Individual study: Free-range reintroduction of the western barred bandicoot Perameles bougainville, Heirisson Prong, Shark Bay, Western Australia
Richards J.D. & Short J. (2003) Reintroduction and establishment of the western barred bandicoot Perameles bougainville (Marsupialia: Peramelidae) at Shark Bay, Western Australia. Biological Conservation, 109, 181-195
Since European settlement, continental Australia has lost many of its small- and medium-sized mammals, with eighteen extinctions and 26 species suffering drastic range contractions. Furthermore, reintroductions into arid areas have a very high rate of failure due largely due to predation by domestic cats Felis catus and European red fox Vulpes vulpes and dispersal upon release. The western barred bandicoot Perameles bougainville became extinct on mainland Australia in the late 1920's or 1930's, and has since persisted on Bernier and Dorre islands in Shark Bay, Western Australia. In this study, the effectiveness of a hard-release reintroduction programme of western barred bandicoot to the core conservation area on Heirisson Prong spit, which is connected to the mainland, is evaluated.
Study site: The 12 km² core conservation area of Heirisson Prong is a spit projecting into Shark Bay, with a dry, warm Mediterranean climate. It is dominated by sand dunes, which are interspersed by sand plains, and the dominant vegetation is low heath (Thryptomene baeckeacea and Melaleuca cardiophylla) and low scrub (Acacia ligulata and A.tetragonophylla). The core conservation area is fenced with a predator-proof barrier stretching across the narrow neck of the peninsula and ending below the low water line, and non-native predators have been excluded.
Translocations: Western barred bandicoots were trapped in November 1995 at White Beach, Dorre Island and kept in a predator-free refuge until hard-release. For more details see case 378.
Radio-collars: All bandicoots were collared prior to their release. Collars were 8 g in weight and constructed by Titley Electronics (Ballina, New South Wales). They had a brass loop antennae and 12 cm whip aerial connected to a two-stage model GP1 Mircolite transmitter and two lithium batteries (life four weeks), housed in dental acrylic and heat shrink tubing.
Hard-release reintroduction: Fifty-one bandicoots were released in total. In May 1997, five (3 male, 2 female) were released to a 'familiar' site and five (3 male, 2 female) to an 'unfamiliar' site. The familiar site was adjacent to the predator-free refuge, which had an established population, and the unfamiliar site was 2.5 km to the north. Sites were similar in topography and vegetation. Subsequently, four releases were made to the familiar site, and individuals were released as follows: 2 (both males) in June 1999; 25 (5 males, 20 females) in August 1999, 12 (3 males, 9 females) in September 1999; and two males in October 1999. Bandicoots were released at dusk into straw-filled PVC tubing, from which they could exit at will. Hard-release was used; no supplementary food was provided and they were not held temporarily at the release location.
Monitoring of bandicoots: Radio-telemetry stations were erected on low hills at each release site. For the first three nights after release, bandicoots were located every hour from 20:00 until 06:00 hrs, and the direction and intensity of each signal recorded. Also, for eight to eleven days animals were radio-tracked to their diurnal nest sites. At three-monthly intervals, cage traps were set at 100 m intervals along 40 km of track throughout the core conservation area for two nights. Collars were removed when an individual was trapped.
Distance travelled: The majority of the ten bandicoots released in May 1997 remained close to their release sites in the first week: six males travelled a mean of 872 m, and four females a mean of 115 m. However, one male had travelled 4.1 km, and was recaptured and returned to the release site to prevent it from escaping the core conservation area. Excluding this male, the five remaining males travelled a mean of 222 m in the first week.
Of the bandicoots released in 1999, 54% of females (n = 13) and 50% of males (n = 18) remained within 500 m of the 'familiar' release site. The maximum distance travelled was 3.1 km for a female and 2.3 km for a male.
Survival: Of the ten bandicoots released in May 1997, all survived the first week after release. Three returned to the predator-free refuge during the second week, and six of the remaining seven were alive after one year. Of the 41 animals (12 male, 29 female) released in 1999, 25% of males and 52% of females were not recaptured after release and 33% of males and 14% of females were captured only within the first two months after their release.
Population establishment: In July 1998, bandicoots were trapped throughout the central section of Heirisson Prong between the two release sites. By February 1999, males were captured at the southern boundary fence of the core conservation area and the northern tip of the spit, and in October 1999 males and females were captured throughout the peninsula.
Population estimate: In October 1999, a mark-recapture estimate of the population suggested that there were 130 bandicoots (100 and 355 lower and upper 95% confidents limits) on Heirisson Prong.
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