Water Deer Distribution - Home Counties and Cambridgeshire
The Home Counties
Currently, we know almost nothing about the colonisation of Buckinghamshire by this species, despite it seemingly being the county in which it first gained a foothold in the wild. Based on data provided to me by the Buckinghamshire and Milton Keynes Environmental Records Centre, covering 1969 to 2017, Chinese water deer are primarily distributed in the north-east of the county, east of the A418 and north of the A41. There are, however, a rash of reports between Aylesbury and Winslow along the A413. There are several records north of Leighton Buzzard, between Bletchley and the Bedfordshire border (with Woburn) and north of the M1, around Newport Pagnell.

The Bedfordshire Natural History Society has maintained early records submitted by their members and much of this information has been published over the years in their annual report, The Bedfordshire Naturalist. It should be noted, however, that records obtained by the Society are patchy, and seem largely focussed on sightings away from the Woburn estate where numbers had apparently increased sufficiently on peripheral farmland for 20 to be shot in 1972.
In the 1971 Bedfordshire Naturalist, David Anderson notes that when the Society was founded in 1946 there were no deer of any species recorded in the county. Presumably, the water deer living in the surrounds of Woburn Abbey were not reported to the Society, because Anderson gives the first report, describing two or three animals seen at Eversholt, south-east Bedfordshire, early in November of 1969. A second report was made in 1973 and a couple more in 1974.
While the number of records in the known areas had increased, by 1977 there was still “no known spread” of this species, and after very few sightings for the following few years, in 1981 Anderson wrote of how he continued to be “pessimistic about its status in Bedfordshire”. Things picked up in 1982, however, with several sightings from existing sites and one from a new location, and again in 1984, which saw three new sites added to the list, resulting in Anderson describing Bedfordshire to as 'of national importance' for water deer in 1985. Two new locations were added in 1988 and records began coming in from further afield during the early 1990s, including a buck killed on the A600 near Chickslade in 1992. A further 14 sites were added between 1996 and 1998.

Despite posing a rather formidable barrier to dispersal, Society member Bernard Nau, writing in 1992, noted that the M1 had been crossed by at least December 1975, when one turned up in scrub at a vehicle test track in Millbrook, central eastern Bedfordshire, some three kilometres (just under two miles) east of the motorway.
Cambridgeshire
Woodwalton Fen (WWF) remains a stronghold for the water deer in East Anglia today, and its colonisation has been well-studied by Arnold Cooke and Lynne Farrell. A 208-hectare (514 acre) mosaic of open grassland, heathland and mixed fen vegetation with blocks of sallow-dominated willow scrub and birch/alder-dominated woodland, Woodwalton Fen provides seemingly ideal habitat for this small deer, and colonisation appears to have begun in 1962; the population was well-established by the end of the decade.

Water deer tracks were first noticed in compartment 58 of the reserve by J. Antony Thompson and Gordon Mason in November 1962, and a single fawn was recorded in 1963 and another in 1964, although at the time these were assumed to be muntjac. It wasn't until January 1971, when a dead animal and several live individuals were identified by deer biologist Raymond Chaplin, that it was recognised that these were in fact water deer. Chaplin estimated the population at WWF to be between 50 and 75 deer in 1972. According to Norma Chapman's short paper to Deer in 1995, this population originated from a small number of Woburn stock released in the vicinity between 1947 and 1952.