Sika Deer Projects

An Online Presentation of 'Diurnal variation in foraging behaviour of the Japanese Sika Deer on Lundy Island' by S.J.Rodway-Dyer' is available

Sika deer (Cervus nippon) were introduced to Lundy in the 1920s. Although not native British animals, they now live completely wild. They are most usually seen on the east side of the island in the rhododendron thickets and gulleys around and to the south of quarter wall. In recent years the population seemed to have increased considerably: up to 30 different individuals were counted during the 1995 field course and between 35 and 40 were estimated in 1996. In addition, during the last five years the deer had become less fearful and more easily observed.  Under some conditions, sika deer can become quite tame; the ones on Lundy never are, and unfortunately there has been a cull a short time ago, whereby about 20 to 25 animals were shot. The remaining ones are now extremely shy.

From former observations, the herd appeared to include about 9 males, one 8-point, one 7-point, three 6-points, one 5-point and several young prickets, though at least one stag had suffered antler damage in the recent rut. It would be interesting to identify the remaining individuals as well as their social groups and venures.

Female groups tended to number between 5 and 8 animals, though we had seen up to 15 together. These groups include the yearling females and those yearling males with undeveloped horns that are too young to associate with the stag parties; yearling males and females cannot be distinguished reliably under the conditions where we see them, but they are distinguishable from the adult females. Although April is the very beginning of the calving season, it is possible that fawns will be seen. It has not yet been established whether there is any social structure within the mature female group, and it would be well worth looking at that, and considering what effect it would have on offspring or yearlings. This would involve looking at the relations of young animals with each other and other adults as well as with their adults. It is sometimes possible to hold a female group in view for quite a long time in the early morning.

Without large numbers of observers, and with no possibilities of tagging the animals, studies of the female deer are hampered by difficulties in confirming sightings, and recognising individuals. As a result, many recent projects have looked at group size and composition, in relation to variables like vegetation and cover. The preferred foraging areas of male and female groups appear to differ, with the males predominantly remaining in the gullys while the females range more widely. Sex differences in habitat use are widespread in sexually dimorphic ungulates though the phenomenon is puzzling, particularly when females use better habitats than males. Some have suggested that males are forced by female grazing pressure into marginal habitats, the so-called 'indirect-competition hypothesis'. This could be tested by indentifying preferred foraging areas and then collecting vegetation from these. Standard ecological techniques for vegetation sampling (eg. Quadrat method) should be employed, though the steep and sometimes inaccessible nature of the terrain may impose some compromises.

During the day the deer tend to forage in groups close to cover, but at dusk they can often be seen collecting together and moving towards the fields to feed. It is suspected that they remain here most of the night, and consequently can be seen in mixed-sex groups very early in the morning. It is not clear whether there are other nocturnal habits or feeding areas, but single females with fawns have been sighted moving across the top of the island. Systematic observation of the deer quickly reveals patterns of movement, grouping and behaviour, and close investigation of these may shed further light on the use the deer make of the island's various microenvironments.

Some attempts have been made by students to elicit and record alarm calls from the deer, but these have generally succeeded in getting only a few calls, not a sufficient sample for systematic study. Alarm calls are in the form of a shrill whistle. It would be interesting to explore the context in which they are made, and to establish whether particular members of the group are more likely to make them. It is also unclear whether alarm calls are aimed at the intruder or are for the benefit of the rest of the group (see Smith, 1984). It would be possible to look for alarm calls in the context of a project on the closely related question of vigilance patterns: it is still not clear how vigilance differs between male and female groups, and between males and females in mixed-sex groups.

In summary, the following projects are suggested:

• Determine the preferred foraging areas of male and female deer, and sample vegetation from them to investigate differences. There are important safety issues here, and you must not compromise your safety by trying to reach areas where the deer can go easily but you cannot.
• Record vigilance (often recognizable by the animal having its head up from the browsing position), and if possible alarm calls, of individual animals within groups. Look for any evidence for individual specialisation in vigilance or alarm calling, and for differences between males and females in both single-sex and mixed-sex groups.
• Observe male groups, identify individuals, and note the social behaviour shown between each pair of individuals. Relate your observations to published accounts of Sika social behaviour. Can the pairwise relationships be integrated into a description of a general social structure, such as a dominance hierarchy?
• Observe female groups. Note the social behaviour shown between yearlings, and between yearlings and adults, also the behaviour of and towards any fawns. Again attempt to integrate pairwise relations into a social structure, though this will be more difficult given that you are unlikely to be able to recognize individuals from one sighting to another

Those involved in deer projects should be prepared for very early mornings (5.30am ish) and late afternoon/early evening forays. Temperatures at these times can be very low, and sucessful observation depends on absolute stillness. Even if the weather is good large numbers of layers should be worn. The deer respond acutely to smell as well as sight and sound, so observers need to be aware of wind direction and avoid horizons. Observations are usually recorded onto a dictaphone for subsequent transcription. Patience and the ability to tolerate frustration are essential; the payoff is the sense of achievement when you manage to collect data from such shy and unusual animals (see The Deer Sika).

There is a small population of Sika deer at Paignton zoo. They are strongly habituated to humans, so their behaviour is not a good guide to that of wild animals. But you can get close to them, so a preliminary foray to look at them might help you get a clear idea of the physical characteristics of the deer.

References

• The Animal Diversity Web of the University of Michigan's Museum of Zoology has a comprehensive entry on Sika deer.
• Horwood, M T (1981) Sika Deer. .......599.7357 [provides a general introduction to Sika deer]
• Putman R J (1988). The natural history of deer .......SL 599.7357 [deals with all aspects of all species of British Deer]
• Boddington S (1987). Factors affecting vigilance in the Japanese Sika Deer of Lundy Island. 38th Lundy Field Society Report
• Bathe G & Scriven H (1975). The Japanese Sika Deer of Lundy Island. 25th Lundy Field Society Report
• Koga T & Ono Y (1994). Sexual differences in foraging behaviour of sika deer. Journal of Mammalogy, 75(1), 129-135
• Long, A.M., Moore, N.P. & Hayden, T.J. (1998). Vocalizations in red deet (cervus elaphus), sika deer (cervus nippon) and red x sika hybrids. Journal of Zoology, 244, 123-134
• Ratcliffe, P (1987). Distribution and current status of sika deer, Cervus nippon, in Great Britain. Mammal Review, 17(1), 39-58
• Smith, S (1984). Vocal and allied activity of New Forest Sika deer. Deer, 6(3), 79-90 

In addition, there may be other articles on sika or on deer generally in the Lundy file in the resouce room available for you to borrow.