Journal archives for July 2021

01 July, 2021

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 ( 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 ( and 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 and

caudal flag (large) of Philantomba monticola aequatorialis and and

ambivalent pedal flag of adult Philantomba monticola bicolor

pedal flag of infant of Philantomba monticola monticola and and Philantomba monticola aequatorialis

Posted on 01 July, 2021 04:18 by milewski milewski | 4 comments | Leave a comment

04 July, 2021

Describing the adaptive colouration of Thomson's gazelle

A bleeze is a bold pattern of animal colouration conspicuous to scanning predators even when the figure remains stationary. This is based not on hues but on dark/pale contrasts. A flag is a smaller-scale pattern of dark and/or pale which becomes conspicuous when the body-part in question is moved; this pattern is relevant both to predators and socially (i.e. for intraspecific communication). A semet is a pattern so small-scale and faint that it is insignificant to scanning predators; it is socially relevant but only in motion and only at close quarters.

Thomson's gazelle (Eudorcas thomsoni) is a suitable species to start with, because its colouration shows negligible sexual dimorphism, minimal change from birth to maturity, minimal subspecific variation, and minimal individual variation except on the forehead and rostrum. The species seems to wear graphic, stereotyped insignia except for subtle variation on the front of the face which may perhaps aid individual recognition.

Thomson's gazelle possesses a lateral bleeze (conspicuous in full profile), a posteriolateral bleeze (conspicuous when the figure is facing obliquely away), a caudal flag (when the black tail is wagged, flicked or raised as a signal) and possibly a buccal semet (accentuating the act of chewing, which is significant for social vigilance).

The following illustrate these patterns.

Lateral bleeze in adult males (see and and and, adult females (see, juvenile males (see and, and infants (see and

Posteriolateral bleeze in adult males (see, adult females (see and and infants (see There is an erectile aspect to the posteriolateral bleeze by virtue of the flaring of the fur on the buttocks, particularly in infants and while stotting.

Caudal flag (see and and The caudal flag is proportionately largest, and most likely to be erect, in infants.

The case for a buccal semet in Thomson's gazelle rests on the malar stripe pointing to the mouth. It is difficult to interpret the malar stripe, which runs diagonally across the side of the face from the eye, as having any other function. See and and

Posted on 04 July, 2021 10:24 by milewski milewski | 1 comment | Leave a comment

05 July, 2021

How the intelligence of the smallest duikers helps to explain their behaviour

Duikers (cephalophin bovids) are brainier than other ruminants (see

This may help to explain why the blue duiker (Philantomba monticola) is so diurnal, so playful, so family-minded, so deceiving in certain ways, and so specialised for 'mutual kissing' by means of both the tongue and the glandular cheeks.

Play behaviour in adulthood is generally associated with intelligent species. Ungulates tend to have about average braininess for mammals, and accordingly play in infancy but not in adulthood.

Duikers are exceptions to this, and in the case of the blue duiker adult males are particularly playful (e.g. see video in and caption to

Several kinds of small ruminants besides the blue duiker are monogamous for life, but this species has slow reproduction relative to its body size, and is unusually tolerant of juveniles remaining in the natal territory after sexual maturity. This presumably gives the offspring opportunities to learn from the experience of their parents, which is typical of primates rather than ungulates.

Females, although married, are like all ungulates in allowing copulation only at the peak of oestrus. In the face of an impatient husband, females of the blue duiker sometimes use a deceptive tactic of distraction: they 'cry wolf' using a whistle that is otherwise used only as an anti-predator alarm.

The blue duiker is the prime example of allogrooming in bovids, and perhaps in all ruminants. The tongue is far longer than can be explained in terms of foraging (see, and is used to lick a partner's fur in surprisingly frequent and extensive bouts of reciprocal grooming (see and

This intimate behaviour aids familial bonding and exceeds what can be explained by hygiene and removal of ticks. It seems analogous to mutual grooming in monkeys.

The blue duiker has a large maxillary gland running along each cheek (see and Whereas most bovids use the facial glands mainly for masculine marking of the territory, the blue duiker is odd in the extent to which the animals scent-mark each other's bodies, with females reciprocating fully.

What is more, the mutual anointing extends to simultaneous pressing of the glands to each other, thus mixing secretions. This is similar to the human 'cheek-kiss' but far more intimate. And, most surprisingly, rival males mutually cheek-press their glands together before fighting violently, in what is more like a gentlemanly 'handshake before duelling'.

Posted on 05 July, 2021 12:36 by milewski milewski | 4 comments | Leave a comment

06 July, 2021

Adaptive colouration in bambi species of Cephalophus

Bambis are a category of ruminants defined by average adult body mass, in females, of 15kg or less. Among duikers (cephalophin bovids) bambis occur in three genera.

In Sylvicapra, all four of the northern subspecies (coronata, campbelliae, pallidior and hindei/nyansae/madoqua including high-latitude ecotypes) are bambis. In Philantomba (see, all the species and subspecies are bambis. In the speciose genus Cephalophus, only four species are bambis: adersi, natalensis, harveyi and rufilatus. This Post describes the adaptive colouration of the last three species, which complement each other in distribution from southeastern South Africa across the equator to Senegal.

The bright hues of bambi species of Cephalophus are not obvious to the eyes of either the duikers or their non-human predators, which are instead sensitive to motion in dark and pale. Viewing the figures through this adaptive filter, we can ignore most of the features mentioned in taxonomic descriptions and field guide-books. All three species are effectively plain-coloured, allowing them to blend into their surroundings even in daylight. No aspect of their colouration is likely to be conspicuous to scanning predators as long as the figure remains stationary.

However, three parts of the body have patterns noticeable enough to aid social communication at close range and in motion: the tail, the front of the ears, and the mouth. Such communication remains secretive with respect to predators.

The following photos illustrate the species (harveyi is effectively similar):

Cephalophus natalensis and and and

Cephalophus rufilatus and and

The tail is small and inconspicuous when kept still. However, it is frequently flicked in normal activities, and the tassel is pale enough (natalensis, see, dark enough (rufilatus) or both (harveyi) to accentuate the motion to group-members by daylight. All three species may thus qualify as possessing a caudal semet.

Were the ears coloured cryptically in keeping with the overall colouration, they would be plain, and hard to see even in photos. Instead, the front of the ear tends to have a dark mark. For natalensis see and and and and . For rufilatus see and and and The markings hypothetically accentuate the normal rotations of listening, as well as any flicking to shoo insects, producing an auricular semet.

Finally, the mouth: in all three species the side of the mandible is pale except ventral to the overhanging upper lip, where it is dark; and the upper lip tends to have a narrow edging paler than the rhinarium. This pattern, which would be accentuated by chewing, hypothetically qualifies as a buccal semet. See and and the second and fifth photos in and The buccal semet is similar in Sylvicapra: and

Posted on 06 July, 2021 01:20 by milewski milewski | 0 comments | Leave a comment

07 July, 2021

Building a search-image for three species of blue duiker

An approximate map of the distributions of the various subspecies of the blue duiker (Philantomba monticola) is in I see two main disjunctions, namely the gap between Zimbabwe and Malawi and the gap between the East African coast and the Ugandan region. Should the blue duiker be split into three species accordingly?

Groves and Grubb (2011, despite splitting the blue duiker into ten species, regard the East African coastal form as a mere subspecies of aequatorialis of Congo-Uganda. This seems odd in terms of discontinuity of distribution and patterns of colouration.

Groves and Grubb focussed on chromatic distinctions between fawn and grey which may possibly be more distraction than taxonomically significant. Because the visual systems of neither duikers nor their predators are sensitive to hues, such variation can be thought of as 'genetic drift' rather than adaptation. It is the tonal (dark/pale), not the chromatic ('red'), aspects of colouration that are likely to be adaptively significant (i.e. produced by natural selection) and thus most indicative of speciation.

The taxa congicus, melanorheus and aequatorialis of equatorial Africa, from Cameroon to western Kenya, possess a horizontal dark/pale contrast (ineptly described as a 'stripe' by Groves and Grubb) on the hindquarters. See and and In coastal East Africa there is hardly a trace of this feature (see and The difference is one of kind rather than degree. So I suspect that sundevalli, far from being a mere variant of aequatorialis, is not even the same species.

Another example of too much variation to be plausible within a single species is in the colouration of the feet (which are not even mentioned by Groves and Grubb 2011). See and and . The markings on the feet are faint but seem absent in most other forms of the blue duiker. Unfortunately I do not know where the animals in these photos come from.

My criticism of Groves and Grubb in the case of the blue duiker is not so much that they over-split but that they may not have made the right splits.

I offer the following search-image to naturalists. It may be possible to distinguish 1) a southern species, from South Africa to Zimbabwe, 2) an East African coastal species extending inland to Malawi, and 3) a widespread species of the central rainforest block and surrounding savanna/forest mosaics including Zambia.

For those keen to 'get their eye in', please practice on and and the photos linked in my first comment below.

Posted on 07 July, 2021 06:19 by milewski milewski | 1 comment | Leave a comment

Photos cannot fully replace paint in the best field guide-books for the larger mammals

With the proliferation of photos on platforms such as iNaturalist, it is easy to assume that the kinds of paintings seen in field guide-books such as Dorst and Dandelot (1970), Haltenorth and Diller (1977) and Kingdon (1997) are 'so last-century' that they can be discarded.

Well, not so fast, in the case of artist Pierre Dandelot (see

The advantage of good scientific art, in the context of identification of species in the field, is that it reduces distracting detail and 'caricaturises' the appearance usefully.

Just as the candle was not made obsolete by the electric bulb, the deceptively rough-and-ready water colours of Dandelot (see and and and will never be fully upstaged by technical progress.

The best paintings in field guide-books can be compared to portraits of human faces. No number of high-tech photos will ever make artists like Anh Do obsolete (see

This is because seeing is ultimately done by the mind, not just the eyes, and even a realistic artist should subtly guide us where and how to look (e.g. see

Also see

Helmut Diller was a peer of Pierre Dandelot, but his busy style (e.g. see and and is memorable more for how not to than how to.

Diller's paintings are unnecessarily painstaking, and miss the key points; they confuse with detail as much as photos do, but without the accuracy.

The difference between these scientific artists:
Dandelot understood intuitively that search-images depend on interpretation and emphasis.

And so, we can greatly add, by contributing photos to iNaturalist, to the quantity of descriptive material. However, beyond a certain limit it becomes quality rather than quantity that sharpens the eye for species-identification.

And the value added by Dandelot (and to a lesser degree by Jonathan Kingdon) is similar to that added by making certain kinds of movies by artificial animation instead of real actors.

Also see and

Posted on 07 July, 2021 23:14 by milewski milewski | 0 comments | Leave a comment

09 July, 2021

Adaptive colouration in wildebeests, part 1: an introduction to large-scale, conspicuous features

Most species of ungulates have certain inconspicuous features and certain conspicuous features of colouration, depending on the range/scale.

Wildebeests (Connochaetes, are relatively large-bodied, extremely gregarious, and typically found in open vegetation. This leads to the questions:

  • what is the overall effect at a distance, and
  • how does this differ among the various species and subspecies?

All forms of wildebeests have some degree of brindling (, which in principle serves to detract from conspicuousness ( However, this is usually outweighed by features of colouration that are adaptively conspicuous to scanning predators by day.

For example, mearnsi ( advertises itself rather than trying to blend into the background ( and

What is particularly noteworthy about this genus is the diverse ways in which the dark/pale contrasts have been achieved.

So, let us examine adults of the various species/subspecies (

In gnou (, conspicuous overall darkness ( and and is achieved mainly by a poorly-understood anti-sheen quality of the pelage. This is based on the physical structure of the hairs as much as their pigmentation.

In other forms of wildebeest, this anti-sheen effect is less extreme, and is combined with a sheen effect on the rump (broadly-defined).

This combination of anti-sheen and sheen is most easily illustrated in mearnsi. The figure combines overall darkness with a pale-looking rump (

The impression of pale on the rump is produced by sheen rather than depigmentation ( and and and and scroll in and and

In albojubatus (, the beard and cheeks are conspicuously pale relative to the dark front of the face ( and and

In taurinus, the figure tends to look dark, with some degree of paleness owing to sheen on the rump. However, this is possibly the form with the least conspicuous colouration, overall ( and and and

In mattosi (, the dark mane is permanently erect. This, in combination with the dark beard and front of the face, gives the anterior of the figure in profile a conspicuously dark emphasis ( and

In johnstoni ( there is, in some individuals, a bold whitish (depigmented) bar on a dark-pigmented face ( and

In cooksoni (, the front of the face is conspicuously dark relative to the pale forequarters (e.g. see fourth photo in

Returning to gnou:

Both the mane and the tail can be conspicuously pale, by way of depigmentation.

The overall result is as follows:

To be continued in

Posted on 09 July, 2021 00:09 by milewski milewski | 20 comments | Leave a comment

Adaptive colouration in wildebeests, part 2: facial, nuchal, caudal, and pedal flags

...continued from

(The distributions of forms of Connochaetes can be seen in ; mattosi occupies the western, major lobe of the blue area, in Botswana, Namibia, Zambia, and Angola.)

We have seen that the overall colouration of wildebeests (Connochaetes) is ambivalent in terms of the distinction between adaptive conspicuousness and adaptive inconspicuousness.

The overall figure is darkest in gnou, taurinus, mearnsi, and mattosi, intermediate in johnstoni, and palest in albojubatus and cooksoni. In the former four forms, the figure is dark enough to be conspicuous at a distance even while stationary.

The following nicely illustrate the adaptive conspicuousness, in the form of overall darkness, in
mearnsi: and

No form of wildebeest is conspicuously pale overall. Furthermore, all of the pale features seen in the various forms are variable according to individual, age, soiling (particularly by dust), perspective, and illumination.

However, the following parts of the body are potentially pale enough to be adaptively conspicuous:

  • restricted patches on the front and/or sides of the face,
  • the beard,
  • the base of the mane, from crown to withers,
  • the rump, extending to the back, and
  • the long hairs of the tail.

How should we categorise the various conspicuous features of colouration in Connochaetes?

A BLEEZE is a feature of dark/pale contrast, large enough to reveal the whole stationary figure at the range relevant to scanning predators. This is epitomised by Damaliscus pygargus pygargus (

A FLAG is a relatively small dark, pale, or dark-and-pale feature that becomes conspicuous to scanning predators once the body-part concerned is moved.

There is no clear example of a bleeze in wildebeests. This is because the pale features are not large enough or consistently pale enough to be reliably conspicuous in the stationary figure.

However, in several forms, an effect similar to that of a bleeze is potentially created by the sheen on the rump, in bright sunlight near midday. This may possibly have an ultraviolet component.

The following illustrates the pale rump in mearnsi: and and sixth photo in and and

In wildebeests, several categories of flags occur:

  • facial (on the front and/or sides of the head, extending to the beard; these are further examined in part 3),
  • nuchal (on the dorsal part of the neck and the withers, i.e. involving the mane),
  • caudal (on the tail and its base), and
  • pedal (on the feet; evidence for a pedal flag in infants/juveniles of wildebeests will appear in part 5.)


A facial flag is present in albojubatus (also see part 3), and ambivalently present in mearnsi and cooksoni.

The following illustrates albojubatus, in which the front of the face is black, and the cheeks and beard are pale: and

This flag is configured in such a way that the paleness of the beard can be most obvious when that of the cheek is shaded:

The beard is not pale enough in mearnsi (see and to qualify as a facial flag, except when backlit ( and and and

The dark surfaces of the face and throat are expanded, in gnou, by dark tufts and a dark beard ( and In the case of mattosi, the dark beard is particularly well-developed (

However, in neither case is dark/pale contrast involved in these adornments. Therefore, these forms do not qualify for facial flags (except possibly in the case of infants of mattosi).

The case for a facial flag in johnstoni rests mainly on the whitish bar across the rostrum (see and However, this is too inconsistently to qualify.


The clearest example of a nuchal flag occurs in gnou (see part 1 for illustrations).

In mattosi, some individuals, in certain illuminations, show pale along the base of the mane:

In albojubatus, the withers are so pale (partly owing to sheen) that, in certain illuminations, they contrast with the lax, black mane:


The tail is so large that all forms of wildebeest probably qualify for a caudal flag (e.g. see taurinus

However, the case is strengthened in albojubatus and cooksoni, in which the blackish of the swishing tail contrasts in certain illuminations with the particularly pale and sheeny hindquarters (see and and

The simplest example of a caudal flag occurs in gnou, in which the long hairs of the tail tend to be noticeably pale. The following, of all the photos on the Web, perhaps shows this feature most clearly:

The tail-tassel of this species is usually far from white (possibly owing to dust).

However, it is large enough to be conspicuous (and probably audible) at distance when swished (see and and and and

This would be enhanced with backlighting (

For further views of the conspicuously pale tail of gnou, please see: and and and and and

The following illustrate the caudal flag in albojubatus:


Please see part 5 of this series.

to be continued in

Posted on 09 July, 2021 05:36 by milewski milewski | 11 comments | Leave a comment

Adaptive colouration in wildebeests, part 3: focussing on the facial flag

The question has arisen of which forms of Connochaetes possess a facial flag. Here I focus on the facial profile and neck (excluding gnou), looking for fairly large-scale dark/pale contrasts.

In mearnsi, there is no case for a facial flag.

mearnsi and and third photo in

In albojubatus, the case for a facial flag is based on the crisply-defined dark on the front of the face relative to the pale on the cheeks and beard.

albojubatus and and and and and and

In taurinus eastern form, there is no case for a facial flag.

taurinus eastern form and and and

In taurinus western form, there is no case for a facial flag.

taurinus western form and and

In cooksoni, the case for a facial flag is ambivalent. The cheeks are pale but the dark on the beard and front of the face is not particularly crisply-defined.

cooksoni and and and second photo in and

In johnstoni, some adult male individuals have a bold white bar across the rostrum. However, this seems insufficient to outweigh the fact that the dark front of the face is particularly narrow in this form.

johnstoni and and

In summary, a facial flag is clear only in one form of wildebeest. This is albojubatus (see and and, which is as pale as any form of wildebeest while retaining a wide and maximally dark front of the face.

Posted on 09 July, 2021 09:01 by milewski milewski | 3 comments | Leave a comment

Adaptive colouration in wildebeests, part 4: brindling

Wildebeests (Connochaetes) are odd for wild ungulates in possessing irregular, individually variable, vertical streaks, this dark fur being more pigmented than the ground-colour and of a different texture. The resulting brindling reflects light less than the ground-colour does, owing to both pigmentation and the structural properties of the hairs. Skin-folds are also involved (e.g. and zoom in on

Compare the following two views of albojubatus: and There is individual variation, but the difference in the darkness of the brindling seems to be partly or largely owing to the angle of the light.

As a form of striping (see, brindling should aid inconspicuousness. However, any type of disruptive colouration in wildebeests would seem incongruous because they do not hide in vegetation.

Brindling varies among the forms of wildebeest, as follows.

In gnou, brindling is present but usually unnoticed (see and

In the western form of taurinus (see and and, brindling is poorly-developed.

In the remaining forms, brindling is well-developed. Individuals vary in johnstoni (see and and and For cooksoni see For mearnsi see and

In the eastern form of taurinus, brindling would seem to aid inconspicuousness of the figure at distances relevant to scanning predators, particularly because this form lacks conspicuous dark/pale contrasts at this scale (e.g. see However, all forms of wildebeest the lack countershading on the belly and have dark on the brisket. Thus even the eastern form of taurinus retains a conspicuously dark ventral silhouette when the sun is above. And indeed the whole figure remains conspicuously dark at distance (see

This inconsistency, between striping, which tends to break up the figure, and a dark ventral silhouette, which tends to define the figure, poses a puzzle in the adaptive colouration in wildebeests (see part 8).

All wildebeests formed mixed groups with the plains zebra (Equus quagga). Is brindling analogous with the striping of zebras, or perhaps a subtle form of mimicry? Please see my explanation for striping in zebras (, based on a shimmering effect in predatory eyes, retarding assessment of the individual body-condition in the prospective prey.

Look at a few photos of zebras with small, relaxed eye-movements. You may notice a disconcerting shimmering. Now try the same for 'brindled gnus'. I see less of this effect, possibly because the brindling is not crisp and regular enough to confuse the optical system.

The bottom line for now: the brindling of wildebeests remains one of the more puzzling features of adaptive colouration in ungulates.

Posted on 09 July, 2021 19:33 by milewski milewski | 1 comment | Leave a comment