University of Groningen Co-existence and niche segregation of three small bovid species in southern Mozambique Prins, HHT; de Boer, WF; van Oeveren, H; Correia, A; Mafuca, J; Olff, H; Boer, Willem F. de Published in: African Journal of Ecology DOI: 10.1111/j.1365-2028.2006.00619.x IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2006 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Prins, HHT., de Boer, WF., van Oeveren, H., Correia, A., Mafuca, J., Olff, H., & Boer, W. F. D. (2006). Co- existence and niche segregation of three small bovid species in southern Mozambique. 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For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 29-09-2021 Co-existence and niche segregation of three small bovid species in southern Mozambique Herbert H.T. Prins1*, Willem F. de Boer1,2, Herman van Oeveren1, Augusto Correia2, Jorge Mafuca2 and Han Olff13 1Resource Ecology Group, Wageningen University, Bornsesteeg 69, 6708 HM, Wageningen, The Netherlands, 2Department of Biological Sciences, Eduardo Mondlane University, C.P. 257, Maputo, Mozambique and 3Laboratory for Plant Ecology, University of Groningen, P.O. Box 14, 9750 AA, Haren, The Netherlands forestie`re. On s’attendait a` voir une diffe´rentiation dans les Abstract choix alimentaires afin de re´duire la compe´tition parmi ces Niche segregation among three small antelopes – red duiker, se´lecteurs de concentre´s de taille semblable. La composition common duiker and suni – was investigated in a coastal alimentaire ne changeait pratiquement pas parmi les dif- savanna woodland/forest mosaic. It was expected that these fe´rentes classes de ve´ge´tation. Chez les trois espe`ces d’antil- similar-sized concentrate selectors would show differenti- opes le nombre d’e´le´ments alimentaires fut grand, avec un ation in diet choice to decrease competition. Diet composi- minimum de 70 aliments diffe´rents par espe`ce. Le niveau de tion did not vary significantly among the different spe´cialisation alimentaire fut bas, avec seulement 10% des vegetation types. For all three antelope species, the number e´le´ments alimentaires consomme´s en exclusivite´ par chaque of dietary items was large, with a minimum of 70 different espe`ce. Le grade d’e´le´ments alimentaires fut corre´le´ de food items per species. Dietary specialization was low, with manie`re positive parmi les espe`ces pendant la saison des only 10% of the food items being exclusively used by each of pluies, et moins pendant la pe´riode se`che. L’e´tendue de leur the species. The ranks of food items were positively corre- die`te diminua d’une manie`re importante pendant la pe´riode lated among species in the wet season, but not in the dry se`che. L’utilisation d’espe`ces exclusives fut beaucoup plus season. Diet breadth significantly decreased in the dry sea- importante pendant la pe´riode se`che, avec les plus basses son. The use of exclusive species was significantly larger in valeurs chez le ce´phalophe de Grimm. Le chevauchement the dry season with lowest values recorded for the common d’aliments pendant la saison des pluies fut majeur, mais duiker. Diet overlap in the wet season was considerable, but diminua d’une manie`re importante pendant la pe´riode significantly decreased in the dry season, the time of food se`che, quand les aliments furent difficile a` obtenir. Les don- scarcity. The dry season data showed evidence for niche ne´es obtenues pendant la pe´riode se`che de´montre`rent des segregation, although this was not based on displacement. preuves d’une se´gre´gation des niches, quoique ceci ne fut pas As niche segregation in the dry season was coupled to a base´ sur le de´placement. Puisque la se´gre´gation des niches random apportionment of diet items among antelope pendant la pe´riode se`che fut lie´ea` un partage ale´atoire species, it cannot be interpreted as the result of competitive d’e´le´ments alimentaire parmi les espe`ces d’antilope, ceci ne displacement. peut pas eˆtre interpre´te´ comme le re´sultat du de´placement compe´titive. Key words: antelope, competition, diet overlap, faecal analysis, resource partitioning Re´sume´ Introduction La se´gre´gation des niches chez trois petites antilopes - le Related species that live together are thought to show ce´phalophe du natal, le ce´phalophe de Grimm et le suni – fut specialization or niche differentiation to avoid competition. e´tudie´e dans une foreˆt de la savane littorale/mosaı¨que Niche differentiation may result from habitat segregation, morphological adaptations (e.g. of the gut to feeding *Correspondence: Tel.: +31 317 483900; Fax: +31 317 484845; browse or grass), or behavioural adaptation (e.g. special- E-mail: [email protected] ized dietary adaptations). Morphological specialization Ó 2006 The Authors 186 Journal Compilation Ó 2006 East African Wild Life Society, Afr. J. Ecol., 44, 186–198 Niche segregation of small bovids 187 could be advantageous if it diminishes resource competi- three are important for small antelopes. The grass plains tion with other species. However, it may result from his- are low-lying plains that are seasonally inundated, char- torical interspecific competition, or the ‘ghost of acterized by the absence of trees. Sand forest is found in the competition past’ (Connell, 1980). This makes finding southern and eastern undulating part of the reserve and causes of niche segregation difficult, because competitive has developed around lakes and on top of the sand dunes; forces in the past are difficult to appraise. typical understorey species are Panicum deustum, Phyllan- Studies of interaction between herbivores in multi-species thus sp. and Acacia kraussiana. Savanna is found on the assemblages are scarce, yet there has been considerable slopes between the dune sand forests patches; it has a well- speculation about the actual mechanisms of niche parti- developed herbaceous layer interspersed with trees. tioning (Jarman & Sinclair, 1979; Jenkins & Wright, 1988; de Boer & Prins, 1990; Mathur, 1991). Hence, it is difficult to The small bovid assemblage prove whether an ecological segregation implies a lack of interaction, or an explicit response to competition. Most The most abundant antelopes are reedbuck (Redunca proof for competition among sympatric herbivores is based arundinum Boddaert) and duiker species (Tello, 1973). on circumstantial evidence (Keiper, 1985; Putman, 1996). Common duikers are abundant in the reserve, preferring Numerical analyses of population responses are desirable to savanna and sand forest. The reserve is further used by a confirm the existence of competition (Prins, 1996). Experi- small elephant (Loxodonta africana Blumenbach) popula- mental studies are scarce, and most evidence for competition tion (de Boer et al., 2000). Large predators, or other larger between herbivores comes from systems in which livestock grazers and browsers have gone extinct from the area. was introduced, displacing native herbivores (Loft et al., These three small, ‘primitive’ antelope species are not 1987; Loft, Menke & Kie, 1991; Ragotzkie & Bailey, 1991; dependent on water, all territorial, and forage on a wide Voeten & Prins, 1999; Prins, 2000; Mishra et al., 2004). range of browse items, often on fallen leaves, fruits and Theoretically, competitive interactions among herbivores pods (Kingdon, 1982, 1997; Lawson, 1989). The simi- are predicted to be the most severe between species that have larity in diet overlap was also noted by Hofmann (1973) the same feeding style and similar body weights; when body regarding suni and red duiker in Kenya. The three species weights are different, it is predicted that species may parti- have rather similar weights, and all three are concentrate tion resources by size and quality, such that each species has selectors with high fermentation rates (Kingdon, 1982). exclusive resources (Belovsky, 1986; Prins & Ol, 1998; The questions are, thus: (i) how these three species are able Ritchie & Ol, 1999). In this study, we quantified niche seg- to co-exist, (ii) to what extent these species have segregated regation among three small antelopes (red duiker Cephalo- their diets, and (iii) whether this segregation is a strategy phus natalensis Smith, common duiker Cephalophus grimmia to prevent niche overlap and reduce competition. L., and suni Neotragus moschatus von Dueben), all bovids Suni (4–6 kg: Kingdon, 1997; 8 kg: Hofmann, 1973) (Kingdon, 1982). These antelopes co-exist in the same ha- mainly live in coastal shrub and sand forest; they do not bitat despite their similar size. Consequently, we explored need to drink water but can survive on the moisture their diet and habitat use in three habitats in southern content of their food (Somers, Rasa & Apps, 1990; King- Mozambique to determine how they partition resources.