The role of carbon dioxide as stimulant and attractant to the sand tampan, Ornithodoros savignyi (Audouin)

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.