Foraging Ecologies of Giraffe (Giraffa Camelopardalis Reticulata)
Total Page:16
File Type:pdf, Size:1020Kb
Foraging ecologies of giraffe (Giraffa camelopardalis reticulata) and camels (Camelus dromedarius) in northern Kenya: effects of habitat structure and possibilities for competition? David A. O’Connor1,2,3*, Bilal Butt2 and Johannes B. Foufopoulos2 1San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA, 92027, U.S.A., 2School of Natural Resources and Environment, University of Michigan, 440 Church St. Ann Arbor, Michigan, 48109-1041, U.S.A. and 3National Geographic Society 1145 17th St., NW, Washington, DC, 20036, U.S.A. Abstract au Kenya, ou ces especes sont recemment devenues The foraging ecologies of reticulated giraffe (Giraffa camel- sympatriques. La popularite croissante des dromadaires opardalis reticulata) and domestic camels (Camelus drome- dans la region a suscite des inquietudes au sujet des darius) were examined in the Laikipia District of Kenya, impacts sur l’environnement et d’une eventuelle competi- where these species have recently become sympatric. tion pour les ressources avec les girafes sauvages. Nous Camels increased popularity in the region has lead to avons recolte des donnees sur l’alimentation des deux concerns about their environmental impacts and possible especes au moyen de scan de groupe de deux minutes, qui competition with wild giraffe for resources. We gathered enregistraient la hauteur a laquelle les animaux mangea- foraging data on both species using 2-min group scans ient et les plantes preferees. Des transects ont permis de that recorded feeding heights and plant food preferences. recolter des echantillons de vegetation dans les zones ou les Transects sampled the vegetation in areas where foraging observations alimentaires ont ete faites. Les girafes femelles ^ observations were recorded. Giraffe females feed at lower se nourrissent plus bas que les males et les dromadaires elevations than males, while female camels feed below femelles se nourrissent plus bas que les girafes des deux both sexes of giraffe. There was very little observed overlap sexes. Nous avons observetres peu de recouvrement des in food preferences between the species. However, habitat preferences alimentaires des deux especes. Le type d’hab- type has an effect on foraging ecologies of both giraffe itat a un effet sur l’ecologie alimentaire des girafes des deux sexes, but habitat did not influence camel foraging. Camel sexes mais il n’influence pas l’alimentation des dromad- herder husbandry techniques also influence camel forag- aires. Les techniques d’elevage des dromadaires influen- ing dynamics. These findings have important implications cent aussi la dynamique alimentaire des dromadaires. Ces in achieving the twin objectives of wildlife conservation resultats ont d’importantes implications pour atteindre le and pastoralist livestock production in northern Kenya. double objectif de la conservation de la faune sauvage et de la production d’un betail pastoral dans le nord du Kenya. Key words: camel, conservation, foraging ecology, giraffe, pastoralist Resume Introduction L’ecologie alimentaire de la girafe reticulee (Giraffa camel- opardalis reticulata) et celle du dromadaire (Camelus Eastern Africa’s semi-arid ecosystems exhibit dynamic dromedarius) ont ete etudiees dans le District de Laikipia, interactions between pastoralist cultures, wildlife, com- plex rainfall patterns and soil types (Kjekshus, 1996). This includes 46 extant free-ranging ungulate species *Correspondence: E-mail: [email protected] (Owen-Smith &Cumming,1993),aswellasthreedominant © 2015 John Wiley & Sons Ltd, Afr. J. Ecol., 53, 183–193 183 184 David A. O’Connor et al. livestock species: cattle (Bos spp.), goats (Capra hircus) and Linnaeus). Domestic camels are more drought tolerant sheep (Ovis aries). African herbivores are categorized into a than cattle, performing well in adverse conditions, and browsing and a grazing guild (du Toit, 1995); within each have lower energy requirements (Farid, 1995; Maloiy, guild, coexisting species tend to have differing body sizes and Rugangazi & Rowe, 2009). feeding strategies (Woolnough & du Toit, 2001). With such Camel foraging is under studied (Dereje & Uden, 2005). complexity, it is vital to better understand how shared food Few studies exist currently on the effects of introduced resources partitioned among coexisting species (Sinclair, camels on ecosystem function and the resident herbivore 1979; Butt & Turner, 2012). communities. Camel browsing may affect forage availabil- Competition between herbivores depends on numerous ity, vegetation composition or structure. One particularly factors, and African ungulate guilds partition existing important relationship could exist between domestic cam- plant resources along temporal and spatial axes els and reticulated giraffe. Both are large ungulate brows- (McNaughton & Georgiadis, 1986; du Toit, 1990). Con- ers, with the ability to feed across a large vertical spectrum. sidering the spatial axis, browser species maximize nutri- This research explores the foraging preferences of domes- tional and energetic intake by focusing their feeding on tic camels and wild reticulated giraffe by investigating: different heights of vegetation (Pellew, 1984; Cameron & 1 Is there overlap between camel and giraffe feeding du Toit, 2007). Although there is a clear stratification in heights and preferred plant food species? feeding preferences, overlap does exist (du Toit, 1990). 2 Are there differences between adult female and adult Such overlap in resource usage sets the stage for possible male giraffe foraging ecologies across habitat types? competition for browse resources (see Prins & Fritz (2008)). Pastoralist livestock systems occur across much of the Methods East African savannah, with livestock herds often over- lapping spatially with wild herbivores, and utilizing the Study area same resources. In areas where such livestock grazing occurs, it represents an added layer of pressure on the Field data were gathered between May and August 2011 vegetation available for wild herbivores. Livestock feeding on the 19,873 ha Mpala Research Centre (MRC) in and husbandry could have significant knock-on effects on Laikipia Province (north central Kenya). Camels are kept the functioning and structure of the savannah system, as as livestock at MRC, providing the opportunity to compare well as on the availability of browse (Butt & Turner, 2012). the foraging ecologies of domestic camel and the coexisting However, a species that exists alongside people, livestock wild reticulated giraffe. and wild ungulates – the giraffe (Giraffa camelopardalis Camels are managed at MRC in a quasi-pastoralist reticulata de Winston) – has been thought to escape such fashion; herded during the day, and returning each resource overlap with either wildlife or livestock (Ciofolo & evening to a boma (temporary animal enclosures built Le Pendu, 2002). This is primarily due to giraffe’s capacity either of cut acacia branches or of mobile metal fencing). to feed on vegetation out of reach of other ruminants, and Western Mpala is composed of topographically flat, its ability to travel long distances in search of forage (du ‘black cotton’ vertisol (clay) soils characterized by extreme Toit, 1990; Young & Isbell, 1991; Bond & Loffell, 2001; shrink-swell movements, that destroy the roots of most Woolnough & du Toit, 2001; Parker & Bernard, 2005; plant species (Pringle et al., 2010). This produces a low Fennessy, 2009). diversity savannah with 97% over story cover of Acacia Pastoralist herders aim to manage their livestock for drepanolobium Harms ex Y. Sjostedt,€ and ground cover maximum productivity with respect to environmental composed of five grass species and two forbs (Young, conditions (Galvin, 1992; Ellis & Galvin, 1994; Galvin, Stubblefield & Isbell, 1997; Young et al., 1998). Coppock & Leslie, 1994). Changes in climate and more Eastern and northern Mpala is composed of infertile red frequent droughts represent a serious challenge to African sandy loams (alfisols; locally termed ‘red soil’). This soil pastoralists (Davies & Bennett, 2007; Homewood, 2008; type supports a diverse, structurally variable bushland Butt, 2010; Kiage, 2013). One way pastoralists have dealt habitat with a patchy understory of perennial grasses, with aridity in some environments is to change herd and a canopy cover dominated by A. brevispica Harms, composition from cattle-dominated groups to including A. mellifera Benth and A. etbaica Schweinf (Augustine & sheep and goats or even camels (Camelus dromedarius McNaughton, 2004; Kinnaird & O’Brien, 2012). © 2015 John Wiley & Sons Ltd, Afr. J. Ecol., 53, 183–193 Foraging ecologies of giraffe and camels 185 Between these areas is a transition zone, which supports plant species (See Fig. S1, Tables S1 and S2). Only data a savannah dominated by perennial grasses with widely from adult giraffe and adult female camels are included spaced shrubs, including species from both the black here. Male camels were not observed due to low stocking cotton and red soil habitats (see Fig. 1). These three soil numbers and field time limitations. types produce vegetation types that are very different in species richness, and result in distinct habitat structures Reticulated giraffe surveys and observations (Augustine & McNaughton, 2004; Kinnaird & O’Brien, 2012), allowing for comparison with herbivore foraging Giraffe were surveyed between 6:30 am and 11:00 am ecology across these three soil types. and again from 3:00 pm to sunset, to avoid