Britain's deer species by Derek Crawley - Invasive Species Week

Derek Crawley is the lead author of the Atlas of the Mammals of Great Britain and Northern Ireland (D Crawley et al 2020). He is the founder member and Chair of the Staffordshire Mammal Group and a verifier of mammal records. Twitter: @poofinder.

Invasive non-native species are a global problem, affecting biodiversity and causing substantial economic damage. As the atlas coordinator for the Mammal Society I have a good idea where to find all six deer Species in the UK. I travel a lot for work so on a couple of occasions I have managed to see all the species of deer in a single day traveling from Bedfordshire to Wiltshire. Of the six species, only two are native the red and roe deer, even if roe deer had to be reintroduced in southern England due to hunting and shooting causing local extinctions. The other four (fallow, sika, muntjac and Chinese water deer) have all either escaped for deer parks or been deliberately introduced to areas for sporting interest. While red and fallow are easily kept together in parks, in the wild they do not tend to mix even when present in the same forest.

The population and distribution of all the deer species is increasing and their impact on their environment and interaction with us is also increasing. Being the natural grazers of Britain all the farmed cattle and sheep compete with them for food but deer at partly animals of the forest and do a great deal if damage to young trees affecting their growth and the value of timber. As deer numbers increase roads traffic casualties occur more often.  Over 50,000 deer get hit by vehicles every year and even the small muntjac can cost over £5000 pound worth of damage.

Red Deer are the biggest  identifiable by their dark brown red coat and light yellowish rump patch the stags having up to 16 points on their antlers. They stand at about 1.20cm at the shoulder. They are mostly found in upland areas with many southern populations having escaped from deer parks.

Fallow come in a variety of shades due to inbreeding in park stock but typically have light brown colour with white spots on its back. The buck’s antlers have some points coming of a thin flat section. Their white rump patch has a border of black with a black stripe on its tail and they stand 90cm at the shoulder.

Sika deer have a localised distribution with hotspots across the country. They are similar in size to fallow, they can have spots on the body or be quite dark but they always have white spots on their hind legs. The white rump has a black strip on top but no black on the tail. This invasive species can mate with red deer and their offspring are fertile causing some to say that there are few pure genetic red deer left in the country.

The native roe deer has a more solitary life and is uniformly brown with a white rump patch standing at 70cm at the shoulder it is the most widespread being reordered in nearly every county. The male buck has short 3 pointed antlers.

The more recent establishment of muntjac deer is due to escapes from collections and deer parks and is a rapidly spreading shy animal that hides in the undergrowth but becoming bolder as the population grows so that it’s locally commonly seen in gardens and parks with a disregard for people. It stands at just 50cm at the shoulder similar to a Labrador, but it’s a rich dark brown with a white under tail which it displays when frightened and running away. Both male and female have tusks but the male also has small antlers. It has had an impact on the flora of woodlands from grazing as well on shoots form coppiced trees. It has been spreading out from the Home Counties slowing moving north and out to the east and west of southern England.

Chinese water deer have the smallest distribution thriving in the wetlands and arable fields across East Anglia and Bedfordshire. These deer have no antlers but tusks which are bigger in the males. They are light brown to gray in colour with no identifiable feature on the rump but do have the look for a teddy bear from its facial features.

As the invasive species spread it puts more pressure on our native red and roe from competition of resources and genetic integrity. The Mammal Society strongly encourages people to report all mammal sightings, including deer, so we can monitor the spread of invasive mammals and changes to our wildlife distribution using the free Mammal Mapper phone app.

For more information on Invasive Species Week visit the GB NNSS website. 

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