Water Deer Interaction with Other Species

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Domestic animals & livestock

Arnold Cooke has mentioned to me that, in his experience, water deer seem to particularly avoid fields containing sheep, but generally any with grazing livestock. Indeed, in his 2019/20 Surveillance Report from Woodwalton Fen (WWF) in Cambridgeshire, he noted:

"...there was 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)."

Further, in his 2009 paper on water deer in farmland to the journal Deer, Cooke reported that the likelihood of deer being recorded in the fields inside WWF during October and November between 1982 and 2009 fell from 68 to 13 when cattle were introduced, climbing back to 68 after the cattle had been removed. The suggestion is that the cattle altered the habitat by substantially reducing the amount of scrub, which was an important component of territories.

I have observed water deer using the same fields as horses and cattle both in Bedfordshire and Norfolk, but never sheep fields, and, in Buckinghamshire, Sharon Scott tells me that she sees water deer move fields when sheep are put in. Indeed, I know of only one confirmed report of the two species cohabiting, received by Arnold Cooke from 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."

Sheep are highly selective feeders, like water deer, and can graze down to a sward height of only two centimetres (0.8 in.), while cattle tend to be much less selective and not graze vegetation below about five centimetres (2 in.). I know of no data on minimum sward height in water deer, but my observations on road killed specimens leads me to believe that they would struggle to subsist on a sward height of only two centimetres and are likely to be out-competed by sheep, possibly explaining why they're seldom found together. Whether they persist in fields with other livestock is likely to depend on the stocking density, habitat composition and value of the habitat to water deer, as well as the proximity of suitable habitat.

I have come across a couple of examples of hand-reared water deer displaying imprinted or affiliative behaviour with pet animals. A photograph published in the Daily Telegraph on 7th June 1965, for example, showed three two-day-old fawns, born at Twycross Zoo, huddled with a Great Dane called "Prince", who had taken the role of a surrogate mother after their dam apparently abandoned them. Similarly, I have received descriptions from one of the animal care staff at Whipsnade Zoo telling how the water deer fawns they have raised over the past couple of years follow them around the enclosures like puppies and can suffer separation anxiety, calling in a manner akin to fawns separated from their mother. Experiences recounted to me by keepers who have hand-reared fawns suggests a substantial individuality among the animals.

In his 1953 article to Country Life, Kenneth Whitehead described a doe ("Dawn") hand-reared from a few hours old by T.A. Hayward who formed a close bond with the family's Angora rabbit, the pair having apparently grown up as "inseparable companions", and engaged in play with the family's cat. Generally, wild deer appear suspicious or fearful of domestic dogs, but Whitehead wrote:

"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."

Finally, the recent reintroduction programs in China, led by Min Chen at the East China Normal University, have suffered setbacks owing to the presence of feral dogs on the sites. In a short article to the Deer Specialist Group Newsletter in 2024, Chen and Shanghai Pudong New Area Forestry Station biologists Haiming Tang and Qiuting Chen described how packs of feral domestic dogs were seen chasing, attacking, and feeding on the carcasses of water deer released at sites in Laogang and Nanhui during 2020 and 2021, respectively. The deer rapidly adapted to try and avoid the dogs by using the areas at different times, but they continued to be chased, disturbed, and predated. In the article, the scientists also noted how even if the dogs weren’t directly attacked by the dogs, the disturbance they faced from being chased often left them stressed and deer were chased into dense forested areas with which they were unaccustomed:

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

Other deer species

While researching this article, I came across a handful of anecdotal accounts suggesting an inverse relationship between water deer and Reeve's muntjac (Muntiacus reevesi). One November 2019 thread on The Stalking Directory, an online forum for deer stalkers and game managers, for example, included a stalker in Essex who noted how the number of water deer sightings increased dramatically when they started a heavy cull of muntjac in their woods. Sightings of water deer on the site had apparently been sporadic for many years before the cull. Such anecdotal observations align with the modelling carried out by Pelayo Acevedo and colleagues, published in Diversity and Distributions in 2010, which predicted that water deer were weak competitors compared with other deer species.

To the best of my knowledge, the only empirical evidence indicating that muntjac may limit water deer persistence comes from Arnold Cooke's observations in Cambridgeshire. Cooke has documented an inverse relationship between water deer and muntjac presence at Monks Wood, Holme Fen, and in the south of the Woodwalton Fen (WWF) reserve since the muntjac began to colonise (in 1970, the mid-1970s, and 1980, respectively). It appears that, where the two occur sympatrically (i.e., ranges overlap), muntjac may at least partially exclude water deer from drier woodland, thereby restricting them to wetter areas of willow carr, reeds, and open fields. There was no noticeable effect on numbers of water deer seen elsewhere on the WWF reserve or on adjacent farmland relative to muntjac presence. In Muntjac and Water Deer, Cooke notes that a similar negative relationship has also been recorded in China, and postulates that heavy defoliation of shrubs, particularly bramble, which is an important winter food for both species, may limit available winter forage for water deer. In a 1998 paper to Deer, Cooke suggests that more efficient or earlier utilization of bramble by muntjac in the winter may explain why muntjac sightings persistently increased while water deer sightings declined at Holme Fen between 1990 and 1997.

In addition to removing or reducing available winter browse, the presence of muntjac alone may be sufficient to discourage water deer from feeding. During a camera-trapping study of deer browsing on bramble and ivy at WWF during the late autumn and winter of 2011/12, Cooke found that water deer were hardly ever recorded feeding on the stands and, in Muntjac and Water Deer, Cooke summarized:

"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."

Indeed, one video showed a water deer sniffing at a bramble frond that had been nibbled by muntjac and turning away. Cooke also noted how muntjac, being more tolerant of disturbance than water deer, may have adapted more readily to the increased leisure use of the sites, particularly by dog walkers, although this alone cannot explain the change at all sites.

Intriguingly, a thermal drone survey over an estate in Norfolk during the winter of 2023/24 showed a noticeable separation between muntjac and water deer on the site, with what appeared to be limited intermixing. This is obviously only a single timepoint and nothing conclusive may be drawn from it, but speaking with Arnold about the results, we both commented how the distribution made us think of his findings at Woodwalton.

By and large, my observations of water deer and muntjac together have involved individuals foraging and mostly ignoring one another. In his 1981 book Mammal Watching, however, Michael Clark mentioned that one of his tame muntjac bucks killed a water deer buck he shared a pen with while excited about a doe in oestrous. The water deer apparently didn’t fight back. This is the only account of muntjac fighting with a water deer of which I'm aware.

I'm not aware of any data on interactions between water deer and any of the other three species with which their ranges overlap. If populations of red (Cervus elaphus) and fallow deer (Dama dama) are sufficiently high, there is the potential for competition with water deer, but the presence of robust populations of red and fallow in East Anglia do not appear to have been detrimental to the persistence or spread of water deer. Roe deer have been slow to colonise much of Bedfordshire and Cambridgeshire, and this may, in part, reflect the abundance of water deer (and muntjac) in these counties, but this remains unproven at the time of writing. Certainly, on the farm on which I have been camera-trapping during summer and winter since January 2019, roe are relatively common and I have recorded females with twins during four summers despite sustained water deer (and muntjac) presence.

Other wildlife

The Norfolk Bird and Mammal Report for 1997 carried a note about the apparently playful chasing of pheasants and a fox by a water deer, although there is no specific detail given. Sharon Scott and I have observed foxes hunting for small mammals in the same fields where water deer are grazing or resting, without apparently generating any significant interest. Similarly, I have several trailcam videos of foxes and water deer within a few metres of one another, even walking past each other, without showing any particular interest. That said, John Heathcote has sent me video footage of a water deer chasing a fox, something he tells me he has seen on many occasions on his Norfolk estate. Endi Zhang, during his Ph.D. studies at Whipsnade in the early 1990s, recorded that foxes killed 86% of fawns born at Whipsnade and that the zoo had to reinforce some of their enclosures to prevent foxes getting in. Similarly, in a 2014 article to Sporting Rifle, Paul Childerley considered that "keepered ground has been the key to [water deer] survival and subsequent establishment in the wild" owing, in part, to fewer foxes.

Broadly, there are no data of which I'm aware to suggest that foxes represent a significant threat to healthy adult water deer, their main impact being on fawn recruitment, but I have seen footage from Germany of a fox taking (or attempting to take) an eight-month-old fallow fawn. The fox was shot as soon as it had pinned the fawn, so it is impossible to know whether it could've killed the animal. I have also seen photos of foxes carrying dead white-tailed deer (Odocoileus virginianus) fawns, although it is unknown how the foxes came across them. The fallow and whitetail fawns were both larger, although perhaps not heavier, than most mature water deer.

In their extensive report on deer impacts in the Norfolk Broads, published in February 2025, the Broads Authority note that, based on thermal drone surveys, water deer are clearly the most abundant species, especially in the fens and marshes in the southern catchments where densities may exceed one per hectare, above the densities reported to trigger damage. Increased browsing damage from these and red deer has also been reported, including of water deer feeding on milk parsley (Peucedanum palustre), which is a vital food plant for caterpillars of the endangered swallow-tail butterfly (Papilio machaon). Freelance swallow-tail researchers Kevin Radley and Hannah Breach told me, in May 2025, that the deer "are grazing eggs and caterpillars along with the plants so potentially reducing both the butterfly and the food plant", although there's more work to be done to understand how significant this is for the butterflies.

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 of which are 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.

Plants

The most obvious way in which deer interact with plants is by eating them, sometimes browsing or grazing to the extent where recovery is prevented. It is also well known, however, that like many other mammals, deer can aid dispersal by carrying seeds, either on their fur or in their digestive tract, and depositing them away from the parent plant. The dispersal of seeds through ingestion and defecation by animals is known as endozoochory, and I know of only one study involving water deer, the results of which were published in two papers, one in Global Ecology and Conservation in 2020 and the second in Seed Science during 2022.

In the Civilian Control Zone (Paju City, Gyeonggi Province) of South Korea, adjacent to the Demilitarized Zone between South and North Korea, Seoul National University biologists Seung-Kyung Lee and Eun Ju Lee identified 35 plant species in the pellets of water deer they collected between April 2017 and March 2018. During the feeding trials, only about 30% of the seeds consumed were recovered in the droppings (i.e., 70% were at least partially digested by the deer). In germination tests, 1,655 seeds of 18 families, 29 genera and 35 species germinated when extracted from the pellets, with eight seeds germinating per pellet group on average. Sixty-three percent of viable seeds were forbs (especially Chenopodium album, Potentilla supina, Lindernia dubia, and Stellaria aquatica), while graminoids (i.e., Cyperus difformis, Digitaria ciliaris and Panicum bisulcatum) made up 27%. Hence, species from shrubland and wet and dry meadows, where water deer were most likely to be found, were also most likely to be dispersed by the deer, accounting for 90% of the total number of species. Only just under 6% forest species were found. The greatest number both of seeds and species dispersed were found during the autumn, the peak seeding period in South Korea. In their 2020 paper, Lee and Ju Lee note that while water deer aren't what we'd consider an effective dispersal agent for seeds, the graminoid species dispersed had no special dispersal adaptations and didn't produce fleshy/edible fruits, suggesting that they hadn't evolved to disperse using water deer and Hydropotes was acting as an "ecological filter", influencing plant populations and communities in the lowlands of the country.

Some study has also gone into the impact of the deer faeces itself on the germination of seeds. In a 2014 Korean paper to the Journal of Wetlands Research, Hyomin Park and Sangdon Lee demonstrated that application of low to moderate amounts of composted water deer dung significantly increased the growth of peas (Zea mays) sown in nutrient-poor soils with nutrient profiles matching that of marshes and fallow land. Over-application of dung, or application to seeds sown in high nutrient soils impeded growth. The authors point to the carbon:nitrogen ratio of water deer dung being lower than that of other animal waste currently used as soil conditioner and, as such, that this may represent an alternative and better suited fertilizer. Following this discovery, Park, Lee, and Seunghoon Chun found that water deer faeces also affected carbon dioxide flux in soil, potentially facilitating soil material circulation. These data, published in the same journal the following year, indicate that the presence of water deer droppings increased the CO₂ flux (respiration) of the soil by as much as 20-times over the control. In other words, compared with soil without deer poo, the application of dung significantly increased the exchange of CO₂ between the soil and the atmosphere, which in turn indicates a boost in the biological processes that drive this process (e.g., decomposition of organic matter and respiration from plant roots and microbes). Despite the foregoing, however, in a 2025 paper to Seed Science Research, Seung-Kyung and Eun Ju concluded that the presence of water deer faeces didn't significantly increase germination in any of their trials, although they did note a number of limitations in their methodology and called for further research on the topic. We also do not know whether passage through the gut of water deer affects the germination potential of seeds (i.e., whether seeds exiting in pellets are more or less likely to germinate than they would've been prior to being eaten), although it is perhaps unlikely. Data provided by Diego Torres and colleagues in their meta-analysis of the influence of mammalian gut passage on seeds, which looked at 115 mammal and 448 plant species and was published in Mammal Review in 2020, suggest that deer gut passage does not enhance the germination potential of seeds, although their literature analysis included only three deer species (Dama mesopotamica, Odocoileus virginianus and Odocoileus hemionus).