Caudal flagging in the white-tailed deer (Odocoileus virginianus) is surprisingly complex

Anyone with an interest in ungulates knows that the white-tailed deer (Odocoileus virginianus, https://www.inaturalist.org/taxa/42223-Odocoileus-virginianus) raises its tail, showing the white underside.

However, what is not widely realised is how complex, versatile, and expansive the demonstrations of alarm are in this species.

The white-tailed deer, engaged in foraging, jerks up its head in routine vigilance, then lowers the head to resume foraging. Each time it suddenly raises the head, it tends to flick the tail.

When the white-tailed deer suspects the approach of a predator, it shows various combinations of 'foot-stamping', tail-flagging and alarm-sneezing, as follows.

• The forefeet are lifted high but not stamped hard, suggesting that the main message sent is olfactory, from the interdigital glands.
• The tail may be raised to a rigid horizontal position (https://www.facebook.com/MPGWildlife/videos/753907188442406), and this seems to be a purely visual signal.
• Sometimes, the signal instead given is that the tail is flicked up synchronously with each alarm-sneeze, without any piloerection of white pelage on the hindquarters.

Variation in the repertoire thus depends on the pattern of movement of the tail, and whether white hairs are piloerected (flared) or not (https://www.youtube.com/watch?v=Bf1j33Ja1so and https://www.youtube.com/watch?v=zAVb_Jj1CC0 and https://www.youtube.com/watch?v=5fM9qlBsMYE).

Sometimes the tail remains down, but the long pelage on the buttocks is piloerected as the animal stands in initial alarm (http://mtnhp.org/thumbnail/defaultGen.aspx?itemid=391827&maxWidth=1024&maxHeight=768 and third photo in https://www.mossyoak.com/our-obsession/blogs/deer/how-to-read-whitetail-body-language).

As suspense builds, the animal may flick the tail up and down, without piloerection, while walking stiff-legged, before running.

Once fleeing begins:

• the white hairs on the underside of the tail and/or on the buttocks may be piloerected (see https://www.olo-7.top/ProductDetail.aspx?iid=57741356&pr=22.99 and third photo in https://www.welcomewildlife.com/white-tailed-deer/ and https://wdfw.wa.gov/species-habitats/species/odocoileus-virginianus-leucurus).
• the tail may be wagged from side to side while erect and flared, and
• sometimes, the animal stots (https://www.flickr.com/photos/conradkuiper/40834012061 and second photo in https://owenslaterphotography.com/category/north-american-wildlife/mammals/white-tailed-deer/).

Erection of the tail and piloerection on the tail/buttocks tend to be most frequent in

• open vegetation, and
• females and juveniles (https://www.flickr.com/photos/23326338@N04/8988960173/).

Adult males sometimes tuck the tail while fleeing, thus failing to show any caudal flag (https://fineartamerica.com/featured/high-flying-white-tail-deer-gordon-allen.html ). This may tend to be when females are absent.

The sexual difference in displays is consistent with the tendency for males to have relatively short tails and relatively short pelage on the buttocks.

I remain unsure about the incidence of stotting in the white-tailed deer, as opposed to the mule deer, or hybrids between O. virginianus and O. hemionus. This uncertainty adds to the overall complexity of the reactions of the white-tailed deer in alarm.

Posted on June 19, 2021 09:29 AM by milewski