Parasites can shape the foraging behaviour of their hosts through cues indicating risk of infection. When cues for risk co-occur with desired traits such as forage quality, individuals face a trade-off between nutrient acquisition and parasite exposure. We evaluated how this trade-off may influence disease transmission in a 3-year experimental study of anthrax in a guild of mammalian herbivores in Etosha National Park, Namibia. At plains zebra (Equus quagga) carcass sites we assessed (i) carcass nutrient effects on soils and grasses, (ii) concentrations of Bacillus anthracis (BA) on grasses and in soils, and (iii) herbivore grazing behaviour, compared with control sites, using motion-sensing camera traps. We found that carcass-mediated nutrient pulses improved soil and vegetation, and that BA is found on grasses up to 2 years after death. Host foraging responses to carcass sites shifted from avoidance to attraction, and ultimately to no preference, with the strength and duration of these behavioural responses varying among herbivore species. Our results demonstrate that animal carcasses alter the environment and attract grazing hosts to parasite aggregations. This attraction may enhance transmission rates, suggesting that hosts are limited in their ability to trade off nutrient intake with parasite avoidance when relying on indirect cues.

Colophospermum mopane is the dominant tree or shrub within mopane woodland in the subtropical areas of southern Africa’s savanna ecosystems. This article provided a review on the adaptation capabilities of mopane against fire, browsing activity and environmental stresses. It further reviewed and tested the extent to which rainfall, temperature, altitude and soil types had an effect on the distribution of mopane in southern Africa. Mopane is adapted to survive moisture stresses, low nutrient environments and even disturbances caused by fire and browsing by large herbivores through its physical, physiological and chemical responses. Adaptation of mopane to various stresses enables it to dominate the low-lying areas of southern Africa’s savannas. The distribution of mopane is best associated with low to moderate rainfall (R2 = 0.38), high temperature (R2 = 0.42), low altitudes (R2 = 0.44) and a variety of soil types. An increase in the annual rainfall ( 800 mm) and altitude ( 800 m.a.s.l.), coupled with a reduction in the minimum temperature and acidic soil, limits the distribution of mopane. Mopane in South Africa occurs under similar environmental conditions to those in Zimbabwe and Zambia, but quite different from those in Angola, Namibia, Mozambique, Malawi and Botswana where mopane occurs.

One of the consequences of impacts of elephants and ¢re on woodlands is a change in woody cover, which often results in major challenges for wildlife managers. Changes in miombo woodland cover in and around Sengwa Wildlife Research Area (SWRA) between 1958 and 1996 were quanti¢ed by analyzing aerial photographs.Woody cover in SWRA decreazed from 95.2% in 1958 to 68.2% in1996, with a lowest mean of 62.9% in1983. The annual absolute rate of woody cover change in SWRA increazed from À1.1% per annum between1958 and1964 to a recovery of 1.6% per annum between 1993 and 1996, while the annual relative rate increazed from À1.1% per annum between 1958 and 1964 to 3.3% per annum between 1993 and 1996. There was a strong negative correlation between elephant densities and woody cover in SWRA, suggesting that loss of woodycover was mainly due to elephants.Woodland recovery after 1983 was due to reductions in elephant populations through legal and illegal o¡-take and reductions in ¢re frequency. Surrounding areas experienced less woody cover losses than SWRA, mainly due to tree removal by locals whose densities increazed after the eradication of tsetse £y in the 1970s. Re¤ sume¤Une des conse¤ quences de l'impact des e¤ le¤ phants et des feux sur les fore" ts s'exprime par un changement du cou-vert ligneux qui pose souvent de fameux de¤ ¢s pour les gestionnaires de la faune. Les changements du couvert forestier a' Miombo, qui sont survenus a' l'inte¤ rieur et aux alentours de l'Aire de Recherche sur la Faune de Sengwa (SWRA) entre 1956 et 1996, ont e¤ te¤ quanti¢e¤ s gra" ce a' l'analyse de photos ae¤ riennes. Le couvert forestier de la SWRA a diminue¤ de 95.2% en 1958 a' 68.2% en 1996, la moyenne la plus basse e¤ tant observe¤ e en 1983, avec 62.9%. Le taux annuel absolu de changement du couvert forestier dans la SWRA est passe¤ de^1.1% par an entre 1958 et 1964 a' une restauration de 1.6% par an entre 1993 et 1996, tandis que le taux annuel relatif augmentait de^1.1% par an entre 1958 et 1964 a' 3.3% par an entre 1993 et 1996. Il existait une forte corre¤ lation ne¤ gative entre la densite¤ des e¤ le¤ phants et le couvert forestier de la SWRA, ce qui laisse supposer que la perte de couvert forestier e¤ tait due principalement aux e¤ le¤ phants. La restauration de la fore" t apre' s 1983 e¤ tait due a' des re¤ ductions des populations d'e¤ le¤ phants suite a' des pre¤ le' vements, le¤ gaux ou non, et a' une baisse de la fre¤ quence des feux. Les zones adjacentes ont subi de moins fortes pertes du couvert forestier que la SWRA, et celles-ci e¤ taient principalement dues a' des coupes faites par les locaux dont la densite¤ a augmente¤ suite a' l'e¤ radication de la mouche tse¤ -tse¤ dans les anne¤ es 1970.

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This study examines the extent of elephant damage in two State Forests and investigates whether wildlife utilization, particularly of elephant (Loxodonta africana), produces economic returns which offset the negative impact of elephant damage on the timber resource. Eight common timber species were studied; 25% of trees >9.5 cm diameter at breast height (dbh) sampled had been damaged by elephants or other herbivores. P. angolensis, one of the most economically important timber species, was the worst affected; 67% of trees ~3 4 cm dbh had been damaged by elephants. The results indicate that elephant can cause mortality of trees, and 13% of P. angolensis sampled had been killed by elephants. Elephant appear to be limiting recruitment into exploitable size classes. Simple economic calculations estimate that the benefits derived from elephant trophy hunting (US$0.35 ha-' y -') outweigh the timber losses caused by elephant (US$O. 15 hay -I). The economic value of hunting in the Forests is shown to be greater than the value of extractable timber. ResumeCette etude examine l'itendue des degats d'klephants dans deux For& d'Etat et pose la question de savoir si l'utilisation de la faune sauvage, et particulikrement de l'elkphant (Loxodonta africana), genere des retombees economiques qui compensent l'impact nkgatif des degats des elephants sur la resource en bois. Huit especes communes d'arbres furent Ctudiees; 25% des arbres de plus de 9,5 cm de diametre a hauteur de poitrine (dbh) echantillonnes avaient Cte endommages par les elephants ou d'autres herbivores. P. angolensis, l'une des especes d'arbre les plus importantes economiquement, etait le plus gravement affecte; 67% des arbres de moins de 34 cm dbh avaient Cte endommages par les elephants. Les rksutats indiquent que l'klephant peut causer la mortalite des arbres et que 13% des P. angolensis echantillonnes avaient ete tues par les elephants. L'elkphant semble limiter le renouvellement parmi les classes de tailles exploitables. De simples calculs economiques suggerent que les benefices derives de la chasse sportive ti ]'elephant (US$0.35/ha/an) compensent les pertes causees aux arbres par les elephants (US$O. 1 5/ha/an). La valeur Cconomique de la chasse dans les For& s'avere donc plus elevke que la valeur du bois exploitable.(0, 1996 East African Wild Life Society.

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Changes in structure and composition of miombo woodlands mediated by elephants and fire were studied in 26-year-old permanent transects established in 1972 in north-western Zimbabwe. Elephants caused 48% decline in proportions of large trees (>11 cm diameter), significant reductions (30.9-90.9%) in tree heights, reductions in stem areas (43.5%) and densities (2.5%) of all trees. There were increases in proportions of small trees (64.8%), shrub canopy volumes (271%) and shrub densities (172%). These increases are attributed to natural recruitment because of longer fire-free periods and reduction of tree suppression effects on lower strata as a result of elephantinduced tree declines. Frequencies of occurrence of most species dropped by 28-89.6%. Brachystegia boehmii was replaced by Pseudolachnostylis maprouneifolia as the most dominant tree, largely because of high elephant preference for Brachystegia boehmii. A new suite of species, dominated by Combretaceae, increased in dominance resulting in local floristic changes. Reductions in old elephant (33.4%), old unknown (89.9%) and new elephant (13.7%) damage suggest that elephant occupancy of miombo woodlands has declined, possibly because of limited availability of preferred browse species. This study clearly shows that elephants and fire have contributed significantly to the changes in miombo woodlands in the area.Key words: elephant damage, fire, miombo, Sengwa, Zimbabwe (9,9%) et « nouveaux dus aux éléphants » (13,7%) suggère que l'occupation des forêts de miombo par les éléphants a diminué, peut-être à cause de la disponibilité limitée des espèces fourragères qu'ils préfèrent. Cette étude montre clairement que les éléphants et les feux ont contribué significativement aux changements survenus dans les forêts de miombo de la région.

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