Data useMasters Project
RationaleOnly a handful of studies have been made on otters in Malaysia. Whereas in Sabah, published information on the occupancy or habitat usage of otters is absent and accurate distribution of otter species is not well known in Borneo. Therefore, it is vital for researchers to focus on the study of otters in Sabah especially in their distribution and ecology as healthy river system and riparian reserves across the state play an important role in their survival. In Southeast Asia, the ecological function of riparian reserves is not precisely recognized (Gray et al., 2014). There are several studies done demonstrated how riparian reserves are able to serve as crucial environment for terrestrial invertebrates (Gray et al., 2014; Gray et al., 2015), fish (Giam et al., 2015) and aquatic invertebrates (Harding et al., 2006) as well as fundamental habitats and corridors for seed-dispersing forest birds (Şekercioğlu et al., 2015).
Out of the 13 species found worldwide, three reside in Borneo with certainty; they are Asian Small-Clawed Otter (Aonyx cinereus), Hairy-Nosed Otter (Lutra sumatrana) and Smooth-Coated Otter (Lutrogate perspicillata). The IUCN Red List classifies both A. cinereus and L. perspicillata as ‘Vulnerable’ while L. sumatrana as ‘Endangered’ (Wright et al., 2015; Aadrean et al., 2015; de Silva et al.,2015). L. sumatrana is the rarest and least understood among the three species found in Borneo and it is also endemic to Southeast Asia (Aadrean et al., 2015). All populations are declining due to various pressures, mainly the loss of habitat through anthropogenic destruction, pollution and illegal poaching (wildlife trade & product). There is clear evidence that all three species occupy separate niches in the ecosystem yet they do occur sympatrically (Kruuk et al., 1994). The species that is most likely to be found at the study site is A. cinereus as it has a wide range of habitat preferences.
MethodsThis project will explore up to 18 streams located within primary forests, logged forests and oil palm plantations to investigate the distribution, habitat use and ecology of otter species in the study site. Apart from areas under SAFE, supplementary sampling will take place in riparian areas of adjacent oil palm plantations which are under Benta Wawasan Sdn. Bhd. and Sabah Softwoods Sdn. Bhd. Data from otter sign surveys through this research will be compared between riparian zones in areas currently being cleared for oil palm plantations (R0, R15, R30, R30N, R60, R120), established riparian reserves in oil palm plantations outside SAFE (RR2, RR3, RR7, RR12, RR14, RR16), forested control rivers (RLFE, RVJR, LFE) and control rivers in oil palm plantations with no riparian zone (ROP2, ROP9, ROP10).
Two techniques will be used in the observation of otter occupancy in the study site which includes: visual sign surveys and habitat characterization. Visual sign surveys through opportunistic observation will be carried out along stream banks to verify the existence of otters and to compare the differences in habitat use intensity between forested areas and oil palm estates. Each of the streams will be surveyed on two occasions by utilizing a 500 m walking visual sign transect carried out on each site. The visual signs comprises of direct encounters, spraints (faeces), foot prints and dens which will be documented. Spraints and prints will be aged (> 2 days, < days) to prevent repeated samplings.
Habitat characterization will be determined by the attributes of streams and shorelines, recorded at regular intervals along each transect to predict otter occupancy through the establishment of potential habitat covariants. Physical habitat data will comprise of stream type (run, riffle, pool and cascade), width, depth, and stream and shoreline substrate. Stream types are categorized as: run (smooth, non-turbulent flow), riffle (turbulent flow over rocks), pool (no flow) or cascade (vertical drop in flow). All refuges for instance boulders and logs will also be recorded. Vegetation of banks will be categorized by height, canopy cover and distance to stream edge. A 5 x 5 m vegetation plots will be applied in each riparian site to determine the degree of disturbances through the characteristics and condition of vegetation at the river bank. Altitudes of all areas will be verified by a handheld GPS (Garmin) while canopy cover will be distinguished by collecting photos of the canopy in each segment using a digital camera and then transferring the image wirelessly or by physically moving the memory storage card from the camera to the computer. The images will then be analyzed using the software ImageJ.
Site occupancy and detection probability of an individual will be by applying the modeling approach based on Mackenzie et al. (2006) which accounts for the likelihood of an individual inhabiting the area and being detected during a survey. The presence of otters dependent on habitat covariates will be modeled by the program PRESENCE (Hines, 2006).