Water Deer Territory & Home Range - Size

For many mammals, home range increases with the mean body mass, reflecting the greater energy expenditure of larger individuals. Similarly, ranges tend to increase with increasing metabolism, decreasing with increasing concentration of food resources. This relationship can be flexible within a given species, however, and at Branféré Zoological Park, for example, Gérard Dubost and his team found that, to the exclusion of immature bucks: “The more an animal weighed, the larger the area it occupied regardless of age, sex or season”. At Whipsnade, by contrast, Stefan Stadler observed the home range size of males didn't appear to be determined by body weight, while that of adult females probably was. When population density increased at Whipsnade, territorial bucks reduced their overall range size, but kept the size of their territory (i.e., the defended bit) constant.

In the literature, reported home range size varies considerably, from about one to 700 hectares (2.5 to 1,730 acres), with ranges in winter usually significantly larger than in summer. The studies with which I'm familiar also identified larger ranges for females than males, varying with age. Stadler, for example, found that adult and subadult does had similarly sized ranges at Whipsnade, while Dubost and colleagues at Branféré, and Xin He and co-workers in China, both recorded subadults having larger (sometimes much larger) ranges than adult females. Most studies also show that does range more widely while pregnant and lactating, presumably allowing them access to a greater quantity and/or variety of food.

Based on data on 58 free-ranging deer at Whipsnade, collected between November 1986 and January 1989, Stadler found that non-territory holding bucks ranged over an average of 18 hectares (44 acres), while those with territories utilised a much smaller area, only around two hectares (5 acres) and with about one hectare being actively defended (i.e., the territory). Territorial males also significantly reduced their annual home range size (by up to 40%) from one year to the next, while ranges of non-territorial bucks remained pretty consistent. The average core area used by both groups did not change significantly, perhaps reflecting the quality of the territory. Indeed, the core areas of territorial males were about half the size of non-territorial bucks (i.e., 0.5 vs. 1.1 ha / 1.2 vs. 2.7 acres). Also at Whipsnade, during early December in the late 1960s, Raymond Chaplin spent three hours watching the rut in Valley Meadow. In his unpublished research notes, he comments on there being 30 adult males in the field, but only four territories, each about 90 yards across, occupied by a single master buck and with females resting at the centre. Assuming these were roughly square, these rutting territories were in line with those reported by Stadler, each being around 0.68 hectares (1.7 acres).

For the Whipsnade study population as a whole, consisting of 58 individuals, Stadler found home range size varied considerably from year to year, but on average in any given year adult males used the smallest annual home range (12 ha / 30 acres); significantly smaller than the 37.5 ha (92.6 acres) used by yearling males, 34 ha (84 acres) by yearling females, and 30 ha (74 acres) of adult females. Territories (i.e., the core areas from which other deer were chased) in any given year again showed males using a significantly smaller area (just over one hectare / 2.5 acres) than any other class. Yearling males, yearling females and (for most of the year) adult females didn't maintain territories in the aggressive-exclusion sense, but their core areas (i.e., where they spent a majority of their time) tended to cover three or four hectares (7-10 acres). Seasonal home ranges at Whipsnade were largest between May and July at 10 to 15 ha (25-37 acres) for females, while bucks ranged over less than five hectares in any given season. Fawns moved over a couple of hectares during their first three months of life, increasing to 10 ha (25 acres) by their first winter. Young males (i.e., those less than two years old) were often seen feeding or resting within the territories of dominant bucks before being driven off. During his study, Stadler recorded two male fawns remaining in an area of about a hectare that wasn't occupied by an adult male, suggesting this may be the preferred area size when not being pushed around or having to travel more widely for food.

Relatively few data exist from the wild. At Woodwalton Fen, limited observations on five identifiable deer during the mid-winter rut by Arnold Cooke and Lynne Farrell suggested ranges varied between five and 15 hectares (12-37 acres). Based on five females and three males during the 1988/89 rut at Poyang Lake, China, Lixing Sun and Bing Xiao recorded bucks setting up territories of around 0.5 hectares (1.2 acres) clustered together but without overlap, while females ranged over a non-exclusive area of 20 to 40 hectares (49-99 acres), five hectares (12 acres) of which was used intensively. Across the year, the Poyang females ranged over up to 120 hectares (300 acres); no equivalent range was estimated for males.

Remaining in China, between June 2010 and December 2011, Xin He and colleagues at the East China Normal University radio-tracked 12 animals released into Nanhui East Shoal Wildlife Sanctuary in 2010 as part of a reintroduction programme. The data from this study are provided here for reference, but clearly highlight how different statistical methods of estimating home range size (mean convex polygon, or MCP, and fixed kernel estimation, 95% FKE, in this case) can produce grossly different results, and numbers should be treated sceptically.

In their 2016 paper to Animal Production Science, He and co-workers report an expansive MCP home range of between 245 and 1,559 ha (605-3,852 acres), the smallest being an adult male and the largest a subadult female. The mean MCP range, based on all animals tracked, was 671 ha (1,658 acres), while the FKE method suggested 262 ha (647 acres). According to MCP, bucks had smaller home ranges than does, averaging 494 (1,220 acres) and 788 ha (1,947 acres), respectively, while FKE showed no significant difference at 258 and 265 ha, respectively. Both methods did, however, show subadult does ranging over more than twice the area of adult females and indicated that their ranges overlapped more than those of adults. Overall, the ranges varied with season, largest in winter (275 ha MCP or 403 ha FKE) and smallest during summer (120 ha MCP or 131 ha FKE). Home range overlap varied from exclusive (e.g., bucks during the rut) to 851 ha (2,100 acres), the latter between a subadult and adult doe - the average was 422 ha (1,403 acres). Outside of the rut, bucks overlapped ranges, but by less than does, averaging 135 ha (334 acres), although two bucks were estimated to overlap by 385 ha (951 acres). Does appeared to overlap with one another by more than they did with bucks. The largest home range overlaps occurred in winter. In their short paper to the Pakistan Journal of Zoology in 2015, the same team note that ranges were wider in the first six months after release, contracting significantly thereafter. Presumably, there was an initial period of movement to establish familiarity with the region.

At two sites in northern South Korea, Ewha Womans University biologists Baek Jun Kim and Sang-Don Lee tracked four deer, two of each sex, between July and December 2009. The small sample size and problems with the equipment meant that the dataset is highly variable and should be treated with caution, but they remain the only Korean data of which I am aware and are included for completeness. In their paper to the Journal of Ecology and Field Biology in 2011, the researchers report an average (MCP) home range size of 280 ha (692 acres), being slightly larger during the night (240 ha / 593 acres) than by day (190 ha / 469 acres). Ranges were also significantly larger in summer than spring, at 470 ha (1,160 acres) and 50 ha (123 acres), respectively. Males also moved over slightly larger areas than females: 330 ha (815 acres) versus 230 ha (568 acres). Finally, In a paper to the Korean Journal of Veterinary Service during 2021, Bae Dong Jung and colleagues at Kangwon National University reported that a single female water deer GPS tracked for 10 days in South Korea during summer used between 0.11 and 28 ha (0.3-69 acres) per day, with a daily average of 5.3 ha (13 acres). (The confidence limits for this average was 7.4 ha, illustrating how high the variation was in daily area used.)