Sika

The Ecology of Japanese Sika 

 (Cervus nippon nippon)

INTRODUCTION

There is considerable debate over the origin of Sika (Cervus nippon) which have a number of distinct races, the principal ones being Formosan, Manchurian and Japanese. Whilst there are physical differences between them – for example, Formosan and Manchurian tend to be larger than Japanese; Manchurian stags have wider spread antlers, with a reddish velvet in contrast to the black of the Japanese; and Formosan Sika have a yellowish brown summer coat, changing to a light brown in winter rather than the grey of Japanese - taxonomists are not agreed on the origins of the races, and conflicting views exist over hybridisation with Chinese Wapiti leading to the mainland races. The issue of hybridisation with Red deer has received sensational coverage in the UK popular press of late, generating a need for more research and a greater understanding of Sika, their origins and their future.

Having acknowledged the academic debate involving Sika in general, this article shall concentrate on Japanese Sika (Cervus nippon nippon), drawing on practical experience of the herd local to the Purbeck region of Dorset.

HISTORY AND DISTRIBUTION

Japanese Sika were probably first brought to England in 1860 when a pair were presented to the Zoological Society of London and exhibited in Regent’s Park. Thereafter many parks and zoological gardens throughout Britain came to introduce Sika. Escapees and deliberate releases led to feral Sika faring very differently across England, Scotland and Ireland with their greatest success in the latter two countries. The current national distribution reveals a widespread if haphazard range. It is interesting that of the eleven areas in England recorded as having feral Sika in 1964 (Whitehead), only in South-East Dorset and the southern part of the New Forest can they be said to have truly flourished.

Sika arrived in Dorset through two separate introductions: the first in 1895 at Hyde House Park north of Wareham and a second on Brownsea Island in Poole Harbour the following year. Whilst it is believed that the Sika released onto Brownsea Island started to swim ashore on the night of their release, the first escape from Hyde House was not recorded by the neighbouring Trigan Estate until 1927. There were further escapes from Hyde House during the 1930s, and the whole herd was released during the Second World War when the government took over the running of the estate. The South Dorset distribution of Sika lies within the Poole Basin but is spreading beyond the normally defined limits of Poole in the East, Bere Regis in the North and Dorchester in the West.

By comparison, Sika were introduced into the New Forest when a pair were given to John, second Baron Montague of Beaulieu, by King Edward VII from his Windsor estate just after the turn of the century. This first pair was penned at Thorns Beach but escaped into Sowley Wood the same year. A second pair arrived a year later and were released in Ashen Wood. The present New Forest herd originated from these animals and so prolific was it that culling became necessary by 1930.

DESCRIPTION

Sika calves at birth have a distinctive baby coat similar to the summer coat of the hind, albeit browner and with fewer spots.  The caudal patch is much reduced in size and with very little pure white, most of the hairs being fawn coloured and lacking the normal black surround.  Between one and two months of age  the black border to the caudal patch begins to become more prominent, starting at the root of the tail and gradually spreading down either side till it is complete at about three months. From two months the bright baby coat starts to fade and the white markings on the flanks become less pronounced. By the third month the calf is nearly in its winter coat, with the change complete when the hinds’ coats are still at their brightest or just beginning to fade.

Adults in summer coat are a brighter chestnut than their newly born calves and have a greater variety in the quantity and type of white spotting and harnessing, which usually includes a row of white spots down either side of the dark dorsal stripe. Stags typically appear darker than hinds at all times of the year. The winter coat of the hind is a fairly uniform light grey, lighter on the neck and under parts with occasional faint spotting on the flanks, presumably faded remnants of the white spots of the summer coat. The stags are notably darker around the neck and shoulders and may also show white spots bordering the dorsal stripe. In all adults and older calves there is a light coloured band in a shallow U running from between the eyes up towards the ears - a distinguishing feature of Sika.

In both summer and winter coats, adults may or may not have a black line down the dorsal surface of the tail. When present it can vary between thin and scarcely visible to broad and obvious. These pelage differences do tend to fuel speculation about the hybridisation factor among Sika mentioned above. Less varied is the metatarsal gland conspicuously outlined in white on all Sika except very young calves in their baby coat.

ANTLER DEVELOPMENT

Stag calves begin to develop pedicles at six months and these produce single spikes in their second year. These spikes can vary considerably in length from about 6 cm to as much as 25 cm and, as one might expect, the weaker prickets will have spikes of differing lengths. Occasionally a stag at this age might have one or two top forks, but normally a pricket’s un-branched spikes are replaced in its third year by 6 points. In its fourth or possibly fifth year and thereafter a stag will carry a full rack of 8 points.

It is relatively common for stags to develop 7 point heads as adults, where the side tine in the top fork fails to fully develop for one reason or another. How long a stag remains in his prime with a full head before beginning to ‘go back’ is unclear, but it seems likely that this would be between 3-5 years (i.e. aged 7-9 years). What is also worth noting is the whitening of the tines through the course of the winter and the noticeable antler chipping which occurs from the stag’s arrival in hard horn through to casting in April.

HABITAT

Sika have a preference for an acid soil habitat to which they gravitate, especially in winter. Pine forests, Sitka Spruce, Larch with boggy ground and heather all suit them. The Purbeck region adds broad-leafed woodland, permanent pasture, arable land and banks of gorse to the aforementioned eco-systems and offers sufficient choice, it would appear, to keep even the most discerning Sika contented. Heath and rhododendron, classic flora of acidic soils, are particularly widespread here. The coastal range of South Dorset includes acid sands and gravel of the London and Reading Beds and Bagshot Sands, but the area also includes outcrops of chalk and Purbeck limestone. The more inaccessible parts of the region, which are not farmed intensively and enjoy minimal human disturbance, in particular promote a thriving population of high density. This, coupled with a tendency towards localised migration onto the richer pickings of cultivated land in the summer, can bring Sika into conflict with agrarian interests. The twin aims of maintaining healthy deer free from the stress of over-population and avoiding high levels of crop damage necessitate a considered deer management plan.

FEEDING HABITS

Sika are predominantly grazers, feeding heavily on grasses, broadleaf buds and twigs, heather, fruits, fungi and acorns. Their success in Scotland proves that they can adapt to the relative sparseness of thick conifers and rough grazing. They are fond of water-bank growth and are keen on hazel, which they are prone to chew and strip. Whilst the author’s experience of New Forest Sika is very limited, a clear distinction has been drawn (The Social Organisation and Ecology of the Japanese Sika Deer in Southern England, JCE Mann, PhD Thesis, Southampton University, 1982) between these as browsers and the Sika of Dorset as grazers. In Purbeck they can be seen doing both, nevertheless they are predominantly grazers.

Although Sika generally feed at night, they can occasionally be seen feeding in undisturbed areas at almost any time of the day. As a rule one would expect to see these crepuscular (meaning preference for twilight) animals in the last two hours of daylight or during the first hour after dawn on their way to and from their feeding grounds. Whilst in the evening they will probably feed their way out of cover, in the early morning they seem to be single-mindedly travelling back to cover when observed. They are certainly less affected by inclement weather when compared with Roe deer, being quite happy to feed in steady rain, although they are less inclined towards stormy conditions or strong cold wind.

SOCIAL STRUCTURE

The social structure of Sika seems to vary from region to region. In Dorset the picture of single sex groups throughout the year, with the exception of the rut (mid-September to the end of November) does not generally apply.

From November onwards one does tend to find hinds and calves congregating together, with the stags exhausted from the rut seeking the solace of stag groups. And in March the stronger yearling stag calves may well leave their mothers to join a stag group. However, in April one will find stags coming into velvet mixing with hinds until about August when, once they are in hard horn, they seem to separate out with stag groups forming once again. There is considerable variation to any one image of social structure as much depends upon the relative health of the animals concerned. Sparring will occur in early September as the stags start to reach their peak condition, thickening out significantly in the neck and shoulders, as well as developing a strong body aroma. But at this stage big stags are still prepared to tolerate the presence of prickets and lesser males. By mid- to late September the bigger stags capable of defending territory will be doing so without any tolerance of a viable competitor. The younger stags will satellite around the master stags and try to take advantage of their fatigue towards the end of the rut, thus providing these youngsters with a much anticipated opportunity to cover a hind. With calves and followers, the winter hind groups distinct in their congregation can grow to a significant size, with 15-20 animals not being unusual.

An autumn reverse migration from cultivated land back onto sparser, undisturbed ground and traditional rutting stands is a characteristic prelude to the rut in many parts of Purbeck. This underlines the need for careful planning of any deer management which should take allowance of such population dynamics and must involve careful liaison with local farming and forestry interests.

ANNUAL CYCLE

Most calves are born in late May and through June, although they can be born well outside this period. The particular timing for a hind calving has much to do with her condition and body weight through her period of gravidity and, in the case of the occasional precocious pregnancy, sexual maturity at the time of the rut. Weaker hinds will not go to full term. Sika have a high reproductive success rate, especially in a strong herd with a favourable habitat. Analysis of one local deer management group’s cull records and data from 1998 revealed a fecundity rate of over 92.6% in mature hinds culled after 1 December and a combined rate of 90.5% in mature and yearling hinds. Sika drop single calves, with the stronger stag calves leaving their mothers for stag groups in March and the yearling hind calves being driven away at their mother’s next calving. Unlike Roe they do not appear to have a significant mortality rate over their first winter. Up to about five months of age calves can be identified by their size, but they grow so fast that thereafter they are less easily recognised unless they are standing with their mothers. However, the fact that they only have one pair of molars means that a calf’s jaw is appreciably shorter, giving the head a chubbier appearance. By eight months they may only be two inches shorter at the shoulder than the hind and 10 lbs lighter, although the heavier stag calf may actually weigh the same. As the winter develops, the darker coat of a stag calf will generally become more noticeable and by about March they are showing small pedicles, although not absolutely all stag calves develop these.

During the rut, stags mark out and defend a territory rather than a harem as with Red stags. However, the distinction is blurred by the fact that stags, while patrolling the boundaries of their territories, will seek out hinds to try to subdue them or to drive them to a rutting stand where, if in season, the stag will cover them. Hinds will still need to move out from any rutting stand in the evening to feed and so the need for the stag to patrol his boundaries, see off interlopers and gather up hinds goes on. Hinds can be covered when acquiescent as well as when apparently resistant. A hind in season might bleat a protest at an interested stag which can lead to all stags within earshot turning up to contest her, frequently involving the hind being chased around by a number of suitors. Presumably it is the strongest who wins out and frequently this stag will prefer to force himself on the hind rather than wait for compliance.

Territories are marked by a stag thrashing the ground cover of heather and gorse with his antlers, leaving circular patches at intervals along the boundaries and some fraying of perimeter trees. Fighting between stags is commonplace, as is apparent from the number of heads with damaged or missing tines and the limping stags which can appear after the rut. Wallowing is universal and these sites also indicate an actively  territory. Stags generally have a filthy matted appearance, particularly around the neck and shoulders, from wallowing and this ‘war paint’ is embellished by the fronds of grass, heather and bracken which can stick in their antlers as a result of fraying. They complete this impressive ensemble by being at peak condition by the start of the rut, having built up a considerable amount of fat deposit, with an enlarged and shaggy neck. They also stink of both musk and their own urine which they add to their wallow. Some stags also develop what are referred to as ‘milky tears’ - a thick fluid, probably from an orbital gland.

Once the rut is over, stags return to the normal routine of crepuscular movement and nocturnal grazing to begin to recover both weight and strength after the stresses and strains associated with mating and defending a territory. Traditional rutting stands having now been vacated, stags become much more evident and begin to congregate in stag groups again, although mixed groupings may also be seen.

VOICE AND CALLS

The astonishing rutting call associated with Sika stags is primarily designed to attract the attentions of a hind in season. Whilst the call which has terrified many an unsuspecting stranger to the rut into thinking they have just heard some terrible murder take place is perhaps the most notorious, it is by no means the only rutting sound to be heard. A single whistle, rising to a peak before tailing off and usually repeated three times is perhaps the commonest call of the rut. A noise rather like a witch’s cackle ("yak, yak, yak") registers a stag’s annoyance and is often followed by the sound of direct confrontation - clashing antlers. If one is able to get close to a hind in season one might be able to hear her bleat, indicating receptiveness.

In addition to calls associated with the rut, Sika have a distinctive alarm whistle or squeak, which both hinds and stags can give, although the latter is of a lower pitch. When uncertain of something or unsure of the source of another deer’s alarm, Sika will face the direction of potential danger and move their heads up and down in nervousness or crane their necks from side to side trying to get a better view. If still undecided they might make a few hesitant steps forward, raising first one forefoot with the ‘forearm’ or shank horizontal and the foot pointing down, hold this position for a short while, then put the foot down and repeat the performance with the other forefoot (rather like a Lippitzaner in slow time). Although hardly visible head on, the erectile hairs of the caudal patch usually fan out to display a state of alarm to any other deer. When the degree of alarm becomes too much to stay still, Sika will bound off, jumping off all four feet together as though mounted on springs. Reminiscent of African plains antelope, this unusual movement is known as pronking.