Journal archives for March 2024

March 01, 2024

How do impalas manage to graze, despite their narrow muzzle?

Impalas (Aepyceros) are basically grazers.

However, unlike other grazing ungulates, they have a narrow muzzle.

How can this anomaly be explained?


The relationship of impalas to lawns is somewhat confusing.

Impalas are not lawn-formers and -maintainers in the same sense as wildebeests (Connochaetes) and the hippopotamus (Hippopotamus amphibius).

However, they are

  • capable of grazing the short grass on lawns, by virtue of their 'muscular lips', and
  • particularly associated with lawns in the sense of nocturnal avoidance of trees and shrubs.

The latter relationship is epiphenomenal, in the sense that impalas congregate in treeless vegetation at night as an anti-predator tactic, and this then tends to lawn the grass.


Impalas resemble the African savanna buffalo (Syncerus caffer) in that they need grass taller than a lawn, for adequate foraging.

However, the reasons differ.

The African savanna buffalo uses its mouth differently from impalas. It has blunt, clumsy lips, but it uses its prehensile tongue to sweep grass into the mouth.

Impalas seem never to extend the tongue more than 1 centimeter during foraging. Instead, they reach into the sward, using the narrow muzzle to select the grass leaves while avoiding the culms.

Posted on March 01, 2024 02:42 AM by milewski milewski | 7 comments | Leave a comment

March 02, 2024

Variation in the size of the rhinarium in bovid and cervid ruminants

Rusa timorensis

Rusa unicolor

Rangifer tarandus

Posted on March 02, 2024 07:02 AM by milewski milewski | 28 comments | Leave a comment

March 04, 2024


At 6.41 in, please see the caudal flag of the snow leopard, which allowed the film-makers to spot it at distance. This caudal flag was not activated in the stalking sequence we are commentating. The caudal flag of the snow leopard differs somewhat from that of the leopard, in that a) it is not raised as high, b) it is white rather than black and white, and c) has white hair that is terminally fluffy rather than ventral-subterminal and hardly fluffy.


The above two photos show the difference in the caudal flag

Caudal flag not activated at 17.50 in

Around 21.58 in, we see juvenile playing, showing development of caudal flag, and - more to point - chasing a rolling pebble downhill.

43.52 in shows that the caudal flag is actually ventral-subterminal, but seems terminal because the tail is sharply curled near the tip while held low overall,

45.04 pectoral flag

Just tryinghttps://

Posted on March 04, 2024 01:47 AM by milewski milewski | 1 comment | Leave a comment

March 07, 2024

Adaptive colouration in the European fallow deer (Dama dama)

The menil morph of D. dama is noteworthy in combining classic camouflage colouration (spotted tracts of pelage) with the kind of conspicuous dorsalisation of white ventral parts that we see in Asian wild asses, the springbok, and certain other gazelles.


Even in individuals lacking much dark trimming on the frontofear, the earstalk, between the ear-feather and the head, tends to be narrowly dark. This tends to make the ears conspicuous in overall dark/pale contrast. Most individuals have limited = minor dark/pale contrast about the nose/mouth/chin/crookofthroat, so that this part of the animal is not accentuated. The ventral surface of the head (between the manidibles) seems, in all individuals in winter pelage, to be paler than the cheeks. However, pale at the crookofthroat is less consistent, being absent in some adult females in winter pelage. Pale at the orbits is overall not an important feature of D. dama in winter pelage. In some individual adult females, there remains a faint horizontal pale stripe on the upper part, but not upper border, of the medium-tone flank-band. The inner surface of the upper hindleg is whitish, with an abrupt border at least halfway to hock-level. However, countershading offers little explanatory value here. I have yet to see an adult male specimen of D. dama in winter pelage with dark rims on the frontofear. In males, pale is better-developed on the ventral part of the neck than in females, in winter pelage. The hard antlers in winter pelage are not conspicuously pale, nor pale-tined.

Posted on March 07, 2024 04:48 AM by milewski milewski | 0 comments | Leave a comment

Illustrations of stotting gaits in cervine deer (Cervidae: Cervinae)

There are many genera and species of cervine deer (

This Post is a preliminary attempt to illustrate the stotting gaits of this clade.


Posted on March 07, 2024 11:01 PM by milewski milewski | 0 comments | Leave a comment

March 09, 2024

Glandular contrasts between Aepyceros (impalas) of Africa and Odocoileus (white-tailed, black-tailed, and mule deer) of the Americas

@tonyrebelo @jeremygilmore @ludwig_muller @christiaan_viljoen @nyoni-pete @capracornelius @aguilita @tandala @dejong @zarek @jwidness @jakob @bobby23 @paradoxornithidae @beartracker @oviscanadensis_connerties @muir @botswanabugs @matthewinabinett @gigilaidler @variani18 @angeldv @jandutoit

Also please see

The bovid genus Aepyceros ( and the cervid genus Odocoileus ( are biologically comparable.

The former ( tends to be the most abundant ruminant in its habitat in southern and East Africa. The latter is the only ruminant of similar body size, shape, and colouration in much of North, central, and South America (

In this Post, I compare the various externally-expressed glandular organs ( in the two genera, in anatomical order from anterior to posterior.


A nasal gland is present in Odocoileus (, but unrecorded in Aepyceros.

This corresponds to the fact that the rhinarium - and particularly its moist surface - is far smaller in Aepyceros ( than in Odocoileus ( and

The functions of the secretions of the nasal gland probably include facilitation of vomeronasal olfaction (

Both Aepyceros and Odocoileus use the vomeronasal organ in the flehmen response ( and and and

However, the American genus may, in addition, have a broad vomeronasal olfactory facilitation, lacking in the African genus.

In both genera, there is an uninvestigated possibility of pheromonal/scent-production by nasal glands, spread by alarm-sneezing/snorting.


Both Aepyceros and Odocoileus are unusual among ruminants, in that preorbital glands are absent/poorly-developed.

Their only incidence is in adult males of Odocoileus in rutting condition. They have a masculine function in olfactory marking of plant stems/foliage, in combination with the licking of these objects (


The main function of salivary glands is in eating. However, there is a possibility of olfactory communication, by means of active or passive protrusion of the tongue.

Both genera show passive lingual protrusion ( and However, only Odocoileus uses the tongue for social licking/grooming.


In adult males of both Aepyceros and Odocoileus, masculine olfactory marking of vegetation is carried out by rubbing the pelage of the forehead on plants.


Aepyceros is unusual among both bovids and cervids in lacking interdigital glands, as well as having feet so specialised that dewclaws/false hooves are absent.

Odocoileus possesses interdigital glands on both fore- and hindlegs.

Furthermore, the American genus is somewhat unusual in that it exhibits demonstrative postures/gaits, which potentially promote and advertise the emission of interdigital secretions in an anti-predator context. I refer to stotting in Odocoileus hemionus hemionus and 'foot-stamping' in Odocoileus virginianus.


Preputial glands are absent in Aepyceros, but present in mature males of Odocoileus.


Please see the pale patch on the inner surface of the hock ( in, which shows an adult female individual of Odocoileus virginianus in summer pelage.

Tarsal glands are unrecorded in bovids, including Aepyceros.

The tarsal gland in Odocoileus is a feature of the pelage rather than a gland. It functions

  • to culture microbes intensively, based partly on the urine that is dribbled on to it by means of special squatting postures, and thus
  • to function mainly socially, producing olfactory signatures distinctive individually and according to sex, age, condition, and status.


Please see

Metatarsal glands occur in certain cervids, but are unrecorded in bovids other than Aepyceros.

Their function seems to be specialised: they react to anti-predator alarm by releasing olfactory signals, presumably detectable to both other members of the group and the predators themselves.

In the case of Odocoileus hemionus columbianus, the garlic-like odour of alarm is perceptible to humans.

The metatarsal glands in Aepyceros and Odocoileus are similar in anatomical position, on the lower hindlegs. However, they differ in that, in Aepyceros,

Within Odocoileus, there is noteworthy variation in the degree of development of the metatarsal gland both between and within species. The gland is better-developed in O. hemionus than in O. virginianus, and within the latter species it tends to be absent in the tropics and subtropics.


Caudal glands are unrecorded, and presumably absent, in Aepyceros, in line with most bovids.

However, caudal glands are known in Odocoileus.

As in the case of metatarsal glands, caudal glands are better-developed in O. hemionus than in O. virginianus. They presumably function mainly in anti-predator alarm.



Overall, the glandular profiles of Aepyceros and Odocoileus are surprisingly different, in ways unexplained by the fact that Aepyceros is sociosexually territorial, whereas Odocoileus is not.

The main similarities are

  • masculine sebaceous function in the pelage of the forehead, and
  • metatarsal glands, ostensibly functioning to signal anti-predator alarm, particularly during bounding/kick-stotting/stotting.

Aepyceros is poor in glands generally, and is extreme in lacking interdigital glands, a category common to various ruminants. For its part, Odocoileus is extreme in the degree of development of its tarsal glands, a category absent from all bovids.

Females of Aepyceros have only one important type of gland, viz. the metatarsal gland, and even this is thought not to be used sociosexually.

Compared to other bovids, Aepyceros communicates unusually raucously (

This auditory emphasis may perhaps partly explain the limited olfactory communication in Aepyceros.

The glandular differences shown above may also be partly related to the remarkable disparities in gaits and postures between the two genera (

These differences are greatest between the common impala (Aepyceros melampus) and the Rocky Mountain mule deer (O. hemionus hemionus,, as follows.

The common impala

By contrast, the mule deer


Also see

Posted on March 09, 2024 03:24 PM by milewski milewski | 36 comments | Leave a comment

March 10, 2024

March 13, 2024

Kobus kob kob as the West and Central African counterpart for the common impala (Aepyceros melampus), part 1


The distribution ranges of Kobus kob (the kob) and Aepyceros melampus (the common impala) are mutually exclusive.

Both species

  • are medium-sized, evenly-proportioned, brown antelopes with moderate sexual dimorphism (horns restricted to males), and
  • eat mainly grass, are gregarious and active mainly diurnally, and have a territorial sociosexual system.

Kobus kob occurs in the Guinea savannas of West and north-central Africa and South Sudan ( Aepyceros melampus occurs in the savannas of southern and East Africa, favoring thorn savanna over miombo woodland (

This biogeographical and ecological separation suggests that the two taxa share a single niche in a loose sense, partitioning Africa so that one or the other occupies any given area.

The most important evidence of this is that A. melampus, although abundant in East and southern Africa, is absent across the vast savannas of the other half of the continent.

Given this scenario of approximate ecological equivalence, it is worth comparing Kobus kob ( with A. melampus in various biological features.

More particularly, in this Post I focus on the most widespread subspecies, namely Kobus kob kob (

This, the nominate subspecies, occurs from Senegal ( in the west to Chad ( in the east, a distance of nearly 5,000 kilometers - entirely devoid of any species of Aepyceros.


So, the central question is:
To what degree is K. kob kob ( just a 'western/northern impala', under a different name?

For illustrations of Aepyceros melampus, see my many Posts (


Kobus belongs to the tribe Reduncini, whereas Aepyceros belongs to the tribe Aepycerotini. This means that


Kobus kob kob is similar in body mass to Aepyceros melampus.

Important for this comparison is the fact that K. k. kob is much smaller than K. k. thomasi, a better-known subspecies occurring in Uganda (pages 191-195 in

The similarity in body size can be illustrated indirectly by using Bubulcus ibis for scale ( and and

Kobus kob kob differs from A. melampus in

Infants of K. k. kob are far less 'leggy' than those of A. melampus. Please compare with, and also see and

Form of horns

The horns are similar in size and shape in the two taxa (

Sexual dimorphism

The degree and nature of sexual dimorphism are similar in K. k. kob and A. melampus.



The hooves of K, k. kob are larger than those of A. melampus. The difference is particularly great in the case of the false hooves/dewclaws, which are well-developed in the former, but absent in the latter.


In both K. k. kob and A. melampus, dark bare skin shows at the stifle-fold. However, this is far less extensive in the former ( and than in the latter (


In both K. k. kob and A. melampus, the rhinarium is small. However, the latter is extreme in this respect (


In both K. k. kob and A. melampus, the tail


In both K. k. kob and A. melampus, there are two pairs of teats (mammillae).


In both K. k. kob and A. melampus, external glands are poorly-developed relative to most other ruminants, and interdigital and caudal glands are absent.

However, the two taxa differ in that

  • preorbital glands are present (small) in K. k. kob, as opposed to absent in A. melampus,
  • K. k. kob possesses inguinal glands, instead of the metatarsal glands possessed by A. melampus.


Both K. k. kob and A. melampus are whitish on the ventral surface of the torso, and the inner surface of the upper hindlegs ( In K. k. kob, the posterior surface of the upper foreleg is whitish ( and However, in the latter this is crisply-defined.


Both K.k. kob and A. melampus

However, the tone on the flanks is far less distinctly defined in K. k. kob ( than in A. melampus ().


In K. k. kob, dark pelage accentuates the anterior surface of the legs, particularly the forelegs ( In A. melampus, such accentuation is minimal, being restricted to the fetlocks, and absent from most individuals.


Kobus kob kob and A. melampus differ categorically w.r.t. the pattern of colouration on the buttocks (compare and with and


The tail shows a dark/pale contrast when swished, in both K. k. kob and A. melampus. However, this accentuation is minimal in the former (compare and with and and

Ear pinnae

In both K. k. kob and A. melampus: and and

Both K. k. kob and A. melampus possess a pedal flag, consisting of pale pasterns offset by dark ( and and and and and and and


In both K. k. kob and A. melampus, mature males possess a whitish patch on the anterior surface of the neck, adjacent to the lower jaw (

This feature

  • is moderately sexually dimorphic, emphasising the masculine brawniness of the neck, and
  • is conspicuous enough to qualify as a gular semet/flag.

to be continued in

Posted on March 13, 2024 12:24 AM by milewski milewski | 64 comments | Leave a comment

March 14, 2024

Kobus kob kob as the West and Central African counterpart for the common impala (Aepyceros melampus), part 2

...continued from



Reduncin bovids usually walk with a gait that I call a semi cross-walk, suited to slippery ground, wading, and (in the case of Redunca) cover-dependence and crypsis.

A semi cross-walk is sometimes evident in K. k. kob ( and and and and, with excellent clarity,

Furthermore, K. k. kob sometimes cross-walks while wading (

However, K. k. kob usually walks with a gait that I call an amble ( and and and and and and and and and and

In this way it is convergent with A. melampus, which ambles (

The diagnostic criterion is as follows. Please focus on the hind hoof.

  • in a semi cross-walk, the hind leaves the ground before the opposite fore touches the ground, whereas
  • in an amble, the hind leaves the ground only once the opposite fore has touched the ground.

The following, showing a semi cross-walk in A. melampus, is unusual in my experience:


Kobus kob kob has not, as far as I know, been recorded stotting. However, both K. k. thomasi and K. vardoni are known to stot, indicating a similar gait in the nominate subspecies.

Aepyceros melampus does not stot, but instead kick-stots - unlike any other ungulate.


Kobus kob kob differs from A. melampus in that it does not bound.

(The similarity shown in the following is misleading. Kobus vardoni here is stotting, instead of bounding like the accompanying A. melampus:


Deliberate jumping of fences

I lack information on the jumping of fences by K. k. kob. However, other reduncins are known to jump fences deliberately. This suggests a considerable difference, because A. melampus does not deliberately jump fences even as low as 1.2 m high.


Reproduction is far less seasonal in K. k. kob than in A. melampus.

Gestation is longer in K. k. kob (261-271 days, referring to sspp. other than K.k. kob) than in A. melampus (190-210 days).

This is despite the fact that neonates are less massive in the former (4-5 kilograms in ssp. other than K. k. kob) than in the latter (4-5.5 kilograms).

The hiding period of infants is longer in K. k. kob than in A. melampus.

Overall, these results show K. k. kob to be considerably less precocial than A. melampus.


In both K. k. kob and A. melampus, olfactory communication for sociosexual purposes seems to be downplayed, relative to most ruminants.

Remaining glands (inguinal and possibly subauricular in the former, metatarsal in the latter) may function mainly in an anti-predator context (

Reuncins are the tribe of bovids most associated with marshes. Where Kobus vardoni overlaps ecologically with A. melampus, it tends to range farther from trees on to alluvial plains. However, K. k. kob may be the form of Kobus most emancipated from the immediate vicinity of water, and most tolerant of woody vegetation. If so, this would indicate a degree of functional convergence with A. melampus, in complete allopatry.

Kobus vardoni replaces Kobus kob south of the equator. It is not mutually exclusive with A. melampus ( and

However, K. vardoni

Kobus vardoni is also more plain-coloured ( than K. k. kob, with

These differences indicate ecological separation between K. vardoni and A. melampus, allowing their partial sympatry.

Posted on March 14, 2024 01:32 AM by milewski milewski | 32 comments | Leave a comment

March 16, 2024