Wildlife & Ecological Investments Field Research Programme 2014
Total Page：16
File Type：pdf, Size：1020Kb
Wildlife & Ecological Investments Field Research Programme 2014 Overview for Balule Game Reserve Contributors - Tomos Avent, Caz Schiess, Henrietta Chilton & Elme Breytenbach In 2012 Wildlife & Ecological Investments started a research and training programme in Struwig Eco Reserve. Since then, over 800 students from more than 20 countries have joined our College, Undergraduate and Masters training programmes in Savannah Ecology, Southern African Conservation, and Bush-craft Training. Our team on the ground have also helped restore and maintain the road network throughout OREC, especially through rock packing and soil filling rill erosion, vegetation clearing, and continued work on mitre drains and bolsters. The purpose of this report is to introduce the ongoing research work on Struwig and present an overview of the data collected so far in 2014. Due to the limited area of operation and traversing on OREC, our research programme has thus far been limited to small-scale bird, invertebrate, habitat, herbivore and predator monitoring projects. In the future we would like to expand our research focus to help address larger questions pertinent to the conservation management of Balule Game Reserve. The following report will be broken down into research themes, first outlining our survey approaches, then summarizing our data and, if appropriate at this point, some research findings. At the end of some sections I suggest some of the further work that would be possible if we are able to expand the programme into a larger area. It is not the purpose of this overview to go into detailed methods and justifications of our survey work, but copies of these can be obtained on request – please email [email protected]. Report Themes 1. Habitat Assessment ………………………………………………………………………………………….……….. Page 2 2. Bird Surveying.………………………………………………………………………………………………….……….. Page 8 3. Predator Monitoring …………………………………………………………………………………………………. Page 12 4. Elephant Monitoring …………………………………………………………………………………………………. Page 22 5. Game Monitoring …………………………………………………………………………………………….……….. Page 23 6. Invertebrate Sampling ….…………………………………………………………………………………………… Page 25 1 1. Habitat Assessment Habitat Analyses have been conducted at 15 sites each winter since 2012 (sites mapped in Figure 1). Figure 1. Habitat Assessment and Bird Point Count Survey Sites At each habitat assessment site our teams record all woody vegetation over 1 metre tall, detailing species name, height class, basal stem diameter, average stem diameter (for multi-stemmed bushes), the width of the widest point of the canopy, and the extent of elephant and fire impact. A qualitative and quantitative evaluation of elephant impact (and fire although the fire data is not featured in this report) is graded according to the Walker scale as detailed below: TYPE: CODE: Pulled or kicked out A Pushed over and dead or apparently dead B Main trunk broken, is or appears to be dead C Main trunk broken but re-sprouting or likely to re-sprout D Pushed over but still alive E Main trunk tusk-slashed F Main trunk debarked (% of the circumference) *G Roots exposed and eaten (% of the circumference) *H Primary branches broken *J Secondary and/or smaller branches broken *K None: Z 2 *Impact types G, H, J, K must be quantified according to the percentage classes given below. The percentage classes refer to the percentage of the total canopy volume (J & K) and are estimated. In the case of exposed roots and debarking of the main trunk (types G & H), the percentage of the root base or trunk's perimeter (i.e. a circle) affected must be estimated and coded accordingly. 1-10% 11-25% 26-50% 51-75% 76-90% 91-100% Over the period 2012-2014, our research teams have identified 61 tree species in and around our Habitat Assessment sites on OREC (Figure 2). The habitat assessments involved the surveying of 1864 trees over the three year period. Abutilon angulatum Commiphora mollis Gymnosporia senegalensis Acacia burkei Commiphora pyracanthoides Hippocratea longipetiolata Acacia erubescens Crossopteryx febrifuga Karomia speciosa Acacia exuvialis Croton megalobotrys Lannea schweinfurthii Acacia gerrardii Dalbergia melanoxylon Lantana camara Acacia grandicornuta Dichrostachys cinerea Mundulea sericea Acacia karroo Diospyros mespiliformes Manilkara mochisia Acacia nigescens Ehretia amoena Ozoroa paniculosa Acacia Senegal Euclea divinorum Pappea capensis Albizia harveyi Euclea natalensis Peltophorum africanum Boscia albitrunca Euclea undulate Philenoptera violacea Cassia abbreviate Grewia bicolor Schotia brachypetala Cissus cornifolia Grewia caffra Sclerocarya birrea Coddia rudis Grewia flava Spirostachys africana Colophospermum mopane Grewia flavascens Terminalia prunioides Combretum apiculatum Grewia hexamita Tricalysia junodii Combretum collinum Grewia inaequilatera Tricalysia lanceolata Combretum hereroense Grewia monticola Ximenia americana Combretum imberbe Grewia villosa Ximenia caffra Combretum mossambicense Ziziphus mucronata Grewia subspathulata (hybrid of Commiphora Africana G.monticola & G.bicolor)) Figure 2. A species list of trees identified on OREC over the period 2012-2014 3 This initial analysis covers the following questions: i) Are certain tree species more impacted by elephant? ii) Are elephants having a greater impact on certain height categories of trees? iii) Are there differences in the relative level of elephant impact between sites? To calculate the proportion of trees impacted relative to their abundance, ‘impact scores’ were generated. Firstly, a tree was classified as ‘impacted’ if it had been recorded in any of the impact categories (excluding the ‘Z’ no impact category). If the only impact to the tree was in categories G, H, J or K, the tree was only classed as ‘impacted’ if one or more of the associated percentages was over 50%. More rigorous impact scores have been calculated using the Walker Scale for other WEI projects but we were aiming to create a quick and easily repeatable method to assess the data for OREC. To create an impact score for each tree species we first calculated the percentage of trees impacted within each species and then calculated: - the percentage of total trees impacted for each species ( % Impacted = (no. of trees of the species impacted / total no. of trees impacted ) x 100) - the percentage of total trees for each species (% availability = (no. of trees of species / total no. of trees) x 100) - an impact score for each species (Impact Score = % impacted / % availability) This method of creating impact scores was then repeated for enquiries ii) and iii), using the relevant categories – i.e. height categories (ii) and survey site locations (iii) rather than species. The differences between impact scores for each category were evaluated for independence using Chi-squared tests. An impact score of above 1.0 will demonstrate ‘selection’ for that species, where as an impact score of below 1.0 will demonstrate a lack of selection. We therefore assume that species showing some level of impact but not ‘selected for’, are chosen by elephants due to their high availability rather than a preference by the elephants. Again, this analysis is designed as a quick and easy method to identify patterns and indications of associations. Further analysis and behavioural observation would be required to confirm the 4 selectivity behaviour of elephants in the OREC area. The analysis in this report only includes the 2013 data, a summary of which is illustrated in Table 1. Number of Sites Surveyed 17 (two additional sites were selected) Number of Trees Surveyed 771 Number of Trees Impacted 97 % of Trees Impacted 12.58 Number of Tree Species 38 Number of Tree Species Impacted 17 % of Tree Species Impacted 44.74 Table 1. A table summarising the research effort and results from the Habitat Assessments in 2013. The no. of species listed here is lower than those stated in Fig 2. as Fig 2. includes different sites assessed in 2012. i) Tree species impact selectivity by elephant The 2013 data indicated that 13 of the 17 species impacted by elephants were selected for by the elephants (impact score >1.0) (Figure 3). There was a statistically significant difference between species, with Sclerocarya birrea and Peltiphorum African displaying the highest impact scores of 7.95. Tree species selection by Elephants in 2013 100.00 10.00 1.00 % Impact % Availability 0.10 Impact Score Figure 3. The analytical variables describing species impacted by elephants in 2013. The % availability illustrates the relative abundance of each species in the survey sites. The % impact illustrates the percentage of total impacted tree of each species. Impact scores <1.0 indicate impact is due to abundance of the species rather than selection by elephants. 5 ii) Elephant impact in different tree height classes The highest impact scores were seen by trees in the largest height category (10m-20m) with over 30 % of trees in that category displaying impact (Figure 4). Although there is only a low percentage of total trees impacted in this group (Figure 5), this is more likely to be a reflection of the low number of individuals in this height category. Further analysis of tree species most impacted within this group alone would be useful to highlight the more vulnerable mature trees of the larger species. 25% of trees between 4m-6m were impacted by elephant (Figure 5), the group also displaying a high impact score. Around 18% of all impacted trees fall in this category (Figure 4). The height category with the greatest percentage of total