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Report Submitted By
This report is the outcome of a brief study that was carried out by Care Earth at the request of Professor M S Ananth, Director (IIT-Madras). The field studies were carried out by Dr C Arivazhagan, Conservation Biologist (Care Earth) and Mr N Muthu Karthick, Junior Research Fellow (Care Earth).
Introduction
Bonnet Macaque (Macaca radiata) is endemic to southern India. The species that is largely arboreal is at present found in the all types of habitat, especially those created and maintained by human beings. The estimated population size of the macaque is around 170,000 in just the four southern states, of which Tamil Nadu is known t be home to about 16,000 individuals (Kurup, 1981).
Amongst primates found in southern India, bonnet macaque is the only species that often gets into conflicts with people in both urban and rural areas. The city of Chennai has a sizeable population of the macaque; of which a significant proportion may be found within the IIT-Madras, Guindy National Park and Raj Bhavan habitat complex. Despite efforts to capture and relocate the macaque, there has been a steady increase in the population of this primate in the campus and that has led to conflicts within and across species (including human). Attracted to human habitats by food, water and shelter these troops have invaded residential and hostel premises leading to resentment by a section of the campus residents.
Distribution and Abundance
The distribution of the macaque was assessed over the entire campus in July 2011. Troop size and movements were studied on the campus (see details in Table 1 and Map). In all 195 macaques split across seven troops were distributed in and around Hostels, Academic Buildings, Residential Areas and the Administration Block. The present population size suggests that there has been an increase in the population since 2008. A brief census conducted by Care Earth in 2008 estimated the population as around 150 individuals.
Table 1: Number of troops of the Bonnet Macaque and their distribution on the Campus
|
Identity |
Location of Sightings |
Troop size |
Remarks |
| MT1 | Cauvery Hostel Narmada Hostel | 41 | This troop moves between the Cauvery and Narmada hostel area |
| MT2 | Electronic Engineering | 34 | This troop moves between Electronic Engineering and play ground area |
| MT3 | Administration Block | 27 | This troop moves between the Administration Block and Central Work Shop area |
| MT4 & MT5 | Residential area (1st Cross Road to 7th Cross road) | 9 & 33 | These troops mostly operate in the residential area from 1st cross road to 7th cross road; sometimes split |
| MT6 | Adyar Avenue and Delhi Avenue | 17 | This troop moves between Adyar Avenue and Delhi avenue in the residential zone |
| MT7 | Nursery and Warden Quarters | 34 | This troop moves between Nursery, Warden Quarters and Garbage site. It also moves to Sharavathy and Sarayu hostels. |
Note: MT4 &MT5 have overlapping ranges and hence only 5 areas of operation are marked on the map
Demography
The bonnet macaque usually lives in multi-male & multi-female troops; the troop size varies from 9 to 41 individuals on the campus. According to Roonwal & Mohnot (1977) and Kurup (1981) the troop size varies from 5 to 75 individuals in the wild. Elsewhere in Bangalore, in a study of 21 troops of wild bonnet macaque, the troop size varied from 5-32 (Sinha, 2005). Although troop size may be highly variable in a particular ecological area, it tends to be much smaller in natural forests and significantly larger in or near human habitation (Krishnan, 1972, Singh et al, 1984, Sinha and Dutta Roy, 2000). Going by Prater (1965) we may consider the benchmark troop size as between 20-30 individuals.
Each troop typically consists of one to several adult males and females and a variable number of sub-adults, juveniles and babies (infants) of both sexes. Similarly the ratio of different age-sex classes within troops shows some variation across ecological habitats (Pirta et al, 1981, Singh et al, 1984); the most interesting aspect being the adult males to adult females ratio. The adult male to adult female ratio in the campus during the present study is 1:1.6.
Generally within a troop the age-sex distribution follows a pattern presented in the figure below. Adult females make up for 24% of the troop followed by sub-adult females 16%, infants 16%, juveniles 15%, adult males 15% and sub-adult males 14% (see Figure).
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Identifying Troops
Each troop was identified based on the troop size, range of movement and natural markings such as tear or cut on ear, scars on the face, etc. During our observation we identified four distinct individuals representing three troops (see Photos).
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Above: MT3 Sub-adult Male (left); MT 3 Adult Male (right) Below: MT5 Adult Male (left); MT6 Adult Female (right) |
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Human-Macaque Conflicts and other Impacts
Studies world-over have suggested that macaques have the potential of causing severe socio-economic and environmental damages to people and their belongings. Macaques damage plants and cause inconvenience to pet animals and people. Macaques are also known to carry and transmit several diseases, including Herpes B-virus, which afflict humans (Colin, 2010).
On IIT-Madras campus macaques entering hostels and residential areas tend to scare the residents. Our observation suggests the following:
Home Range Size and Carrying Capacity
Study of home range size and carrying capacity of landscapes that sustain bonnet macaques are limited. An India-Japan collaborative project carried out during the 1960s in the outskirts of Dharwar (Karnataka) has provided certain useful insights (Sugiyama, 1971). According to this study, bonnet macaque troops (in near natural areas bordering forests) move across 730-880m/day. Sugiyama (1971) has estimated the home range, for an average troop as 40ha. Interestingly, the size of the troops that he studied are comparable with that on the Campus; the largest being around 40 animals. The largest troop when followed closely moved within 40ha of the landscape in Dharwar.
Yet another study in Karnataka (Bangalore) that was carried out around the same time estimated the home range as 50ha suggesting a limit of 2 troops/100ha (Rahman and Parthasarathy, 1967). More recently, a study of 21 wild troops on the Gandhi Krishi Vigyan Kendra (University of Agricultural Sciences), Bangalore also estimated the troop density as 2/100ha (Sinha, 2005).
Given the size of the Campus and the limited availability of natural habitat, the present macaque population that exists as 7 troops may be on the higher side. Considering the extent of around 230ha and the fact that a large part of the Campus is built up, a manageable population should be limited to 3 (taking 50ha as the average size of the home range) or 4 (if 40ha is taken as the average size of the home range).
Managing the Macaque so as to minimize conflicts and nuisance
Considering the limited extent of the Campus, including its natural areas, and the fact that macaques, like other animals, take advantage of the available food and shelter (and the lack of natural predators) proliferate managing the species is a challenging task. Since the troops are operating within specific limits of the Campus, it should be possible to work out locale-specific management strategies. The following are some of the recommendations:
Engaging monkey-watchers: the menace of macaques entering corridors and toilets in the hostels can be controlled by engaging men and women (as appropriate) who are capable of chasing the animals without hurting them. This could be achieved, for instance by engaging irulas and/or retired animal keepers of the Forest Department (and Zoo) on a full-time basis. These watchers can be provided accommodation in the hostels (or close by) and they shall drive out the macaques as and when necessary. The watchers should be provided with whistles that they blow while the parade the area and drive the animals. The macaques will soon recognize the whistle and run away on hearing it. This intervention could be tried out initially and used as a short-term strategy.
Limiting the availability of food: effort should be made to curb the availability of domestic food and other edible wastes. Macaques tend to proliferate and become aggressive wherever there is a continuous supply of food and when troops meet at a common source of food. Feeding macaques, directly or indirectly, must therefore be strictly curbed during the short and long terms. According to primatologists, within the social system of macaques, offering food to an individual is a sign of submission. Subordinate animals in a troop use this gesture to appease aggressive and dominant animals. A human-being that offers food is only seen as a subordinate and hence the animals tend to place greater demand.
Birth Control: Colin (2010) has described the effectiveness of birth control on invasive macaques. Use of laser technique to sterilize adults, although expensive, has been employed widely. However, this could be a long-term strategy and its feasibility on the Campus needs to be assessed.
Removal and Relocation: removing macaques and relocating them have been the traditional method adopted in managing the species. However, unless carefully planned and executed, family groups tend to get split causing undue trauma amongst macaques. Further, relocated animals, unable to find their troop-mates are likely to wander into adjoining villages and across roads. Relocation should therefore target an entire troop and remove all the members at the same time. This may be feasible when the smallest troops are targeted. At present, the troops MT4 and MT6 are the smallest and they can be fully relocated. In addition to this, the troops that have more than 30 animals can be targeted wherein, males can be selectively removed. Adult males are known to move between troops and balance the sex ratio. Considering the average troop size of 30 animals and the ideal density of troops as 3-4, it may be easier to manage the bonnet macaque on the Campus if the population size is maintained between 90 and 120 animals.