We studied the ranging patterns of three troops of Hanuman langur (Semnopithecus entellus) in Kumbhalgarh Wildlife Sanctuary, 200 km south of Jodhpur, in the western Aravalli Hills of Rajasthan, India. The home ranges were 106, 45, and 70 ha. This study suggests that the availability of preferred foods, including farm crops and provisioned food, determine the day range of langurs. Comparison of the day ranges of these troops suggests that langurs will raid crops whenever the opportunity is available. They also readily accept foods supplied by humans. Their exploitation of these foods reduces day lengths and range size compared with troops living in forested areas.
The home range is the area normally traversed by an individual or group of animals during activities associated with foraging, resting, mating, and shelter seeking (Burt 1943). The ways in which primates use their home ranges vary enormously. Groups of the same species may differ in their ranging temporarily or permanently, during different times of the day, different seasons, and years, besides showing spatial differences across habitats. A number of factors such as the quality and abundance of food items, their distribution in time and space, the size and composition of the foraging group, body weight, and population density may influence the ranging behavior of primates (Dunbar 1988). Human influences such as provisioning (Wada 1983), and habitat disturbance, such as logging (Johns 1983), also strongly affect home range size and ranging behavior. In Hanuman langurs, home ranges often overlap, even quite extensively. In bisexual troops home ranges can vary from 7 to 1,300 ha, and can be even larger for all-male bands — 430 to 2,200 ha (Jay 1965; Sugiyama et al. 1965; Vogel 1971; Mohnot 1974; Roonwal and Mohnot 1977; Rajpurohit 1987; Srivastava 1989; Rajpurohit and Sommer 1993; Bennett and Davies 1994; Chalise 1995; Schuelke 1998; Chhangani 2000).
We recorded the ranging behavior of three troops of Hanuman langur at the Kumbhalgarh Wildlife Sanctuary (KWS) in northwestern India. Although living in areas that appear generally similar, the langurs confront subtle differences in a number of ecological aspects that affect the resources available to them.
The Kumbhalgarh Wildlife Sanctuary (KWS) of 585 km2 is between 20°05′ and 23°3′ N, and 73°15′ and 73°45′ E, 200 km south of Jodhpur in the western Aravalli Hills of Rajasthan, India (Fig. 1). Altitude ranges from 288 m to 1,215 m a.s.l. KWS has distinct winter, summer and monsoon seasons. Summer temperatures generally fluctuate between 30°C and 35°C, but can get as high as 46°C during May and June. The mean temperature in winter is 5°C, and it can be as cool as 2°C in December–January. The average annual rainfall during the 4-year study period was 725 mm: maximum 950 mm and minimum 403 mm (Chhangani 2000). The forest is broadly dry deciduous or woodland type, dominated by gorya dhawa (Anogeissus latifolia), salar (Boswellia serrata), gol (Lannea coromandelica), kherni (Wrightia tinctoria), dhawa (Anogeissus pendula), kumbat (Acacia senegal), khair (Acacia catechu), ber (Ziziphus mauritiana), and dhonk (Butea monosperma). The undergrowth consists mainly of jharber (Ziziphus nummerlaria), ardnsa (Adhatoda vasica), gangan (Grewia tenex), franger (Grewia flavescens), kanter (Capparis separaia), and lantana (Lantana camara). Some climbers and grasses are also found.
Other notable animals of the KWS include leopard (Panthera pardus), hyaena (Hyaena hyaena), Indian wolf (Canis lupus), jackal (Canis aureus), sloth bear (Melursus ursinus), four-horned antelope (Tetracerus quadricornis), chinkara (Gazella g. bennetti), porcupine (Hystrix indica indica), samber (Cervus unicolor), blue bull (Boselaphus tragocamelus), toddy cat (Paradoxorus hermaphordiatus), jungle cat (Felis chaus), fox (Vulpes bengalensis), crocodile (Crocodilus palustris), and rock python (Python molurus).
Study groups and ranging
The three focal troops of this study were the Savika troop (BS-2), the Ranakpur temple troop (BS-5) and the Forest troop (BS-10) (Table 1). The home ranges of these troops were plotted on the basis of the marked quadrates they used (each quadrate was 100 m × 100 m). Quadrate numbers and the position of the animals were recorded at the point between every two focal samples. The study period was January to December 1996. Day range size was calculated by the number of quadrates used from dawn to dusk and was recorded for a minimum of eight consecutive days (range, 8–10 days) in a month.
Home ranges of the three focal Hanuman langur troops BS-2, BS-5 and BS-10. during the period January 1996–December 1999.
Home range and day range
During the study period (January–December 1996), the Savika troop (BS-2) used 106 quadrates; a home range of approximately 106 ha. Similarly, the Ranakpur temple troop (BS-5) and the Forest troop (BS-10) used 45 and 70 quadrates, respectively; home ranges of 45 ha and 70 ha (Table 1).
Savika troop (BS-2): The number of quadrates used per day by the Savika troop (BS-2) ranged from 10 to 30, and the annual mean day range size was 21.1 ha. The smallest number of quadrates were used in April (mean of eight days: 17.8) and maximum number of quadrates in June (mean of eight days: 26.3) (Table 2; Fig. 2).
Number of quadrates used by the Savika Hanuman langur troop (BS-2) during 1996.
Ranakpur temple troop (BS-5): During the study period the number of quadrates used per day by the Ranakpur temple troop (BS-5) varied from 6 to 22, and the annual mean day range size was 12.27 ha. The smallest numbers of quadrates were used in January (mean of 8 days: 8.3) and the maximum number of quadrates in July (mean of 8 days: 16.1) (Table 3; Fig. 3).
Number of quadrates used by the Ranakpur temple Hanuman langur troop (BS-5) during 1996.
Forest troop (BS-10): The total number of quadrates used by the Forest troop (BS-10) ranged from 9 to 28, and the annual mean day range size was 19.74 ha. The smallest number of quadrates were used in March (mean of 8 days: 15.8), and the maximum number in July (mean of 8 days: 23.0) (Table 4; Fig. 4).
Number of quadrates used by the Forest Hanuman langur troop (BS-10) during 1996.
The langur troops traveled most during the months of June and July. This is probably related to food shortage — April, May, June, and July are the driest months in KWS — and animals are forced to move over a wider area to procure food and water.
Factors influencing ranging pattern
The availability of food in the home range, its distribution, and type and abundance in time and space influence day range size. In this study we recorded the percent time spent in eating different types of food and compared them with day range size and number of quadrates used by the three focal troops in different months. For this we took the largest and smallest day range traveled in each month by the three different troops. We also calculated the percent time dedicated to their natural diet and to crops by the Savika troop (BS-2), and the percent time dedicated to natural food and provisioned food by the Ranakpur temple troop (BS-5). We also calculated the percent time dedicated to different plant parts, such as leaves, flowers, and fruits by the forest troop (BS-10) on each of those days.
The Savika troop (BS-2) covered 26.08 quadrates (range, 22–30) every month in their largest day range. On these days 78% (range, 61.9%–92.6%) of their feeding was dedicated to their natural diet, and 21.9% (range, 7.4%–38.1%) to crops. They covered 15.8 (range, 10–21) quadrates every month on the smallest day range when 56% (range, 45.1%–68.9%) of their feeding was dedicated to their natural diet, and 44% (range, 26.3%–54.9%) to crops. This clearly suggests that Savika troop BS-2 had a larger day range when eating more of their naturally occurring food than when they were raiding crops. The details of the largest and smallest day ranges and relative proportions of feeding time spent on naturally occurring foods and crops are given in Tables 5 and 6.
Savika troop (BS-2): The smallest day range size in each month and percent time dedicated to their natural and cultivated food on those days (Chhangani, 2000).
The Ranakpur temple troop (BS-5) traveled a mean of 16.9 (range, 11–25) quadrates, when their diet was composed of 65% naturally occurring foods and 35% provisioned food. The smallest average day range was 7.9 (range, 6–12) quadrates, and the diet averaged 57% naturally-occurring foods and 43% provisioned food, indicating that they tended to travel less on days when they spent more time eating provisioned foods (see Tables 7 and 8).
Ranakpur temple troop (BS-5): Largest day range in each month by and percent time dedicated to their natural and provisioned food on those days (Chhangan, 2000).
Ranakpur temple troop (BS-5): Smallest day range in each month and percent time dedicated to their natural and provisioned food on those days (Chhangani, 2000).
The day range size of the forest troop (BS-10) tended to be larger (mean, 24.4 quadrates used) when the troop ate more flowers (28%) and fruits (42%) and fewer leaves (26%). The BS-10 troop traveled over smaller day ranges (mean, 14.5 quadrates used) when they ate relatively more leaves (62%) and fewer flowers (16%) and fruits (20%) (see Tables 9 and 10).
Forest troop BS-10: Largest day range in each month and percent of feeding time dedicated to leaves, flowers, and fruits on those days (Chhangani, 2000).
Forest troop BS-10: Smallest day range in each month and percent of feeding time dedicated to leaves, flowers and fruits on those days (Chhangani, 2000).
All groups tended to use large trees for their sleeping sites in limited portions of their home ranges (about 100–150 m2). Sites were one large tree, or two to six small trees, or a combination. The Savika troop (BS–2) used four sleeping sites during the year: all were along the road. Of these, one was a single Ficus benghalensis tree, and the other three sites were three to five Azadirachta indica, Ficus racemosa, and Eucalyptus camaldulensus trees (Table 11). The Ranakpur temple troop (BS-5) used three sleeping sites: two were a single large tree, one was Ficus benghalensis and the other was a Tamarindus indica, whereas the third site was two trees — Tamarindus indica and Azadirachta indica (Table 11). The Forest troop (BS-10) used five sleeping sites, all of them of two to six trees, including Lannea coromandelica, Boswellia serrata, Azadirachta indica, Albizia procera, and Anogeissus latifolia. The heights of the sleeping trees of the three groups ranged from 6 to 20 m (Table 11).
Sleeping sites, sleeping trees and their heights for the three focal troops in KWS study area.
Shifting sleeping sites
Temporary shifts in sleeping sites were observed on a number of occasions in bisexual (including the three focal groups) as well as all-male bands. Sleeping site “b” of the Savika troop (BS-2; see Table 11) was next to a farm: the troop moved there to raid the maturing crops. When chased by the farm owners and their dogs they would revert to sleeping sites “a” and “c.” The temple guards would chase the Ranakpur temple troop (BS-5) from sleeping site “a,” because they would spoil their offices. Sleeping sites used by the Forest troop (BS-10), on the other hand, were evidently related to the presence of predators. The toddy cat (Paradoxorus hermaphordiatus), for example, would cause females carrying infants to move to the canopy or thin branches of neighboring high trees). Larger predators would result in the troop moving to a different sleeping site the next day, choosing especially the thin branches of such high trees as Lannea cormandelica or Anogeissus latifolia. Some trees, such as Ficus benghalensis, have branches that are big and low and easier for panthers (Panthera pardus) and other cats to climb. Other reasons for shifting sleeping sites included attacks by honeybees (Apis dorseta) and Black-rumped Flameback (Dinopium benghalense). Although roaming bands of male langurs would sometimes sleep with the bisexual troops, at other times they could be the cause for them to move away. Two large troops (B-8 with 11 3 and B-9 with 74 individuals), for example, would often flee when confronted by an all male band (AMB4) of only 21 individuals.
A number of factors are responsible for variation in the langur home range size, including availability and abundance of food, the availability of agricultural crops and provisioned food, group size and composition, population density, predator pressure, and agricultural activity and human interference, besides other environmental factors (see, for example, Jay 1965; Clutton-Brock 1977; Isbell 1983; Kimura 1999; Masaaki and Imaki 1999). Hanuman langur troops are hardy and adaptable, and the availability of food and its distribution is the major factor (Raemakers 1980; Marsh 1981; Isbell 1983; Bennett 1986; Newton 1992), as we found at KWS.
In this study, the home range used by the Ranakpur temple troop (BS-5) was 45 ha, which is similar to those of the garden troops of Jodhpur (60–96 ha) studied by Mohnot (1974) as well as at Kailana, Jodhpur (40 ha) (Agoramoorthy 1987), and Mt. Abu (38 ha) as found by Hrdy (1977). The home range of the Savika troop (BS-2) was larger at 106 ha and approximates to those found for the open habitats of Jodhpur (74–132 ha) by Mohnot (1974), Borries (1989) (100 ha) and Srivastava (1989) (150 ha). At Shimla, Sahoo (1993) estimated a mean home range for langurs in forest habitat to be 136 ha. The Forest troop (BS-10) was 70 ha, which is closer to that found for the langurs at Sariska National Park, Rajasthan (60 ha), studied by Vogel (1971).
The day range sizes of the three groups varied markedly and were influenced by resource availability (crops and provisioned food) besides habitat quality. The density and diversity of trees, shrubs and herbs varied considerably. More than 50% of dissimilarity was of vegetation found between troop BS-2 and troop BS-10. Tree felling, farming, human interference, grazing pressure, and predation were factors varied among the troops and were also considered when studying their feeding and ranging behavior (Chhangani, 2000). The differences in home range size between focal troops were quite evident, while, interestingly, the day range size in general was quite similar. The Ranakpur temple troop (BS-5) with a home range of 45 ha traveled through a mean of 12.27 ha with a mean of 16.9 quadrates on larger day ranges and mean 7.9 quadrates on smallest day ranges per day. Whereas troops BS-2 and BS- 10 with larger home ranges sizes of 106 ha and 70 ha, maintained similar day ranges sizes, averaging 21.10 ha and 19.74 ha. Both troops showed almost similar means for their largest (means 26.08 [BS-2] and 24.4 [BS-10]) and their smallest day ranges (means, 15.8 [BS-2] and 14.5 [BS-10]).
Home range size differs widely in different distributional zones of Semnopithecus entellus, and we may tentatively generalize that they are more extensive in open habitats than in forest (Mohnot 1974; Roonwal and Mohnot 1977). Sugiyama et al. (1965) observed that sparse food availability forced langurs to travel more widely.
This study is a part of the Indo-US Primate Project (IUSPP), a collaborative programme of the Ministry of Environment and Forests, Government of India, and the U.S. Fish & Wildlife Service. (Grant Agreement INT/FWS-22). We thank Dr. Ashok Purohit, Head, Department of Zoology, J. N. V. University, for help and facilities provided, and Mr. David A. Ferguson, U.S. Fish & Wildlife Service and Prof. Charles Southwick, Advisor to the IUSPP, for their administrative and scientific support. Comments by Dr. Anthony B. Rylands, Conservation International, were much appreciated. We are also grateful to the State Forest Department staff and officials of Kumbhalgarh Wildlife Sanctuary, especially former A. C. F. Shri Lalit Singh Ranawat and present A. C. F. Shri Bhopal Singh Rathore, and to Shri Madan Mali, field assistant, for their support during this field study. We also thank Mr. Bundu Khan for his help in writing this paper.