Water Deer Interaction with Other Species

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Domestic animals & livestock

Arnold Cooke has observed that water deer seem to particularly avoid fields containing sheep, and more generally any field with grazing livestock. In his 2019/20 Surveillance Report from Woodwalton Fen (WWF) in Cambridgeshire, he noted "a clear inverse relationship for the years up until 2018/19 between average count of water deer during February-April and the average number of fields with livestock (out of the total of nine)". His 2009 paper in International Urban Ecology Review quantified this: the number of deer being recorded in fields inside WWF during October and November between 1982 and 2009 fell from 68 to 13 when cattle were introduced, recovering to 68 after they were removed. Cooke suggested the cattle had altered the habitat by substantially reducing scrub cover, an important component of water deer territories.

My own experience is broadly similar. Water deer are infrequently seen in fields with livestock, though I have observed them alongside horses and cattle in both Bedfordshire and Norfolk, and Michael Anker, Project Lead for the Norfolk Deer & Wild Venison Strategy, told me in December 2025 that he has recorded water deer and cattle sharing fields at the Welney WWT reserve, each apparently indifferent to the other. Sheep are another matter. I have only once seen water deer in a field with sheep -- three bucks that had established small territories near Woburn in December 2024 -- and the coexistence struck me as unusual, not least because Sharon Scott tells me she regularly sees water deer vacate fields when sheep are introduced in Buckinghamshire. It's possible that the Woburn bucks had already established their territories before the sheep arrived and were reluctant to abandon that investment. Whatever the explanation, sharing a field with sheep appears genuinely uncommon, and I know of only one other confirmed report – passed to Arnold Cooke by Roy Butters, a deer stalker and volunteer ranger on the Great Fen:

"Last week [w/c 6th Feb 2017] ... We saw a Chinese water deer lying in a field amongst a large flock of sheep. As this was something I had not previously seen, I wondered whether the deer had something wrong with it. About two hours after the first sighting we returned to the location and saw the deer grazing amongst the sheep. It looked in good condition and was moving normally. The graziers arrived to check on the sheep, so the sheep moved away from them and bunched up. I was amazed to see the deer position itself right in the middle of the bunch and stay there until the graziers moved on. The deer and sheep then resumed their grazing. That is the first time that I have seen a deer of any species acting in such close consort with livestock."

Why might water deer and sheep make such uneasy neighbours? Sheep are highly selective grazers, like water deer, and can graze a sward down to just two centimetres (0.8 in.) – well below the five centimetres (2 in.) or so that cattle will typically leave. I know of no data on the bite depth of water deer, nor the minimum sward height water deer require, but my observations of road-killed specimens lead me to suspect they would struggle to subsist on a two-centimetre sward and may simply be out-competed. Indeed, given that the water deer's digestion is tuned to high-protein, low-fibre vegetation, it seems unlikely they'd be able to feed efficiently at swards shorter than about 4 cm (1.6 in.); below this they're eating mostly fibrous stems. There's also the question of lanolin, the natural wax secreted by sheep's sebaceous glands: it's the primary active ingredient in Trico deer repellent spray, and experiments with lanolin-containing soap applied to forestry stalls suggest it deters deer unless they are hungry enough to override the aversion. Whether water deer persist alongside other livestock more generally is likely to depend on stocking density, habitat composition, and how much suitable alternative habitat is nearby.

Hand-reared water deer, meanwhile, can form surprisingly close bonds with other species. A photograph published in the Daily Telegraph on 7th June 1965 showed three two-day-old fawns born at Twycross Zoo huddled with a Great Dane named Prince, who had assumed the role of surrogate mother after the fawns were apparently abandoned by their dam. More recently, a member of the animal care staff at Whipsnade Zoo described to me how fawns hand-reared there over the past couple of years follow their keepers around the enclosures like puppies and can suffer separation anxiety, calling in a manner reminiscent of fawns separated from their mothers; with keepers noting considerable individuality among the animals.

In his 1953 Country Life article, Kenneth Whitehead wrote about a doe named Dawn, hand-reared from a few hours old by T. A. Hayward, who formed what was apparently an inseparable bond with the family's Angora rabbit and engaged in play with their cat. Wild deer are generally wary of dogs,but Dawn was a notable exception:

"There is no doubt that she is fond of all other creatures. Recently two impish dogs came barking outside the low wire fence which surrounds the garden, and Dawn, instead of being afraid, ran straight up to them and rubbed noses with them through the netting. This behaviour is the more unaccountable because, generally speaking, water-deer seem unable to protect themselves from dogs, either by fighting or by flight."

Dogs have posed far more serious problems for water deer reintroduction efforts in China. Work led by Min Chen at East China Normal University has suffered significant setbacks due to feral dogs at release sites. In a 2024 article in the Deer Specialist Group Newsletter, Chen and Haiming Tang and Qiuting Chen of the Shanghai Pudong New Area Forestry Station described how packs of feral dogs were observed chasing, attacking, and scavenging water deer released at Laogang and Nanhui in 2020 and 2021 respectively. The deer adapted by using the sites at different times from the dogs, but the harassment continued. Even when attacks did not result in direct kills, the stress of repeated chasing drove deer into unfamiliar forested terrain, with fatal consequences:

"In their haste, they may collide with hard tree trunks instead of soft reeds, leading to fractures and fatalities."

Muntjac and other deer

While researching this article, I came across a handful of anecdotal accounts suggesting an inverse relationship between water deer and Reeves' muntjac (Muntiacus reevesi). One thread on The Stalking Directory from November 2019, for example, included a report from a stalker in Essex who noticed a dramatic increase in water deer sightings after beginning a heavy cull of muntjac in their woods – a site where water deer had been spotted only sporadically for years beforehand. Such observations align with modelling by Pelayo Acevedo and colleagues, published in Diversity and Distributions in 2010, which predicted that water deer are weak competitors relative to other deer species.

The most substantial empirical evidence that muntjac may limit water deer comes from Arnold Cooke's long-term observations in Cambridgeshire. As muntjac began colonising Monks Wood (1970), Holme Fen (mid-1970s), and the southern part of WWF (1980), Cooke documented a consistent inverse relationship between the two species at each site. Where they occur sympatrically (overlap), muntjac appear to at least partially exclude water deer from drier woodland, pushing them into wetter habitats -- willow carr, reedbeds, and open fields -- though no comparable effect was observed on water deer numbers elsewhere on the WWF reserve or on adjacent farmland. In Muntjac and Water Deer, Cooke notes that a similar negative relationship has been recorded in China, and suggests that heavy defoliation of shrubs, particularly bramble as a key winter food for both species, may reduce the forage available to water deer. A 1998 paper in Deer developed this further, proposing that muntjac's more efficient or earlier exploitation of bramble in winter may explain why muntjac sightings at Holme Fen rose steadily between 1990 and 1997 while water deer sightings fell.

Beyond direct competition for food, the mere presence of muntjac may be enough to deter water deer from feeding. During a camera-trapping study of deer browsing on bramble and ivy at WWF in late autumn and winter of 2011/12, Cooke found that water deer were rarely recorded actually feeding at the stands. As he summarised in Muntjac and Water Deer:

"In videos of water deer, smelling was twice as frequent as browsing, whereas for muntjac, browsing videos were six times more numerous. It is possible that water deer were in part deterred by the smell of muntjac."

One video captured a water deer sniffing a bramble frond that had been nibbled by muntjac before turning away. Cooke also noted that muntjac, being more tolerant of disturbance than water deer, may have adapted more readily to increased recreational use of these sites -- particularly by dog walkers -- though this alone cannot account for the pattern across all sites.

An intriguing footnote came from a thermal drone survey over a Norfolk estate in winter 2023/24, which showed a marked spatial separation between muntjac and water deer, with little apparent intermixing. A single survey at one point in time is far from conclusive, but when I discussed the results with Arnold Cooke, we both remarked on how closely the distribution echoed his findings at Woodwalton. More recently, in April 2026, Ben Harrower, director of BH Wildlife Consultancy, told me that this pattern appears consistently across their drone surveys in Norfolk and Suffolk. In the Norfolk Broads in particular, water deer dominate the wet areas, appear in some woodland, and turn up in the occasional field; and Ben suggested that overlaying the hydrology onto their survey maps would probably reveal a clear gradient: the wetter the ground, the more water deer predominate over muntjac.

Any displacement of water deer by muntjac appears to be passive rather than the result of direct aggression – with one striking exception on record. In his 1981 book Mammal Watching, Michael Clark recounted how one of his tame muntjac bucks killed a water deer buck sharing the same pen while aroused by a doe in oestrus, the water deer apparently offering no resistance. It is the only account of lethal muntjac aggression towards water deer I am aware of; in my own experience, the two species encountered together generally forage in proximity and largely ignore one another.

As for the other deer species whose ranges overlap with water deer, I am not aware of any data on direct interactions. Sufficiently high densities of red (Cervus elaphus) and fallow (Dama dama) deer could in principle bring them into competition with water deer, but robust populations of both in East Anglia do not appear to have impeded water deer's persistence or spread there. Roe deer have been slow to colonise much of Bedfordshire and Cambridgeshire, and it is tempting to wonder whether the abundance of water deer (and muntjac) in those counties is partly responsible, though this remains unproven. On the farm where I have been camera-trapping since January 2019, roe are relatively common and I have recorded does with twins in four successive summers, apparently coexisting without difficulty alongside a sustained water deer and muntjac presence.

Foxes

The Norfolk Bird and Mammal Report for 1997 carried a note about a water deer apparently playfully chasing both pheasants and a fox, though no further detail was given. In my own experience, foxes hunting small mammals in fields where water deer are grazing or resting generate little apparent interest, and I have several trailcam clips of the two species passing within a few metres of one another without reaction. Sharon Scott has made similar observations. That said, John Heathcote has sent me footage of a water deer chasing a fox -- behaviour he tells me he has witnessed several times on his Norfolk estate -- so the relationship is not entirely one of mutual indifference.

The more significant interaction is predation of fawns. During his PhD research at Whipsnade in the early 1990s, Endi Zhang recorded that foxes were responsible for 86% of fawn mortality there, eventually forcing the zoo to reinforce enclosures to keep them out. In a 2014 article in Sporting Rifle, Paul Childerley made the broader point that keepered ground, with its reduced fox pressure, has been central to water deer's survival and establishment in the wild.

There are no data of which I am aware to suggest foxes pose a meaningful threat to healthy adult water deer, but the question of what foxes are capable of is not entirely settled. I have seen footage from Germany of a fox pinning an eight-month-old roe kid -- though the fox was shot immediately, so whether it could have made the kill remains unknown -- and photographs of foxes carrying the bodies of sizeable white-tailed deer (Odocoileus virginianus) fawns, though in those cases it is unclear whether the foxes killed the animals or came across them already dead. Both the roe kid and the whitetail fawns were larger than most adult water deer, if not necessarily heavier, which raises the question of whether foxes might occasionally take weakened or injured adults.

Butterflies

A conservation project at Woodwalton Fen attempted to reintroduce the large copper butterfly (Lycaena dispar) between 1969 and 1973, but repeatedly failed – partly, it was believed, because water deer were eating the greater water dock (Rumex hydrolapathum) on which adults laid their eggs, though Arnold Cooke told me recently that he does not think this was the primary cause. Andrew Pullin and colleagues, in their chapter on the large copper in the 1995 book Ecology and Conservation of Butterflies, noted spring counts of water dock showing browsing damage from water deer, particularly on plants growing in standing water. In his 1977 paper in Biological Conservation, Eric Duffey was more explicit:

"Dock plants are also influenced, to some extent, by the resident population of the Chinese water deer, which was first recorded on the Fen in the late 1950s. These small deer are now numerous and are probably responsible for grazing the first leaves of the docks which appear in the spring. Damage of this type has been frequently recorded where the vegetation is short and it may deprive the larvae of food material when little growth is available."

More recently, an extensive report on deer impacts in the Norfolk Broads, published in February 2025, has raised concerns about a species that, unlike the large copper, still clings on in Britain; but only just. Mike Harding notes in the report that, based on thermal drone surveys, water deer are clearly the most abundant deer in the Broads, particularly in the fens and marshes of the southern catchments, where densities may exceed one per hectare – above the threshold at which browsing damage has been reported in other habitats. Among the plants affected is milk parsley (Peucedanum palustre), the sole larval food plant of the swallowtail butterfly (Papilio machaon), which in Britain is found at only around 16 sites in the Norfolk Broads and nowhere else. Freelance swallowtail researchers Kevin Radley and Hannah Breach told me in May 2025 that deer are "grazing eggs and caterpillars along with the plants, so potentially reducing both the butterfly and the food plant", though further work is needed to establish whether this is having a measurable effect on swallowtail populations. Given how restricted the butterfly's British range is, the question seems urgent.

Other animals

The 2025 Broads Authority report also mentions that the combined impact of grazing on the reeds by red and water deer have resulted in a change in the vegetation structure, density, and height, which they believe is impacting the populations of bitterns (Botaurus stellaris) and bearded tits (Panurus biarmicus); both reedbed specialists. Concerns were also raised that the paths created through the reedbeds by deer, including water deer, could be leveraged by foxes hunting for birds, although subsequent investigation failed to find any evidence to support this.

One final, curious observation comes from footage recorded by remote trail cameras placed among rushes at the edge of a small pond in Buckinghamshire during the summer of 2025. That summer, like the preceding spring, was notably dry across much of southern and central England, and the steadily shrinking water level appeared to draw deer to the pond throughout the season. On two occasions -- one involving a roe deer (Capreolus capreolus) doe and the other a water deer doe -- individuals were filmed moving through the rushes towards the water while carrying what could only be described as a swarm of flies across their backs and upper flanks. Notably, there were no obvious flies on the head or face. The insects remained in place as the deer moved, and in neither case did the animals attempt to dislodge them; nor was there any visible skin rippling of the kind typically seen when deer are being irritated by biting flies. This was consistent across all four 60-second video clips (two per animal). Both does appeared to be in good condition, and the flies seemed to be congregating on the outer guard hairs rather than directly on the skin.

Plants

The most obvious way deer interact with plants is by eating them, sometimes browsing or grazing to the point where recovery is prevented. Less obviously, they also aid dispersal, carrying seeds either on their fur or through their digestive tract and depositing them away from the parent plant. Dispersal via ingestion and defecation is known as endozoochory, and I am aware of only one study examining this in water deer, the results of which appeared across two papers: one in Global Ecology and Conservation in 2020 and a second in Seed Science in 2022.

Working in the Civilian Control Zone (Paju City, Gyeonggi Province) adjacent to the DMZ, Seoul National University biologists Seung-Kyung Lee and Eun Ju Lee collected water deer pellets between April 2017 and March 2018 and identified 35 plant species within them. Feeding trials suggested that only around 30% of consumed seeds survived passage through the gut intact; the remaining 70% being at least partially digested. Germination tests on seeds extracted from the pellets yielded 1,655 viable seeds from 35 species across 18 families and 29 genera, averaging eight seeds per pellet group. Forbs accounted for 63% of viable seeds -- notably Chenopodium album, Potentilla supina, Lindernia dubia, and Stellaria aquatica -- while graminoids (Cyperus difformis, Digitaria ciliaris, and Panicum bisulcatum) made up 27%. Together, species from the shrubland and wet and dry meadows that water deer most frequently inhabit accounted for 90% of all species dispersed, with forest species making up just under 6%. Dispersal peaked during autumn, coinciding with the main seeding period in South Korea. The researchers noted in their 2020 paper that while water deer are not especially effective seed dispersers, the graminoid species they dispersed lacked dedicated dispersal adaptations and do not produce fleshy fruits, suggesting they had not evolved to exploit water deer as a vector. In this sense, Hydropotes may be acting as an "ecological filter", shaping plant community composition in the lowlands of the Korean peninsula without having been specifically targeted by the plants it disperses.

Some research has also examined the effect of water deer dung on germination and soil chemistry. In a 2014 paper in the Journal of Wetlands Research, Hyomin Park and Sangdon Lee showed that applying low to moderate amounts of composted water deer dung significantly boosted the growth of maize (Zea mays) sown in nutrient-poor soils (profiles matching those of marshes and fallow land), though over-application, or application to already nutrient-rich soils, impeded growth. The authors noted that the carbon-to-nitrogen ratio of water deer dung compares favourably with other animal waste currently used as a soil conditioner, suggesting a potential alternative fertiliser. The following year, Park, Lee, and Seunghoon Chun published findings in the same journal showing that water deer dung also affects CO₂ flux in soil: the presence of droppings increased soil respiration by as much as twenty times compared with dung-free controls – a substantial boost to the biological processes, including decomposition and root and microbial respiration, that drive carbon exchange between soil and atmosphere.

Against this, a 2025 paper in Seed Science Research by Seung-Kyung and Eun Ju found that the presence of water deer dung did not significantly increase germination rates in any of their trials, though the authors acknowledged methodological limitations and called for further work. Whether gut passage itself affects the germination potential of seeds -- that is, whether seeds exiting in pellets are more or less likely to germinate than they would have been had they not been eaten -- also remains unknown, though it may be unlikely. A meta-analysis by Diego Torres and colleagues, published in Mammal Review in 2020 and drawing on data from 115 mammal and 448 plant species, found no evidence that deer gut passage enhances seed germination potential, though only three deer species were included in the analysis – none of them water deer.