Water Deer Reproduction - Suckling Behaviour

Drink up!

The suckling behaviour of water deer has been reasonably well described. Fawns are suckled roughly every four hours, meaning the dam returns five or six times over the course of a day – though Raymond Chaplin noted considerable variation between individuals: Pippa suckled her twins five or six times daily, while Becky nursed her single fawn far less often. Chaplin also observed that does may suckle a distressed fawn outside the normal schedule, adding occasional extra feeds. During the first few suckling bouts, enzymes curdle the milk in the fawn's stomach to form a dense, cheese-like mass known as a "milk lump" -- or naikuai / zhāng bao in Chinese -- which slows digestion and naturally extends the intervals between feeds, and has been highly prized in Chinese traditional medicine for centuries.

Most observers agree that the peak suckling period lasts around three weeks, after which feeds become less frequent, usually tailing off entirely by around eight weeks. Occasionally, suckling may continue for longer, however, sometimes as late as 12 or 13 weeks, and Steve Carter photographed two almost-grown fawns suckling at Titchwell Marsh, Norfolk, in mid-September 2025. Chaplin's does were at either end of this range: Becky weaned her fawn at just four weeks, while Pippa continued nursing her twins for eight. By the standards of other British deer this is a short lactation. It's not uncommon for roe (Capreolus capreolus), fallow (Dama dama), and red deer (Cervus elaphus) to suckle their offspring sporadically well into October or November, at nearly six months of age. I have never observed or read of water deer attempting anything comparable, but would be glad to hear from anyone who has.

What prompts a doe to return to her hidden fawn is not fully understood. In her 1978 PhD thesis on the red deer of the Scottish island of Rum, Marion Hall suggested, however, the most likely trigger is the physical discomfort of a full udder:

"The mother's approach is possibly stimulated by a full udder, and if male calves do take more milk from her during each visit, so that it takes longer for her udder to become full again, this may explain the tendency for male calves to be visited less frequently than females."

It's an intriguing idea, and one that may well apply to water deer too. At Whipsnade, Endi Zhang observed that dams typically visited their fawns five or six times a day, each visit lasting a few minutes (two minutes on average) and combining suckling with grooming. He described two distinct patterns of initiation. In the first few days after birth, the dam would approach the fawn directly, sniff and lick it, and the fawn would rise to suckle. Once the fawn was a few days older, the doe would halt five to ten metres (16-33 ft) away and stand motionless, fixing her gaze on the spot where the fawn lay hidden; within seconds the fawn would rise and come to her, sometimes making nose-to-nose contact before nursing began. (As fawns grow older they become increasingly independent and find their own hiding spots, so the dam presumably returns only to the approximate area rather than knowing exactly where her fawn is.) Zhang also noted that very young fawns appeared to suckle for as long as they wished, but that when older does began terminating bouts themselves – raising their hindquarters and stepping sharply forward to break contact. At Branféré Zoological Park in southern Brittany, Christiane and Robert Mauget found that 63% of suckling bouts were initiated by the dam rather than the fawn.

Fawns appear to suckle from all four teats, though Chaplin observed that those in the groin were sought preferentially. This is interesting because in other species -- red deer and pigs, for example -- it is the anterior teats that produce the highest volume and most concentrated milk and are therefore most competed for, though no equivalent studies exist for water deer. In his PhD thesis, Zhang described the progression clearly:

"When very young, fawns searched for the teats at different parts of the dam's body, most often at the front legs, but when they were a few days old, they immediately rushed towards the inguinal region."

Water deer fawns also exhibit what is sometimes called a "food stroke" or Milchtritt ("milk step"): a behaviour recorded across several deer species in which the suckling young makes sharp, rhythmic upward kicks with one or both forelegs against the mother's flank or groin, apparently to stimulate milk flow. In a 2011 paper in Biological Bulletin Reviews, Vladimir Prikhod'ko and Elena Zvychainaya described this behaviour in musk deer and noted its occurrence in water deer too, citing Hans Frädrich's 1966 paper in Zoologischer Garten – a reference I have not been able to verify directly. Zhang's own thesis records "the 'milk step', where fawns make rapid kicks with one front leg, was often observed", and Dubost and colleagues described the same behaviour as "blows of young with one foreleg to the female's hind leg". Stefan Stadler, studying the same Whipsnade population, noted the milk step alongside a rapid upward thrust of the head. Such headbutting is known to stimulate the milk ejection reflex (let-down) in several ungulates, though in Stadler's observations it appeared to cause the mother obvious discomfort, frequently prompting her to terminate the bout.

Nursing is occasionally done with the doe lying down -- more likely in the hours immediately after birth -- but both doe and fawn typically stand. The body position matters: in a 1998 paper in Acta Theriologica Sinica, Zhang described the characteristic posture required for successful nursing:

"Successful suckling seemed to depend on the dam and the fawn getting into the 'inverse parallel' position described [in] sheep. In this orientation, the fawn's muzzle pushed against the teat while dam stood firmly with her head turned back, nosing at the fawn's hindquarters. Her back was arched and her hind leg extended in a way which raised the teat and made it more prominent."

Suckling bouts are short and shorten further as fawns age. At Branféré Zoological Park in southern Brittany, Gérard Dubost and colleagues recorded a mean duration of around a minute and 35 seconds in the first week after birth, rising to just under two minutes at two to three weeks, then falling steadily to just over a minute at four to six weeks, and only 42 seconds by seven to nine weeks. At Whipsnade, vegetation often obscured the fawns, but Stadler managed to observe 74 suckling bouts averaging around a minute each (mean 57 seconds). In 43 cases where sex could be determined, females suckled for an average of 75 seconds and males for 55 – a difference that, while suggestive, was not statistically significant. The age-related decline seen at Branféré was mirrored at Whipsnade: bouts averaged 102 seconds in the first month, 40 seconds in the second, and 27 seconds in fawns older than two months. On the whole, male and female fawns appear to suckle for broadly similar durations, and while two fawns may nurse simultaneously, a doe with several young may equally feed each one in turn.

The shortening of suckling bouts with age likely reflects several overlapping factors. The initial need for a high nutrient intake to fuel this species' rapid early growth may demand longer bouts at first; Zhang observed that fawns at one to two days old suckled weakly and inefficiently, requiring extended feeding sessions before settling to around 43 seconds per bout by a week old. Hand-reared fawns collected from a reserve in China showed the same pattern: Hua Shen and colleagues reported in a 2007 paper in the Journal of Animal Husbandry and Veterinary Medicine that young fawns had little instinct to suckle and had to be force-fed, remaining poor sucklers until roughly a week of age – "eats less and spits out more", as the team memorably put it. As Chaplin noted in Deer, it is also worth bearing in mind that a fawn's stomach is not built to handle large volumes of fluid: the capacity is small, the milk is concentrated, and frequent short bouts suit the system better than long infrequent ones.

Stadler remarked that fawns younger than five days often looked visibly exhausted after nursing, which probably explained why they sometimes appeared to end bouts of their own accord. By two weeks, stronger and more robust, the dynamic had reversed: it was now almost invariably the mother who called time, most often simply by walking forward a step or two.

We know nothing about alloparental care -- also known as cooperative breeding, where a dam suckles or tends a fawn other than her own -- in wild water deer, and the species' broadly solitary nature suggests it may be uncommon. In captivity, however, where animals are kept at higher densities than they might naturally tolerate, it has been observed repeatedly. Peter Scherpe's 1971 thesis described an "aunt" figure in his captive study group who regularly groomed and suckled another female's fawn. At Whipsnade in August 1987, Stadler documented a male fawn nursing from an unfamiliar female who initially accepted him; after about 15 seconds she sniffed him, apparently registered the mistake, and moved sharply some 20 metres (66 ft) away to resume feeding. More typically, females responded to strange fawns with open aggression, kicking out at them with their forefeet; something I have observed both bucks and does do.

The most detailed picture of alloparental behaviour comes from Branféré Zoological Park in southern Brittany, where both Gérard Dubost and colleagues and Christiane and Robert Mauget documented it extensively. In their 2009 paper in Current Zoology, the Maugets reported that just over 10% of suckling bouts they recorded were non-filial. Females did not reject unrelated fawns outright if they were already caring for their own young, but invested significantly less in them: a female would groom her own fawn around 55 times on average, compared with roughly three times for an unrelated one, and rested with her own fawn for a cumulative total of around 86 minutes versus approximately three for a stranger's. Writing in Acta Theriologica in 2011, Dubost and colleagues noted that suckling and cleaning of unrelated young was common at Branféré, but never substituted for true maternal care – all fawns that lost their mother within the first eight days of life died, despite receiving allosuckling from other females.

More recently, Li Min's 2022 Master's thesis described similar patterns at Huaxia Park, where females occasionally groomed and suckled fawns that were not their own, though with markedly less investment: biological fawns were suckled 3.5 times more often and for 2.7 times longer than unrelated ones. One notable exception was a female who adopted an orphaned fawn after its mother died, nursing it more frequently and for longer than other dams nursed their own young. Cortisol analysis of droppings suggested that fawns receiving allosuckling were no more physiologically stressed than those nursing from their biological mothers – a finding that, given the disparity in care, is perhaps surprising.

Suckling is not always successful, particularly in very young fawns or when dam and fawn fail to align in the inverse-parallel configuration (head to tail) that appears necessary for nursing to proceed. Mothers sometimes reject attempts outright. One particularly well-documented example, observed by Endi Zhang at Whipsnade on the afternoon of 6th June 1993, illustrates the persistence this can demand: a male fawn made ten attempts to suckle over a 12-minute period while trailing his dam, all of which she rejected, though she did pause to groom him. Thirty minutes later he tried again -- 18 more attempts -- before finally being allowed to nurse for 37 seconds.

Milk matters

Data on Chinese water deer milk are sparse. The Animal Diversity Web states that the milk is high in protein and antibody content, though without citing a source. Chaplin describes it as "rich and nourishing, with the first few feeds being predominantly colostrum", which is consistent with what we know of ungulate physiology more broadly. Because the epitheliochorial placenta of ungulates blocks the transfer of immunoglobulins -- the large protein molecules central to antibody production -- fawns are born in a hypo- or agammaglobulinaemic state, with few or no circulating immune proteins, and must take in colostrum rapidly after birth to acquire passive immunity. Yong Xia and colleagues, writing in Modern Preventative Medicine in 2008, found that water deer colostrum is around 39% protein and contains 17 amino acids, seven of them essential. Inorganic analysis revealed a calcium content of almost 960 mg per 100 g of dry powder, alongside copper, manganese, zinc, and other trace minerals.

Chaplin analysed a small milk sample and found it contained 18.4% total solids, 6% fat, 8% protein, and no lactose – a notably different composition from both cow's milk (approximately 3.6% fat, 3.3% protein, 4.1% lactose) and human breast milk (3.5% fat, 1.5% protein, 7% lactose). In some deer, red deer among them, milk composition shifts across the lactation period; whether this is true of water deer is unknown.

Zhipeng Li and colleagues analysed the milk of eight does kept on a farm in Yancheng, China, for bacterial content, and found a notably high microbial diversity – higher than that recorded in reindeer. The dominant genera were Pseudomonas spp. and Acinetobacter spp. (each around 12% of genera present), with smaller contributions from Chryseobacterium spp. and Corynebacterium spp. (each around 5%) and Comamonas spp. (4%). At the phylum level, Proteobacteria dominated (60%), followed by Actinobacteria (15%) and Bacteroidetes (14%). The stress of labour is known to increase gut permeability in many mammals, allowing bacteria to translocate from the gut into the milk; writing in Scientific Reports in 2017, Li and colleagues suggest that the demands of water deer's characteristically large litters may intensify this stress response, resulting in greater permeability and a correspondingly richer milk microbiome.

This rich milk fuels rapid early growth. At Whipsnade, James Kirkwood and colleagues tagged and weighed 79 mother-reared fawns living free-range in the park, finding that growth followed a roughly linear trajectory across the first month: fawns began at around one kilogram and reached almost three kilos (6 lb 9 oz.) by 30 days, gaining an average of 70 grams per day. Hand-reared fawns in the same study gained 50-70 grams (1.7-2.5 oz.) per day, falling to around 40 g (1.4 oz.) per day after weaning. In a 1990 paper in the Journal of East China Normal University (Mammalian Ecology Supplement), Li-xing Sun and Helin Sheng reported that fawns in Shanghai gained 90-106 g per day (3-4 oz.) consistently across their first month, reaching around 12 kg (26 lb 6 oz.) by six months of age. Taken together, these figures suggest fawns can add between 50 and 100 grams (up to 3.5 oz.) daily in the first month or so, and have reached roughly 80% of adult body weight by six months – a growth trajectory that, even by the standards of small deer, is impressively fast.