Adaptive colouration in the largest living cervid, the moose (Alces alces)

@muir @matthewinabinett @aguilita @tonyrebelo @jeremygilmore @beartracker

At first sight, Alces alces seems nondescript in colouration (https://www.inaturalist.org/observations/19029155 and https://www.inaturalist.org/observations/4336204).

Valerius Geist, on pages 229-232 in Grzimek's Animal Life Encyclopedia (https://en.wikipedia.org/wiki/Grzimek%27s_Animal_Life_Encyclopedia), exaggerates somewhat when he states:
"European moose are dark brown with white legs, and American moose are black with a light saddle patch on the back, light-brown legs, and facial markings that vary between the sexes. In the female the face and nose are red-brown, while the bull has a black nose".

The following verify that the head tends to be paler than the neck and torso, in females of A. alces in North America (https://www.inaturalist.org/observations/178372818 and https://www.dreamstime.com/bull-moose-water-image259482733). However, this applies to some degree also in Europe (https://www.inaturalist.org/observations/175016790 and https://www.inaturalist.org/observations/174910182).

Overall, sexual differences in the colouration of the pelage of A. alces are remarkably limited (https://www.youtube.com/watch?v=bujmogxgtp4 and https://www.youtube.com/watch?v=tsZUaGIt-r8 and https://www.google.com.au/search?q=Moose+mating&sca_esv=567242663&sxsrf=AM9HkKnsy5ar25NAM_QxNryBAc4ELWtrPA%3A1695294882706&source=hp&ei=oiUMZd3UJtixoATxmJzQAg&iflsig=AO6bgOgAAAAAZQwzssn9atv3I45ihgDieVv4Z3QxBVPr&ved=0ahUKEwjdrZPKybuBAxXYGIgKHXEMByoQ4dUDCAs&uact=5&oq=Moose+mating&gs_lp=Egdnd3Mtd2l6IgxNb29zZSBtYXRpbmcyBRAuGIAEMgUQABiABDIFEAAYgAQyBRAAGIAEMgUQABiABDIFEAAYgAQyBRAAGIAEMgUQABiABDIFEAAYgARImklQzg5Y-j5wAXgAkAEAmAGuA6AB_BiqAQkwLjEuOS4xLjG4AQPIAQD4AQGoAgrCAgcQIxjqAhgnwgIEECMYJ8ICCxAAGIAEGLEDGIMBwgIREC4YgAQYsQMYgwEYxwEY0QPCAgsQLhiDARixAxiABMICCxAAGIoFGLEDGIMBwgIHECMYigUYJ8ICCBAuGIoFGJECwgIIEAAYgAQYsQPCAggQABiKBRiRAsICCxAuGIoFGLEDGJECwgILEC4YgAQYxwEYrwE&sclient=gws-wiz#fpstate=ive&vld=cid:25246631,vid:YvNAJLygu9w,st:0).

Infants, although noticeably paler than adults, have colouration so plain that it, too, is nondescript (https://www.inaturalist.org/observations/4097272).

Seasonal changes in colouration are limited, resulting from the single annual molt in spring/early summer. In winter, the pelage remains dark enough to be conspicuous against snowy backgrounds, even at distance (https://www.inaturalist.org/observations/148799385 and https://www.inaturalist.org/observations/135953868).

Despite the initial nondescript impression, my close scrutiny has revealed several noteworthy patterns of colouration, which deserve names, in A alces.

For example, the following shows a fibular flag, anterior auricular semet, and buccal semet in an adolescent female individual in the spring season, in Alces alces gigas: https://www.inaturalist.org/observations/163382249.

Although these features are subtle, individually variable, and perhaps seasonally variable, they seem fairly consistent among the various subspecies.

CORNUAL FLAG

The antlers of A. alces, borne seasonally by males, tend to be conspicuously pale on the upper (dorsal) surface. This is noticeable only innthe subspecies with the largest antlers

The cornual flag is derived essentially from the natural paleness of dry bone (https://www.inaturalist.org/observations/127384241).

However, in A. alces,

• the antlers are paler than those of other cervids, and
• the palmate surface of the antlers is far larger than in other cervids (https://www.cbc.ca/news/canada/north/possible-world-record-size-moose-shot-in-yukon-1.2075442).

This makes the antlers conspicuous, even at distance (https://www.inaturalist.org/observations/4612251), particularly in A. a. gigas and (presumably) A. a. buturlini.

The cornual flag in A. gigas

• is apparent mainly in autumn, and
• hypothetically functions intraspecifically, aiding sexual attraction, male advertisement, and masculine rivalry.

Cornual flag in Alces alces gigas:
https://www.inaturalist.org/observations/183421987
https://www.mediastorehouse.com/nature-picture-library/danny-green/moose-bull-alces-alces-walking-forest-clearing-15316906.html
https://www.inaturalist.org/observations/183421709
https://www.inaturalist.org/observations/458438

Cornual flag in Alces alces shirasi:
https://www.inaturalist.org/observations/147438040

FIBULAR FLAG

https://www.closertothewild.com/gallery/p/style-01-slgxj-738cj-bnn5s-3e26g-rewyc-36zgb
https://www.shutterstock.com/image-photo/winter-sunny-day-young-moose-cow-2125295291
https://www.dreamstime.com/stock-photography-bull-moose-image21621952
https://www.dreamstime.com/wet-cow-moose-standing-forest-image183436539

Please see https://www.inaturalist.org/journal/milewski/84573-a-new-feature-of-adaptive-colouration-in-ungulates-the-fibular-flag-part-2-alces-alces-cervidae#

The fibular flag is best-developed in the nominate subspecies, A. a. alces, of Europe and western Russia.

The role of sheen deserves investigation.

The following shows the extreme development of the pale pelage in A. alces, in which it encompasses most of the hindleg (https://www.inaturalist.org/observations/112176729).

PEDAL FLAG

A case can be made that A. alces possesses a pedal flag, in some individuals. This applies particularly to the nominate A. a. alces.

This pedal flag consists of conspicuous pale on hocks and carpals (particularly on the posterior surface of the carpals), extending to varying extent down the lower limbs towards the hooves, and connected to the fibular flag where the latter is present. The fetlocks and pasterns themselves tend not to be whitish (https://www.shutterstock.com/image-photo/front-split-hoofs-moose-standing-on-727556374), except in the nominate A. a. alces.

https://www.inaturalist.org/observations/51436631
https://www.inaturalist.org/observations/33064841
https://www.dreamstime.com/large-brown-black-bull-moose-standing-park-image193883277
https://www.dreamstime.com/stock-photo-moose-bull-elk-standing-road-image66248282

To the degree that the pedal flag is valid in A. alces, it is linked to, and subsidiary to, the fibular flag.

ANTERIOR AURICULAR SEMET

Please see https://www.inaturalist.org/journal/milewski/55694-ten-best-illustrations-of-auricular-semets-in-deer#

One of the most consistent patterns of colouration in A. alces is a small-scale dark/pale contrast on the anterior base of the ear pinna (https://www.dreamstime.com/stock-photo-moose-north-america-elk-europe-alces-alces-largest-extant-species-deer-family-moose-distinguished-image50713041).

The location of this pattern is such that it accentuates the movements of the ears, in vigilance and emotional expression. Such accentuation is hypothetically adaptive in social (intraspecific) interactions, and may additionally function in anti-predator, defensive displays.

Several other genera of cervids possess auricular semets. However, that of A. alces is restricted to the anterior surface, and has its own particular configuration.

The following show the anterior auricular semet in various subspecies of A. alces:

A. a. americana:
https://www.inaturalist.org/observations/183781173
https://www.inaturalist.org/observations/165912205

A. a. gigas:
https://www.inaturalist.org/observations/172965903
https://www.inaturalist.org/observations/15093287

A. a. andersoni:
https://www.inaturalist.org/observations/170210903
https://www.inaturalist.org/observations/166029819

A. a. shirasi:
https://www.inaturalist.org/observations/174251418

The following show that the anterior auricular flag, although absent in newborns, develops before the infantile colouration is lost, and before the muzzle develops:
https://www.inaturalist.org/observations/133091834
https://www.dreamstime.com/stock-photo-small-moose-few-days-standing-woods-next-to-pine-tree-image53403214.

BUCCAL SEMET

The peculiar muzzle of A. alces is so distracting that the colouration around the mouth may go unnoticed. Furthermore, this colouration is subtle and individually variable.

However, there tends to be a pattern in which the dark chin and lower lip are offset by pale ventral to the gape (https://www.inaturalist.org/observations/152098783 and https://www.inaturalist.org/observations/148835598 and https://www.inaturalist.org/observations/13505171 and https://www.dreamstime.com/stock-photo-moose-eating-green-grass-near-water-grand-tetons-national-park-image50021650).

This hypothetically accentuates the chewing movements of rumination, thus aiding vigilance where two or more adult/adolescent individuals are within sight of each other while resting (https://www.dreamstime.com/stock-photos-moose-image20463023).

Buccal semet in Alces alces buturlini:
https://www.alamy.com/female-moose-alces-alces-in-profile-kronotsky-zapovednik-nature-reserve-kamchatka-peninsula-russian-far-east-december-image263189582.html?imageid=8337E994-E81B-42C7-9D06-32050AEFBBE0&p=216449&pn=1&searchId=693543c6c0b82d61e979d27d23f7d17f&searchtype=0

Buccal semet in Alces alces gigas:
https://www.inaturalist.org/observations/153275621
https://www.inaturalist.org/observations/2646616
https://www.inaturalist.org/observations/13172080

Variation in this feature deserves further investigation. The pattern seems clearest in spring. The following, taken in summer, shows its minimal expression (https://www.inaturalist.org/observations/114831099).

Of all the features described here, the buccal semet is the most precocial, in the sense that the lower lip is dark even in infants (https://www.inaturalist.org/observations/29864809).

Publicado el 19 de septiembre de 2023 00:46 por milewski