Social Aspects of Wallowing Behaviour in Red Deer Herds

1. What they did

Wallowing in mud is well known in deer and cattle, but earlier work on deer mostly linked it to the rut, hot weather, biting insects or the moult. The authors noticed red deer wallowing in other seasons too and asked what social role wallowing might play.

They drew on observations they had already made for other studies:

• Two enclosure herds in the Black Forest in late winter. One held a 5-year-old stag, a 6 to 7-year-old hind with her calf, and a yearling hind. The other held an old but still dominant stag, a spike, three hinds and a calf. Every animal was known individually and its place in the rank order was known. There were more wallows than animals in each enclosure.
• A free-ranging alpine herd of about 150 red deer in summer, mostly stags in velvet with some barren and yearling hinds, on a high pasture with many wallows big enough for 20 to 30 stags at a time. Few animals were individually known and none were marked, so the authors sorted stags into age classes by antler length, measured by eye in multiples of ear length.

They described typical wallowing events in detail, counted who displaced whom at the wallow in one enclosure, and counted how many animals of each class wallowed in two summer wallowing events.

2. What they found

One wallow at a time

• Wallows were plentiful in both the enclosures and the alpine area, yet a herd usually used only one wallow at a time, even with many empty wallows nearby. That one wallow could not hold everyone.
• Wallowing could be started by any animal, of any age. Others were drawn in by the sight or sound (pawing, snorting, groaning) of animals already wallowing, and the wallow filled within a very short time.

A ritual before wallowing

When there was time, the deer followed almost the same steps: pawing the mud with one front leg, then the other; touching and gently rubbing the mud with the forehead; kneeling on the forelegs; lying down; and rolling from one side over the back to the other. Hinds rolled right over often; an antlered stag did so only once.

Rank order at the wallow (enclosures)

• In two detailed events in February, the dominant stag repeatedly pushed hinds, the yearling and the calf out of the wallow with antler threats and chases, sometimes without wallowing himself. The older hind in turn chased, kicked and bit the yearling hind and the calf to keep them out.
• In the Aildwald enclosure, 37 competitive encounters were recorded: 18 by the stag, 13 by the older hind and 6 by the yearling hind, so encounters became fewer further down the rank order. The calf never displaced anyone, but threatened back 3 times. The authors saw similar “nuisance” behaviour from calves in free-ranging herds and put it down to calves not yet having a place in the hierarchy.
• Events often ended in play, such as a game of “tag and catch” lasting about 10 minutes with the whole group taking part.

Mass wallowing in the summer stag herd

• The big herd wallowed together repeatedly, mostly between 13:00 and 16:00, when the animals regrouped after dispersing into the forest in the morning. In the enclosures, wallowing happened at any time of day.
• About half the herd wallowed in each of the two fully recorded events (73 of 147 animals, and 47 of 91).
• Wallowing was concentrated in the largest-antlered stags: 84% and 92% of stags with antlers about 3.5 ear lengths, and 82% and 86% of those with 4 or more, compared with 8% to 12% of stags with the shortest antlers. A drawing from a photograph shows mainly big-antlered stags in the wallow and smaller ones only standing by.
• Stags in velvet were generally very tolerant of each other. The little pushing, threatening, kicking, biting and chasing that did occur was concentrated around wallows and just before resting (over the best resting spots). Competition happened mainly between stags with similar antler length.
• Afterwards, younger stags often frolicked and jumped while others rested beside the wallow. Events lasted from 10 to 15 minutes up to 30 minutes or more, sometimes ending in a sudden, flight-like departure, especially when older, high-ranking stags led it.
• Animals that had wallowed were easy to tell apart: their coats were grey or blackish with mud, while the others stayed bright red. The colour depended on the wallow: peat wallows rich in organic material, or more loamy ground.
• On days without an opening wallowing “party”, the big herd was more spread out over its range, often for longer.

3. What they concluded

• Wallows were not in short supply, but because a whole herd crowded into one wallow at a time, that wallow became a limited resource, and the rank order showed itself there. The authors see this as the basis of the social side of wallowing outside the rut.
• Wallowing is often started by younger animals and seems to draw in older, dominant ones, leading to competition that displays rank.
• In summer, food is plentiful and stags in velvet do not defend their rank all the time. The authors conclude that wallowing and the competition around it help integrate younger animals into the stag (bachelor) herd. This may be linked to the display role of wallows and wallowed stags in the rut.
• Because the summer herd usually wallowed at the start of its shared activity periods, the authors suggest wallowing helps synchronize the herd’s activity.

6. Other technologies, skills or innovations

• Age classes of unmarked stags estimated by eye from antler length, as multiples of ear length.
• Behaviour sequences recorded from photograph series and shown as drawings.