Elephant herbivory in Majete Wildlife Reserve, Malawi

Abstract

Elephants have a major influence on vegetation structure, composition and ecosystem processes, and are primary agents of habitat change in Africa. At moderate-to-high population densities, elephants can damage vegetation, especially when enclosed in protected areas. This study examines the effects of elephant browsing on woody trees in Majete Wildlife Reserve (WR), south-western Malawi. Regression analysis is used to assess the associations of six factors known to drive elephant browsing in other areas and determine which ones have the most influence on browsing at Majete WR. Twenty-four per cent of tagged trees had been subject to elephant browsing. The model with vegetation type, stem diameter and distance from permanent water correctly predicted browsing for 80% of the observations. Elephants mostly favoured riparian woodlands, followed by Acacia-dominated woodland and Brachystegia-dominated woodland. Browsing occurrence was negatively related to distance from permanent water and diameter at breast height(DBH). A larger number of trees, sampled at random and covering a larger portion of the reserve would provide more reliable estimates of browsing and related factors. Knowledge of time-and sitespecific factors affecting elephant browsing can be used to forecast future habitat transformations and manipulate the range of the elephants within the reserve. R esum eLes el ephants ont une influence majeure sur la structure et la composition de la v eg etation et sur les processus ecosyst emiques, et ce sont des acteurs primordiaux des changements d'habitats en Afrique. Lorsque leur densit e de population est de mod er ee a elev ee, les el ephants peuvent endommager la v eg etation, surtout s'ils sont enferm es a l'int erieur d'une aire prot eg ee. Cette etude examine les effets des el ephants qui consomment des arbres ligneux dans la R eserve de Faune (RF) de Majete, au sud-ouest du Malawi. Nous utilisons une analyse de r egression pour evaluer les associations de six el ements connus pour influer sur l'alimentation des el ephants en d'autres endroits, et pour d eterminer lesquels influencent le plus la consommation des el ephants a la RF de Majete. Vingt-quatre pourcents des arbres marqu es ont et e touch es par des el ephants. Le mod ele comprenant le type de v eg etation, le diam etre des troncs et la distance par rapport a un point d'eau permanent a permis de pr edire correctement 80 % des cas de consommation par les el ephants. Les el ephants privil egiaient surtout les forêts riveraines, suivies des forêts domin ees par l'Acacia et par celles domin ees par Brachystegia. Les cas de consommation etaient n egativement li es a la distance par rapport a un point d'eau permanent et a la dbh. Un grand nombre d'arbres, choisis au hasard et couvrant une grande partie de la r eserve, permettraient d'obtenir des estimations plus fiables de la consommation des el ephants et des facteurs qui y sont li es. Ce que l'on sait des facteurs sp ecifiques du temps et du site affectant la consommation des el ephants peut servir a p...

Mallard resource selection trade‐offs in a heterogeneous environment during autumn and winter

“…We also detected that these priors assisted with achieving model convergence. To construct discrete choice models, we identified the independent variables whose area estimates within choice sets that were not highly correlated (pair‐wise | r | < 0.8) using the Pearson correlation matrix for each season and each diel period (Staub, Binford, & Stevens, ). This process reduced convergence issues with multicollineartiy but retained variables of biological interest.…”

“…To construct discrete choice models, we identified the independent variables whose area estimates within choice sets that were not highly correlated (pair-wise |r| < 0.8) using the Pearson correlation matrix for each season and each diel period (Staub, Binford, & Stevens, 2013 Information Table S2). We ranked the four candidate models by their deviance information criterion (DIC), the Bayesian analog to Akaike's information criterion (Beatty et al, 2014b;Burnham & Anderson, 2002;Spiegelhalter, Best, Carlin, & van der Linde, 2002).…”

Inhibitory geostatistical designs for spatial prediction taking account of uncertain covariance structure

“…Annually, the precipitation is 680–800 mm in the eastern lowlands and 700–1000 mm in the western highlands (Wienand, ). With an average daily temperature of 28.4°C, the wet season is slightly warmer than the dry season (average daily temperature 23.3°C), although the hottest months are September to November, at the end of the dry season (Staub, Binford, & Stevens, ).…”

African elephant in a cleft stick : choosing between starving or dying from thirst in arid savanna

“…In regions where elephant density is high, there is a long standing perception and inconclusive debates that elephant have adverse impacts on habitats (de Beer et al, 2006, Staub et al, 2013 and also, sometimes, on other species (Cumming et al, 1997) through their foraging behaviour of pushing over, uprooting and snapping trees (Staub et al, 2013). The question of whether elephant numbers should be controlled or not has been the subject of debates for decades with contradicting proposition on how this should be addressed (Laws, 1970b, Caughley, 1976, Myers, 1973, Owen-Smith et al, 2006, Van Aarde and Jackson, 2007.…”

“…Studies on wildlife populations, especially on the African elephant, have attracted immense attention because of the long standing perception that an increase in elephant numbers have an adverse impact on vegetation (Glover and Sheldrick, 1964, Laws, 1970b, Myers, 1973, Ben-Shahar, 1993, de Beer et al, 2006, Staub et al, 2013, and sometimes, on other species (Cumming et al, 1997 through their foraging behaviour of pushing over, uprooting and snapping trees (Staub et al, 2013).…”