Caudal flags in porcupines

Various mammals possess a caudal flag. This is defined as a pattern of dark and/or pale on the tail, in some cases extending to the adjacent rump or haunches, that is inconspicuous when the figure is stationary or at rest, but conspicuous when activated by movement.

Typical examples of caudal flags occur in

'Porcupines' (https://en.wikipedia.org/wiki/Porcupine) are two families of rodents, namely Erethizontidae and Hystricidae, in which certain species have evolved extreme defences in the form of spines (https://www.inaturalist.org/journal/milewski/65187-similarities-differences-between-the-porcupines-of-different-hemispheres-erethizon-vs-hystrix-part-2#).

In this Post I ask 'which of the 28 species of porcupines possess a caudal flag'?

The answer seems to be: three species, namely Atherurus africanus and two of the eight species of Hystrix. However, all of these are odd compared with other mammals.

The caudal flag in Atherurus, which is pale (https://ainawgsd.tumblr.com/post/181842995325/embed and https://www.agefotostock.com/age/en/details-photo/african-porcupine/FTF-R10000143/1), is odd in that

  • it functions as much audially as visually,
  • it is easily lost, during the lifetime of the individual, by means of autotomy, and
  • it may be conspicuous only in ultraviolet.

The two species of Atherurus share the same design of the tail, in which the hairs of the tassel produce a rattling sound when shaken (https://animaldiversity.org/accounts/Atherurus_africanus/). However, it is only in A. africanus that the paleness of the tassel qualifies as conspicuous, at least in terms of the spectrum visible to the human eye.

The caudal flag in Hystrix africaeaustralis and H. indica (https://www.alamy.com/stock-photo-indian-crested-porcupine-hystrix-indica-also-known-as-the-indian-porcupine-124427947.html and https://www.alamy.com/stock-photo-indian-crested-porcupine-hystrix-indica-also-known-as-the-indian-porcupine-124427951.html), which is likewise pale and produces rattling sounds, is odd in that

  • it functions as much audially as visually,
  • it becomes visible only when the pelage of the body is erected, and
  • it is less conspicuous than the dark/pale pattern of the pelage of the posterior part of the body.

Although some photos of Trichys (e.g. https://www.ecologyasia.com/verts/mammals/long-tailed-porcupine.htm) show the tail tassel to be pale, this probably does not qualify as a caudal flag.

Posted by milewski milewski, May 17, 2022 10:54

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