Optimising reintroduction success by delayed dispersal: Is the release protocol important for hare-wallabies?

The transfer of threatened animals from one location to another in order to benefit the species is a technique frequently used by animal conservation managers. However, very few of these relocations have experimentally assessed the relative merits and disadvantages of commonly used release techniques. The premise examined in this study was that a higher degree of site fidelity should be advantageous for an individual through a soft release protocol. Two species of hare-wallaby, mala (Lagorchestes hirsutus) and merrnine (Lagostrophus fasciatus), were fitted with radio-collars and reintroduced in August 2001 onto Peron Peninsula in Western Australia. These threatened species were reintroduced using two release strategies (soft versus hard release), and their movements and body condition were monitored, for a period of four weeks post-release, using radio-telemetry and trapping. Each species averaged decreases in body condition index when exposed to both experimental release protocols. A total of 11 animals (32%) emigrated from the release sites, with 10 of these animals being male. Importantly, no relationship was found between site fidelity and release method, although body condition was significantly higher in mala which dispersed, and there was observational evidence for a male-biased dispersal for merrnine. Although the number of released individuals of each species was low, this study demonstrates an interesting trend which indicates that soft release techniques do not necessarily to confer an advantage to the successful immediate establishment and survival of either hare-wallaby species in the short term. We recommend that managers involved with species reintroduction programs consider the costs and potential outcomes of designing and installing soft release enclosures.