Mark Welsh Wildlife Ecology and Management Essay 2003
The Consequences of Sika Introduction on the Red Deer Population
Introduction
The red deer (Cervus elaphus) history in Scotland has been tied to that of the country as a whole. Like many species to day it find its future threatened by the actions of humans. However, unlike most threatened animals it is not through direct damage of habitat or resources that it finds itself in danger but by an indirect, blind introduction of a non native species, the sika deer (Cervus nippon).
Red Deer in Scotland
Red deer are the largest remaining wild mammals to be found in the Scottish countryside. Today the largely left to roam semi-wild and hunted or farmed for their meat, hide and antler velvet. They are herd animals closely related to Elk. Stags (males) on average can weigh up to 450 - 500 pounds and hinds (females) average 250 pounds.
Traditional red deer populations were kept in check by natural predators such as the wolf and wild cats. Today man, deases and starvation are the only real threats to the numbers. In some areas there numbers are so great that they are perceived as a pest, feeding on crops, stripping woodland and destroying gardens. The reason for their enormous success in recent decades is due to the large hunting estates land management policies. The introduction of large scale sheep farming in the mid eighteenth centuary caused massive social upheaval to the Highland populations and dessimated the natural fauna of Scotland. As a by product (later actively encouraged) this left the red deer exposed and easier to shoot. This spawned and expanded the hunting industry making accessable to city gentlemen and so encouraged the careful management of red deer populations.
Sika Deer
Sika deer are a small to medium sized deer that, are compact in form with relatively dainty-legs and have a short, trim, wedge-shaped head. And significantly smaller in stature than their red deer relatives. Females have a pair of black bumps on the forehead, their placement corresponding to that of the males’s antlers.
Coloration is brown to a deep, mahogany brown mottled with numerous white spots. The degree of spotting is highly variable, however, and in some individuals spotting may be absent. A distinctive, white rump patch is evident, especially when the animal is alerted.
They are native to Japan and asia but were first brought to Scotland in the 1860s to be exhibited in deer parks or private gardens. Some were deliberately released (in Kintyre) whilst others escaped during the two World Wars and established feral populations. They are now established in Argyl and the great glen with a second population arising in the borders. They are expanding northwards, prefering wet areas with acidic soil.
Sika are very productive, can reach higher densities than red deer in similar habitats, and are more difficult to control. There is evidence that sika compete with native roe deer and that they are equally, if not more, damaging than red or roe deer and can restrict the range of tree species planted
Hybridisation Effect
The red deer and the sika are two independant species that are genetically closely related permitting these two species to Hybridise ie they can mate with each other to produce viable fertile young which exhibits a mixture of traits from each of the parent species.
Significant evidence exists from research done by The University of Edinburgh that cross-breeding exists in the areas with high sika deer populations. This has lead to a dilution of the original Scottish red deer genotype and will eventually lead to a loss of genetic integrity permanently changing the red deer morphology in Scotland. A report by Josephine Pemberton of Edinburgh University states that the red deer population in Scotland could be bred out of existence in 50 years. This has marked consequences. The Scottish red deer’s would increasingly resemble the smaller Sika deer with less ornate antlers. This has great implications for the shooting industry. It could be argued that sika deer and their hybrids are a sporting resource on their own right. However the reality is that vey few are stalked commercially leading to a decreased demand. Mostly this is to do with asthetics people preferring not to shoot a relatively unattractive hybrid. More importantly the tourist industry could suffer a decline. This has grave financial consequences for the local communities and could influence the current management strategy of existing populations.
Additionaly, the red deer, sika hybrids could have a different feeding, mating and behavioural strategies with a potential to alter the landscape.
Only some island populations of Red deer remain unaffected by hybridization Lewis, Harris Uist, and Arran are a few examples. At present these red deer appear to not contain any sika morphological traits. However some islands have fared less favourabley. It is known that Skye, Scalpay and Raasay have been colonized by sika deer swimming across open channels of sea.
To correct or limit the hybridisation problem some management strategies have already been employed by the Scottish Deer Commission. An active culling of Hybrids and sika deer could be encouraged. This would obviously presented with some difficulties due to the expanse of the habitat and the roughness of the terrain. Some say that it is already too late to save the red deer and it is near impossible to remove the genetic input of the sika from mainland populations.
Conclusion
Sika will continue to spread throughout the available range. Within present constraints of knowledge and resources little can be done to prevent their colonisation and hybridisation. It is, however, possible to slow their spread by shooting colonising animals and by reducing source populations. Rigorous controls to reduce sika populations throughout their range need to be adopted, to minimise damage to woodlands and agriculture, and to reduce the risk of hybridisation. Possibley the Secret to saving the magnificent red deer of Scotland lies in the refugee populations ont he remote islands and it is their imtegrity that must be preserved by the enforcement of existing legislation preventing the transport of sika deer..
notes by PK: references were not given