The utilization of large savanna trees by elephant in southern Kruger National Park

Shannon, Graeme; Druce, Dave J.; Page, Bruce R.; Eckhardt, H.C.; Grant, Rina; Slotow, Rob

doi:10.1017/s0266467408004951

Cited by 90 publications

(140 citation statements)

References 34 publications

(62 reference statements)

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“…The relatively lower stem density and survival rate after elephant utilization probably lead to more open woodlands in the granite lowveld. The negative correlation between elephant numbers and tree densities in most height classes in our study area, and in other areas (Cumming et al 1997;Whyte et al 2003;Shannon et al 2008;Woolley et al 2011), together with the population changes of the browser and grazer species, indicate in this instance that elephant might compete with other browsing species and facilitate grazers, especially megagrazer species, i.e., hippo, white rhino, and buffalo, through a decrease in tree cover and an increase in grass. Also, the proportion of browse consumed by other herbivores, aside from elephant, decreased over time.…”

Section: Discussionsupporting

confidence: 56%

“…Both negative and positive effects of elephants on other herbivore species have been claimed, as a consequence of the impact of elephants on the vegetation structure, biomass, and species composition. Elephants are known to push over, debark, and break trees, and various studies have found a decline in tree densities in the presence of elephants (Cumming et al 1997;Shannon et al 2008;Woolley et al 2011). Even at comparatively low elephant densities (<0.2 elephants/km 2 ), the densities of certain tree species show signs of decline (Cumming et al 1997;Shannon et al 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Elephants are known to push over, debark, and break trees, and various studies have found a decline in tree densities in the presence of elephants (Cumming et al 1997;Shannon et al 2008;Woolley et al 2011). Even at comparatively low elephant densities (<0.2 elephants/km 2 ), the densities of certain tree species show signs of decline (Cumming et al 1997;Shannon et al 2008). By the early 2000s when elephant densities exceeded 0.5 animals/km 2 in the Kruger National Park (KNP), the extent of the woody layer in parts of the Park had shown significant decline (Whyte et al 2003), and elephants are regarded as the primary agent of treefall, especially of trees in the 5-9-m height class (Asner and Levick 2012).…”

Section: Introductionmentioning

confidence: 99%

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Elephant-mediated habitat modifications and changes in herbivore species assemblages in Sabi Sand, South Africa

Boer

Oort

Grover³

et al. 2015

Eur J Wildl Res

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Elephant Loxodonta africana conservation might indirectly influence the wider herbivore community structure, as elephants have the ability to significantly modify the savanna habitat. Uncertainty remains as to the consequences of these effects, as elephants might either compete with other species or facilitate foraging especially for grazers and smaller browsing species by increasing the amount of grass or the amount of browse at lower feeding heights. We studied these potential cascading effects of elephants by using 16 years of data (1992-2011) from the Sabi Sand Wildtuin, South Africa, which showed a steady increase in elephant densities from 0.12 to 2.03 elephants/km 2 over this period. We demonstrate that tree densities, and browse availability at feeding heights below 2 m, decreased with increasing elephant densities, and that there was no positive effect of elephants on browse availability. The changes in elephant densities were good predictors (R 2 adj >0.50) in explaining population fluctuations of other herbivore species. The total body mass of grazers increased more than that of the browsers, shifting the community toward a grazer and megaherbivore-dominated community. An increasing density of elephants changes the composition of the herbivore community, as mesobrowsers are unable to benefit from the impact of elephants on trees, but megagrazers show strong positive responses. Hence, changes in elephant densities as a result of poaching or conservation may trigger cascading community effects. These are neglected but important consequences of (negative or positive) human impacts on elephant numbers, especially in restricted areas such as reserves and national parks.

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Section: Discussionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Elephant-mediated habitat modifications and changes in herbivore species assemblages in Sabi Sand, South Africa

Boer

Oort

Grover³

et al. 2015

Eur J Wildl Res

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“…Large trees play an important role within the ecosystem by providing habitat and shade to several species and food for many browsers (Shannon et al 2008), as well as increasing the nutritional status of the herbaceous layer for grazers (Treydte et al 2008). Trollope et al (1998) showed that the interaction of elephant impact and fire can have a profound effect on woody vegetation structure and composition, and suggested that an increase in elephant density (.0.36 individuals/km 2 ) could lead to structural changes across the KNP landscape.…”

Section: Introductionmentioning

confidence: 99%

Identifying drivers that influence the spatial distribution of woody vegetation in Kruger National Park, South Africa

Scholtz¹,

Kiker²,

Smit³

et al. 2014

Ecosphere

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Abstract. Understanding the dynamics of woody tree species distribution in savanna systems remains a challenge despite considerable attention the topic has received in recent years. Disturbances such as fire and elephant effects on woody vegetation are well documented, yet the influence of these factors on emerging landscape-scale patterns such as height and species distributions continue to be poorly understood. The aim of this study was to identify how a suite of environmental variables (rainfall, temperature, aspect, slope, geology, fire frequency and elephant density) and their relative contributions, may affect woody species distribution in relation to structural height classes. Using the Maximum Entropy model for three structural height classes of the fifteen most frequently occurring woody species in the Kruger National Park (South Africa), the environmental variables best explaining each species distribution were identified. The three structural classes were defined to capture canopy height categories of specific management interest, namely Shrub (0.75-2.5 m), Brush (2.5-5.5 m) and Tree (over 5.5 m). The weighted contributions of environmental variables for each species and its associated size class were further analyzed for similarities using a resemblance matrix based on the Bray-Curtis similarity index coupled with a hierarchical clustering test. Our main findings suggest that the patterns and processes driving woody composition and structure are largely decoupled and that the distribution of different structural classes of a particular species may not be driven by the same environmental variables. Future studies should take cognizance of this as ignoring one or the other may lead to confounding results.

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“…Kokwaro, also known as Marula is highly selected by the African elephant (Loxodonta africana Blumenbach) (Shannon et al, 2008), and hence heavily utilized (Jacobs and Biggs, 2001). The repeated browsing by elephants causes serious damage through breaking and removing of branches, and by preventing or reducing recruitment and regeneration (Balfour et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Elephant damage to Sclerocarya birrea on different landscapes

Seloana¹,

Kruger²,

Potgieter³

et al. 2017

Int. J. Biodivers. Conserv.

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The African elephant (Loxodonta africana Blumenbach) is a keystone species and ecosystem engineer. Elephants can cause serious damage to important trees, with only certain species being targeted such as Marula (Sclerocarya birrea A. Rich. Hoscht). High levels of elephant utilization may to some extent, compromise the viability of some woody plant populations leading to vegetation changes coupled with a possible loss of species diversity and/or structural diversity. In order to quantify their effect a study was initiated in 2014 to investigate their effect on tree height, degree of branch damage, the extent of debarking, and degree of stem damage. This was done within elephant's frequently and non-frequently used sites, and a neighbouring enclosure (control site). One hundred and fifty (50 per site) mature S. birrea trees were randomly selected within each site. Tree height was recorded using clinometers, degree of branch damage, extent of debarking (circumference debarked using different percentages of intensity) and degree of stem damage were assessed using different categories. Results indicated that the type elephant damage in both the frequently and non-frequently used sites was different, varied in intensity. A high proportion of Marula trees had been damaged. The size distributions of the trees showed that there was no regeneration. Furthermore, this study also demonstrated that elephants are able to damage Marula trees in several ways, the most destructive being bark stripping and pushing over trees. It is concluded that elephant impact is a powerful mechanism in shaping the structure and composition of Marula woodlands in the Atherstone Collaborative Nature Reserve. The findings of this study provide valuable baseline data and acts as a starting point for the introduction of adaptive management principles in small savanna reserves. This can be achieved by an intensive management programme responding to slight changes in the vegetation and would necessarily involve controlling elephant numbers.

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The utilization of large savanna trees by elephant in southern Kruger National Park

Cited by 90 publications

References 34 publications

Elephant-mediated habitat modifications and changes in herbivore species assemblages in Sabi Sand, South Africa

Elephant-mediated habitat modifications and changes in herbivore species assemblages in Sabi Sand, South Africa

Identifying drivers that influence the spatial distribution of woody vegetation in Kruger National Park, South Africa

Elephant damage to Sclerocarya birrea on different landscapes

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