Abstract:
Sand tampans cause irritation and losses among cattle in the sand veld areas of the Kalahari and South West Africa. They appear above the ground in response to a stimulus. The nature of this stimulus was investigated in the laboratory and in the field, in the hope that the knowledge so gained would lead to a means of control. These studies showed carbon-dioxide to be the main factor which caused tampans to surface. In the laboratory concentrations of 5 per cent CO₂ and higher proved to be effective stimulants. In the field 100 per cent CO₂ was used, liberated from a cylinder and from dry-ice. It caused marked stimulation and attraction of tampans, so that large numbers could be collected at the source of liberation. In one instance 4553 tampans were collected in 2 hours when using a small piece of dry-ice as attractant. At Onderstepoort 5 per cent CO₂ was liberated in a tampan-infested open air enclosure covered with an 8 in. depth of sand to resemble Kalahari conditions. As little as 1 litre per minute of 5 per cent CO₂ caused tampans to surface and move towards the CO₂ source. Even a slight breeze did not prevent them from surfacing and eventually locating the CO₂ source. At low temperatures, e.g. 52° F, tampans were not attracted by CO₂ unless activated by disturbing the sand in which they occurred. Laboratory investigations into the role of heat and moisture as tampan attractants showed that CO₂ activation was necessary before tampans would react to heat and moisture. Moist objects alone were unattractive, warm objects attractive, but warm-moist objects were the most attractive. In all experiments in the laboratory only a proportion of the tampans present reacted to the stimuli tested. It seems at present impractical and uneconomical to attempt to control tampans over large areas with traps containing CO₂, but it will be of great use in sampling tampan populations.
