Lon Grassman studied the felid community in several National Parks and Wildlife Sanctuaries in Thailand in the 1990s.
His article "Ecology and Behavior of the Indochinese Leopard in Kaeng Krachan National Park, Thailand" was published in 1999, of which excerpts are presented here.
Between February and September 1996 two adult male Leopards and one adult female were captured and radio-collared. Leopards exhibited no signs of physical stress during sedation, and all animals were released in good physical condition. Male Leopards L350 and L600 were of the yellow pellage phase, while female L700 was of the black phase.
Movement data on Leopards were derived from a total of 202 radio locations gathered from February 1996 through February 1997. The overall home range size for male Leopards L350 and L600 was 17.3 sqkm and 18.0 sqkm respectively, while female L700 exhibited an overall home range size of 8.8 sqkm.
Males L350 and L600 had a range overlap of 8.1 sqkm, although at no time during this study were these two males recorded within one kilometer of each other within the overlap area. Female L700's range overlapped with L350 by 8.0 sqkm and with L600 by 2.9 sqkm. There were marginal shifts in home range size during the wet and dry seasons with the largest sizes occurring during the wet season.
Leopards utilized river and valley corridors and the main road proportionately more than forested terrain. Lower elevations within the study site (500-600 m) were utilized more frequently than higher elevations (700-900 m).
Leopards were active during 546 of 1,120 activity readings. Daily activity levels indicated that Leopards exhibit arrhythmic activity dominated by crepuscular and nocturnal tendencies with peak activity occurring between 06:01 to 09:00 h, and 18:01 to 21:00 h. Diurnal activity was clustered towards early morning and late afternoon, while the greatest concentration of inactive period readings was during mid-day (12:01 - 15:00 h) and late night (24:01 - 03:00 h). Activity varied little between months.
A total of 41 Leopard feces, one regurgitation sample and one carcass discovery showed that Leopards utilized at least nine prey species. Hog badger Arctonyx collaris accounted for 41% of total feces collected while other important prey species included Barking Deer Muntiacus muntjak (20%) and Wild Pig Sus scrofa (7%).
All scat samples contained only one prey item. Four of five unidentified scat samples were produced from meaty meals, which lacked guide hairs for comparison, which probably were of large ungulates.
Tiger sign was never encountered within the study area, hence Leopards were considered to be the dominant terrestrial carnivore. As all Leopards were healthy adults with established, stable home ranges, the dominant environmental influence on Leopard behavior appeared to be prey availability.
The opportunistic hunting strategy of Leopards accounts for a greater prey base and variety when preferred prey are not available. In Kaeng Krachan National Park Leopards maintained a relatively small home range size while satisfying their dietary requirements. This was likely a reflection of opportunistic hunting behavior combined with adequate prey densities of species such as Hog Badger Arctonyx collaris. Hog badger were heavily utilized by Leopards possibly due to their greater densities than barking deer.
Leopards, like all big cats, require adequate living space, water and prey to sustain viable populations. In Kaeng Krachan National Park, although habitat and water resources appeared adequate, low densities of barking deer and sambar were probably the direct result of illegal hunting. Further decline of deer populations will force Leopards to prey upon less preferable, smaller species, and ultimately lead to the extinction of the tiger in Kaeng Krachan National Park, which must have these prey in order to survive. Throughout Thailand the greatest threats to Leopard survival remain habitat loss and reduction of prey through illegal hunting. Of these, loss of habitat represents the most serious and immediate threat to Leopards. Thailand must continue to vigorously protect its established parks and wildlife sanctuaries from illegal logging and encroachment, in addition to establishing new protected areas where Leopards now range but are afforded little legal protection. Protected areas must be patrolled diligently against poaching, with arrests leading to strong penalties.