Development of captive bongos (Tragelaphus eurycerus): Activity budgets and developmental milestones

The development of changes in visual orientation, posture, activity budgets, and behavioral milestones was examined in five bongo calves which were observed from birth to 4 or 6 months of age. The only significant change in the calves' visual orientation was an increase in orientation to food. Reclining declined significantly over weeks, while standing increased and moving did not change. Overall, stationary behaviors dominated the activity budget, but decreased significantly over the study. The category that included locomotion, object exploration, and auto-play did not change, while forage and rumination increased significantly. Contrary to expectation, the decline in suckling was not significant. Affiliative interactions with the dam decreased significantly during the study, but increases in affiliation with other bongos were not significant. Levels of agonistic behavior between the calves and their dams and other herd members were low throughout the study, and did not change significantly. One female calf achieved several developmental milestones later than the others. It is suggested that these differences may have been influenced by the dominance status of her dam. The results conform to the general developmental pattern of “hider” bovids. Bongos, however, show somewhat different patterns of social development than eland, which are reported to be more precocial in expression of aggressive and sexual behaviors. © 1992 Wiley-Liss, Inc.     

Survival and reproductive performance of female Glossina morsitans morsitans when maintained on the blood of different species of wild mammals

A study was carried out to determine the effect on the reproductive performance of female Glossina morsitans morsitans Westwood when allowed to feed, in vitro, for 63 days on fresh defibrinated blood of buffalo, bushbuck, cattle, eland, oryx, warthog, waterbuck or wildebeest. There were marginal differences in the survival and reproductive performance between eight different groups of tsetse, 200 per group, when fed on the blood of these mammalian species. When allowed to feed for 14 consecutive days on the blood of buffalo, wildebeest or warthog, the mean number of feeds were 6.2 +/- 0.3, 6.5 +/- 0.3 and 6.3 +/- 0.3, respectively. The mean weight of the bloodmeal taken also did not differ significantly between these three groups. Whereas the protein patterns of the blood plasma of the above eight host animals were different, the protein patterns of the haemolymph from tsetse fed on the blood of these hosts were identical. It is thus concluded that the preference shown by tsetse for some mammalian species investigated here may not be based on any aspect of the nutritional value of their blood.     

Interactions between large African browsers and thorny Acacia on a wildlife ranch in Kenya

Some plants respond to browsing with compensatory regrowth of plant tissues and with increased thorn growth. Associations between browsers and their preferred forage were examined through wandering quarter vegetation sampling and observational studies in an effort to understand how some plants respond to browsing by large African herbivores. Acacia seyal (n = 2680) A. drepanolobium (n = 1850), and Balanites glabra (n = 960) were three species of frequently browsed indigenous plants examined on Game Ranching Ltd. in Kenya. There were several statistically significant associations revealed. Individual A. seyal exposed to intensive browser utilization were observed to lose shoot tips, produce long thorns, and have relatively few flowers and fruits. Browser utilization was associated with increased lateral branching in A. drepanolobium and with an increased occurrence of short, thickened spines in B. glabra. Thorns, spines and flowers were measurable indicators of relative browser utilization, and may be useful features to monitor in the management of large African mammals and their prickly forage     

Chinko/Mbari drainage basin represents a conservation hotspot for Eastern Derby eland in Central Africa

One of the largest of antelopes, Derby eland (Taurotragus derbianus), is an important ecosystem component of African savannah. While the western subspecies is Critically Endangered, the eastern subspecies is classified as least concern. Our study presents the first investigation of population dynamics of the Derby eland in the Chinko/Mbari Drainage Basin, Central African Republic, and assesses the conservation role of this population. We analysed data from 63 camera traps installed in 2012. The number of individuals captured within a single camera event ranged from one to 41. Herds were mostly mixed by age and sex, mean group size was 5.61, larger during the dry season. Adult (AD) males constituted only 20% of solitary individuals. The overall sex ratio (M:F) was 1:1.33, while the AD sex ratio shifted to 1:1.52, reflecting selective hunting pressure. Mean density ranged from 0.04 to 0.16 individuals/km², giving an estimated population size of 445–1,760 individuals. Chinko harbours one of the largest documented populations of Derby eland in Central Africa, making Chinko one of its potential conservation hotspots.     

Effect of eland density and foraging on Combretum apiculatum physiognomy in a semi-arid savannah

We studied the impacts of eland density on the physiognomy of Combretum apiculatum . We divided the study area into two zones: high eland density zone (≤8 km from watering point) and low eland density zone (≥8 km from watering point). Eland density was determined in each zone using walking transects. Combretum apiculatum height and diameter and levels of eland damage were measured in each zone. Eland density was 1.92 and 0.86 km⁻² for high and low-density zones respectively. We recorded 239 C. apiculatum trees, 138 in low-density zone and 101 in high-density zone. Mean C. apiculatum height was 2.88 ± 0.67 m and 5.05 ± 1.04 m for high and low eland density zones respectively. High eland density prevented the recruitment of C. apiculatum from the 2.6–5.5 m height class to the >5.6 m height class. Although extensive tree damage occurred at <2.5 m height stratum, C. apiculatum showed resilience as recruitment into the 2.6–5.5 m height class continued. We concluded that high eland density prevents recruitment of C. apiculatum to higher height classes while at the same time causing extensive tree damage at lower height strata.     

Response of native ungulates to drought in semi‐arid Kenyan rangeland

The distribution and abundance of native ungulates were measured on commercially managed, semi‐arid rangeland in central Kenya over a 3‐year period that encompassed severe drought and above‐average rainfall. Native ungulate biomass density averaged 5282 kg km^?2 over the study and was dominated by elephant (Loxodonta africana), impala (Aepyceros melampus) and dik‐dik (Madoqua kirkii). Biomass density of domestic cattle (Bos taurus) averaged 2280 kg km^?2 during the study. Responses of native ungulates to severe drought were variable. Impala densities were similar to or greater than densities for similar habitat in protected areas, and varied from 12 to 16 km^?2 during and following the drought to 24–29 km^?2 following above‐average rainfall. Dik‐dik densities were also greater than densities reported for protected areas and were surprisingly stable throughout the study despite the wide annual fluctuations in rainfall. Elephant migrated out of the region during drought but were present at high densities (2.9–5.2 km^?2) during wet seasons, consistent with telemetry studies emphasizing the importance of Acacia bushland habitat on commercial rangelands for the migratory portion of the Laikipia–Samburu elephant population. Results show that substantial densities of native browsing and mixed‐feeding ungulates can occur on rangeland managed for commercial beef production and suggest that the capacity for ungulates to move over large spatial scales (>100 km²) and to shift distributions in response to locally variable thunderstorms may be important for sustaining these populations.     

Diet composition and habitat selection of eland in semi-arid shrubland

This study investigated the diet composition and habitat selection of eland in semi-arid shrubland, dominated by microphyllous and leptophyllous browse species offering low leaf: stem ratios. Browse (succulent, forb and woody species) contributed 94% to the annual diet of eland. The annual proportion of grass in eland diet was low (6%), even though palatable grass species were abundant in habitats favoured by eland. Most grass was eaten in the early wet season when grasses offered young green foliage. Woody species comprising dwarf shrubs and shrubs made up the bulk of the food eaten by eland. In each season, favoured woody species contributed substantial proportions to the diet of eland. Eland used the plateau habitats in the early wet season, but valleys and slopes in the late wet and dry seasons. Habitats favoured by eland contained high abundances of plants of woody species favoured by eland. Chemical analysis indicated that woody species favoured by eland offered lower total fibre contents than other woody species available to eland. The results of the study indicated that eland are browsers that select browse of low fibre content.     

The influence of large mammalian herbivores on growth form and utilization of mopane trees, Colophospermum mopane, in Botswana's Northern Tuli Game Reserve

Mopane veld is of great value to the general ungulate spectrum in times of drought, and it is capable of retaining its dominance in a community even in the presence of extremely heavy browsing pressure imposed by large browsing mammals. Scrub mopane (hedges) has been regarded as resulting from excessive browsing pressure by large mammals, especially elephants. Both the nutrient and chemical composition of mopane twig bark were investigated, the seasonal results being related back to the seasonal utilization of branches by large mammals. Mopane twigs were most palatable in winter. Eland feed on mopane throughout the year irrespective of palatability. Elephants were rarely present in the scrub mopane area before the onset of spring rains, when the major mopane leaf flush occurs independently of rainfall. The impact of both species was not excessive and recruitment of mopane seedlings does occur. Herbivore browsing is responsible for a mopane morph which buds early and continues to produce accessible, nutritious leaves even when heavily browsed. Many browsing ungulates are reliant on this resource during the stressful transition from spring to summer in south-eastern Botswana.     

Relationships between protease activity, host blood and infection rates in Glossina morsitans sspp. infected with Trypanosoma congolense, T.brucei and T.simiae

Abstract. Midgut protease activity in Glossina morsitans centralis and G. m. morsitans , at 48h post bloodmeal averaged 1.8IU of trypsin-like activity. These two tsetse subspecies differ in their susceptibility to trypanosome infection. Except for low levels in flies fed on waterbuck blood (0.7IU), activity did not differ in flies fed a variety of host bloods (goat, pig, cow, buffalo, eland) and trypanosome species ( Trypanosoma congolense, T.brucei, T.simiae ). Protease activity was also not correlated with infection rates, despite large differences in infection rates among experiments. Nevertheless, addition of 0.06M D(+)-glucosamine to parasitaemic blood resulted in a three-fold reduction in protease activity, coincident with a large increase in infection rate. This effect did not occur when parasites or D(+)-glucosamine were added alone to the bloodmeal, suggesting that the effect was due to metabolism of D(+)-glucosamine by parasites.     

The effect of host blood in the in vitrotransformation of bloodstream trypanosomes by tsetse midgut homogenates

Abstract. Midgut homogenates prepared from Glossina morsitans morsitans , that had previously been fed on different host blood samples, were tested for their abilities to transform bloodstream Trypanosoma brucei into procyclic (midgut) forms in vitro. Compared to rat and goat blood samples, eland blood had the least capacity to support trypanosome transformation, whereas buffalo blood showed intermediate capacity. Fractionation of rat blood showed the importance of the cellular portion since both rat and eland red blood cells (RBCs) supported the process. Virtually no transformation was observed in rat and eland plasma or serum fractions. Suspending rat blood cells in eland plasma led to a reduction in parasite transformation rates. Further experiments showed that the RBC membranes were also capable of supporting the process. These results clearly show the important role played by blood, especially the red blood cells, in the transformation of bloodstream trypanosomes. In addition, the low transformation rates observed in eland blood is due to an inhibitory factor(s) present in the plasma fraction.