W. van Hoven

Condensed tannin as anti-defoliate agent against browsing by giraffe (Giraffa camelopardalis) in the Kruger National Park

Abstract The feeding behaviour of giraffes in the Kruger National Park, South Africa, was observed over 12 months and the diet analysed for condensed tannin content. Supportive evidence was found for plant defence against excessive browsing by means of tannin biosynthesis. Condensed tannin negatively influenced acceptability and nutritional value of dietary browse to giraffes. The giraffes avoided high condensed tannin levels. Tannin content of dietary foliage increased due to browse disturbance. Tannin levels fluctuated daily within the canopy of individual plants in relation to change in temperature, light intensity and phenological status of the foliage.

THe use of purified condensed tannin as a reference in determining its influence on rumen fermentation

1. Tannins were purified from the leaves of trees forming part of giraffes diet in the Kruger National Park. 2. In general, hydrolysable tannin formed less than 10% of the total purified crystal complexes, condensed tannin and possibly some non tannin phenols forming the balance. 3. Each tree species condensed tannin gave a different calibration curve and these were used in the assay. 4. Volatile fatty acid production during in vitro fermentation was greatly reduced when the substrate contained more than 6% condensed tannin.

Pregastric and caecal fermentation in dikdik (Madoqua kirki) and suni (Nesotragus moschatus)

1. 1. In dicotyledon eating dikdik (Rhynchotragus kirki) and suni (Nesotragus moschatus), rumen-reticulo (RR) fermentation rates (μmol gases β gDM−1β hr−1) in vitro were rapid, ranging from 524 in tropical Kenya to 395 in subtropical South West Africa (dikdik) and averaging 535 in Kenyan suni. 2. 2. In dikdik RR, amylolytic activity greatly exceeded cellulolytic activity. 3. 3. Two Entodinia species were found in 9 out of 12 dikdik. 4. 4. RR digestion in dikdik and suni is characterized by rapid rates at pH > 6.1, high amylolytic activity, scarcity of protozoa and fast turnover.

Tannins and digestibility in the steenbok (Raphicerus campestris)

1. The influence of tannins on the digestion of a small ruminant was investigated. 2. A 1% tannic acid diet was compared with a normal diet. 3. The digestion of protein decreased by 7.04%, fibre by 9.77% and energy utilization decreased by 7.94%. 4. Tannic acid has a marked depressing effect on the digestibility of the steenbok.

Five new species of Trichostomatida (ciliated protozoa) from the colon of wild African rhinoceroses

Five new species of Charonina Strand, 1928 were revealed, in addition to 41 species of 20 other apparent genera, in a survey of ciliated intestinal protozoan endocommensals of both black and white wild African rhinoceroses. Charonina species infected the ventral and dorsal region of the ascending colon, where the average total protozoan populations (× 103/ml digesta fluid) were 100 and 80, respectively, in the white and 270 and 260, respectively, in the black rhinoceroses. Charonina species constituted up to 50% in the ventral and 25% in the dorsal populations. Measurements in micrometres and specific characteristics of the five species are: C. odontophora n. sp. length 70±5.7, width 32±7.2, dorso-ventral thickness 7±1.1, slender ovate-lanceolate-shaped body with frontal lobe and prong-like protrusion in oral-opening; C. tortuosa n. sp. length 87±9.3, width 42±5.3, dorso-ventral thickness 15±2.7, body-shape ovate-lanceolate without frontal lobe, oral-opening with longitudinal ridge, cytopharyngeal canal with sharp bend after emerging from oral-opening; C. dicerotis n. sp. length 67±8.6, width 37±4.0, dorso-ventral thickness 12±2.2, body-shape ovate-lanceolate without frontal lobe, oral-opening without ridge, cytopharyngeal canal curved without sharp bend; C. tenuis n. sp. length 56±10.0, width 16±4.1 at anterior end and 10±2.7 at posterior end, dorso-ventral thickness 7±1.2 at anterior end and 5±1.1 at posterior end, body-shape cone-like with longitudinal striations and frontal lobe; C. tetragona n. sp. length 58±4.7, width 26±3.2, dorso-ventral thickness 12±1.8, body-shape rectangular with frontal lobe and caudal flaps. The length, width and dorso-ventral thickness of the five species are on average in the approximate ratio of 6:3:1, thus showing them to be dorso-ventrally compressed. The body conformation of C. tetragona n. sp. closely resembles that of Didesmis quadrata Fiorentini, 1980, but is distinguished from the latter by the absence of a concrement vacuole and the presence of an elongate cytopharyngeal canal.

The vegetation and identification of management units of the Imberbe Game Lodge in the mixed bushveld of the north-western Transvaal

An analysis of the vegetation of the Imberbe Game Lodge in the mixed bushveld of the north-western Transvaal is presented. Releves were compiled in 39 stratified random sample plots. Four distinct plant communities were identified by means of Braun-Blanquet procedures. The data were ordinated using detrended correspondence analysis (DECORANA) to investigate possible relationships and gradients in and between the plant communities. Three management units were determined by means of a vegetation ordination. A hierarchical classification, description and ecological interpretation of the plant communities as well as a description of the management units are presented.

A gradient analysis and selection of key ecological species for veld management in a degraded environment near Villa Nora, north-western Transvaal, South Africa

An indirect gradient analysis was carried out on vegetation and environmental data collected in a disturbed area of the Mixed and Arid Sweet Bushveld near Villa Nora, north-western Transvaal. Vegetation ordination axes were correlated with environmental variables deduced to have influenced plant species composition. Soil type proved to be the most significant variable, followed by bush density and canopy cover. Herbaceous species most responsive to the discerned gradients were selected as key ecological species using multiple regression analysis. These species are useful indicators of habitat type and range condition.

The phytosociology and structure of vegetation near Villa Nora, north-western Transvaal, South Africa

The phytosociology and structure of the woody layer of the Mixed and Arid Sweet Bushveld near Villa Nora, north-western Transvaal, is presented. Releves were compiled in 46 stratified random sample plots. The Braun-Blanquet procedure and Variable Quadrant Plot Method revealed three distinct plant communities, two sub-communities and six variants which correlated with soil type. A hierarchical classification, description and ecological interpretation of the vegetation units are presented. The results of a D ecorana ordination corroborate the vegetation units and associated ecological interpretation of the Braun-Blanquet classification. Three areas uniform in vegetation and soil type were identified as suitable management units for game ranching.