Rattus villosissimus (Rat) release and trapping dataset 

Sampling Design: Mark-Recapture Repeated Measures Survival Analysis Systematic Sampling 

Fauna Sampling Technique: Marking/Tagging Trapping Arrays 

Measurements: Raw Observations; Raw Observations - Binary Data; Raw Observations - Categorical Data; Raw Observations - Continuous; Data Raw Observations - Count Data; Raw Observations - Ordinal Data 

Measured Attributes: Abundance Location Population Size Population Structure Presence/Absence 

Elliott Trapping, PIT-tagging, weighing, scoring body condition, determining gender : We constructed two 12.5-ha rat-proof enclosures, each divided in half, one half allowing cats and dingoes access (the fence was low enough at 0.9 m that cats could easily jump over) and the other half surrounded by a taller (2 m) electrified floppy-top fence to exclude mammalian predators. We refer to these as low-fence and high-fence treatments. To prevent small mammals from moving in or out of these treatments, a strip of smooth poly-belt, 40 cm high was attached to the inside lower section of all fences. The two enclosures were ~13 km apart. Enclosure I was in low (~10 m high) open woodland co-dominated by mixed Eucalyptus spp. and Terminalia spp., over a mixed Triodia spp. hummock grassland and mixed shrub understorey on sandy soils. Enclosure II was in similar low open woodland, but tree cover comprised Eucalyptus spp. and Cooktown Ironwood Erythrophleum chlorostachys, over a tussock grassland dominated by Chrysopogon spp., on sandy/lateritic soils. Mean percentage vegetation cover at rat height (10 cm above ground) was higher in Enclosure I than Enclosure II, but similar between the low and the high fence treatments within each enclosure. We introduced populations of the long-haired rat Rattus villosissimus (Status Least Concern, IUCN 2013), to all enclosure compartments for the purpose of this experiment. We collected 20 free-ranging R. villosissimus from Quoin Island about 530 km west of Wongalara (14°730'87'' S, 126°730'56'' E, 219 ha), NT, in April 2011. To provide the numbers needed for introductions, these rats were initially housed and captive-bred, with handling kept to a minimum, at the Territory Wildlife Park before each release. In April 2012 we released 46 captive-bred rats as many as available into Enclosure I: 13 females and 10 males in the low-fence treatment and 11 females and 12 males in the high-fence treatment, with similar age composition in each group. In October 2011 we released 31 rats into Enclosure II, five rats (three females, two males) originating from Quoin Island, and the rest bred in captivity. Seven females and nine males were released into the low-fence treatment, and nine females and six males into the high-fence treatment. All were at least 1.5 months old and fully weaned; most (66%) were adults (> 60 g). All were marked with passive integrated transponder (PIT) tags. Rats of sufficient size (~ 100 g) were fitted with radio-collars (~ 4 g). In Enclosure I, seven rats (five males, two females) were radio-collared at release in each treatment. In Enclosure II, 10 rats (five males and five females) were radio-collared at release in each treatment. The fate of released rats was also monitored using live-trapping at intervals of approximately two months. Thirty-six aluminium box-traps (Elliott design) were arranged in a uniform pattern in 0.4-ha grids in each of the four enclosure halves. Traps were baited with a mixture of rolled oats and peanut butter, set in the late afternoon and checked at first light on the following day. Due to logistical constraints, the number of trapping sessions and their duration (number of nights) differed between enclosure sites, but not between the paired compartments (low fence and high fence) of each enclosure. In Enclosure I, trapping commenced two months after release of rats. Seven trapping sessions of between two and four consecutive trap nights were carried out (24 trap nights in total). In Enclosure II trapping commenced six months after the release of rats because of limited access during the wet season. In this enclosure, nine trapping sessions of between two and four consecutive nights occurred (29 nights in total). At each capture, individuals were identified, weighed and sexed. Body condition was scored using the method of Ullmann-Culleré & Foltz (1999), from category 1 = emaciated to 5 = obese. Recruits (i.e. individuals trapped in the enclosures that were not part of the initial release) were PIT-tagged at first capture.