Water Deer Activity - Types of Activity

It is again studies in captivity that have provided some insight into the activities in which water deer can be found engaged. I will summarise some of these studies here because they're the only data we have, but it should be recognised that these are not necessarily representative of wild deer.

Most direct observation studies suggest that most of a water deer's active period is spent feeding. - Credit: Marc Baldwin

At Whipsnade, Endi Zhang found that, on average, feeding was the main activity during the daytime. Indeed, over the study as a whole, grazing accounted for about half of the time they were observed to be active during the day, although this was closer to 60% in the summer. Resting took up about 40% of their time fairly consistently across the seasons, while standing, social interactions, walking and grooming constituted the remaining 12% or so. There were some sexual differences in these patterns, with bucks devoting more time to both walking and social interactions than does.

We have very few data on the activity budgets of wild deer, although the scant observations we do have they appear to align with the behaviour of captive individuals in at least some aspects. Both sexes are “on the move” and interacting socially the most during the winter rut, while females spend much of their time feeding during the summer, when the demands imposed by lactation are high. I know of no direct observation studies of water deer activity during the night, but on a handful of occasions I have made observations in Bedfordshire late into the evening during mid-December, I have found bucks and does either resting together or feeding.

In common with other species of deer, while at rest water deer lie on one side of the body, with their legs tucked up against their stomach. While resting or ruminating, the deer's head will be upright, and the ears erect as the animal periodically scans for danger. In captivity, I have seen deer propped up against fences or walls, exhibiting a more upright positioning of the body, the legs almost underneath the animal. During sleep, the head is brought down and tucked against the legs, giving a curled position similar to that of a cat, with the ears remaining erect. The choice of resting site varies, but the species appears to prefer areas either with vegetation sufficiently tall and dense to hide them completely or, in open landscapes, field centres that presumably provide a clear panorama to scan for approaching danger. In my experience, water deer can 'disappear' into only a few centimetres of vegetation.

A water deer buck curled up asleep. Head on the ground or tucked up (cat-like) indicates sleeping, while deer at rest or ruminating will lie on one side with their feet tucked in but head held up. - Credit: Marc Baldwin

Francois Feer, in his 1982 paper, described how, as a prelude to lying down, they sniff the area before raising a front foot that is rocked or swung forwards and slightly to the side, as if 'hoofing into the void'. This is repeated alternately with both front feet, then both rear feet, before the animal sniffs the ground again, turns around and lays down. Feer noted that this sniffing and turning may be completed several times before finally settling, and he observed the same pattern prior to lying down in short and tall vegetation, although the feet were lifted higher in taller vegetation. As the activity seems to have the effect of removing and/or flattening the vegetation, Feer considered the behaviour was intended to prepare the resting place in the very dense vegetation of their native habitat. I have observed the forefoot scratching ahead of settling several times, but have only seen the full sequence Feer described once.

Water deer are quite easily disturbed, and prone to fleeing. My experience, and that Arnold Cooke gives in Muntjac and Water Deer, has been that these deer primarily react to disturbance in two ways: they crouch down and try to go unnoticed, even when the vegetation is short or sparse; or they'll explode away in a manner reminiscent of brown hares, sometimes exhibiting a leaping/bounding action, legs flung out high behind in a 'semi-kick' that brings the hooves almost level with the top of their back. Cooke suggests this bounding escape, which he notes appears more common in open landscapes, may be the water deer equivalent of the pronking behaviour we see in other deer. Describing the escape behaviour in his original 1870 description of the species, Robert Swinhoe wrote:

In running they cock their ears, round then fore legs, bend rip their hind legs, hog their rumps, and scurry away with little quick leaps, very much after the manner of a Hare.”

Water deer aren't built for endurance and when fleeing in open habitats will frequently drop down into shallow depressions in the ground to hide. They can "disappear" in only a few centimetres of grass. - Credit: Marc Baldwin

While quick to flee, as tends to be the case with so-called “saltatorial runners”, water deer do not appear to be built for endurance and they will often drop down suddenly into cover once sufficient distance has been introduced between them and the source of the disturbance. Writing in 1950, Kenneth Whitehead suggested that the short distance sprint-and-drop method was probably a throwback to “their jungle days, when 'lying doggo' in dense cover was their best mode of escape”.

During his analysis of gait in 79 mammals filmed running in slow motion, published in May 1977, University of California, Davis zoologist Milton Hildebrand described how deer, including water deer, have only one suspended phase during a gallop: the “extended suspension”. This means that all feet are only off the ground simultaneously during the stretch of the bound. Hildebrand looked at which feet hit the ground first while running (the “lead sequence”) and classed water deer as having a rotary gait sequence. In other words, if the right hind foot hits the ground just before the left, so the right front foot hits the ground before the left front. To the best of my knowledge, there are no confirmed data on how fast this species is capable of running, nor the maximum distance over which speeds can be maintained.

In his 1998 book Deer of the World, Valerius Geist commented on how the saltation mode of escape employed by water deer puts great physical pressure on the lower hind legs, driving the evolution of massively muscled haunches and a long, muscular back. The haunches are certainly much more muscular and powerful than the front legs, and presumably richly endowed with fast-twitch (white or glycolytic) muscle fibres to allow the rapid propulsion from a standing, crouching or lying start. In her allometric analysis of deer limbs, Rutgers University zoologist Kathleen Scott observed that water deer were the only small cervid with markedly elongated limbs, the greatest elongation being in the forelimbs such as to produce limbs of almost equal length. Scott suggested that, although their choice of reedbed and tall grass habitat provides sufficient height of cover, the relative openness may place a greater premium on speed. Heavy undergrowth is not an environment in which speed is either desirable or necessary, which might explain why similarly sized cervids living in dense scrubby/wooded habitats (e.g. muntjac and pudu) have shortened limbs, allowing them to move more easily through brush and probably making them less noticeable.

Water deer tend to be quick to flee. They are very agile, allowing them to twist from their resting position to escape in virtually any direction (left). While fleeing they often kick out their hind legs in what might be an anti-predator action (right). - Credit: Marc Baldwin

The powerful hind quarters don't only generate explosive speed, they also make water deer reasonably good jumpers, although my experience has been that they prefer to go through or under fences where possible. As part of a project to look at reducing deer-vehicle collisions in South Korea, a team of researchers led by Hee-Bok Park, at the National Institute of Ecology, studied the behavioural response of water deer to fences of differing heights. While the deer were generally reluctant to jump obstacles, they could easily clear fences up to a metre (3 ft 4 in.) in height, doing so from a standing start. Fences between 1.2 and 1.5 metres (4-5 ft) were less likely to be crossed but could still be cleared with a running jump. A few deer were even able to jump a 1.8m (6 ft) fence.

As their name and habitat selection attests, water deer are at home in wet/flooded areas and, in common with most deer, are strong swimmers. Arnold Cooke tells me that he has only once observed a water deer swimming at Woodwalton, when he disturbed one beside the Great Raveley Drain on the east side of the reserve and it leapt into the water to escape. In Muntjac and Water Deer, Cooke recounts several observations described to him, however, including of animals swimming between areas of prime habitat on the Norfolk Broads, and a particularly interesting incident where three water deer were swimming in floodwater that had encroached into Dunwich Forest in Suffolk after a storm surge in December 2013; one individual apparently browsing on flooded gorse before swimming away through about 1.5m (5 ft.) of flood water when approached. I have only ever seen photos and video of swimming behaviour in this species. Nonetheless, in their preliminary study on the population of Zhoushan Island and adjacent islets, published in Acta Theriologica Sinica during 1984, Helin Shen and Houji Lu note that the deer swam several kilometres between the islands in the archipelago looking for food and avoiding hunters. In his detailed review of the ecology of Korea's Demilitarized and Civilian Control zones (DMZ and CCZ, respectively), published in 2013, Kwi-Gon Kim wrote of the water deer:

“[it] likes water. It swims twice a day and drinks often, especially more during summer when it is hot.”

While seemingly less common in England, water deer readily live up to their name in their native China and Korea, taking to the water to cross between islands as well as to feed on aquatic plants. - Credit: Willem van der Merwe

Interestingly, despite Kim's observation, water deer are rarely observed drinking here in England.

Finally, while I know of no resting metabolism data for water deer, Barkley Hastings and colleagues, in their 1989 paper to the Journal of Zoo and Wildlife Medicine, calculated the normal activity heart rate for water deer as 130 beats per minute, with 28 breaths per minute.