Despite the terms sometimes being used interchangeably, ecologists recognise a distinction between an animal's home range and its territory. A home range is the area an animal uses during its normal activities, and this may overlap with neighbouring individuals. Within the home range is a smaller (core) area to which the individual is “spatially bonded”. In other words, much of the individual's time is spent here and this area is defended from others - this is a territory. Indeed, Stefan Stadler considered territorial bucks to be those that showed scent-marking behaviour within the same small area and returned it shortly after being driven off by disturbance, which was generally not the case for females or non-territorial males.
A territory can be thought of as the minimum exclusive area required by an individual at a given time, and it's important to recognise that this is flexible. Indeed, it's difficult to provide a meaningful average home range or territory size because they vary according to several factors, including population density, age, sex, size, weather and climatic conditions, the season, and human-induced changes such as disturbance and construction. In water deer, rutting territories are typically established by bucks in locations frequented by females and may be isolated or clustered like a mosaic, according to the distribution of females.
The following (i.e., Laying down roots below, and the companion section Space to roam) is a general summary of the spatial use by water deer. Values are given for specific habitats and/or seasons but should be considered examples only. (Note: For a description of the aggressive behaviour employed to maintain territory, see Types of behaviour—Aggression and Reproduction—Male-Male Aggression)
Laying down roots
Broadly speaking, Chinese water deer are a seasonally territorial species. Mature males can live peaceably with one another outside of the winter rut, although there are reports of territorial chasing and scent marking throughout the year, particularly during the spring. Paul Childerley has observed a few chases between bucks that have involved vocalisation and “dancing” during March and April at Beckerings, for example, and at Woodwalton Fen Arnold Cooke and Lynne Farrell recorded bucks becoming very aggressive during the spring of 1977. In their study population of 22 deer living around China's Poyang Lake during 1988/89, Lixing Sun and Bing Xiao found marking behaviour and chases between males declined from about four per hour during the winter to only one every two hours in April, indicating a significant drop in territorial behaviour outside the rut. Likewise, Stefan Stadler observed most aggression and scent marking among bucks during the winter but described males continuing with dung-marking behaviour even in summer (see: Excretion Marking), suggesting that, in some locations at least, bucks may be permanently territorial.
Their observations at Poyang Lake led Sun and Xiao to the conclusion that the territorial system was more akin to some African ungulates (i.e., an intermediate form between resource defence territories and classical leks) than other deer. The bucks followed the females to better feeding grounds, where they established their territories; one of the males abandoned his territory after the does that had been visiting shifted elsewhere, rather than retaining it in the hope of more female interest. My observations here in England also suggest an element of resource defence, bucks holding areas that are attractive to females in some way, and during his observations of the species at Whipsnade, Stefan Stadler reached a similar conclusion. In his Ph.D. thesis, he explained:
“Territory holders did not defend a female (or a group of females), as females move freely over the ranges of several territory holders. When females were in or close to oestrus, and only at this time, males tried to keep those particular females within the boundaries of their territories by herding them. Thus, it seems more likely that males defended an area that contained resources valuable to the females. The mating system of the CWD population at Whipsnade Park may, therefore, be described as a resource defense mating system.”
Certainly, males seem to exhibit a highly flexible territory arrangement, such that some may retain them year-round, while others may not hold one at all or only do so for a few weeks during the rut. As discussed previously, however, a winter territory seems necessary for bucks if they're to stand any chance of breeding; males without a territory apparently being less attractive to does. We might expect, therefore, that all bucks at least attempt to hold a territory at some point in their lives, and data collected at Branféré and Whipsnade indicate this is unlikely before their second winter. Indeed, Stadler recorded how yearlings “strived to establish territories” at 15 to 18 months old but were rarely successful until at least 20 months of age. The picture appears similar in the wild and, in his 2019 book Muntjac and Water Deer, Arnold Cooke commented how:
“First-winter bucks in the less crowded environment of Woodwalton Fen have apparently occasionally held compartments, but their success at mating remains unknown.”
A buck may become a territory holder either by ousting an existing territory holder or by setting up a territory between those of other males and gradually extending the patch. Indeed, Stadler observed one tagged juvenile buck “floating” around between established territories until it fought and displaced a buck from a territory, and subsequently maintaining it for at least a year. Such usurping by a juvenile buck was rare, however, and Stadler described the start of territorial development beginning with males alternatively feeding and resting in the same area. Other subdominant males, and sometimes females, were chased away and the new owner started showing marking behaviour before being seen in parallel-walk contests with neighbouring territory holders who, in most cases, finally drove them away. In some cases, Stadler recorded how a fawn would develop an attachment to a small area and become aggressive towards other males in the vicinity, although it would always submit to established neighbours. A period of continued aggression and scent-marking would sometimes lead to the establishment of, and gradual expansion of, a territory. Stadler explained how young bucks (after weaning) gradually increased their ranges, peaking in home range size (and core area size) as yearlings and dropping to their minimum home range sizes at the age of 21 months, when several of them successfully became territorial. Even if territory wasn't established, fawns tended to remain in, or close to, their original home range upon independence.
At Whipsnade, Stadler observed that four (31%) of the 13 adult bucks he studied retained their territories throughout the 27 months of his study. At Woodwalton, Cooke and Farrell noted two essential components of territories occupied for long periods, and typically by bucks in the best condition, were rich, open feeding areas and dense, tangled scrub or similar vegetation (i.e., reedbed, willow carr, etc.) in which to rest, ruminate and probably feed to some extent. Areas with little or no dense vegetation in which to lie-up were rarely tenanted for long, and typically only by immature bucks. In the Buckinghamshire countryside, Sharon Scott tells me the mature bucks move around according to what's happening on the land (e.g., according to crop rotations, organised shoots, etc.), indicating they may not hold the same territory for long.
Writing in his 1977 paper to The Quarterly Review of Biology, Norman Owen-Smith noted that, among ungulates, “At any one time only a proportion (between one-third and two-thirds) of the adult male segment of the population exhibits territoriality”. A rough calculation by Stadler suggested this largely held true for Whipsnade's deer. Stadler's observations suggested each territorial buck inhabited about one hectare (2.5 acres), which meant there could be a maximum of 65 territories established on the 65 ha (161 acre) site. Four censuses of the population found a maximum count of 96 adult bucks on the study site, indeed suggesting at least one-third of the male portion of the population was excluded from establishing a territory.
Given that not all males are able to establish a territory, yet having one appears a typical requirement of breeding, it's unsurprising that territorial bucks show high site fidelity. Intruders are chased from the territory, sometimes several hundred metres away, and I've seen chases at Whipsnade where a buck has been chased across three or more territories, resulting in consecutive bucks breaking off and picking up the chase in a “pass the baton” manner. Territory holders will quickly return to their core area once a rival has been ejected. Also at Whipsnade, Raymond Chaplin described how territory contenders were chased well away from a territory, before the master buck quickly returned, while bucks accidentally straying into a territory were only chased to the territory boundary. Stadler observed how bucks did not generally follow a female if they left his territory, and this aligns with my experience both at Whipsnade and in the wild. In short film by The FieldSports Channel released in February 2015, Paul Childerley noted that mature bucks won't leave their territories, even in the face of the cars and lamps of coursers, making them easy targets for the dogs. Presumably, such close territorial association reflects both the jeopardy of loss if the master buck is away too long, and that following females or non-threatening bucks outside one's territory tempts attack from neighbouring males.
The situation for does is different, and in his thesis Stadler remarked how, to assure reproductive success, females don't need to restrict themselves to a small area and evict like-sex individuals. Instead, it's advantageous for them not to be attached too closely to a certain site, allowing for greater flexibility to long-term changes in the quality of the habitat. Females may, however, exhibit some very limited territoriality during the spring, and several authors note a tendency for them to become aggressive towards females who stray too close shortly before giving birth, evicting interlopers from their chosen birth site. In their 1983 booklet on water deer, Cooke and Farrell note of the spring chasing that it “may be related to the (re-)establishment of territories in which the females will give birth”. At Branféré Zoological Park, Gérard Dubost and colleagues found that females showed a much greater overlap in ranges than males, their ranges becoming more exclusive in the run-up to parturition up until the fawns were around three weeks old. It should be noted, however, that while does will chase away other females from the natal site for a couple of weeks, there is no indication of the patrolling or scent marking we see in bucks. Females may also chase away their offspring during the autumn, ahead of the rut, but this does not appear to be a territorial response; more a “cutting of apron strings”.