Caudal flagging in Thomson's gazelle compared with the goitered gazelle

(writing in progress)

Eudorcas thomsoni is common in the Serengeti and elsewhere in East Africa. However, the following are the only photos I have found of adult females stotting:

This confirms that E. thomsoni erects the tail while stotting, even in adulthood.

What this suggests is that Eudorcas differs from other gazelles in having a clear dichotomy in its caudal flagging. While walking and milling around nervously, the caudal flagging consists of a hanging tail, strobed right across the white buttocks from side to side. While stotting, the caudal flagging consists of erecting the tail.

In normal running, there is no caudal flagging in adults (

However, there is caudal flagging in infants/juveniles ( and

To show the differences from E. thomsoni in caudal flagging, here is Gazella subgutturosa: and and and and and and and and

It is clear that Gazella subgutturosa typically, and consistently, flees with the tail erect. This differs from Eudorcas thomsoni, which has similar caudal flagging only a) in infants, and b) in adults while stotting. It also differs from most other spp. of Gazella.
Here are illustrations of three aspects of the camposematic displays of Gazella subgutturosa, relevant to our current discussion.
Firstly, in we see that the erection of the conspicuous dark tail in mild alarm is accompanied, while the animal is walking briskly away from the intruder, by a noticeable twitching. The tail is peculiarly stiff yet peculiarly twitchy, which I suppose informs the potential predator that the individual is fit and highly strung, as it were.
Secondly, in we see that the tail does seem to be twitched compulsively even when it is hanging down, and the animals do not seem to be alarmed. So G. subgutturosa may be similar in this respect to E. nasalis after all.
Thirdly, the following three photos were all taken in Xinjiang, western China. The first two show how conspicuously dark this rather pale species of gazelle manages to be in snowy surroundings; I suspect some kind of antisheen effect resulting from the microstructure of the surface of the hairs. The third photo, taken in the same region, shows how pale this species can look in snow-free surroundings. Because this species looks so pale in summer, its relative darkness in winter is noteworthy and supports the case for camposematism. I do not yet understand how the same pelage can have sheen effects in some circumstances but antisheen effects in other circumstances. Do you have any explanation?
Gazella subgutturosa:

Gazella subgutturosa:

(writing in progress)

Posted on September 01, 2022 03:29 AM by milewski milewski


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