ECOLOGY AND FEEDING BEHAVIOR OF ASSAMESE MONKEYS (Macaca assamensis) in MID-HILLS OF NEPAL

Abstract

A study on Assamese monkeys (Macaca assamensis) was performed in the Kaligandaki river basin (KRB) of western Nepal and in the Budhigandaki river basin (BRB) of central Nepal. The field study was conducted from February 2015 to January 2016 spending 1804 hours to explore the ecology and feeding behavior of Assamese monkeys. During the study period, a total of 42 individuals of Assamese monkeys with two troops (Palpa troop n=24 and Syangja troop n=18) with mean group size 21 in KRB and that of 43 individuals with three troops (Rigdikhola troop n=16, Rockybhir troop n=13 and Siurenitar troop n=14) with mean group size 14.33 in BRB were recorded. Pearson’s Chi-squared test (χ2 = 20.5511, p = 0.665) and Fisher’s exact test (p = 0.861) show that there is no significant difference in distribution pattern of Assamese monkeys among blocks (Block A, Block B, Block C, Block D and Block E). Two troops of Assamese monkeys, one from KRB named as Kaligandaki focal Assamese Syangja troop (KFAST) and other from BRB named as Budhigandaki focal Assamese Siurenitar troop (BFAST) were monitored using scan sampling and focal animal sampling methods to understand the ecology and feeding behavior of the monkeys in two different topographical river system of Nepal. Botanical quadrate sampling (20 m  20 m) plotted in different altitudinal areas of KRB forest revealed that Trichilia connaroides was the dominant plant species with relative density 35.68% and relative frequency 8.38% while Shorea robusta was the dominant plant species with relative density 29.75% and relative frequency 8.87% in BRB forest. Different quadrate plots and vegetation analysis revealed that the Assamese monkeys of KRB and BRB were found inhabited in sub-tropical deciduous riverine forest with rocky cliffs habitat. Kaligandaki Assamese monkeys frequently used leaf of Albizzia chinensis and that of Budhigandaki used leaf of Lagerstroemia parviflora as major food throughout the year. Most of the botanical quadrate plots also included Albizzia chinensis species in Kaligandaki area and that of Lagerstroemia parviflora species in Budhigandaki area although dominated by Trichilia connaroides in Kaligandaki and Shorea robusta in Budhigandaki. Further, the sleeping sites of the Assamese monkeys during night time were found on rocky cliffs and rocky outcrops of both the river basin rocks. These rocky cliffs and rocky outcrops were very close with specific food plants of the monkeys in both the sites that might help them to prefer this type of habitat. Four major behaviors namely feeding, resting, moving and grooming were recorded. During 716 hours of observation period in Kaligandaki, the total feeding time spent by Assamese monkeys was 294.7 hours (41.16%) and in Budhigandaki during 691 hours observation period, the total feeding time spent by the monkeys was 306.5 hours (44.36%), as highest in both sites followed by resting, moving and grooming. Special emphasis was given to time investment and food intake by the monkeys. They preferred fruits (27.19% in Kaligandaki and 29.54% in Budhigandaki) as the highest intake per year in gram percentage followed by mature leaf and others, however the feeding time spent per year was higher on mature leaf (30.02% in Kaligandaki and 29.04% in Budhigandaki) followed by fruits and others. This shows from the results that food intake amount and time investment on feeding of different plant parts may differ depending on the nutritive value of food availability. Data from systematic behavioral observations were analyzed with reference to that of the vegetation surveys. Assamese macaques invested more than two-fifths (>40%) of the diurnal time on feeding. The two study troops inhabiting highly similar habitats of food plants (Sorensen’s Similarity Index = 0.93) didn’t have a significant difference in the selection of food-plant parts. This concludes that food choice and time investment on the feeding of different plant parts differ depending on the availability of food in the area. Macaques living in comparable habitats with similar food plants have analogous food choices and time investments. Crop raiding by Assamese monkeys is one of the serious problems in both KRB and BRB villages. Maize crop was highly preferred (47.14% in Kaligandaki and 58.43% in Budhigandaki) by the Assamese monkeys as a major crop raid followed by others. Monkeys raid the crops mainly due to the scarcity of natural foods and degradation of their habitats. Therefore, conservation attempts should be focused on this nationally endangered and protected primate species in Nepal in order to provide a practical guide to future conservation.