Interspecific variation in flags as features of adaptive colouration in hares, part 3: Arctic, boreal, and montane species

@brucebennett @oviscanadensis_connerties @don-jean @rangertreaty50 @tfrench @apgarm @jkfrey @ken_j_allison @napoleon1799 @beartracker @johnnybirder

LEPUS ARCTICUS

Lepus arcticus (https://academic.oup.com/mspecies/article/doi/10.2307/3504088/2600694?login=false) is mainly white with black-tipped ear pinnae, although southerly populations feature a summer coat.

This species differs from most other hares in the following ways. It:

All of the above make for a degree of exposure (by daylight) and self-advertisement unusual in hares. The whole figure tends to be so conspicuous that flags are somewhat redundant.

Best and Henry (1994) describe stotting without acknowledging it as such:

"The usual gait is a series of four-legged hops, each hop carrying the hare ca. 1.2 m. Southern populations use this gait almost entirely, but northern races, found on Arctic islands from northern Baffin Island northward, use a different gait (Banfield,1974). Hopping on the hind feet without touching the forefeet to the ground has been reported for L. arcticus (Hall, 1951). When disturbed, the Arctic hare stands erect on its hind legs, forefeet tucked close to its body (Feilden, 1877), and hops about until the source of danger is located (Pruitt, 1960); if not frightened, the hare resumes feeding. If startled, it runs in a series of bounds, generally with one foreleg lifted up. This gives tracks in snow the appearance of having been made by a three-legged animal (Feilden,1877). When a group is frightened, the whole group may stand upon their hind legs and without using their forelegs, hop away in every direction in long jumps; only when they have located the danger do they use all four legs to bound away. When they have gone a suitable distance, some may stand up on their hind legs, and with ears raised look to all sides to get their bearings, and then disappear (Freuchen, 1935). Arctic hares may double back on their own trail for4.5-9.0 m, then leap off to one side. One Arctic hare doubled back for a distance of 300 m (Sutton and Hamilton, 1932)....On Ellesmere Island, a wolf approached a group of 125 Arctic hares in sunlight at 0300 h on 10 August. The hares were grazing over an area of ca. 0.4 ha on a hillside. The wolf singled out an individual at the edge of the group and chased it through the group. The hare being chased hopped rapidly on its hind legs much like a kangaroo, but the remaining hares, after the initial alarm, paid little attention to the wolf running through the group. The hare being pursued ran in a zig-zag manner through the group, then left it to ascend a hill where the wolf captured it (Tener, 1954)."

Note that the above authors assume that the main function of bipedal hopping is to gain height in spotting an approaching predator. More likely it is a display of individual fitness to a predator already spotted.

The mainly greyish summer coat of L. arcticus features at least four flags, viz.:

  • a caudal flag and a pedal flag (by virtue of the fact that the tail and feet remain white throughout the year), as well as
  • two different auricular flags (by virtue of conspicuous dark and pale markings on both the anterior and posterior surfaces of the ear pinnae).

Please see: https://www.inaturalist.org/observations/110623961 and https://www.inaturalist.org/observations/70225456 and https://www.inaturalist.org/observations/66470343.

In the white winter coat, the whole figure is conspicuous when the animal is active on snow-free ground. No particular feature qualifies as a flag, because:

  • the white tail conforms to the rest of the figure, and
  • the dark tips of the ear pinnae are too small to be conspicuous.

What is the function of the dark tips of the ear pinnae?

One possibility is:

to distract the attention of scanning predators away from the real eyes (which are similar in darkness and size, see https://www.alamy.com/stock-photo-arctic-hare-lepus-arcticus-hudson-bay-canada-141449523.html and https://www.alamy.com/adult-arctic-hare-lepus-arcticus-outside-churchill-northern-manitoba-image2868054.html and https://www.reddit.com/r/aww/comments/ocfgc/cute_arctic_harefirst/ and https://www.alamy.com/arctic-hare-lepus-arcticus-in-the-snow-churchill-manitoba-canada-image384835136.html and https://www.alamy.com/stock-photo-arctic-hare-in-snow-17302820.html) when the figure of L. arcticus is inconspicuous by virtue of being stationary on a snowy background.

If so, this would in a sense be the opposite of a flag.

Lepus othus (https://en.wikipedia.org/wiki/Alaskan_hare) seems similar to L. arcticus, with respect to the occurrence of flags.

LEPUS AMERICANUS

Lepus americanus is unlike L. arcticus in having inconspicuous colouration and behaviour.

This species is plain-coloured in most subspecies, in summer coat and winter coat. Caudal and auricular flags are poorly-developed.

There are pedal and auricular flags in transitional coat (see https://www.jstor.org/stable/1374046) in some subspecies/individuals:

Summer coat:
https://www.shutterstock.com/nb/image-photo/eastern-cottontail-standing-on-edge-path-680897974
https://www.inaturalist.org/observations/90729949
https://www.inaturalist.org/observations/101379283
https://www.inaturalist.org/observations/95089838
https://www.inaturalist.org/observations/105434881
https://www.inaturalist.org/observations/89503059
https://www.inaturalist.org/observations/102531373

Winter coat:
https://www.inaturalist.org/observations/106555675
https://www.gettyimages.com.au/detail/photo/snowshoe-hare-portrait-royalty-free-image/584421721?adppopup=true

Lepus brachyurus (https://www.inaturalist.org/taxa/43139-Lepus-brachyurus) of Japan seems similar to L. americanus (see https://animalia.bio/japanese-hare). Some individuals in the summer coat show a small caudal flag (short tail with dark on the upper surface and pale on the lower surface) but no auricular flag. Some individuals in what may be a seasonally transitional coat show an auricular flag on the posterior surface of the ear pinnae, consisting of pale with a dark patch at the tip (https://en.wikipedia.org/wiki/Japanese_hare#/media/File:Lepus_brachyurus,_March,_Tsukuba,_Japan.jpg).

LEPUS TIMIDUS

Lepus timidus (https://academic.oup.com/mspecies/article/doi/10.2307/3504302/2600716?login=false) is not as plain-coloured as L. americanus, being in some respects intermediate among L. arcticus, L. americanus, and L. townsendi. This species is difficult to describe because it has so many subspecies.

In the winter coat, L. timidus possesses no flags (https://www.inaturalist.org/observations/40365203 and https://www.inaturalist.org/observations/48219583).

However, in subspecies L. t. scoticus and L. t. canescens, the winter coat is not white, and the anterior surface of the ear pinnae remain dark enough possibly to qualify as an auricular flag.

In the summer coat:

Autumn coat
https://www.inaturalist.org/observations/63896793
https://www.inaturalist.org/observations/36055131
https://www.alamy.com/stock-photo-mountain-hare-lepus-timidus-scotland-uk-121902717.html

Spring coat
https://www.inaturalist.org/observations/48175173
https://www.inaturalist.org/observations/42304908

The following show possible stotting in L. timidus: https://www.alamy.com/mountain-arctic-hare-lepus-timidus-cairngorm-scottish-highlands-image6960489.html and https://www.alamy.com/stock-photo-the-mountain-hare-lepus-timidus-also-known-as-blue-hare-here-seen-101106559.html.

In partial summary, interpretation of the colouration of L. arcticus is complicated by the fact that the white colouration occurs not only in snow but also in dark, snow-free terrain. This means that the whole figure of this large-bodied species can be conspicuous by virtue of its paleness. Furthermore, this overall conspicuousness may be consistent with the stotting displays of L. arcticus, which consist of non-quadrupedal gaits unknown in most other species of hares.

to be continued...

Publicado el abril 15, 2022 01:40 MAÑANA por milewski milewski

Comentarios

Great post!

Publicado por beartracker hace casi 2 años

@beartracker Hi Kim, Many thanks, I'm glad you enjoy this topic, with regards from Antoni

Publicado por milewski hace casi 2 años

I love the information on the gaits they use and how it was interpreted. Interesting!

Publicado por beartracker hace casi 2 años
Publicado por milewski hace casi 2 años

Now I have another reason to get up to the high Arctic. It's on my bucket list!
Thanks!

Publicado por ken_j_allison hace casi 2 años

@ken_j_allison You're most welcome.

Publicado por milewski hace casi 2 años

LEPUS AMERICANUS

Zimova et al. (2014, http://rspb.royalsocietypublishing.org/content/281/1782/20140029.full) assume that the function of colouration in the snowshoe hare is for inconspicuousness. That may be true overall, and this species does not even display its tail in flight (http://upload.wikimedia.org/wikipedia/commons/2/2f/Lepus_americanus_5472.JPG)./This is a boreal species (typical of taiga forest both on plains and in mountains, http://en.wikipedia.org/wiki/Snowshoe_hare#mediaviewer/File:Lepus_americanus_map.svg and http://www.hww.ca/assets/images/mammals/snowshoe-hare/snowshoe_map.jpg), non-hibernating, nocturnal/crepuscular, essentially solitary (in the sense that it is not gregarious), and prey to many carnivores in its range (it is the staple diet of the Canada lynx, for example). The snowshoe hare tends to go from boom to bust, the numbers of lynx following suit.

There tends to be a white pedal flag in the brown coat, and the seasonal colour-change is more complex than can be explained in terms of pure crypsis.

Because the species lives in dense populations in boom years, the idea that it is simply ‘solitary’ is naive. Instead, in boom years the animals are forced to interact intraspecifically, maintaining optimal spacing, for which they signal to each other at moderate distance by means of the ears and feet.

The snowshoe hare turns from white in winter to brown/grey in summer. However, this takes up to 10 weeks in spring, and then another 10 weeks in autumn, which means that the animal is in intermediate colours for up to 5 months of the year. In these transitions, the feet tend to be conspicuous, because they are the part that tends to turn white earliest, and turn back to brown/grey latest. The pedal flag is sometimes accentuated by a dark patch immediately adjacent to the white on the hind leg.

http://1.bp.blogspot.com/-jktuQTUhpJw/Tfg3IrroQYI/AAAAAAAAUsE/c2SerN8nYX0/s1600/snow%2Bshoe%2Bharecanmore%2Bjune%2B14%2B2011%2B152.JPG and http://wildlife-photo.cz/UserFiles/FotoGalerie/medium_600/20130508103131.jpg.

Not only the feet but also the ear pinnae tend to lag in seasonal colour-change, with the result that in intermediate colours the ears tend to be conspicuous. This conspicuousness has both dark and pale elements, as shown by the following several photos. The pattern seems to be that the ears tend to retain their winter white colour, and then feature dark contrasts even when the white has receded.

I hypothesise that the animals are signalling intraspecifically, particularly during boom years when populations are densest, to maintain spacing and to avoid competition and disruption of their overall hiding. Both the ear pinnae and the feet can be concealed from predators, the former by laying them flat and the latter by sitting tight and low. So the species has an interesting combination of concealment and advertisement.

The pattern on the ears of the snowshoe hare does not simply change from brown in summer to white in winter. In summer there is some dark/pale contrast on both the front and the back of the ear, using different patterns. There is a lag in the seasonal change of colour, such that the ears tend to be white when the rest of the animal has already turned brown/grey. This seasonal lag is not just a question of transition, because when the white fur on the ears does fall off it tends to be replaced partly by dark short fur/skin pigmentation, maintaining a measure of dark/pale contrast quite separate from the influence of the winter white coat.

Publicado por milewski hace más de 1 año

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