From China to Surbiton: the over-successful muntjac
Charles Smith-Jones is Technical Adviser to the British Deer Society (BDS). While he has a wide interest in all species of deer, he reserves a special admiration for the muntjac which he finds by turns fascinating and enigmatic, but very often its own worst enemy. All photos in this blog are Charles’.
A native of southeast China and Taiwan, where it is very much a forest creature that primarily inhabits the subtropical forests of the region, the Reeves’ muntjac Muntiacus reevesi is a small and rather primitive deer which has changed little in appearance for at least the last 15 million years. Standing just some 50 cm high at the shoulder it is about the size of a springer spaniel. Males (bucks) bear short, simple antlers on long pedicles and have well developed upper canine teeth which they use when fighting with other bucks and for self-defence. Although females (does) also have canines, these are vestigial and not readily visible.
The muntjac first established itself in England towards the end of the 19th century as a result of escapes from collections and some deliberate releases but for a long time remained confined to the general area of Bedfordshire and Hertfordshire. Even by the 1970s the British Deer Society (BDS) only recorded it as being present in forty 10km2 grid squares in central England, while Defra estimated the UK population as not exceeding 5,000 animals. At this point the muntjac’s presence was still considered to be benign. By 2007, however, the number of occupied grid squares had risen to 816 and a 2009 report by the Parliamentary Office of Science and Technology put the population at >150,000. There is no doubt that numbers have continued to grow and it has been suggested that there may now be more than a quarter of a million muntjac in Britain. Such are the secretive habits of this small and elusive deer, though, that it is inevitably difficult to determine the true population size.
The muntjac has three particular features that have helped it to expand its numbers and range in this country. Firstly, and unlike all of the other five UK deer species, it is an aseasonal breeder with no fixed time of year for rutting and subsequent birthing, so fawns can be born at any time of year. So, with sexual maturity attained at around seven months old, gestation lasting another seven, and a doe coming into season within days of giving birth, she spends almost all of her adult life at some stage of pregnancy. As a result the muntjac can breed rapidly despite only tending to produce one fawn at each birthing.
Its second advantage is that, as a species, it is notably robust. British weather conditions, once thought to be a potential check on numbers, do not daunt it and even fawns born during the less clement months of the year have high survival rates. Only the unusually harsh winter of 1962/63 proved sufficiently severe to impact on numbers. The muntjac is also easy to transport and release, being resilient to post capture myopathy. This factor has facilitated its introduction, largely illegally, to parts of the country where it did not formerly exist. Its relatively recent arrival in Ireland can be attributed to such illegal releases.
Thirdly, it is quite prepared to live in close proximity to humans and will readily adopt the habitats provided by overgrown suburban gardens, bramble covered railway embankments, and indeed any other similar environments offering food, security and shelter. It is, however, adept at going unseen and very often the first clue to the muntjac’s presence is its loud, fox-like bark which may be repeated at short intervals for up to an hour at times. Elsewhere, any patch of woodland offering a thick and warm understorey is just as acceptable. Muntjac are now increasingly frequently encountered well within the peri-urban fringe and even in the centres of major cities. If you live just about anywhere in the south of England, and increasingly much of northern England and Wales, the chances are that you will never be far from one.
Rising numbers of muntjac are causing increasing concern for a number of reasons. High population densities can deplete woodland plants through heavy browsing activity, having an adverse effect on not just the flora but also the other fauna that depend on it, and can compete for resources with native species. Increasing levels of agricultural damage are also an issue, as are deer/vehicle collisions. Such are the environmental and economic aspects of growing muntjac numbers that the Invasive Alien Species (Enforcement and Permitting) Order 2019 now prohibits their release into the wild anywhere in England and Wales without a specific license, the import of live muntjac into the UK, the breeding of muntjac in captivity, or the sale of live muntjac. Sadly, the Reeve’s muntjac has become something of an object lesson in ill-advised introductions to an ecosystem that is unable to adequately restrict population growth.
To enable us to fully understand the effects of the muntjac on the wider environment we need to build on our knowledge of how far it has become established in the UK. You can help us to do this by recording your sightings on the Mammal Society’s Mammal Mapper app.
Illustration – BDS 216 Deer Distribution Survey map for muntjac
Key to colour codes:
Green – confirmed only in 2016
Yellow – reconfirmed in 2016 (recorded in 2007 and/or 2011)
Brown – unconfirmed in 2016 (recorded in 2007 and/or 2011)