Animals
Check out more information about the waterbuck in the links below!
Natural HST per Q1,2,3
Natural History Questions
This area will be managed by Robin Vaughn, and will offer some basic information on the behavior, ecology, and history of the waterbuck (Kobus ellipsiprymnus).
Q1. What is the wild habitat of waterbuck?
A1. Waterbuck are distributed throughout Angola, most of southern Zaire, western Kenya, Uganda, and from Ethiopia to Senegal (Skinner 1990). They are typically associated with water, yet are found in diverse habitats including swamps, floodplains, rocky hills, and other environments. Spinage (1982) recorded a mean of 5 dry months and 7 wet months in their habitat during an in-depth study in
Uganda. He also noted a preference of females and bachelor males for highlands as opposed to lowlands; territorial males were distributed more evenly.
Q2. When are waterbuck most active and why?
A2. Spinage (1982) found that waterbuck in Uganda typically grazed for a couple of hours after dawn, then ruminated for about 1 hour, then continued to feed throughout the day. He found peaks in feeding just after noon and about an hour before dark. At night, they typically dozed with eyes half closed.
Relative to activity budgets (Spinage 1982), females during the dry season grazed for about 60% of the day, ruminated for about 20% of the day, rested without ruminating for about 10% of the day, and did other activities for the remainder of the day (e.g., drinking water, walking). Males (during dry and wet seasons) grazed for about 40% of the day, ruminated for about 20% of they day, and rested for about 15% of the day. At nighttime, males fed with increasing frequency from 10pm until 12am (feeding about 50% of the time from 12-2am), then with decreasing frequency until 6am. Females typically nursed calves before 11am, corresponding with a drop in the feeding activity of the mom.
Q3. In the wild, are waterbuck primarily arboreal, terrestrial, or aquatic?
A3. Waterbuck are aquatic/terrestrial, preferring habitats near water and high quality grasses (Skinner 1990).
Q4. What are the main threats to waterbuck in the wild? What are their main predators? Are there any anti-predator behaviors? Where and how do they seek refuge? What does fearful behavior look like?
A4. In the wild, the main threats to waterbuck include predators, disease, and starvation; predation is the main cause of death for fawns (Spinage 1982). Hyenas consume fawns, while lions consume all ages of waterbuck. To reduce predation on their calves, female waterbuck conceal themselves during birth, and appear to ingest defecations of their calves.
When bucks encounter lions, they do not flee, but instead warn others by snorting and indicating the position of the predator (Spinage 1982). Females are generally more alert than males, and they usually get out of the way at the first sign of danger, running away with their necks held stiffly and legs brought sharply up and down. Hurried movement is usually an alarm signal, and waterbuck react to it instantly.
JP: Interpretive naturalists repeat the storyline that waterbuck escape into the water from predators. I did not find any evidence for this in Spinage (1982). However, he does say that individuals suffering from conspecific injuries did stand in water (Spinage 1982: 147).
Q5. What are the primary sensory modalities of waterbucks?
A5. Vision, hearing, and olfaction.
Q6. What is its social structure? What is the typical group size?
A6. The social structure of waterbucks is organized into territorial males, bachelor groups, and nursery groups. Spinage (1982) found that nursery group sizes had a mean of 5 waterbucks, with a range of 1-70; bachelor group sizes contained a mean of 2.5 animals (including “groups” of 1 male).
JP: Spinage (1982:219) counted female group sizes at 12 study sites and reported the means and ranges of values for the wet and dry seasons. The means were on the order of 3-5 females. The largest female groups were at the highest and lowest density sites. The modal group size for both males and females was 2 individuals. Bachelor group sizes did not vary significantly with density.
Q7. Does the social structure change seasonally or throughout the waterbuck’s life?
A7. In winter, when food is less abundant or more scattered, groups become smaller and more fragmented (Spinage 1982). When food (and animals) is more abundant, nursery groups or peer groups may form. At some sites, female group size increased in the wet compared to dry season, and at other sites the reverse trend appeared (Spinage 1982:219). Large groups were more likely in the morning than in the evening, possibly related to higher risk of predation at night. Large groups were more likely in areas with higher population density. Adults are agonistic toward both male and female juveniles, after weaning, which usually occurs about 9 months. Females may wander and are likely to disperse at this age. Spinster groups are usually 1.5 to 3 years, and bachelor groups contain males 1-6 years old (occasionally as young as 0.5 yrs). Females appear to wander until they calve the first time, then to return to that calving site in subsequent years.
Seasonal changes are influenced by latitude and age/sex categories (Spinage 1982:235). In Zambia, there is a birth season (Hanks et al. 1969 cited in Spinage 1982:233).
Q8. Do waterbuck defend territories? Do they maintain a home range? What is the size of their home range/territory?
A8. Male waterbuck are territorial, while nursery and bachelor groups reside on a home range. Sizes of territories are quite variable, and appear to depend more on intra-specific competition than surface area. Mean territory size found by Spinage (1982) was 143-226 hectares (360- 558 acres); in other locations territory sizes varied from 25-250 acres (MacDonald 1984). Overall waterbuck density appears to depend on resources (i.e., food), and densities have been found to vary from 1-100 individuals per square kilometer (MacDonald 1984). Although male waterbuck are territorial, about 50% of territories contain satellite males (MacDonald 1984), who may help defend a territory.
JP: For comparison, the size of the main pasture is 417 acres. Since averages may be deceptive, I checked Spinage (1982: 241) and found that 6-8 bucks maintained discrete ranges of 4-146 ha (9-360 acres) on the Peninsula. Population density was lower on the Ogsa, and the mean large territory size was 226 ha (558 acres: Spinage 1982:244). Males started to defend a territory at 6 years, peaked at 9 years and the oldest was 11 years (Spinage 1982: 243). Males in their prime (8-9 yrs) defended larger territories and had more female visits than those that were younger or older. The average home range for the females is 600 ha (1482 acres: Spinage 1982:224).
Q9. How do waterbuck advertise their home range or territory? How do they attract a mate? Who displays?
A9. Males typically use frontal and lateral displays (e.g., standing very erect with their heads held up) to advertise their territories (Skinner 1990). They may also lower or shake their heads. They court females by rubbing their faces and the base of their horns against the female’s back, and they may rest their head on top of the female’s back, or tap females between the hindlegs with their forelegs.
Q10. Where do waterbuck raise young? What material do they use to build nests/prepare dens? Are both sexes involved in rearing young? Are the young precocial or altricial? How are their young fed?
A10. Female waterbuck conceal themselves to give birth (Spinage 1982), and typically raise young in a nursery group. Young are precocial. They feed via nursing when young, then transition to grazing. Post-weaning, young waterbuck typically maintain their relationship with their mothers.
Q11. How do waterbuck locomote through their habitat?
A11. They walk, trots, or gallop.
Jane says: In the book by Spinage, he explains how the waterbuck stay in one place and do not move or migrate long distances like the wildebeest on the Serengetti.
Q12. What is the waterbuck’s diet type in the wild? Does diet change seasonally or by age?
A12. Waterbuck are primarily grazers, but they also eat some browse (Skinner 1990). They balance protein-deficient browse consumed during the dry season with protein-rich wet season browse (Spinage 1982).
Q13. What do waterbuck feed on in the wild? What variety of food does it need to eat? What behaviors does it use to locate/procure/store different types of food?
A13. Grasses/plants consumed in the wild include couch grass (Cynodon dactylon), buffalo grass (Panicum maximum), spear grass (Heteropogon contortus), finger grasses (Digitaria species), broad-leafed blue grass (Andropogon amplectans), red grass (Themeda triandra), reeds (Phragmites communis), bulrushes (Typha capensis), umbrella thorn (Acacia tortilis), and marula (Sclerocarya birrea) (Skinner 1990). Feeding movements are partly imitative (Spinage 1982); thus, grasses are located partly by following other waterbucks. Food is consumed primarily via grazing, but also by browsing.
Q14. Where do waterbuck sleep or rest? Does that change seasonally?
A14. Waterbuck sleep on the ground year-round.
Q15. When do gestation, birth, and weaning occur?
A15. Gestation lasts for about 280 days (Spinage 1982). Births occur throughout the year, and females typically give birth to a single calf. Reported peaks are in Aug., Nov., and Dec. in Uganda (Spinage 1982); and Oct., Feb., and Mar. in South Africa (Skinner 1990) (note – this is in the southern hemisphere). For females, nutrition appears to be more important during the 1st half of pregnancy than during the 2nd half (Spinage 1982).
Fawn mortality is high, and about 50% of calves die before weaning (Spinage 1982). For those who live, the young are weaned at about 276 days. Waterbuck are “hiders” during the first 2-4 weeks of their lives, meaning that they spend their time in-between maternal nursing visits hiding in tall grasses. During this time, mothers typically visit their calves about once a day; they locate calves by calling them with bleats or snorts (Skinner 1990). After calves are about 4 weeks old, they follow their mom almost continuously, but hide when they lose their mom (Spinage 1982). When a female wants her calf to follow her, she may hold her tail vertically or horizontally.
Q16. What are growth patterns of waterbuck?
A16. Females obtain adult weight by their 4th year, and males by their 6th year (Spinage 1982). However, adult length of the lower leg is obtained in the 3rd year. Horns are 1st visible (as points) at 8 months.
This is a very interesting web site and project.
Congratulations on the excellent work
New Waterbuck calf sighted in Main pasture near the “Big Tank” on 10 Mar 09. Est. age is 2 weeks. Dam had no visible tag or other identifier.
We have now identified the mother of this calf as Slit Ear, on the basis of suckling.
Q: How do the waterbuck compare with other species in terms of gestation and other life histories?
A: See this table compiled by Adam Eyres
http://wfsc.tamu.edu/jpackard/scienceinaction/GestationPeriods.pdf