat in Gabon. The lower number of fruit species found in this study might be explained by the difference of the habitats in which the studied duiker live, and particularly the degradation of the sampling areas in the Ivory Coast and Ghana with a consequent loss of biodiversity. Leaves, like fruit, are an essential component of the food of all forest duikers as the work by Dubost (1984) and Feer (1989) has already demonstrated. This applies also to the savanna duiker, Silvicapra grimmia as shown by Wilson (1966). When rearing young forest duikers Hopkins (1966) found that all of them liked Cassava leaves. The identified tubers and rhizomes belonged exclusively to cultivated plant species (Dioscoreaceae and Araceae) and these were predominantly utilised by the black duiker. No tubers or rhizomes from wild plant species were found and, therefore, this food component was certainly indicative of the particular ecological conditions of a settled and degraded forest area. It probably does not constitute a natural food component. Contrary to the findings of Feer (1989) in C. dorsalis and C. callipygus there were no age-dependent differences in the diets of the examined duiker species. Animal matter was only found in Maxwell duikers in the form of ants. Dubost (1984), however, has shown that ants are appar-
ently part of the natural food spectrum of some duiker species. He observed that C. monticola, C. nigrifrons, C. callipygus and C. dorsalis actively ªhuntedº ants. They were also licked up from the ground when forming ªant roadsº. In captivity duiker have been observed to occasionally consume young birds (Kurt 1963; Schweers 1981). Since no remains of vertebrates were found in any of the stomach contents of this study, it is assumed that such feeding behaviour is rather exceptional. Quantitatively animal matter is certainly of no importance, but it may play a qualitative role in the nutrition of duiker. Seasonal influences on food composition Although production of fruit is lowest during the dry season all three examined duiker species increased fruit consumption during this season. Similarly, Dubost (1984) and Feer (1989) have not seen any decrease in fruit consumption during the dry season. Fruits were obviously sufficiently available all year long even under the more arid climatic conditions in the sampling areas of this study. During the main dry season leaf ingestion decreased in all three duiker species showing a preference for fresh green leaves. Feer (1989) confirmed that C. callipygus and C. dorsalis also preferred green leaves. Since the trees in the sampling areas, particularly in the Toumodi area, largely shed their leaves during the dry season (Guillaumet and Adjanohoun 1971) fresh green leaves are rather more difficult to find by the browsing animal, and this could explain the decreasing consumption of leaves in this season. Tubers were consumed by the black duiker during both seasons, but more frequently during the dry season. In the studies by Dubost (1984) and Feer (1989) in the rain forest of Gabon no evidence was found that tubers and rhizomes constitute components of the natural diet of forest duikers: they were utilised by the black duiker probably only because of their exceptional availability.
Feeding preferences of duiker
75
Habitat preferences
Dissemination of plant species by duiker
According to their diet Maxwell duiker are obviously capable of utilising savanna as well as forest habitats and plant species typical of secondary vegetation including cultivars. Their diet was indicative of a species utilising a diversity of different habitats, and this probably explains the great adaptability of this species to agricultural development and degradation of forest lands. The diet of the red-flanked duiker classified this species as an animal of the moist savanna from where it also forages into adjacent, often degraded forest areas. In the Toumodi area there was a high overlap with the habitats utilised also by the Maxwell duikers, which indicated that the two species are sympatric in distribution. It is remarkable that the diet of the black duiker contained significant quantities of food derived from cultivations, whereas the proportion of material from typical moist forest plants was relatively low. They consumed also typical savanna species which infiltrate the forest zone in the course of agricultural development. However, it should be remembered that the findings in this study refer only to the feeding habitat and other important ecological bonds to the forest habitat may exist. The feeding overlap with red-flanked duiker was much smaller than with Maxwell duiker. The high proportion of plant species occuring both in the savanna and in the moist forest (ªmixed speciesº) in the duiker diets indicates that these animals satisfy their nutritional requirements by consumption of a great variety of plant species. There is no food dependency, specifically with respect to the forest habitat. Whether other ecological dependencies on the forest biome exist cannot be concluded from this study. It is known from other duiker species, for example the Jentink duiker (C. jentinki), that already minor ecological disturbances caused by agricultural development may have very negative effects on the propagation of these species (Roth and Hoppe-Dominik 1990).
It was not possible to examine the germination viability of seeds found in the stomach contents of duiker due to their preservation in formalin. Therefore, this question could only be investigated on the basis of information available in the literature. Gauthier-Hion et al. 1985 studied the effect of duiker amongst other ungulates on Diaspora and found that more Diaspora were destroyed by the digestion process (n = 37) than disseminated (m = 13). However, very small seeds may well be disseminated by duiker, as Alexandre (1982) has shown for Solanum verbascifolium (Solanaceae) and Musanga cecropioides (Cecropiaceae). Therefore, it is quite possible that also Ficus species, fruits of which are preferably consumed by all duikers and contain large numbers of very small seeds, are disseminated by duikers. In this study only relatively few fruits with very small seeds were seen in the stomach contents of duikers: Ficus capensis, F. mucuso, F. vallis-choudae, Solanum erianthum, S. torvum, Anthocleista djalonenesis and Musanga cecropioides. All of these species might be propagated in part by the duiker. Observations of wild ranging duikers (Gauthier-Hion et al. 1985; Wilson pers. comm. 1992) have shown that duikers sometimes spit out fruit pips when ruminating. This behaviour might also contribute to the dissemination of certain plant species.
Acknowledgements We wish to thank Prof. L. Ake Assi for his invaluable assistance with the botanical analysis of the samples and his permission to use the facilities of the Centre Floristique National in Abidjan, CoÃte d'Ivoire. Messrs. P. Koffi Yao and A. Barom helped with the collection of samples at the Toumodi bushmeat market. The Chief Game and Wildlife Officer in Ghana, Mr. G. Punguse, is thanked for permission to collect material from black duiker at Kumasi with the kind assistance of his staff there, Mr. E. Lamptey, Senior Game Warden, and Messrs. O. Mensah and A. Brenya. Dr. B. Hoppe-Dominik kindly advised us on the cuticular analysis of collected samples and is thanked for his interest in this study.
76
T. HOFMANN et al.
Zusammenfassung PraÈferenzen der Futteraufnahme bei Duckern (Cephalophus maxwelli, C. rufilatus und C. niger) in der ElfenbeinkuÈste und Ghana. Mageninhaltsproben von 139 Maxwell-, 15 Rotflanken- und 57 Schwarz-Duckern wurden untersucht zur Feststellung des Spektrums der genutzten Futterpflanzen, von ØsungspraÈferenzen und evtl. jahreszeitlichen oder anderen EinfluÈssen auf die Futteraufnahme, sowie einer HabitatabhaÈngigkeit. Mageninhaltsproben von Maxwell- und Rotflanken-Duckern wurden auf dem Wildfleischmarkt von Toumodi in der ElfenbeinkuÈste und von Schwarz-Duckern in Kumasi in Ghana gesammelt. Die Tiere, von denen Proben genommen wurden, stammten aus einem Umkreis von ca. 25 respective 50 km um die MaÈrkte. Das Untersuchungsgebiet in der ElfenbeinkuÈste ist durch ein Mosaik von GuineaFeuchtwald und Feuchtsavanne charakterisiert, waÈhrend das in Ghana vorwiegend mit degradiertem SekundaÈr-Feuchtwald der Celtis-Triplochiton-Assoziation bewachsen ist. FruÈchte und dicotyle BlaÈtter waren die wichtigsten Futterkomponenten bei allen drei Duckerarten. GraÈser wurden auch bei allen drei Arten gefunden, aber nur in sehr kleinen Mengen. Knollen wurden in groÈûeren Mengen nur von den Schwarz-Duckern aufgenommen. BluÈten und Pilze wurden auch gefressen, hatten aber keine quantitative Bedeutung. Tierische Materie wurde nur bei MaxwellDuckern in Form von Ameisen gefunden. Ducker lassen sich somit nach Hofmann und Steward (1972) als ¹browserª (Blatt und GehoÈlz-Øser) klassifizieren. Die Anteile der wesentlichen Futterkomponenten variierten jahreszeitlich nur wenig; am staÈrksten Art und Anzahl von FruÈchten. Nur wenige der Frucht-Arten wurden offensichtlich bevorzugt genutzt. FruÈchteaufnahme von Maxwell- und Rotflanken-Duckern aÈhnelte einander staÈrker als bei Schwarz-Duckern. Die Futter-Zusammensetzung bei den drei Duckerarten zeigte, daû Rotflanken-Ducker bevorzugt in und um Waldinseln in der Feuchtsavanne aÈsen und daû Schwarz-Ducker gern kultivierte FlaÈchen im und nahe dem Feuchtwald aufsuchen. Maxwell-Ducker zeigten keine ausgepraÈgte futterbedingte Habitat-PraÈferenz. Die Vielseitigkeit ihrer Futteraufnahme weist darauf, daû sie verschiedenste LebensraÈume nutzen koÈnnen. Keine der drei Duckerarten ist futterabhaÈngig vom primaÈren Regenwald, da ein groûer Teil ihrer Futterpflanzen auch im degradierten Feuchtwald vorkommt. MoÈglicherweise tragen Ducker wesentlich zur Verbreitung einiger identifizierter fruchttragenden Pflanzen bei.
References Aeschlimann, A. (1963): Observations sur Philantomba maxwelli (Hamilton-Smith) une Antilope de la ForeÃt eÂburneÂenne. Acta Tropica 20, 341±368. AkeÁ Assi, L. (1984): ªFlore de la CoÃte d'Ivoire: Etude descriptive et biogeographique, avec quelque notes ethnobotaniquesº. Diss. thesis, Faculte des Sciences de L'Universite d'Abidjan. Alexandre, D. Y. (1978): Le roÃle disseÂminateur des eÂleÂphants en foreÃt de Tai. C. I. Terre et Vie 32, 47±72. ± (1982): La dispersion de Solanum verbascifolium en CoÃte d'Ivoire: RoÃle des Cephalophes. Terre et Vie 36, 293±295. Barthlott, W; Martens, B. (1979): CutikularTaxonomie der GraÈser eines westafrikanischen Savannengebietes unter dem Aspekt
der FutterpraÈferenz-Analyse wildlebender GroûsaÈuger. Trop. und subtrop. Pflanzenwelt 30, 687±793. Dubost, G. (1984): Comparison of the diets of frugivorous forest ruminants of Gabon. Mammalia 65, 298±316. Feer, F. (1989): Comparaison des reÂgimes alimentaires de Cephalophus callipygus et C. dorsalis, BovideÂs sympatriques de la foreÃt sempervirente africaine. Mammalia 53, 563±604. Gauthier-Hion, A.; Emmons, L. H.; Dubost, G. (1980): A comparison of the diets of three major groups of primary consumers of Gabon (Primates, Squirrels and Ruminants). Oecologia (Berlin) 45, 182±189. Gauthier-Hion, A.; Duplantier, J.-M.; Quris, R.; Feer, F.; Sourd, C.; Decoux, J.-P.; Dubost, G.; Emmons, L.; Erard, C.; Hecketsweiler, P.;
Feeding preferences of duiker Moungazi, A.; Roussilhon, C.; Thiollay, J.-M. (1985): Fruit characters as a basis of fruit choice and seed dispersal in a tropical forest vertebrate community. Oecologia (Berlin) 65, 324±337. Guillaumet, J.-L.; Adjanohoun, E. (1971): La veÂgeÂtation de la CoÃte d'Ivoire. In: Le milieu naturel de la CoÃte d'Ivoire. Paris: ORSTOM. Henle, K.; Apfelbach, R. (1984/85): Auswilderung und Beobachtungen zur Biologie des SchwarzruÈckenduckers. SaÈugetierkundl. Mitt. 32, 75±82. Hofmann, R. R.; Steward, D. R. M. (1972): Grazer and browser: A classification on the stomach structure and feeding habits of East African ruminants. Mammalia 36, 226±240. Hopkins, J. M. (1966): Observations on the rearing and behaviour of young duikers in captivity. Niger. Fld 30, 118±131.
77
Kurt, F. (1963): Zur Carnivorie bei Cephalophus dorsalis. Z. SaÈugetierkunde 28, 309±313. Roth, H. H.; Hoppe-Dominik, B. (1990): Ivory Coast. In: Antelopes, Global Survey and Regional Action Plans. Part 3: West and Central Africa. Compiled by R. East, IUCN-SSC Antelope Specialist Group. Schweers, S. (1981): Fleischfressende Antilopen. Zoofreund 42, 17±19. Hannover. Wilson, V. J. (1966): Notes on the food and feeding habits of the common duiker, Sylvicapra grimmia in eastern Zambia. Arnoldia 2, 1±19. Authors' addresses: Dipl.-Biol. T. Hofmann, Chrysanderstraûe 147, D21029 Hamburg, Germany (e-mail: [email protected]); Prof. Dr. H. H. Roth, 78 Le Roux Drive, Hillside, Harare, Zimbabwe
Mammalian Biology Zeitschrift fuÈr SaÈugetierkunde
Original investigation
Feeding preferences of duiker (Cephalophus maxwelli, C. rufilatus, and C. niger) in Ivory Coast and Ghana By T. HOFMANN and H. ROTH Receipt of Ms. 31. 05. 2001 Acceptance of Ms. 01. 07. 2002
Abstract Stomach contents of 139 Maxwell, 15 red-flanked and 57 black duiker were analysed with a view to investigating the range of food plants utilised by these animals and to determine their feeding preferences, seasonal and other influences on their diet and habitat dependency. Samples of stomach contents of Maxwell and red-flanked duiker were collected on the bushmeat market of Toumodi in Ivory Coast and those of black duiker at Kumasi in Ghana. The sampled animals originated from an area of about 25 respectively 50 km in radius around the markets. Whereas the sampling area in the Ivory Coast is characterised by a mosaic of Guinean semi-deciduous forest and moist savanna, the sampling area in Ghana is predominantly covered with mostly degraded secondary moist forest of the Celtis-Triplochiton-association. Fruits and dicotyle leaves constituted the most important food component in all three duiker species. Grasses were also found in all species but only in small quantities. Tubers and rhizomes were consumed regularly and in greater quantities mainly by the black duiker. Blossoms and fungi were also consumed by the three species, but had no quantitative importance. Animal matter was found only in Maxwell duikers in the form of ants. Duiker may thus be classified after HOFMANN and STEWARD (1972) as ªbrowsersº. The proportions of the essential food components to eachother varied seasonally very little. Types and numbers of fruits consumed fluctuated mostly with seasons which may, however, be related to their varying availability. Only some of the fruit species were evidently selectively utilised. Fruit consumption by Maxwell and red-flanked duiker was more similar to each other than to that of the black duiker. The food composition in the three duiker species studied showed that red-flanked duiker fed preferably in and around forest patches within the moist savanna, and black duiker frequented cultivations in and near moist forest. Maxwell duiker did not show a marked food-dependent habitat preference. The diversity of their food indicated that they utilise diverse habitats. None of the three duiker species is food dependent on primary forest and a large part of their food plants occurs also in secondary, to a varying degree degraded forest and savanna habitats. Duiker might contribute significantly to the distribution of some of the identified fruit-bearing plant species. Key words: Cephalophus, feeding preferences, Ivory Coast, Ghana 1616-5047/03/68/02-065 $ 15.00/0.
66
T. HOFMANN et al.
Introduction The aim of the present investigation into the feeding preferences of different duiker species was to enhance the knowledge of the selective use of different kinds of food plants by the 3 species of duiker quantitatively and qualitatively. This may have importance with a view to their dependence on specific habitats, their adaptability to anthropogenic modification of their environment and their possible role in the propagation of specific plant species. Sufficiently large numbers of stomach contents become available only on so-called ªbushmeatº markets which exist in many West and Central African countries. The present study was based on the bushmeat markets at Toumodi in the Ivory Coast and of Kumasi in Ghana and included Maxwell, red-flanked and black duiker (Cephalophus maxwelli, C. rufilatus and C. niger) under specific ecological conditions.
Material and methods A total of 154 stomach samples, 139 from Maxwell duikers (C. maxwelli) and 15 from the redflanked duiker (C. rufilatus), was collected at the Toumodi bushmeat market in the Ivory Coast, situated about 180 km north of Abidjan, and another 57 samples from the black duiker (C. niger) at the Kumasi bushmeat market in Ghana, located at about 250 km north of Accra. Whereas the Toumodi region is characterised by a mosaic of Guinean moist forests and savanna, the sampling area in Ghana is predominantly covered with mostly degraded, secondary Guinean moist forests of the Celtis-Triplochiton association. To cover seasonal variation, samples were collected in June/July, Oct./Nov. and Jan./ Feb. Total weights of the stomach contents were determined by first weighing the full stomach and then the empty one. Contents of each stomage were mixed and a sample of them taken at random. As the samples varied in volume and a certain pre-selection of hard and fibrous elements took place, a quantification of the different components of the contents was only possible to a limited degree. Such samples were then preserved in formalin for later botanical examination. The villages from which the duiker had originated were
marked on a map and overall ªsampling areasº could thus be determined. In these areas the vegetational conditions and human activities were studied by interpretation of aerial photographs. All collected samples were taken to the Centre Floristique National (National Herbarium) in Abidjan (Ivory Coast) for botanical analysis. They were washed and passed through a sieve of 1 mm mesh size and all water removed by centrifugation. The contents were then spread out on a large white enamel dish and the different elements macroscopically examined piece by piece with the aid of a tweezers and a magnifying glass. In order to determine at a later date the proportion of gramineae present a 10 ml vial was filled with contents from each sample and preserved in 90% alcohol. Qualitative analysis: All identified fruit, leaves and other plant particles were classified into families, genera and species. These were then broken down into plants predominantly found in the moist savanna, in the moist forest, or cultivated by man. Quantitative analysis: The quantitative representation of the samples was not sufficient since in all cases hard and fibrous elements were separated with bias from the remaining mostly liquid detritus of the contents. The quantification therefore could only be expressed as percentual frequency of any particular plant species and of the different food elements in the sample present in the laboratory. Cuticular analysis: To investigate to what extent duiker feed on grasses, microscopical examination of the cuticular pattern of epidermal particles was employed. This is fundamentally different in monocotyle grasses as opposed to those found in dicotyle plants and fruits (Barthlott and Martens 1979). Determination of utilisation indices for identified fruits: The intensity with which a plant species is utilised by an animal depends on the quantity of the particular species ingested by an animal and the frequency with which this is found in the samples of many individuals of the particular animal species. To determine the degree of utilisation of different fruits indices were calculated according to Dubost (1984) by multiplication of both factors: Pij ´ P'ij = index of utilisation (in percent). Pij is the weight of the fruit ªiº found in all stomachs of duiker species ªjº (in percent), and P'ij is the relative frequency of this plant species in all analysed stomach contents of the particular duiker species ªiº.
Feeding preferences of duiker
Results A total of 131 different plant species of 42 families was identified. Their listing with relevant botanical information may be obtained from the senior author. Consumption of fruits Fruits constitute the essential component of the food of all three duiker species (88 ± 100%). In table 1 (a±c) the types of fruit consumed by the different duiker species during the course of the year are broken down botanically. The number of different types of fruit found must be considered a minimum and fluctuated in each of the three examined duiker species between 0 and 8. On average Maxwell duiker samples (n = 139) contained 3, black duiker samples (n = 57) 2.5 and red-flanked duiker samples (n = 15) 2.9 different fruit species per sample. With 78 different types of fruits Maxwell duiker had the largest spectrum, followed by black duiker with 33 and redflanked with 21 (14.8% of the 88 different types of fruits identified were consumed by all three species of duiker.) 32% of the fruit species were consumed by two of the examined duiker species. Fruit species found exclusively in the diet of only one duiker species constituted 60% of the total number of fruit species found in Maxwell duiker, 24% in black duiker and 5% in red-flanked duiker. Feeding preferences In table 2 apparent preferences for different types of fruit are shown during the collection periods January/February and June/ July in terms of utilisation indices. Only 12 species of fruit-bearing plants had a utilisation index of > 5% of the total of all indices in one or several duiker species. These are defined as ªpreferredº species although it is not known whether they were actively sought or whether they were simply available in abundance due to seasonal factors. Comparing red-flanked and Maxwell duikers it can be seen that all three fruit spe-
67
cies preferred by the red-flanked duiker (Phoenix reclinata, Nauclea latifolia and Ficus capensis) were also preferably consumed by Maxwell duiker. These, however, fed preferably on five other species (Alchornea cordifolia, Blighia sapida, Griffonia simplicifolia, Spondias mombin and Canthium vulgare). The examined black duiker shared only one fruit species (Ficus capensis) with Maxwell and red-flanked duikers and another one (Alchornea cordifolia) with Maxwell duiker. Only four fruit species were found exclusively in the stomachs of the black duiker (Persea americana, Elaeis guineensis, Theobroma cacao and Ficus vallis-choudae). The overlap of fruit species between Maxwell and redflanked duiker was thus greater than between these two species and the black duiker. Only a rather small proportion of the leaves found in all stomach content samples could be botanically identified. Leaves of Manihot esculenta (cassava) were found in 53% of the samples of the black duiker (n = 57) showing the importance of this cultivar for their nutrition. In Maxwell and red-flanked duiker they were found only in 13 and 25%, respectively, of the samples. The leaves of Thonningia sanguinea are of greatest importance to Maxwell duikers (present in 23% of the samples), but were rarely found in black duiker samples and in none of the red-flanked duiker samples. Other leaf species of some importance were Canthium vulgare (present in 14.5% of Maxwell duiker samples) and Alchornea cordifolia (present in 17.5% of black duiker samples). Microscopic examination of epidermal particles showed that grasses were found only rarely and in small quantities, but in all three duiker species with little difference. Tubers and rhizomes consumed by the duikers pertained mainly to the Dioscoreaceae and Araceae and were found most often in the black duiker samples (19%). In Maxwell duiker only two of the above species were found (in 5% of the samples). Redflanked duiker samples contained no tubers or rhizomes.
68
T. HOFMANN et al.
Table 1. Types of fruits consumed by duikers during seasonally different sampling periods + = consumption of fruit with utilisation index < 5% ++ = consumption of fruit with utilisation index > 5% Plant family
Plant species
Habitat (1)
JUN
OCT
JAN/ FEB
JUN/ JUL
NOV
(a) Cephalophus maxwelli ANACARDIACEAE
Mangifera indica Spondias mombin ANNONACEAE Monathotaxis schweinfurthii Uvaria afzelli Uvaria chamae Xylopia sp. (1 art, n. i.) APOCYNACEAE Hunteria sp. Landolphia hirsuta Landolphia sp. (1 art, n. i.) Saba florida ARECACEAE Elaeis guineensis Phoenix reclinata ARISTOLOCHIACEAE Pararistolochia sp. (1 art, n. i.) CAESALPINIACEAE Griffonia simplicifolia Cassia sieberiana Dialium guinense Delonix regia Piliostigma thonningii CARICACEAE Carica papaya CECROPIACEAE Musanga cecropioides CONNARACEAE Byrsocarpus coccineus EUPHORBIACEAE Alchornea cordifolia Phyllanthus discoideus Ricinodendron heudelotii HIPPOCRATEACEAE Salacia elegans Salacia cornifolia Salacia sp. (1 art, n. i.) Reisantia sp. (1 art, n. i.) IRVINGIACEAE Irvingia gabonensis LAURACEAE Persea americana LINACEAE Hugonia planchonii LOGANIACEAE Anthocleista djalonensis Strychnos sp. (1 art, n. i.) MELIACEAE Carapa procera Trichilia prieureana Trichilia sp. (1 art, n. i.) MENISPERACEAE Dioscoreophyllum cumminsii MIMOSACEAE Dichrostachys cinera MORACEAE Ficus capensis Ficus mucuso Ficus vallis-choudae Antiaris africana Treculia africana MUSACEAE Musa paradisiaca OLACACEAE Olax gambecola
K S/F/K F S/F F F S/F S S/F/K S P F S S/F K S K F S/F S/F F F F F P K F S/F S/F S/F
++
+ + +
+ +
+
++ + ++ +
+ +
+ +
++
+ + + + +
+
+
+
+
+ +
+
++ +
+
+
+
+
+
+ + +
+ +
+ +
+ + + + ++
+ + ++ +
+
+ + +
+ + + ++
+
+ +
+ ++
+
++ + + +
+
F S S/F F S S/F P K P
++
++ +
+ ++ + + + +
+
++ + +
Feeding preferences of duiker
69
Table 1. Continue Plant family
Plant species
Habitat (1)
OLEACEAE OPILIACEAE PAPILIONACEAE
Schrebera arborea Opilia celtidifolia Arachis hypogea Mucuna pruriens Rhynchosia pycnostachya Vigna sinensis Canavalia ensiformis Millettia sp. (1 art, n. i.) Vigna sp. (div. arts. n. i.) Atroxima liberica Canthium vulgare Canthium multiflorum Canthium venosum Coffea canephora Dictyandra arborescens Gardenia sp. (1 art, n. i.) Morinda longiflora Morinda morindoides Nauclea latifolia Pavetta sp. (1 art, n. i.) Rytigynia canthioides Allophyllus africanus Blighia sapida Blighia unijugata Deinbollia pinnata Lecaniodiscus cupanioides Paullinia pinnata Chrysophyllum welwitschii Chrysophyllum sp. (1 art, n. i.) Malacantha alnifolia Solanum erianthum Solanum torvum Cola gigantea Sterculia tragacantha Theobroma cacao
F
POLYGALACEAE RUBIACEAE
SAPINDACEAE
SAPOTACEAE
SOLANACEAE STERCULIACEAE
K S/F/K F K K P S/F F S/F F/K
JUN
OCT
JUN/ JUL
+
+
+ + +
++
+
+ + + + ++ + +
F S F S/F S/F F F S/F S/F F F S/F S/F F S/F S/F K
++ + + + + + + + + +
+ ++ +
HIPPOCRATEACEAE LAURACEAE LOGANIACEAE MELIACEAE MORACEAE
Anchomanis difformis Elaeis guineensis Griffonia simplicifolia Carica papaya Musanga cecropioides Alchornea cordifolia Phyllanthus discoideus Ricinodendron heudelotii Salacia elegans Persea americana Strychnos sp. (1 art, n. i.) Carapa procera Ficus capensis Ficus mucuso
+ +
++ +
++
+ + +
++
++
+
+ +
++
+
+ +
+ + + +
+ + + +
(b) Cephalophus niger ARACEAE ARECACEAE CAESALPINIACEAE CARICACEAE CECROPIACEAE EUPHORBIACEAE
NOV
+
+ + + + + + ++ ++ + +
JAN/ FEB
F S/F/K F K F S/F S/F F F K
+ + + + + ++
S/F S/F F
+ ++ +
++
++
+ + + ++ + ++ +
+ + ++ +
70
T. HOFMANN et al.
Table 1. Continue Plant family
MUSACEAE OLACACEAE PAPILIONACEAE RUBIACEAE SAPINDACEAE SAPOTACEAE SOLANACEAE
STERCULIACEAE
Plant species
Habitat (1)
Ficus vallis-choudae Ficus sp. (1 art, n. i.) Antiaris africana Musa paradisiaca Ongogea gore Mucuna pruriens Vigna sp. (div. arts, n. i.) Morinda lucida Morinda morindoides Tricalysia sp. (1 art, n. i.) Blighia unijugata Blighia sapida Chrysophyllum pruniforme Chrysophyllum sp. (2 arts, n. i.) Physalis anguina Solanum erianthum Solanum torvum Solanum lycopersicum Cola gigantea Cola nitida Theobroma cacao
S S/F K F S/F/K S/F F F F S/F F F S/F S/F F K S/F F/K K
JUN
OCT
JAN/ FEB
JUN/ JUL
+ + + + + + +
+ +
+ + + +
+ + +
NOV
+ + + + + + + + + ++
(c) Cephalophus rufilatus ANACARDIACEAE ARECACEAE CAESALPINIACEAE CARICACEAE COMBRETACEAE EUPHORBIACEAE LOGANIACEAE MELIACEAE MORACEAE PAPILIONACEAE RUBIACEAE SAPINDACEAE SAPOTACEAE SOLANACEAE STERCULIACEAE
Mangifera indica Elaeis guineensis Phoenix reclinata Griffonia simplicifolia Carica papaya Combretum racemosum Alchornea cordifolia Phyllanthus discoideus Anthocleista djalonensis Carapa procera Antiaris africana Ficus capensis Ficus mucuso Mucuna pruriens Canthium vulgare Nauclea latifolia Blighia sapida Malacantha alnifolia Solanum erianthum Solanum torvum Theobroma cacao
K S/F/K S F K S/F S/F S/F S/F S/F S/F S/F F S/F/K S/F S S/F S/F S/F F K
+ ++ + + + + + + + ++ + + ++ + + + + ++
°
°
° ° °
°
° ° °
°
(1) F = plant species occurring in secondary as well as primary moist forest; P = typical plant species of the primary forest; K = cultivated plant species; S = plant species of the savanna; n. i. = not identified
Feeding preferences of duiker
71
Table 2. Overview of the types of fruit preferably consumed by the three examined duiker species during the collection periods January/February and June/July Number of examined stomach content samples
C. maxwelli
C. rufilatus
C. niger
n = 62
n = 12
n = 57
Plant species
Ni in % (1)
Plant species
Ni in % (1)
Plant species
Ni in % (1)
Nauclea latifolia Ficus capensis Canthium vulgare Blighia sapida Griffonia simplicifolia Alchornea cordifolia Phoenix reclinata Spondias mombin
17.8 15.5 14.1 8.0 7.7 7.5 6.4 6.3
Phoenix reclinata Nauclea latifolia Ficus capensis
30.7 26.5 20.8
Persea americana Alchornea cordifolia Ficus capensis Ficus vallis-choudae Elaeis guineensis Theobroma cacao
30.4 21.2 16.5 7.1 6.4 6.3
(1) Ni = proportion of utilisation index for the respective type of fruit against the total of all utilisation indices
Blossoms were found in all Maxwell samples, but had no quantitative significance. Fungi were found only in small quantities and could not be identified. Animal matter was present only in form of ants (Paltothyreus tarsatus and Oecophylla longinoda) and only in Maxwell duiker. Seasonal variation of the diets Table 3 shows the seasonal variation of the different fruit species in the diets of the three examined duiker species. Leaves predominated conspicuously over fruit during the rainy season. Tubers and rhizomes were mainly found during the dry season. Flowers were eaten in quantity only during the dry season, fungi during the whole year. In Maxwell duikers there was no significant seasonal change in the number of different types of fruit consumed, whereas in black duiker the number increased slightly in the dry season. In table 4 the consumption of fruits is compared with the periods of fructification of the respective plant species. It shows that some of the fruits are consumed also more than two months before or after the main period of fructification in the particular plant species. This would suggest that they are actively sought also when not present in abundance.
Age-dependent variation of the diets Weaned juvenile Maxwell duikers start feeding on leaves, fruit and tubers when they attain a body weight of about 3±4 kg, red-flanked duiker juveniles at a body weight of about 9 kg, and black duiker juveniles at about 12±14 kg. There was no significant difference between the diets of subadult and adult animals. Dependence of food selection on habitat In order to examine the correlation between food selection and habitat preference the identified food plants were broken down into habitats: (a) primary semi-deciduous moist Guinean forest; (b) both primary as well as secondary moist forest; (c) moist Guinean savanna; (d) both moist forest and savanna (ªmixed speciesº), and (e) cultivations. The percentual presence of fruit preferably consumed by the different duiker species broken down into habitat types is shown in figure 1. The diet of the Maxwell duiker contained the largest proportion of ªmixed speciesº (70.6%) and therefore there was no habitat dependency detectable as regards consumption of fruits. Typical moist forest and savanna species were found at a ratio of 11.2 : 12.1 and cultivated species ranged low (4.5%). Presence of fruits of
72
T. HOFMANN et al.
Table 3. Types of fruits preferably consumed by the examined duiker species broken down into dry and rainy season collection periods (i. e. January/February and June/July) C. maxwelli (n = 31) (1)
C. niger (n = 27) (1)
C. rufilatus (n = 10) (1)
type of fruit (2)
Ni in Fcl. % (3) (4)
type of fruit (2)
17.6 15.7 14.8 12.7 11.1 9.0 5.7
6±8 1±6 11±12 1, 12 2, 11 n. a. 2±4
Alchornea cordifilia 50.3 Ficus capensis 14.6 Persea americana 10.0 Ficus vallis-choudae 5.2
11±12 1±6 n. a. n. a.
57.9 16.0 6.6 5.0
n. a. n. a. 6±8 2±4
Persea americana Theobroma cacao Ficus capensis Elaeis guineensis
n. a. n. a. 1±6 n. a.
Ni in Fcl. % (3) (4)
type of fruit (2)
Ni in Fcl. % (3) (4)
Phoenix reclinata Nauclea latifolia Ficus capensis Theobroma cacao
36.8 22.8 19.7 5.3
Dry season Nauclea latifolia Ficus capensis Alchornea cordifolia Phoenix reclinata Griffonia simplicifolia Mangifera indica Blighia sapida
1.12 6±8 1±6 n. a.
Rainy season Canthium vulgare Spondias mombin Nauclea latifolia Blighia sapida
54.0 12.9 6.4 6.2
(1) Number of stomach content samples analysed (2) Included are only types of fruit with an utilisation index (Ni) > 5% (3) Utilisation index (4) Fructification cycle in months (indicated numerically: 1 = Jan., 2 = Feb., 3 = March etc.); n. a. = no information available (5) Due to the small number of samples collected from C. rufilatus during the period June/July (main rainy season) it was not possible to identify preferred types of fruit for this species Table 4. Fructification cycles of some ªpreferredº food plants in the diet of Cephalophus maxwelli. Collection periods in which respective types of fruit were found and which differed by more than 2 months from the fructification cycle (Fcl.) of the respective plant species are boxed Collection periods Plant species
JAN/FEB
Alchornea cordifolia Anthocleista djalonensis Blighia sapida Ficus capensis Griffonia simplicifolia Nauclea latifolia Phoenix reclinata
+ + + + + +
JUN/JUL
OCT
+ +
+ + +
+
+
NOV
Fcl. (1)
+
11±12 1 2±4 1±6 2, 11 6±8 1, 12
(1) See Table 5
typical primary forest species was also low (1.1%). Of these only Atroxima liberica could be rated ªpreferredº. Red-flanked duiker consumed mainly fruits of savanna species (53.5%) and cultivars (11.6%). Typical forest species constituted only a very small part of their diet (0.7%). The diet of black duiker contained also a high percent-
age of ªmixed speciesº (50.5%) but more forest species (2.3%) than in the other duiker species. Remarkable was the conspicuous use of cultivars (38.4%) which indicates that black duiker frequent cultivated lands for feeding and are not dependent on primary forest habitat with regard to their nutrition.
Feeding preferences of duiker
73
Fig. 1. Proportions of different fruits preferably consumed by C. maxwelli (n = 139), C. niger (n = 57) and C. rufilatus (n = 15) with the respective plant species broken down into different habitat types. The percentages refer to the proportion of the respective species within the total of utilisation indices.
Only leaves of Manihot esculenta and Thonningia sanguinea were identifiable in measurable quantities in the samples of all three duiker species. Normally, duiker do not utilise the tubers of Manihot esculenta i. e. cassava in abundance, but rather feed on its stems, sprouts and leaves. The tubers were, however, particularly important to black duiker. Thonningia sanguinea is a highly specialised parasite of the underbrush, preferably in savanna vegetation (Ake Assi 1984). Henle and Apfelbach (1984/85) have identified this species also as a food plant of the bay duiker (C. dorsalis). In this study it was found almost exclusively in the diet of the Maxwell duiker (27%). Only blossoms of Bombax buonopozense and Ceiba petandra were found in measurable quantities. Both species pertain to the habitat ªmoist forestº with a preference to the forest edges and secondary formations. They were consumed predominantly by Maxwell duiker (in 11% of samples).
Discussion
gestion. Such preference is methodologically difficult to determine as an overproportionate presence alone of any plant in the stomach contents of an animal does not necessarily indicate a ªfeeding preferenceª. It may be due to a greater abundance or easy accessibility. Therefore feeding preferences can reliably be only determined by careful quantitative comparison of the availability of feed plants to the animal and their occurrence in its stomach. This was not possible in the present study and therefore ªpreferenceª denotes only an evidently stronger utilisation of some plant species than others in all samples of one or different duiker species. This was shown by calculation of so-called ªutilisation indexesª. Also, the number of available samples of red-flanked duiker was not representative. Despite the limitations in this respect the qualitative findings are fully valid and allowed to compare feeding habits between the different duiker species and to correlate these to different habitats as the source of identified food components.
Methodology
Food spectrum and its utilisation
Feeding preference is the selective use of a food plant as opposed to casual arbitrary in-
The study has confirmed that duiker are true browsers, utilising grasses only very oc-
74
T. HOFMANN et al.
casionally and in very small quantities. Fruit constitutes the most important element in the nutrition of duiker and this was reported already by Aeschlimann (1963) for Maxwell duiker in the Ivory Coast. In Gabon Dubost (1984) and Feer (1989) calculated fruit to constitute 70±89% of the diet of six sympatric duiker species (C. monticola, C. leucogaster, C. nigrifrons, C. callipygus, C. dorsalis and C. sylvicultor). Such a high proportion of fruit in the diet is known for many other fruit-eating mammals (Gautier-Hion et al. 1980). The average number of fruit species found in Maxwell duiker per stomach content was 3.0, in black duiker 2.5, in red-flanked duiker 2.9. Dubost (1984) found an average of 4±9 and Feer (1989) even of 7.7±8.5 per stomach content of duiker in a largely primary rain forest habitat in Gabon. The lower number of fruit species found in this study might be explained by the difference of the habitats in which the studied duiker live, and particularly the degradation of the sampling areas in the Ivory Coast and Ghana with a consequent loss of biodiversity. Leaves, like fruit, are an essential component of the food of all forest duikers as the work by Dubost (1984) and Feer (1989) has already demonstrated. This applies also to the savanna duiker, Silvicapra grimmia as shown by Wilson (1966). When rearing young forest duikers Hopkins (1966) found that all of them liked Cassava leaves. The identified tubers and rhizomes belonged exclusively to cultivated plant species (Dioscoreaceae and Araceae) and these were predominantly utilised by the black duiker. No tubers or rhizomes from wild plant species were found and, therefore, this food component was certainly indicative of the particular ecological conditions of a settled and degraded forest area. It probably does not constitute a natural food component. Contrary to the findings of Feer (1989) in C. dorsalis and C. callipygus there were no age-dependent differences in the diets of the examined duiker species. Animal matter was only found in Maxwell duikers in the form of ants. Dubost (1984), however, has shown that ants are appar-
ently part of the natural food spectrum of some duiker species. He observed that C. monticola, C. nigrifrons, C. callipygus and C. dorsalis actively ªhuntedº ants. They were also licked up from the ground when forming ªant roadsº. In captivity duiker have been observed to occasionally consume young birds (Kurt 1963; Schweers 1981). Since no remains of vertebrates were found in any of the stomach contents of this study, it is assumed that such feeding behaviour is rather exceptional. Quantitatively animal matter is certainly of no importance, but it may play a qualitative role in the nutrition of duiker. Seasonal influences on food composition Although production of fruit is lowest during the dry season all three examined duiker species increased fruit consumption during this season. Similarly, Dubost (1984) and Feer (1989) have not seen any decrease in fruit consumption during the dry season. Fruits were obviously sufficiently available all year long even under the more arid climatic conditions in the sampling areas of this study. During the main dry season leaf ingestion decreased in all three duiker species showing a preference for fresh green leaves. Feer (1989) confirmed that C. callipygus and C. dorsalis also preferred green leaves. Since the trees in the sampling areas, particularly in the Toumodi area, largely shed their leaves during the dry season (Guillaumet and Adjanohoun 1971) fresh green leaves are rather more difficult to find by the browsing animal, and this could explain the decreasing consumption of leaves in this season. Tubers were consumed by the black duiker during both seasons, but more frequently during the dry season. In the studies by Dubost (1984) and Feer (1989) in the rain forest of Gabon no evidence was found that tubers and rhizomes constitute components of the natural diet of forest duikers: they were utilised by the black duiker probably only because of their exceptional availability.
Feeding preferences of duiker
75
Habitat preferences
Dissemination of plant species by duiker
According to their diet Maxwell duiker are obviously capable of utilising savanna as well as forest habitats and plant species typical of secondary vegetation including cultivars. Their diet was indicative of a species utilising a diversity of different habitats, and this probably explains the great adaptability of this species to agricultural development and degradation of forest lands. The diet of the red-flanked duiker classified this species as an animal of the moist savanna from where it also forages into adjacent, often degraded forest areas. In the Toumodi area there was a high overlap with the habitats utilised also by the Maxwell duikers, which indicated that the two species are sympatric in distribution. It is remarkable that the diet of the black duiker contained significant quantities of food derived from cultivations, whereas the proportion of material from typical moist forest plants was relatively low. They consumed also typical savanna species which infiltrate the forest zone in the course of agricultural development. However, it should be remembered that the findings in this study refer only to the feeding habitat and other important ecological bonds to the forest habitat may exist. The feeding overlap with red-flanked duiker was much smaller than with Maxwell duiker. The high proportion of plant species occuring both in the savanna and in the moist forest (ªmixed speciesº) in the duiker diets indicates that these animals satisfy their nutritional requirements by consumption of a great variety of plant species. There is no food dependency, specifically with respect to the forest habitat. Whether other ecological dependencies on the forest biome exist cannot be concluded from this study. It is known from other duiker species, for example the Jentink duiker (C. jentinki), that already minor ecological disturbances caused by agricultural development may have very negative effects on the propagation of these species (Roth and Hoppe-Dominik 1990).
It was not possible to examine the germination viability of seeds found in the stomach contents of duiker due to their preservation in formalin. Therefore, this question could only be investigated on the basis of information available in the literature. Gauthier-Hion et al. 1985 studied the effect of duiker amongst other ungulates on Diaspora and found that more Diaspora were destroyed by the digestion process (n = 37) than disseminated (m = 13). However, very small seeds may well be disseminated by duiker, as Alexandre (1982) has shown for Solanum verbascifolium (Solanaceae) and Musanga cecropioides (Cecropiaceae). Therefore, it is quite possible that also Ficus species, fruits of which are preferably consumed by all duikers and contain large numbers of very small seeds, are disseminated by duikers. In this study only relatively few fruits with very small seeds were seen in the stomach contents of duikers: Ficus capensis, F. mucuso, F. vallis-choudae, Solanum erianthum, S. torvum, Anthocleista djalonenesis and Musanga cecropioides. All of these species might be propagated in part by the duiker. Observations of wild ranging duikers (Gauthier-Hion et al. 1985; Wilson pers. comm. 1992) have shown that duikers sometimes spit out fruit pips when ruminating. This behaviour might also contribute to the dissemination of certain plant species.
Acknowledgements We wish to thank Prof. L. Ake Assi for his invaluable assistance with the botanical analysis of the samples and his permission to use the facilities of the Centre Floristique National in Abidjan, CoÃte d'Ivoire. Messrs. P. Koffi Yao and A. Barom helped with the collection of samples at the Toumodi bushmeat market. The Chief Game and Wildlife Officer in Ghana, Mr. G. Punguse, is thanked for permission to collect material from black duiker at Kumasi with the kind assistance of his staff there, Mr. E. Lamptey, Senior Game Warden, and Messrs. O. Mensah and A. Brenya. Dr. B. Hoppe-Dominik kindly advised us on the cuticular analysis of collected samples and is thanked for his interest in this study.
76
T. HOFMANN et al.
Zusammenfassung PraÈferenzen der Futteraufnahme bei Duckern (Cephalophus maxwelli, C. rufilatus und C. niger) in der ElfenbeinkuÈste und Ghana. Mageninhaltsproben von 139 Maxwell-, 15 Rotflanken- und 57 Schwarz-Duckern wurden untersucht zur Feststellung des Spektrums der genutzten Futterpflanzen, von ØsungspraÈferenzen und evtl. jahreszeitlichen oder anderen EinfluÈssen auf die Futteraufnahme, sowie einer HabitatabhaÈngigkeit. Mageninhaltsproben von Maxwell- und Rotflanken-Duckern wurden auf dem Wildfleischmarkt von Toumodi in der ElfenbeinkuÈste und von Schwarz-Duckern in Kumasi in Ghana gesammelt. Die Tiere, von denen Proben genommen wurden, stammten aus einem Umkreis von ca. 25 respective 50 km um die MaÈrkte. Das Untersuchungsgebiet in der ElfenbeinkuÈste ist durch ein Mosaik von GuineaFeuchtwald und Feuchtsavanne charakterisiert, waÈhrend das in Ghana vorwiegend mit degradiertem SekundaÈr-Feuchtwald der Celtis-Triplochiton-Assoziation bewachsen ist. FruÈchte und dicotyle BlaÈtter waren die wichtigsten Futterkomponenten bei allen drei Duckerarten. GraÈser wurden auch bei allen drei Arten gefunden, aber nur in sehr kleinen Mengen. Knollen wurden in groÈûeren Mengen nur von den Schwarz-Duckern aufgenommen. BluÈten und Pilze wurden auch gefressen, hatten aber keine quantitative Bedeutung. Tierische Materie wurde nur bei MaxwellDuckern in Form von Ameisen gefunden. Ducker lassen sich somit nach Hofmann und Steward (1972) als ¹browserª (Blatt und GehoÈlz-Øser) klassifizieren. Die Anteile der wesentlichen Futterkomponenten variierten jahreszeitlich nur wenig; am staÈrksten Art und Anzahl von FruÈchten. Nur wenige der Frucht-Arten wurden offensichtlich bevorzugt genutzt. FruÈchteaufnahme von Maxwell- und Rotflanken-Duckern aÈhnelte einander staÈrker als bei Schwarz-Duckern. Die Futter-Zusammensetzung bei den drei Duckerarten zeigte, daû Rotflanken-Ducker bevorzugt in und um Waldinseln in der Feuchtsavanne aÈsen und daû Schwarz-Ducker gern kultivierte FlaÈchen im und nahe dem Feuchtwald aufsuchen. Maxwell-Ducker zeigten keine ausgepraÈgte futterbedingte Habitat-PraÈferenz. Die Vielseitigkeit ihrer Futteraufnahme weist darauf, daû sie verschiedenste LebensraÈume nutzen koÈnnen. Keine der drei Duckerarten ist futterabhaÈngig vom primaÈren Regenwald, da ein groûer Teil ihrer Futterpflanzen auch im degradierten Feuchtwald vorkommt. MoÈglicherweise tragen Ducker wesentlich zur Verbreitung einiger identifizierter fruchttragenden Pflanzen bei.
References Aeschlimann, A. (1963): Observations sur Philantomba maxwelli (Hamilton-Smith) une Antilope de la ForeÃt eÂburneÂenne. Acta Tropica 20, 341±368. AkeÁ Assi, L. (1984): ªFlore de la CoÃte d'Ivoire: Etude descriptive et biogeographique, avec quelque notes ethnobotaniquesº. Diss. thesis, Faculte des Sciences de L'Universite d'Abidjan. Alexandre, D. Y. (1978): Le roÃle disseÂminateur des eÂleÂphants en foreÃt de Tai. C. I. Terre et Vie 32, 47±72. ± (1982): La dispersion de Solanum verbascifolium en CoÃte d'Ivoire: RoÃle des Cephalophes. Terre et Vie 36, 293±295. Barthlott, W; Martens, B. (1979): CutikularTaxonomie der GraÈser eines westafrikanischen Savannengebietes unter dem Aspekt
der FutterpraÈferenz-Analyse wildlebender GroûsaÈuger. Trop. und subtrop. Pflanzenwelt 30, 687±793. Dubost, G. (1984): Comparison of the diets of frugivorous forest ruminants of Gabon. Mammalia 65, 298±316. Feer, F. (1989): Comparaison des reÂgimes alimentaires de Cephalophus callipygus et C. dorsalis, BovideÂs sympatriques de la foreÃt sempervirente africaine. Mammalia 53, 563±604. Gauthier-Hion, A.; Emmons, L. H.; Dubost, G. (1980): A comparison of the diets of three major groups of primary consumers of Gabon (Primates, Squirrels and Ruminants). Oecologia (Berlin) 45, 182±189. Gauthier-Hion, A.; Duplantier, J.-M.; Quris, R.; Feer, F.; Sourd, C.; Decoux, J.-P.; Dubost, G.; Emmons, L.; Erard, C.; Hecketsweiler, P.;
Feeding preferences of duiker Moungazi, A.; Roussilhon, C.; Thiollay, J.-M. (1985): Fruit characters as a basis of fruit choice and seed dispersal in a tropical forest vertebrate community. Oecologia (Berlin) 65, 324±337. Guillaumet, J.-L.; Adjanohoun, E. (1971): La veÂgeÂtation de la CoÃte d'Ivoire. In: Le milieu naturel de la CoÃte d'Ivoire. Paris: ORSTOM. Henle, K.; Apfelbach, R. (1984/85): Auswilderung und Beobachtungen zur Biologie des SchwarzruÈckenduckers. SaÈugetierkundl. Mitt. 32, 75±82. Hofmann, R. R.; Steward, D. R. M. (1972): Grazer and browser: A classification on the stomach structure and feeding habits of East African ruminants. Mammalia 36, 226±240. Hopkins, J. M. (1966): Observations on the rearing and behaviour of young duikers in captivity. Niger. Fld 30, 118±131.
77
Kurt, F. (1963): Zur Carnivorie bei Cephalophus dorsalis. Z. SaÈugetierkunde 28, 309±313. Roth, H. H.; Hoppe-Dominik, B. (1990): Ivory Coast. In: Antelopes, Global Survey and Regional Action Plans. Part 3: West and Central Africa. Compiled by R. East, IUCN-SSC Antelope Specialist Group. Schweers, S. (1981): Fleischfressende Antilopen. Zoofreund 42, 17±19. Hannover. Wilson, V. J. (1966): Notes on the food and feeding habits of the common duiker, Sylvicapra grimmia in eastern Zambia. Arnoldia 2, 1±19. Authors' addresses: Dipl.-Biol. T. Hofmann, Chrysanderstraûe 147, D21029 Hamburg, Germany (e-mail: [email protected]); Prof. Dr. H. H. Roth, 78 Le Roux Drive, Hillside, Harare, Zimbabwe