Action for Primates
Conflict between human beings and non-human primates over habitat is a growing issue. These conflicts are usually due to human population growth and an ever-increasing expansion into and destruction and fragmentation of native habitat, forcing non-human primates to compete with people over land and resources. In an effort to resolve these conflicts, people will often use methods that are inhumane and ineffective. Large numbers of non-human primates may simply be rounded up and killed. Others may be captured alive and used for research and breeding or for the pet and food trade. Although this may provide a short-term reduction in animal numbers, it is cruel and fails to address the issue over a longer period of time. The large scale trapping and exportation of monkeys for the food and research industries is also inhumane. Moreover, this has been shown to be largely ineffectual in reducing damage to human property and crops or in reducing the number of individuals long-term. For example, despite the trapping and export for research of 10,000 vervet monkeys over a 14 year period in Barbados, this did not have the desired effect of reducing crop raiding, as the population of monkeys remained stable due to the species' high breeding rate [§, §].
Complicating this issue is the mistaken belief that free-living (wild) non-human primates are a threat to human health due to transmission of diseases. There is also considerable misinformation about what diseases monkeys carry in general and which might be transmissible to human beings, although there is also a significant risk of disease transmission from people to non-human primates in captivity. There is very little likelihood that free-living non-human primates could transmit any disease to human beings, unless they are brought into close contact with people such as being trapped for the research or 'pet' trade or to be killed as food.
The issue needs to be approached from at least two perspectives. One is changing public behaviour and perception, the other is implementing practical methods that are effective.
Preventive measures: It is essential that people involved with management methods understand that adverse interactions between wild animals such as monkeys and people are usually due to inappropriate behaviour on the part of human beings, not the other animals. Wild animals are typically fearful of human beings. If, however, people feed or in any way tolerate or encourage the presence of the animals, the animals become less fearful. Feeding can also make the monkeys reliant on a human food source (anthropogenic), causing them to spend less time foraging for natural sources of food and can artificially increase 'carrying capacity', causing an increase in reproduction beyond what natural habitat would dictate. It is critical, therefore, that people be taught not to encourage the animals in any way. This includes not only not feeding the animals or having easily-available food sources, but also not making attempts at being 'friendly' with the monkeys.
Educating residents to make changes to their lifestyle will be necessary. Monkey-proofing their trash receptacles and deterring entry into their homes through the use of suitable window screening are essential. Food or garbage must not be allowed to accumulate anywhere the monkeys can have access to it. People must be discouraged from feeding wildlife. For example, in Hong Kong and Singapore, fines are imposed against those people who continue to feed wild monkeys.
A systematic method of scaring away the animals with things like unnatural sounds or the sounds of their predators should be instituted and used consistently every time there is an intrusion. For example, in some communities, specific people are assigned the duty of chasing away monkeys from residential or other areas [§, §]. The same principle can be used for deterring crop raiding [§, §, §]. In some cases, dogs have been used successfully to guard fields of crops or deter monkeys from entering areas of human habitation. Solar powered electric fencing can be economical and effective in reducing access to crops. Another strategy involves the use of laser pointers or taste aversion.
Sterilisation: Sterilisation is an effective long-term solution to help resolve conflicts by ensuring there will be fewer and fewer monkeys over time. It is increasingly being used by authorities who recognise its importance to humanely and effectively provide long-term resolution [§, §, §, §, §, §, §, §]. It should be understood, however, that sterilisation will take time to reduce the number of monkeys in order to result in a reduction in conflict. Because of this, people would still have to do what they could to discourage monkeys.
As for the method of sterilisation, because the monkeys are completely free-living, the most effective method would be to remove the ovaries (ovariectomy) of females, tie off their Fallopian tubes (tubal ligation) or remove part of the Fallopian tubes (salpingectomy). Once done, these methods would ensure that the female would not be able to reproduce. Although easier to do, sterilising the males will be less effective than doing the females, whether surgically or with vaccine, as it will only take one fertile male to impregnate perhaps several dozen females.
Another way to sterilise females (and males) is the use of chemical or similar sterilants. One is GonaCon™ [§, §]. This is a gonadotropin-releasing hormone immunocontraceptive vaccine developed by scientists at the U.S. Department of Agriculture's (USDA) Wildlife Services' National Wildlife Research Center. It has been shown to be effective in a variety of species and may be suitable for non-human primates. It is claimed to be economical and may last up to four years. It has to be injected into the individual, so trapping is still necessary. More information can be found at the USDA Web sites [§, §].
Another is Reversible Inhibition of Sperm Under Guidance (RISUG). This contraceptive was developed for human males, but is being advocated for use in non-human primates. It appears to provide lifelong sterilisation.
As with any sterilisation procedure, a method of permanently marking the animal who has been done has to be instituted in order to prevent duplicative efforts. Also, if a vaccine is used, a means of identifying the animals based on when they were done has to be developed in order to know not only that an individual has been done, but also when it is time to re-vaccinate.
Coexistence: In addition to the above, careful consideration of all the issues may lead to discoveries that allow for reasonable coexistence. For example, in Indonesia, it was found that monkeys and human beings depended on the same native tree and that cultivation of this tree might not only help the ecosystem, it might result in a reduction in crop raiding. In South Africa, crop-raiding baboons could be deterred by planting crops specifically for them some distance from the farm.
Trapping and relocation: This may not be ideal or effective in all situations. Success with this approach depends on having suitable habitat located a sufficient distance away to deter the monkeys from simply returning to the original site. There is no distance that has been shown to ensure their not returning, but perhaps a location at least several kilometres away might be helpful. The area to which the monkeys are to be re-homed would not only have to be suitable for them in terms of food and shelter, it would also have to be free of other similar monkeys, or else they or the other monkeys will simply be chased away. Such a translocation of monkeys took place in India in 1997, when 600 rhesus macaques were successfully moved to different sites following an increase in monkey-human conflict.
Although there is no easy solution to the problem, a continued commitment by the relevant authorities will be essential in developing a plan that works, is humane and is sustainable. A multi-prong approach is likely to yield the best results.
With the deployment of the dogs, the number of wild monkeys spotted in residential areas has sharply dropped, according to the city. Dogs of any breed can be placed in a five-month training session after a trainer deems them capable. They must learn not to injure people, chase only monkeys and return to their owners when called.
It just reduces the troop size for a little while.
The feeding and release of wildlife has been made illegal islandwide with sweeping changes to the Wild Animals And Birds Act passed in Parliament yesterday that confers greater protection on Singapore's native flora and fauna.
Our results suggest that field rangers are a successful nonlethal method for reducing spatial overlap between baboons and urban areas but that intensive, unsystematic herding of the troop does have measurable impacts on behavior and should be prevented.