No abstract

No abstract

The drastic changes in hydroelectric reservoir development created a completely new ecosystem that affects the river, particularly in the inundated area. In this study, five Neolissochilus soroides and Channa lucius were surgically implanted with a unique coded acoustic transmitter to observe the habitat utilisation and movement activity in Tembat Reservoir after the inundation process. All of the individuals were released into the transition zone of the reservoir and observed using passive and active acoustic tracking devices from April to December 2018. Kruskal-Walis test showed no significant difference between the average size of core area for N. soroides and C. lucius, x2(1) = 1.320, p = 0.251. The home range also showed a similar result for N. soroides and C. lucius where there was an insignificant difference, x2(1) = 0.273, p = 0.602. However, duration wise, N. soroides spend more time in the transition zone, R1 (M = 2.71 hrs, SE = 0.38), and C. lucius in the riverine zone, R5 (M = 7.14 hrs, SE = 6.13) and R6 (M = 3.85 hours, SE = 6.36). From the active tracking survey, PCA identified three (62.32%) and four (71.19%) components with eigenvalues greater than 1 for N. soroides and C. lucius, respectively. Three most important habitat parameters for N. soroides were the size of river (r = 0.97), existence of canopy cover (r = 0.77), and substrate type (r = 0.79).While, for C. lucius were mesohabitat type (r = 0.79), distance to riffle (r = 0.97), existence of canopy cover (r = 0.90), and elevation (r = 0.90). A 24-hour movement frequency analysis for both species revealed two active hours of movement at dusk and dawn for both species. From the study, it is known that N. soroides and C. lucius respond differently towards the inundation of the reservoir. The findings in this study can be implemented for effective aquatic management and conservation plan to ensure sustainable dam development.

Context The lack of documentation and detailed assessment of previous sun bear (Helarctos malayanus) release programs raises concerns about bears’ capacity to adapt to their new habitats and key elements of release success. Aims We evaluated the influence of the sun bears’ individual profiles and environmental factors on their adaptability, and investigated their habitat use and movements in the wild. Methods We released 13 rescued sun bears (four wild-caught and nine rehabilitated) to natural habitats between December 2015 and August 2017, and inferred adaptability process by analysing their pre- and post-release data. Key results Post-release monitoring showed that sun bears required at least a month to acclimatise to their release area. No nuisance cases were reported, and bears were observed avoiding monitoring teams in a series of encounters. Principal-component analysis identified a previous history of ill health (e.g. malnutrition), low avoidance of humans prior to release and low potential of release sites as significant factors associated with poor adaptability of released bears. Rehabilitated bears also showed lower adaptability to hilly topography with an average elevation of more than 500 m. Individual profiles of adult physically fit wild-caught bears with high avoidance of humans prior to release were associated with high adaptability. Binary logistic regression indicated that habitat type was the main factor influencing bear movement. Bears had a high affinity for oil palm plantations adjacent to the forest edge. Most habitat use of released bears was close to the forest edge. Conclusions In terms of competition, predation, food availability, and adaptability, the selection of forest edges adjacent to other favourable habitats is perceived as a more opportunistic survival strategy, as long as the bears do not rely on humans to survive and endure with the natural interactions in the wild. Implications This study emphasises the importance of improving the likelihood of survival of rehabilitated bears, especially in the early release phase. Reducing human–bear interaction in rehabilitation centres by practising a buddy system and minimal human contact in captivity considerably enhances release effectiveness.