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MICROHABITAT PREFERENCES OF THE TERRESTRIAL RODENTS AT LAMBUSANGO AND KAKENAUWE FOREST RESERVES
Introduction
The small mammal fauna of Sulawesi is of interest to biologists due to its high level of endemicity. There are 20 species of Murinae in 8 genera found only in Sulawesi ( Corbet and Hill,1992). These species are predominantly forest-adapted mice and rats. Due to the lack of basic imformation on the ecology of these species and the potential threat posed by habitat degregation, it was decided to carry out a study on the microhabitat preferences of terrestrial rodents in the Lambusanga and Kakenauwe reserves.
Aims and Objectives
The aim of this study was to produce a relative estimate of population density of terrestrial rodents at two forest sites (Lambusanga and Kakenauwe) using a mark-recapture trapping programme. In addition, possible microhabitat preferences were investigated by recording habitat variables at each trap site.
Method
The live trapping programme began on the 2nd of July 2001, and continued over four weeks. Trapping grids were established at both Kakenauwe and Lambusanga reserves, with each grid being trapped for four nights on alternate weeks. Each 10 x 10 grid consisted of 100 Longworth traps with 20m inter-trap spacing. Twenty larger Tomahawk traps were also placed at trap stations distributed throughout the grid. This produced a total of 960 trap-nights of data for each site. The traps were checked daily, and morphometric data was collected for all captures. In addition, each individual was given a unique fur clip, allowing it to be identified if recaptured.
Microhabitat preferences were investigated by setting up 5m quadrats centred at each trap station. Within each quadrat, 13 microhabitat variables were recorded. Canopy cover will be assessed from photographs taken above each trap station. The total number of trees (>15cm circumference) and their circumferences were recorded. In addition, the total number of logs within the 5m quadrat was also recorded, as was their length and diameter. Four 1m quadrats were then set up, one in each corner of the 5m quadrat. Within the 1m quadrats the percentage of bare ground, the percentage of surface coral, and the number of woody stems were recorded. The vegetation density at 0.5m and 1.0m above ground level was also assessed looking from each corner of the 5m quadrat towards the trap at its centre. Other information such as the extent of cleared paths within the quadrat was also recorded.
Results
Over 960 trap-nights at Kakenauwe a total of 49 individuals were captured. The predominant species captured was Bunomys andrewsi, with 27 animals caught. The next most frequently trapped species were Maxomys hellwaldii, with 14 individuals captured, and Taeromys celebensis, with six captures. In addition, one rat was caught which was not readily identifiable in the field and therefore was taken as a specimen for identification.
At Lambusanga the capture numbers were lower with a total of only 27 individuals. In addition, the species composition appeared different; here the predominant species was Maxomys hellwaldii, of which 14 individuals were caught. In contrast to Kakenauwe, Bunomys andrewsi was less frequently caught than Maxomys, with only nine animals trapped. No Taeromys celebensis were caught at Lambusanga, however two Paruromys dominator were trapped, as was a single specimen of a Rattus species, which was not possible to identify in the field. One Brown Shrew (Crocidura levicula) was also trapped.
One interesting factor these results highlighted was a large trap-bias. The Longworths were only approximately 2% successful over eight nights, whereas the Tomahawks were approximately 15%. This bias was consistent over both the trapping sites.
Two hundred microhabitat sites have been completed and hopefully the data will allow some interesting conclusions to be drawn. Analysis of the recapture data will be done back in England, where the computer program MARK will be used to produce population estimates. In addition, a Principal Components Analysis will be used to investigate any underlying factors in microhabitat preferences.
Report
A report entitled Microhabitat preferences of small rodents in the Lambusanga and Kakenauwe forest reserves was produced by Charlotte Hodgkins, University of Birmingham in November 2001.