The impact of elephants, Loxodonta africana, on woody vegetation through selective debarking in Samburu and Buffalo Springs National Reserves, Kenya

Abstract

The impact of elephants on the woody plant community through debarking was investigated in Samburu and Buffalo Springs National Reserves, Kenya. Acacia elatior Brenan, the most abundant tree species in the riverine zone, accounted for 68% (n = 1375) of woody plants. A. tortilis (Forsskal) Hayne dominated plots away from the river. Debarking incidences were significantly higher for A. elatior than for other species indicating selective utilization. The riverine zone by virtue of having more trees of the preferred species, A. elatior, had the highest debarking incidences. Presence of very few saplings along the river is attributed to both elephant trampling and herbivory by other species. An estimated 38.5% and 22.5% of the riverine A. elatior and A. tortilis trees respectively, were bound to die within the next 4-5 years because of severe debarking, ‡75% of bark circumference. Debarking was positively correlated with stem circumference; the mediumsized trees being the worst affected by the elephants' selective debarking behaviour. Intense debarking incidences were recorded during the dry season. Through the elephants' selective debarking, the riverine habitat is bound to open up gradually, leading to considerable habitat change in the near future. Elephant impact on vegetation is less away from the river and increases with their densities.Key words: Elephants, Samburu, selective debarking, woody plants condamné à s'ouvrir progressivement, ce qui entraînera un changement considérable dans un proche avenir. L'impact des éléphants sur la végétation est moindre lorsqu'on s'éloigne de la rivière, et il augmente en fonction de leur densité.

Survey ofLoxodonta africana(Elephantidae)-caused bark injury onAdansonia digitata(Malavaceae) within Pendjari Biosphere Reserve, Benin

“…The significant positive correlation between girth and intensity of bark damage do not support the third hypothesis. The tendency of elephants to debark large‐stem trees has been reported previously in East Africa (Ihwagi et al ., ). Nevertheless, this was not consistently confirmed when the data are broken down to each population.…”

“…data.). The impact of elephants on woody vegetation has led to concerns about possible extirpation of some plant species from the PBR as elsewhere in Africa (Ihwagi et al ., ). For example, elephant damage has resulted in dramatic changes in the population structure of Acacia tortilis Hayne (Pellew, ), A. elatior Brenan (Ihwagi et al ., ) and Adansonia digitata L. (Edkins et al ., ).…”

Poaching lowers elephant path tortuosity: implications for conservation

“…scrubland (Pratt et al , Barkham and Rainy ). The major river in the landscape, the Ewaso, supports a riverine forest dominated by river acacia ( Acacia elatior ) and fever tree ( Vachellia xanthophloea ), which attracts large numbers of animals in the dry months (Ihwagi et al ). The diverse plant community supports an equally diverse fauna.…”

“…The diverse plant community supports an equally diverse fauna. In addition to elephants, the ecosystem is home to other large mammals that include reticulated giraffe ( Girrafa camelopardalis ), plains zebra ( Equus quagga ), Grevy's zebra ( Equus grevyi) , Cape buffalo ( Syncerus caffer ), impala ( Aepyceros melampus ), defassa waterbuck ( Kobus ellipsiprymnus defassa ), and common waterbuck ( Kobus ellipsiprymnus ; Ihwagi et al ). Other animal species found in the landscape but in relatively fewer numbers include beisa oryx (O ryx beisa ), eland ( Taurotragus oryx ), and gerenuk ( Litocranius walleri ).…”

How selective are elephants as agents of forest tree damage in Bwindi Impenetrable National Park, Uganda?

“…Although elephants are considered unspecialized feeders (Kingdon, ), some plant species appear preferentially selected by elephants feeding in forests and woodlands (Viljoen, ; Sheil & Salim, ; Boundja & Midgley, ; Ihwagi et al ., ). Such selective impacts have implications for habitat composition and dynamics but are poorly characterized for closed high‐altitude forests.…”