Estimation of the weight and body condition of ostriches (Struthio camelus) from body measurements.

The body dimensions and weights of over 100 ostriches were analysed to investigate which body measurements provided the best estimators of bodyweight. The data were divided between growing and adult birds (below and above two years old) for regression analyses. The residual standard deviation of weight was 0.117 for growing birds, using tibiotarsal length and abdominal girth as predictors. The analogous figure for adults was 0.078 using back length and abdominal girth. An assessment of body condition was made by calculating the average weight-for-size of a bird from skeletal measurements which are unaffected by gross changes in weight, and then comparing it with its estimated or actual weight. These estimates of the weight of a typical ostrich should be useful in veterinary practice, particularly when the weight of a bird is required for the administration of medication.

Vesicular-arbuscular mycorrhizal infection of grass seedlings in a degraded semi-arid savanna in Botswana.

Infection of eight indigenous grasses with vesicular-arbuscular mycorrhizal (VAM) fungi was studied in a savanna in South-eastern Botswana. Infection of seedlings with VAM fungi was rapid just after germination at the onset of the rainfall season. Particularly high infection levels were found in the primary roots of seedlings but levels temporarily dropped with the development of the secondary roots. In 30 % of all cases germinating spores were found to be the source of infection, suggesting an important role for them in semi-arid grasslands. The inoculum potential of soils from eroded and non-eroded sites in the study area was compared. Subsoil was found to have a lower inoculum potential than topsoil. Topsoil from an eroded site without vegetation showed a lowered inoculum potential compared to sites with vegetation present. Topsoil from unvegetated sites where soil material was deposited however, did not always show a lower inoculum potential. This indicates that the transport and redistribution of water and soil material does not automatically result in lower infection levels.