The Complicated History of Monkeys in Hong Kong

There are monkeys in Hong Kong. Forget Hong Kong Island for the time being—in the first part of this article I am concentrating on ‘New’ Kowloon and the New Territories. Unfortunately, the view has been promulgated by some primatologists that these monkeys have been present continuously from before the Second World War, either as original inhabitants or as the result of introduction in the early years of the 20th Century. Sadly, this story seems to have been accepted by the Hong Kong Government’s Agriculture, Fisheries and Conservation Department as the explanation, in part, for the current population of monkeys.

Mainland Hong Kong

The monkeys which at present inhabit the country parks are Rhesus Macaques (Macaca mulatta) or crosses between Rhesus and Long-tailed (also known as Crab-eating) Macaques (M. fascicularis) together with Japanese Macaques (M. fuscata). Because they have been fed by the human population (feeding is now illegal) they make a thorough nuisance of themselves by lining the paths at weekends and stealing food with menaces from passers-by. The males can also be aggressive.

Hong Kong is well within the natural range of the Rhesus Macaque and there are records from the 19th Century. However, it seems that the numbers decreased possibly because of hunting for food as the human population increased. In the early years of the 20th Century Rhesus Macaques were imported and released in the area of the newly-constructed Kowloon reservoir for a bizarre reason. There was concern that fruit from overhanging strychnine trees would fall into the water and poison the public. Because monkeys were thought to be able to eat the fruit without ill effect, some Rhesus Monkeys were introduced in order to reduce the risk of poisoning those drinking the water.

However—and this is the big however—Rhesus Monkeys—and note Rhesus—whether remaining wild or the introduced population appear to have died out completely by the late 1950s to early 1960s. They may have been present in the late 1940s in small numbers. Herklots wrote in his book The Hong Kong Countryside (completed and published after he left Hong Kong in May 1948):

The monkeys that live in the woodland near the Kowloon reservoir are not descendants of the wild stock but of monkeys released during the first world war. During the Japanese occupation of the Colony in the second world war, after the trees had been cut down, the surviving animals scattered. Since the war they have been reported from several districts in the New Territories including their old haunts…

My guess is that the Rhesus Macaques were hunted to extinction or near extinction during the Japanese occupation. Monkeys did feature in Cantonese cuisine and medicine and, moreover, the population was short of food as all accounts of life during that period testify.

The naturalists around in the mid-1960s all seemed to agree that the Rhesus Macaque was extinct in mainland Hong Kong. However, there were monkeys around Kowloon reservoir but of an entirely different species: the Long-tailed Macaque*.

There is also the possibility that Herklots’s book was misleading. When as described above, he wrote that monkeys had been reported in the New Territories after the Second World War it is possible that what had been seen in the late 1940s and early 1950s were not Rhesus Macaques but Long-tailed Macaques. 

In the mid-1960s Patricia Marshall of the Zoology Department wrote in her book, Wild Mammals of Hong Kong (published in 1967):

The group of monkeys living in the Kowloon reservoirs catchment area are long-tailed macaques which were probably released or escaped from captivity during or shortly after the 1939-1945 War. The rhesus monkey (Macaca mulatta) which was once abundant on Hong Kong island and in the New Territories now appears to have died out.

These are photographs I took in December 1967 of the Long-tailed Macaques at the well-known spot near Kowloon reservoir at the 4½ milestone on the Taipo Road:

Long-tailed Macaques near Jubilee Reservoir
on the Taipo Road. December 1967

Later, Rhesus Macaques re-appeared. In 1976, Valentine Lance, also then in Zoology, surveying  the land vertebrates of Hong Kong wrote:

On a bright note in this sad tale is the addition of an animal once lost from Hong Kong and now successfully re-established. This is the Rhesus Monkey (Macaca mulatta). In 1866 Swinhoe noted that they were common on most of the small islands near Hong Kong…and number of them lived in Tai Tam before the second World War. By 1962 they were no longer present in the Colony. Another closely related species, the Crab-eating or Longtailed Macaque (Macaca fascicularis), a more southern common Malayan monkey, successfully established a breeding colony at Kowloon Reservoir (Romer, 1966). This group originated from escaped or released pets. Today there is a flourishing colony of more than twenty individuals in the Kowloon Reservoir catchment area. The rhesus monkeys have only successfully established themselves in the same area in the past few years. Again they are escapees. The criteria for establishing residence is successful breeding. A family with a young baby was seen recently and there are believed to be more breeding pairs in the same area. The two species seem to live fairly amicably side by side in the same restricted habitat. In addition to the colony at Kowloon Reservoir isolated individuals have been seen at Pokfulam Reservoir [Hong Kong Island], Tai Tam Reservoir [Hong Kong Island], and recently at Ma On Shan.

All this seems pretty clear: the present Rhesus Monkey population appears to be derived from animals that escaped or were released in the late 1960s or early 1970s. Unfortunately, as is so often the case, other researchers have not read the relevant literature and ascribe the monkeys to descendants of the pre-Second World War population. Such errors and misinterpretations which omit mention of evidence from the 1960s are, of course, repeated and repeated not only websites, in publications and in newspaper articles but in books on primate conservation. For example, in one relatively recent book it is stated that the introduced Long-tailed Macaques interbred with the existing population of Rhesus. Photographic and observational evidence from the mid-1960s shows that not to be the case; the Long-tailed Macaques were not interbreeding at that time since they alone occupied the Kowloon Hills. Nevertheless, it is true, as David Dudgeon and Richard Corlett remarked in their excellent book on the ecology of Hong Kong, ‘we cannot be certain…that none of the current population are descended from survivors of the original Hong Kong macaques’. The negative is impossible to prove but the probability is highly weighted against a remnant population.

Since the 1970s the population of Rhesus Macaques has increased massively. By 1992 there were around 800 macaques in Hong Kong, 700 of them in the Kowloon Hills and other country parks. But they were not all Rhesus or Long-tailed. Other species kept for some reason either escaped or were released. There are records of Japanese Macaques, Tibetan Macaque (M. thibetana) and a single Pig-tailed Macaques (either M. leonina or M. nemestrina). Hybridisation between three of these species is known, with the production of fertile offspring. (There is a hybrid zone, in northern Thailand, for example, where the Rhesus and Long-tailed meet naturally.) A survey by John Fellowes for the World Wildlife Fund in 1992 found evidence of four species and possible hybrids, as far as they could be identified: Rhesus (pure) 50% of the population; Long-tailed x Rhesus or x Japanese 40%; Japanese (pure) or Japanese x Rhesus 9%; Long-tailed (pure) 1%; Tibetan (0-1%).

The number of Long-tailed Macaques was said to have declined in 1967. Reports in the newspapers blamed trappers for catching the monkeys and selling them as a delicacy for human consumption.  However, there seemed a healthy population in December 1967 when we watched them. In the 1980s in the Kowloon reservoir area, the proportion of Long-tailed in the monkey population fell from 26% to 7% between 1981 and 1987; hybrids between these two from 13 to 3 while the Japanese Macaques fell from 5% to 0.

It appears then that the Long-tailed Macaque population has virtually disappeared together with easily-recognisable hybrids. How much of the Long-tailed genome is present in the present Rhesus population seems to be unknown. Since large traps are available from the sterilisation programme aimed at keeping the population in check, molecular studies are just waiting to be done. But as Dudgeon and Corlett state: ‘It would be interesting to know if the predominance of rhesus macaques reflects a larger founder population (i.e. more releases or survivors) or superior adaptation to an environment which is within the native range of the species’.

Were the Rhesus and other species of monkey recorded escapees or were they released? Explanations I have seen include release by a travelling circus after being prevented from taking the animals to the next destination. Did some escape from food markets? Did well-intentioned individuals buy some from pet shops or markets and release them? Did pet owners release adult monkeys when they turned vicious? Did some escape from private collections?

I do get the impression that the Rhesus Macaques must have been released in substantial numbers, says tens at least, to have multiplied so rapidly and so visibly, rather than in the dribs and drabs of the odd pet escaping or being released and then finding the troupe of Long-tailed Macaques to join. I awoke the other night with a possible explanation. When we arrived in Hong Kong in November 1965, John Phillips (1933-1987, FRS 1981 and later of the University of Hull and Vice-Chancellor of Loughborough University) my PhD supervisor was Professor of Zoology. He told me to get an animal experimentation licence from the government. The government had recently introduced licensing, he said, because some commercial animal testing operations had set up in Hong Kong in order to bypass legislation in their countries of origin and the Hong Kong government wanted to make sure nothing untoward was going on. Yesterday I checked my memory and, indeed, the Animals (Control of Experiments) Ordinance was passed into law on 24 May 1963; it is still in effect. I knew nothing of these laboratories and I don’t think John did either but is it just possible that they had the favourite and cheap primate of the time, the Rhesus Monkey and that after ceasing operations considerable numbers were released into the New Territories?

I know that possible explanation is a long shot but I was intrigued by a paragraph in John Fellowes’s report from 1992. In Tai Po Kau forest reserve, the population seemed to be entirely Rhesus and he wondered if that could reflect a relict population. However, Tai Po Kau was well visited by birders and other naturalists in the 1960s who would surely have spotted a troupe  of monkeys. Is it just possible that the main release of Rhesus Macaques was at or near Tai Po Kau, and that some then made their way to the Kowloon Reservoir area where they found and interbred with the Long-tailed Macaques?

One possibility that I have never seen discussed is that the 'new' wave of Rhesus Macaques from the late 1960s/early 1970s actually arrived from a wild population across the border. By 1985, the nearest wild populations were a long way away in Guangdong or on islands but who knows about the 1960s? Looking at China then from the lookout at Lok Ma Chau, there was just farmland and woods. Could the woods have held a population of monkeys even ones that could have made their way there from Hong Kong in the early decades of the 20th Century?

In summary, the present Rhesus Macaque population of mainland Hong Kong has an interesting history and genetic origin. With molecular techniques already used on two of the species involved†. it should be possible to determine to what extent, if any, the genome of the other macaques (other than the Tibetan which did not appear to have interbred) is still present in the gene pool as well as the size of the founder populations. It is also possible that the geographical origins of the Rhesus Macaques could be determined; are they originally from China or elsewhere in the range, India, for example, which was a major exporter at that time?

Hong Kong Island

Herklots wrote:

On the Island of Hong Kong a monkey family was watched early one morning near Tai Tam reservoir in 1947, and I have had occasional accounts of monkeys having been seen on the Peak and in Deep Water Bay valley. It is possible, but not certain, that these are descendants of the original wild stock [i.e. Rhesus Macaques]…

The monkeys at Tai Tam seem to have disappeared by the early 1960s. Patricia Marshall considered the monkeys on Hong Kong Island, like the Rhesus on the mainland, to have died out. However, monkeys were seen on the Island throughout the 1960s after she wrote her book. There were newspaper reports and a recent request for information from the Facebook Group, Hong Kong in the 1960s, confirmed the presence of small numbers monkeys around various blocks of flats. Lancelot Vance also reported the sighting of individual animals at Pokfulam reservoir and at Tai Tam reservoir. In 1969 a monkey living on Bowen Road was shot by John Romer after it bit a child. There was a considerable fuss in the letters columns of the South China Morning Post. Sightings continued throught the 1970s into the 80s.

The question, as usual, is, were the sightings in the 1960s of descendants of the family group Herklots had seen or of monkeys that had escaped or had been released into the wild more recently? The question is, of course, unanswerable but there were certainly plenty of opportunity for the latter. The British army’s Lyemun barracks had a small zoo; Rhesus Macaques bred there in 1962. Other individuals had wild animal collections in the 1960s and 70s including a Dr Vio who lived on the Peak. The PG Farm, on the site of Ocean Park, a popular attraction for children in the 1960s, had Rhesus Monkeys; at least one escaped—and was recaptured. There were newspaper appeals for people not to keep monkeys as pets. It is fair bet that a few escaped from owners or were released after a first—and usually inevitable—bite.

I have not seen any recent reports of monkeys on Hong Kong Island.

Opportunities for Research

‘Natural’ experiments such as the various introductions of macaques in Hong Kong offer opportunities for research. I have outlined some of the lines which could profitably be pursued and which would throw light on the selective pressures operating to favour, perhaps, the originally native Rhesus Macaque over the closely-related Long-tailed. But as I have also pointed out, we might also get an indication of the origin or origins of the currently highly successful population of Hong Kong monkeys.

And finally…

A photograph of a Rhesus Macaque almost exactly 50 years since I photographed the Long-tailed Macaque within a few hundred metres of this one.

Rhesus Macaque near Jubilee Reservoir catchment. November 2017

*The Hong Kong Government only appears to have realised this in 1966 with the publication of Romer’s note. The Annual Report for 1965: Rhesus monkeys are still found in the vicinity of Kowloon Reservoir in the New Territories, but those which inhabited woods in the Tai Tam area of Hong Kong Island are not known to have been seen during 1965. The 1966 Report had the nearly correct story: Long-tailed or Crab-eating Macaques, a sub-species of those found in Singapore, occur in small numbers in the Kowloon reservoir area and can often be seen near the Kowloon-Taipo Road and at Pipers Hill. These are probably descendants of escaped or released individuals. The indigenous Rhesus Macaques which were present on Hong Kong Island and in the New Territories have now apparently disappeared. No source of information is given in the 1965 Report but the 1966 Report acknowledges the help of Patricia Marshall for the section on wild life.

†Bunlungsup S, Kanthaswamy S, Oldt RF, Smith DG, Houghton P, Hamada Y, Malaivijitnond S. 2017. Genetic analysis of samples from wild populations opens new perspectives on hybridization between long-tailed (Macaca fascicularis) and rhesus macaques (Macaca mulatta). American Journal of Primatology 79. doi: 10.1002/ajp.22726

Dudgeon D, Corlett R. 1994. Hills and Streams. An Ecology of Hong Kong. Hong Kong University Press.
Fellowes JR. 1992. Hong Kong Macaques. Final Report to the WWF Hong Kong Projects Committee. Hong Kong: WWF.
Herklots GAC. 1951. The Hong Kong Countryside. Hong Kong: South China Morning Post.
Hong Kong. Report for the Year 1965. 1966. Hong Kong Government Press.
Hong Kong. Report for the Year 1966. 1967. Hong Kong Government Press.
Lance VA. 1976. The land vertebrates of Hong Kong. In, The Fauna of Hong Kong, edited by B. Lofts. Hong Kong: Hong Kong Branch of the Royal Asiatic Society.
Marshall PM. 1967. Wild Mammals of Hong Kong. Hong Kong: Oxford University Press.
Romer JD. 1966. Long-tailed Macaques in Hong Kong. Memoirs of the Hong Kong Natural History Society 7, 16. I have not been able to track down an easily accessible copy of this paper; therefore I have not read it.
Southwick C, Manry D. 1987. Habitat and population changes for the Kowloon macaques. Primate Conservation 8, 48-49.

Updated 24 April 2018