Surprising differences in displays of the tail between the blackbuck and other gazelles

@tonyrebelo @jeremygilmore @koenbetjes @tandala @oviscanadensis_connerties @beartracker @paradoxornithidae @ludwig_muller @davidbygott @capracornelius

All ruminants with visible tails can swish or flick the tail, to shoo insects attracted to the anus and vulva.

However, gazelles and their relatives (tribe Antilopini, https://www.inaturalist.org/observations?taxon_id=846306) are surprisingly variable in the other uses of their tails, along lines which I have not seen mentioned in the literature.

Let me start with the genera Gazella, Eudorcas and Antilope.

Gazelles and their relatives display their tails mainly

  • in reaction to the appearance of potential predators, and
  • in social interactions within the group.

These categories naturally tend to be blurred in playful behaviours that serve to rehearse reactions to danger.

Most species of Gazella and Eudorcas tend to wag the tail conspicuously, as soon as they go from standing to walking and trotting. They then relax the tail again when galloping (e.g. see Gazella gazella in https://www.youtube.com/watch?v=mDXpdgATnBI).

One way to interpret this is that the animals are signalling to the potential predator (including photographers) that the individual is energetic and alert, and thus not worth singling out for pursuit.

However, Gazella subgutturosa (https://www.inaturalist.org/taxa/568727-Gazella-subgutturosa) and Gazella marica (https://www.inaturalist.org/taxa/568725-Gazella-marica) tend not to move the tail until running. Thereupon, it is held more decidedly erect than in other gazelles (see https://www.istockphoto.com/video/goitered-gazelle-gm483199995-26191233).

And Antilope tends to leave the tail inert throughout the locomotory sequence of reaction to potential predators (see https://www.youtube.com/watch?v=1I5jRQCI3VU), even sometimes when stotting (see https://www.gettyimages.com.au/detail/video/blackbuck-antelope-pronks-on-grassland-velavadar-stock-video-footage/918301414 and https://www.gettyimages.com.au/detail/video/blackbuck-antelope-pronk-on-grassland-velavadar-stock-video-footage/918308808).

The contrast can be illustrated by comparing Eudorcas thomsoni (https://www.inaturalist.org/taxa/74321-Eudorcas-thomsonii) with Antilope cervicapra (https://www.inaturalist.org/taxa/42416-Antilope-cervicapra).

Thomson's gazelle wags its black, long-tasselled tail with particular zeal when milling hesitantly in view of a safari vehicle (e.g. see https://www.shutterstock.com/da/video/clip-1021228609-herd-thomson-gazelles-drinking-waterhole-serengeti-tanzania).

By contrast, no amount of nervousness will get the blackbuck to wag its nondescript tail - which lacks a noticeable tassel - in similar circumstances.

Instead, the blackbuck tends to express its tension at a whole-body scale, by leaping high into the air (see https://www.gettyimages.com.au/detail/video/pronking-blackbuck-females-run-and-leap-on-indian-stock-video-footage/1B02605_0001). Such high leaping is never seen in Thomson' gazelle.

Where the blackbuck - which is the most sexually dimorphic of antilopins - does display its tail is in masculine behaviour (rivalry and courtship, extending to lekking).

Here, the adult male 'hypererects' the tail so that its tip touches the rump (see https://www.inaturalist.org/observations/66647799 and https://www.gettyimages.ca/detail/photo/indian-blackbuck-antelope-cervicapra-male-display-royalty-free-image/90065036?adppopup=true).

This looks more like an olfactory than a visual display. This is because the tail tends to be rather redundant in the whole-body showiness of the black-and-white masculine figure, as he walks with an unusual gait - which seems close to a 'perfect amble' (see https://www.inaturalist.org/journal/milewski/69307-a-new-observation-on-maternal-defensive-behaviour-in-alces-alces#).

However, nobody seems to have found a scent-gland under the tail in the blackbuck. The displays, and lack thereof, of the tail thus remain an odd aspect of this species.

Also see https://www.inaturalist.org/journal/milewski/53340-differences-among-gazelles-in-the-structure-and-function-of-the-tail#.

Posted by milewski milewski, 08 March, 2021 11:33

Comments

The following (https://www.youtube.com/watch?v=MdBJEhzpTI8) is unusual, in my experience, in showing an individual of the blackbuck wagging its tail while walking, much as several spp. of Gazella do.

Posted by milewski 3 months ago (Flag)

Even within Gazella, there is much variation.
G. dorcas flicks a lot before trotting and running, G. cuvieri and G. gazella not so much.
I have had the impression that dorcas is using it not only to signal danger but also to coordinate movement and directedness within the group and within mother-offspring bonds.
It might reflect an alert walk-away-strategy of preparedness which eventually may allow to avoid wasting energy on a panicking flight, which may always pose a risk of injuries. As you mentioned, predators I am sure will understand that they have been spotted.

Posted by capracornelius 3 months ago (Flag)

@capracornelius Many thanks for your comment. An intriguing implication seems to be that, in e.g. adults of Thomson's gazelle, wagging the tail nervously is, in part, a functional replacement for stotting. Some gazelles, such as the springbok, 'wag the whole body' as it were, whereas others, such as Thomson's gazelle, wag just the tail.

Posted by milewski 3 months ago (Flag)

@capracornelius

Your comment stimulated me to dig out my notes on the use of the tail by Gazella arabica, which seems closely related to Gazella dorcas.

The following is what I noted for G. arabica:

"When walking away in mild alarm (after snorting/sneezing), it wags the tail in a staccato way, in which the tail flicks left, then on next stroke right. This strobes the small, black tail across each white cheek of the buttocks, one side at a time."

"At the same moment as the stationary animal alarm-snorts, the tail flicks up and down. Then, as the animal walks off warily in profile, the tail is briskly flicked around, at an approximately horizontal setting. I.e. it is not wagged while hanging, and it is not erected, but instead it is wagged/flicked rapidly while being held at 'half-mast' during the walking gait. Note that the tail, although black, is small and thin; its conspicuousness in profile is a matter of movement, rather than any dark/pale contrast."

Posted by milewski 3 months ago (Flag)

The following (https://www.youtube.com/watch?v=mt0n_yjaRzA and https://www.youtube.com/watch?v=zSP_VR7iLN4 and https://www.youtube.com/watch?v=-0ejhOztiJI) show the movements of the tail in Gazella dorcas, in various gaits and situations.

What seems clear is that G. dorcas displays its tail vigorously while trotting, mainly by keeping it about horizontal and flicking/wagging it from side to side. In this way it differs from adults of Eudorcas thomsonii, which keep the tail down and wag it from side to side mainly while walking nervously, then leaving the tail inactive while trotting.

Posted by milewski 3 months ago (Flag)

The following (https://www.youtube.com/watch?v=crof4r3jOZE) shows the use of the tail by infants/small juveniles of Eudorcas thomsoni, while playfully running and stotting. The movements of the tail differ from those seen above in Gazella dorcas, mainly in that in infants of E. thomsoni there is greater tendency to keep the tail above the horizontal (https://www.alamy.com/thomsons-gazelle-stotting-image259629646.html?imageid=EFAABF8B-00A1-4CBA-8D68-53A855AA9A22&p=42009&pn=1&searchId=3c49af6cb8a3a05fe8eb462ea3360571&searchtype=0).

Even in the case of infants of E. thomsoni, the tail stops moving when the figure is fully stationary.

Posted by milewski 3 months ago (Flag)

The following (https://www.youtube.com/watch?v=VGDR3KO-yoE) is the only video I have seen of Nanger granti (subspecies petersi in this case) playfully stotting. The animals concerned are juveniles, not infants. The stotting gaits include bounding (stiff-legged) and style-trotting. Please note how inert and inconspicuous the tail is, distinguishing genus Nanger from Gazella and Eudorcas.

Also see https://www.alamy.com/two-male-grant-s-gazelles-one-is-jumping-to-show-its-fitness-and-strength-image7487010.html?imageid=5B91C283-33E2-4E25-88D4-EF2911B726D2&p=6945&pn=1&searchId=3c49af6cb8a3a05fe8eb462ea3360571&searchtype=0.

Posted by milewski 3 months ago (Flag)

@beartracker

The following (https://www.youtube.com/watch?v=jEAyuYOIGnU) nicely shows the routine wagging of the tail while walking, in Eudorcas thomsoni.

Posted by milewski 3 months ago (Flag)

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