Hot under the collar: the failure of radio-collars on black rhinoceros Diceros bicornis

Radio-collaring is widely used as a monitoring tool in the conservation of the black rhinoceros Diceros bicornis. We examined rates and causes of radi o-transmitter collar failure on black rhino in the Sinamatella Intensive Pr otection Zone (IPZ), Zimbabwe, between September 1993 and February 2000. Tw o collar designs, hose and strap, were fitted on immobilized rhinos in four main collaring operations. Eighty nine collars were monitored: 28 hose and 61 strap. Within 12 months of placement, all hose collars had failed. Of t he strap collars, 73 per cent of those on males and 44 per cent on females had failed within 12 months. Failure rates were significantly higher in mal es for both collar types. For strap collars older males had higher failure rates than younger males. There was some evidence of a higher failure rate of strap collars during the wet season. Thirteen per cent of strap and 4 pe r cent of hose collars were removed because of poor transmission; 15 per ce nt of strap collars were removed because of injury. The implications of col lar failure rates and the use of rad io-colla ring as a routine protection and/or monitoring strategy are discussed.