Interspecific variation in flags as features of adaptive colouration in hares, part 5: overall discussion

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It is clear that Lepus possesses a complex repertoire of flags.

Are their messages directed to potential predators, or conspecifics, or both? Since most species are effectively solitary, it seems unlikely that the flags function mainly to warn conspecifics. Instead, a plausible function is to signal to the potential predator that

• it has been detected, discouraging further stalking, and
• the individual hare is fit, discouraging pursuit.

Lepus varies in colouration from

• plain-coloured and inconspicuous (e.g. Lepus americanus in full seasonal coats, https://www.inaturalist.org/observations/106555675 and https://www.inaturalist.org/observations/101379283), through
• inconspicuous when the figure is at rest but with up to four clearly-illustrated flags when active (on various combinations of feet, tail, and both the anterior and the posterior surfaces of the ear pinnae) in e.g. Lepus townsendii (https://www.inaturalist.org/observations/43268453 and https://www.inaturalist.org/observations/67069574), through
• conspicuous by virtue of haunch-flags activated by twitching of the skin (Lepus alleni, Lepus callotis), to
• conspicuous on snow-free backgrounds, owing to overall paleness of the figure (e.g. northernmost Lepus arcticus in the winter coat, http://kratlusk.blogspot.com/2010/07/huge-hare-herd-lhh.html).

The above variation corresponds to

• flags poorly-developed, through
• flags well-developed (https://www.alamy.com/stock-photo-a-white-tailed-jackrabbit-running-in-a-field-91812312.html), through
• flags shifted from the extremities to the body itself, where activated by twitching of the skin, to
• flags subsumed by the overall conspicuousness of the figure (plus gregariousness in the case of L. arcticus (https://www.mindenpictures.com/stock-photo-arctic-hare-lepus-arcticus-group-on-tundra-ellesmere-island-nunavut-naturephotography-image00064679.html) and some subspecies of L. timidus).

In the boreal biome, the inconspicuous colouration of L. americanus is consistent with the reliance of this species on

• the cover of woody plants in the case of the summer coat, and
• a background of deep snow in the case of the winter coat.

In the tropics, the poor development of flags in L. nigricollis (https://lakesideindia.files.wordpress.com/2013/03/march-hare.jpg) may likewise be partly explained by the dependence of this Indian species on woody cover - although the vegetation is quite different.

The tail varies considerably among the species of hares in size and shape. It is noteworthy that the conspicuousness of the tail has been reduced in L. californicus (https://sabinonaturalists.org/critters/black-tailed-jack-rabbit/), by the reduction of the dark-pale contrast between the upper surface and the lower surface.

In hares, unlike ruminants, the tail is normally held 'erect' in sitting/crouching postures, being 'lowered' only when the figure stands or locomotes (https://www.alamy.com/black-tailed-jackrabbit-on-the-move-lepus-californicus-hare-native-merced-national-wildlife-refuge-san-joaquin-valley-merced-county-california-image425323824.html and https://www.shutterstock.com/nb/image-photo/wild-grey-rabbit-jumping-around-on-1727626519). The 'erect' tail is inconspicuous because it is close to ground-level and effectively horizontal, and hidden by the curve of the hindquarters (https://www.flickr.com/photos/38971900@N08/15362183597).

The form and colouration of the tail in Lepus falls into at least six categories (qualification for caudal flag denoted by asterisk*), as follows:

Tail proportionately small and correspondingly inconspicuous: alleni (https://www.inaturalist.org/observations/1103230)

Tail of medium size:

• Tail white on white hindquarters: winter coat in arcticus, americanus, timidus, townsendii (e.g. https://fieldguide.mt.gov/speciesDetail.aspx?elcode=AMAEB03040)
• *Tail white on medium-tone hindquarters: oiostolus and summer coat in arcticus, timidus (https://www.agefotostock.com/age/en/details-photo/mountain-hare-lepus-timidus-adult-summer-coat-running-on-moorland-peak-district-derbyshire-england-april/FHR-10514-00281-795)
• *Tail dark on pale hindquarters: callotis (https://inaturalist.ala.org.au/observations/104689188)
• Tail medium-tone on medium-tone hindquarters: californicus, nigricollis (https://www.inaturalist.org/observations/97706483)
• *Tail dark on upper side and pale on lower side, on medium-tone hindquarters: saxatilis, capensis, victoriae, starcki, europaeus, granatensis (e.g. https://www.inaturalist.org/observations/99911341)

*Tail proportionately large and correspondingly conspicuous: townsendii in summer coat (e.g. https://alchetron.com/White-tailed-jackrabbit and https://www.youtube.com/watch?v=IMdfCptUxDc).

Given that the ear pinnae are longer than the tail in all species of hares, it is unsurprising that auricular flags are present in at least ten species.

What is surprising, instead, is that the ear pinnae have inconspicuous colouration in several species. For example, Lepus europaeus and L. capensis are so closely related that they may constitute a superspecies. Yet the latter (https://www.inaturalist.org/observations/70618803) differs from the former (https://www.inaturalist.org/observations/39641267) in lacking dark-pale contrast on the posterior surface of the ear pinnae - the observations of https://www.semanticscholar.org/paper/Ear-flashing-behaviour-of-cape-hares-(Lepus-in-Kamler/b4de4af4953cf3a80c60e22c8867b08feffe6876 notwithstanding.

The relationship between caudal and auricular (on the posterior surface of the ear pinnae) flags falls into the following categories:

• both so poorly-developed that I have found no illustrations (e.g. americanus)
• both present (e.g. europaeus https://www.inaturalist.org/observations/52383467, winter coat in timidus)
• caudal flag present but auricular flag absent (e.g. saxatilis https://www.projectnoah.org/spottings/17736127/fullscreen)
• auricular flag present but caudal flag absent (e.g. californicus https://www.inaturalist.org/observations/79491708, winter coat in townsendii https://www.inaturalist.org/observations/66858691).

There is a tendency in Lepus for the tips of the ear pinnae to be dark. However, it is only in L. townsendii in winter coat that this dark feature constitutes the entire pattern of the auricular flag (on the posterior surface of the ear pinnae). In e.g. L. europaeus, L. granatensis, and L. starcki, and some subspecies/individuals of L. timidus, the auricular flag on the posterior surface of the ear pinnae is punctuated by dark tips, but is conspicuous mainly owing to its paleness relative to the ground-colour of the figure.

The auricular flag on the posterior surface of the ear pinnae of Lepus callotis (https://www.inaturalist.org/observations/84012403) is differently configured from that in L. californicus (https://www.inaturalist.org/observations/39597865), despite these species being partly sympatric.

Lepus alleni is the only species in which the only flag is a haunch-flag, activated by twitching of the skin (scroll in http://feathertailedstories.blogspot.com/2017/). This produces a flashing effect analogous with that in Antilocapra americana (https://en.wikipedia.org/wiki/Pronghorn).

I have been unable to document any flags in several species of Lepus because too few photos are available. This includes e.g. L. coreanus (https://www.inaturalist.org/taxa/43144-Lepus-coreanus) and L. sinensis (https://www.inaturalist.org/taxa/43142-Lepus-sinensis), which occur in Korea and China respectively.

Flags are, by their nature, activated by movement. In Lepus, the movements are complex. In the following, I have tried to list them in increasing order of complexity in the context of reactions to potential predators:

• erecting the ear pinnae shows the auricular flags in all species (https://www.shutterstock.com/nb/image-photo/blacktail-jackrabbit-lepus-californicus-sitting-remote-73173493),
• holding the tail horizontal while fleeing, so that it wags somewhat up-and-down with the gait (https://stock.adobe.com/sk/search/images?k=jackrabbit+running&asset_id=60780157), producing a caudal flag in those species possessing tails with dark on the upper side and contrasting pale on the lower side (pronounced wagging of the tail is unusual in Lepus, with side-to-side wagging not having been recorded),
• going from a crouching to a sitting posture, with ear pinnae erect and flanks visible, can show not only auricular flags but also (in the case of L. callotis and L. alleni) haunch-flags, and possibly (in e.g. L. arcticus in the summer coat) pedal flags,
• fleeing shows auricular (only on the posterior surface of the ear pinnae), caudal, and haunch-flags, but not pedal flags,
• alternating movement of the ear pinnae (left vs right) while fleeing 'flashes' the auricular flag (this has been recorded mainly in L. californicus but probably occurs also in other species),
• alternating twitching of the skin on haunches and flanks (left vs right), as the fleeing individual zig-zags with haunch-flag activated, and
• stotting (recorded unambivalently only in L. arcticus, L. alleni, and L. callotis, all of which use bipedal hopping gaits at times) emphasises the display of all the flags shown by fleeing.

However, please note that caudal flags can be relevant also to intraspecific (particularly sexual) behaviour. During courtship, males of L. europaeus micturate on females while flashing the white lower surface of the tail (https://publish.iupress.indiana.edu/read/how-animals-communicate/section/a65f3527-f41e-4db2-a292-d7334cd4b38e). Similar behaviour probably occurs in other species.

Publicado el abril 16, 2022 10:40 MAÑANA por milewski