Caudal and pedal flags in the smallest duikers

The smallest duikers (cephalophin bovids) fall within the body-size category which I have called 'bambis'. The genus is Philantomba and there are several species and many subspecies.

Because the animals are diminutive and associated with dense vegetation, it is easy to assume that they are nocturnal. However, the blue duiker (Philantomba monticola) is actually among the most strictly diurnal of ruminants. Furthermore it tends to forage in those parts of forests where the understorey is sparsest, possibly because its main foods (fruits and shed leaves) fall from the canopy. What this means is that the active figure of this species tends to be more brightly-lit than its small size and forest environs might suggest. Although it does not enter savannas, the blue duiker is more similar to the bush duiker (Sylvicapra) than to most other duikers (Cephalophus) in its usual visibility while foraging.

The above may help to explain why the tail of the blue duiker is more similar to that of the bush duiker than to those of most of the 16-odd species of Cephalophus. In both cases, the tail has a dark longitudinal tract on its dorsal surface, with white on the sides and on its ventral surface. Most species of Cephalophus differ from this: the tail possesses a tassel and tends to lack white underneath.

The main difference between the blue and the bush duiker, with respect to signalling movements of the tail, is that the diminutive species flicks its tail frequently and vigorously, not intermittently and furtively. Kingdon wrote of the blue duiker: "the...white, crinkled hairs...reflect light so well that the flickering tail resembles a small flashlight going on and off along the dark forest floor".

Another intriguing, convergence between Philantomba and Sylvicapra is that a pedal flag is additionally present in some cases. The pedal flag of Sylvicapra consists of a pale/dark contrast about the feet; although it is consistently seen only in subspecies caffra and splendidula it is already present in the infant (https://wildmoz.com/duiker/). In Philantomba the pedal flag is likewise restricted to certain subspecies and present already in infants, but takes two different patterns. A pattern similar to that of Sylvicapra occurs in at least one subspecies (https://www.biolib.cz/en/image/id359892/ and https://www.agefotostock.com/age/en/details-photo/blue-duiker-cephalophus-monticola-philantomba-monticola/RDC-ad_75447) but has seldom been photographed. The other pattern consists simply of pale pasterns and is present in some individuals but not others.

Although far more photos are needed of the various species and subspecies, the following illustrate these patterns:

caudal flag (small) of Philantomba monticola monticola https://www.youtube.com/watch?v=LmAAmbI5qBY and https://www.youtube.com/watch?v=IsBIBLpsTKc

caudal flag (large) of Philantomba monticola aequatorialis https://www.inaturalist.org/observations/9365312 and https://www.inaturalist.org/observations/68791428 and https://www.inaturalist.org/observations/38455414

ambivalent pedal flag of adult Philantomba monticola bicolor https://www.inaturalist.org/observations/67976262

pedal flag of infant of Philantomba monticola monticola https://www.zooborns.com/zooborns/2012/12/this-blue-duiker-baby-has-a-red-rudolph-nose.html and https://www.facebook.com/WWZAq/videos/327303988270774 and Philantomba monticola aequatorialis https://www.wrcbtv.com/story/43969640/photos-chattanooga-zoo-welcomes-baby-blue-duiker.

Posted by milewski milewski, 01 July, 2021 04:18

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The video in https://wdef.com/2020/07/30/chattanooga-zoo-gets-blue-duikers/ shows that in this unidentified subspecies the tail is relatively large and the pale under the tail is offset by dark not only on the dorsal surface of the tail but also broadly around the base of the tail. There is also a hint of markings on the feet.

Posted by milewski over 1 year ago (Flag)

In Philantomba maxwelli of West Africa, the caudal flag seems absent (see https://www.inaturalist.org/observations/11375750 and https://www.inaturalist.org/observations/1488256).

Posted by milewski over 1 year ago (Flag)

Estes (1991), page 34, states 'This species flicks its tail as regularly as a Thomson's gazelle, but up and down instead of side to side. The flickering white scut is a highly visible signal to nearby family members.'

Posted by milewski over 1 year ago (Flag)

Here is another photo showing a pale pedal flag: https://animalfactguide.com/tag/blue-duikers/.

Posted by milewski over 1 year ago (Flag)

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