milewski's Journal

May 8, 2024

Geckos in Perth and Cape Town

https://www.inaturalist.org/taxa/33449-Christinus-marmoratus

https://www.inaturalist.org/taxa/93486-Afrogecko-porphyreus

https://www.perplexity.ai/search/Of-the-various-8_yzP4WaQQKNSOcNaNj9mQ

Posted on May 8, 2024 09:26 AM by milewski milewski | 0 comments | Leave a comment

May 7, 2024

Differences between Perth (Western Australia) and Cape Town (South Africa) in suburban avifaunas, part 1: black-and-white colouration

@tonyrebelo @jeremygilmore @ludwig_muller @adamwelz

Please see https://www.birdsandblooms.com/birding/bird-photography/black-and-white-birds/

INTRODUCTION

The metropolitan areas of Perth (https://en.wikipedia.org/wiki/Perth_metropolitan_region) and Cape Town (https://en.wikipedia.org/wiki/Cape_Town) are comparable for various reasons, including

  • coastal location,
  • mesic mediterranean-type climates,
  • mainly sandy substrates, and
  • extensive suburbia.

In both cases,

  • the suburban avifaunas are mainly indigenous at a continental scale,
  • there have been significant invasions/introductions of bird spp. indigenous to other regions on the same continents/subcontinents (marked with an asterisk * below), and
  • a few spp. have been introduced from other continents.

AIMS

In this Post, I compare those elements of the suburban avifaunas that have black-and-white overall colouration.

METHODS

In both cases, I have excluded all aquatic birds, whether marine or freshwater. The study spp. are those seen in one's garden and while walking around the suburbs.

RESULTS for PERTH

Black-and-white:

Mainly black-and-white but also featuring grey:

Lacking black but overall strikingly white:

RESULTS for CAPE TOWN

Black-and-white:

Mainly black-and-white but also featuring grey:

The incidence of black-and-white birds in the metropolitan area of Perth exceeds than in Cape Town, according to a combination of

  • phylogenetic diversity,
  • densities of populations, and
  • body size (remarkably large in most spp. in Perth, but remarkably small in Rhipidura leucophrys).

Furthermore, many of the study spp. (other than Threskiornithidae) in Perth vocalise extremely loudly. The calls are

There is a species of Corvus in both locations. However, that in Perth is far more abundant than - and as large-bodied as (https://www.perplexity.ai/search/What-is-the-zFV0nu9SSLmUzx3sFDcDPw) - that in Cape Town.

Additional in Perth is an abundant rook-like, large passerine, belonging to an unrelated family (Artamidae, https://en.wikipedia.org/wiki/Cracticinae). I refer to Gymnorhina tibicen, typical of suburban lawns.

A superspecies of Threskiornis is represented in both metropolitan areas. However, the Australian representative has recently become common in suburban parks, ranging from these into suburban streets. The South African representative - possibly because parks are limited in Cape Town - remains more strictly tied to large rubbish dumps and metropolitan wetlands.

The species in Perth is somewhat larger-bodied than that in Cape Town (https://www.perplexity.ai/search/Which-of-the-IyJ.4bIPTQ6RVCCcAzexpA).

An additional congener has recently invaded Perth spontaneously, foraging mainly in suburban parks (as opposed to depending partly on refuse as in the case of T. molucca). This makes Threskiornis exceptional in contain two coexisting, black-and-white spp. within a single metropolitan area.

A hook-billed cracticid in Perth, weighing about 90 grams, is the approximate ecological counterpart of a laniid (about 40 grams) in Cape Town. The Australian species is the larger-bodied of the two, a caveat being that it is partly grey.

DISCUSSION

The small passerine Rhipidura leucophrys (20 grams) is currently common throughout the suburbs of Perth. It seems to be the only bird species on Earth, weighing less than 25 grams, with an unambivalently bold pattern of exclusively black-and-white plumage.

Rhipidura leucophrys thus has no counterpart in Cape Town, even if one considers the relatively uncommon Melaenornis silens.

Black-and-white, and all-black, are unusual colourations for small birds. Among the few examples worldwide are:

A possible explanation for the commonness of conspicuously marked - and correspondingly noisy - large birds in Perth relates to the relatively light regime of predation on the 'island continent'.

And, indeed, T. molucca, C. coronoides, and G. tibicen, and particularly G. cyanoleuca, and R. leucophrys, are remarkably habituated to human proximity, to degree unknown for any indigenous bird in Cape Town. They allow close approach in the case of the first three spp., and actually approach gardeners to < 1 meter in the case of the last two spp.

Furthermore, G. tibicen actually attacks humans during its breeding season (https://www.science.org.au/curious/earth-environment/how-survive-magpie-swooping-season and https://neoskosmos.com/en/2019/10/02/dialogue/opinion/why-are-dangerous-australian-magpies-so-different-to-their-docile-european-counterparts/ and https://www.qld.gov.au/environment/plants-animals/animals/living-with/magpies/swooping and https://blog.nationalparks.nsw.gov.au/how-to-avoid-being-swooped-by-a-magpie/ and https://www.magpiealert.com/ and https://en.wikipedia.org/wiki/Animal_attacks_in_Australia).

In this context it is worth considering the mainly black colouration of Accipiter melanoleucus in Cape Town. This raptor (adult female body mass 0.75-1 kg) preys typically on columbids, which it hunts by stealth. Its colouration functions for concealment rather than advertisement, because it hides in the crowns of trees, and any white bib is in a relatively hidden position anatomically.

Posted on May 7, 2024 12:18 AM by milewski milewski | 12 comments | Leave a comment

May 6, 2024

Why are infants of the pronghorn (Antilocapra americana) less cursorial than those of the common impala (Aepyceros melampus)?

Everyone knows that the pronghorn (Antilocapridae: Antilocapra americana) is exceptional in its speed and endurance in running.

I refer to this as hypercursoriality ().

Among bovids, the most cursorial species belong to the tribe Alcelaphini, which run with great speed and endurance. However, the pronghorn is more cursorial than any alcelaphin.

However, the pronghorn is anomalous in a certain way: its infants hide immobile for three weeks before they and their mothers resume their normal gregariousness.

For comparison, infants of the alcelaphins Connochaetes and Damaliscus tend to run with a group right from birth. They are 'followers', not 'hiders'. Why do infants of the pronghorn not perform likewise?

Furthermore, even impalas (Bovidae: Aepycerotini) - which bound prodigiously but are not reputed to be particularly enduring runners - have cursorial infants, which join the group after a hiding period of only a few days.

Making the comparison between pronghorn and impala even more meaningful is the fact that both have synchronised breeding. Most offspring are born within as brief a period each year as in the western white-bearded wildebeest (Connochaetes mearnsi), in which the infants are so precocial that they are fully cursorial shortly at only a few days old.

There are three possible explanations for the apparent incongruity between the hypercursoriality of the pronghorn in adulthood and its immobile hiding in infancy, as follows:

  • The pronghorn produces usually two infants (twins) per birth, as opposed to the single infant born in most comparable ruminants; thus, the infants are too small to be cursorial for the first three weeks of life, hiding instead.
  • Infants of the pronghorn are indeed large-bodied and long-legged enough to run fast and far, but are physiologically and behaviourally committed to a tactic of immobility, for various reasons such as the availability of cover in the form of sagebrush (Artemisia tridentata) in the typical habitat of the pronghorn.
  • The real strategy of the pronghorn in infancy is to combine immobility while hiding with extreme speed and endurance once found and attacked by a predator, which would be mean that the species could actually be regarded as hypercursorial at all ages.

In increasing order of maternal body mass:

Eudorcas thomsoni 18.5 13.5%
Procapra gutturosa 13%
Antidorcas marsupialis 30 12.5%
Aepyceros melampus 45 11.1%
Damaliscus pygargus phillipsi 60 10.8%
Damaliscus lunatus 110 10.0%

For the pronghorn: 45 6.7%

Reference for infant hiding period: https://academic.oup.com/jmammal/article/87/2/312/870959

Reference for neonatal body mass: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4667974/

https://www.jstor.org/stable/4599618

https://www.nytimes.com/1996/12/24/science/pronghorn-s-speed-may-be-legacy-of-past-predators.html

https://www.researchgate.net/publication/229195900_Birth_Synchrony_and_Survival_of_Pronghorn_Fawns

https://scholarworks.umt.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=7555&context=etd

Posted on May 6, 2024 01:59 PM by milewski milewski | 8 comments | Leave a comment

May 1, 2024

Sundry aspects of the adaptive colouration of the pronghorn (Antilocapra americana)

https://www.inaturalist.org/journal/milewski/93100-an-index-to-my-posts-about-the-pronghorn-antilocapra-americana

https://www.kimballstock.com/preview.asp?db=a&image=WLD+21+TL0012+01

MASCULINE DISPLAYS

Kitchen D W and Bromley P T (1974) Agonistic behavior of territorial pronghorn bucks. Paper no. 18, pp. 363ff, in The behaviour of ungulates and its relation to management, ed. by V Geist and F Walther. IUCN Publications new series no. 24, vol. 1.

The territorial male reacts to trespassing conspecifics by snort-wheezing, "In 83.5% of the observations the snort-wheeze was associated with erection of the median gland...mane and upper 1/3 of the rump patch (Figure 4)". The caption of Figure 4 states "Stance of a buck doing the snort-wheeze call: mane, median-gland, and upper 1/3 of rump patch erect."

Closest-quarters mutual displays between males: "Partial erection of the mane and upper 1/3 of the rump patch, and a slight raising of the ears was noted in some encounters (Fig. 6)" (this is when the individual male has lost confidence). "Fig. 6. This buck has lost his confidence in an encounter with the buck in Fig. 5. Note the tail is raised, upper part of the rump patch and mane are partially erect, and the ears have moved to a neutral position."

Tooth-grinding by males can be heard by humans up to 10 meters away.

"Fig. 9. This is a territorial buck during a running chase, Note: (1) median gland is erect, (2) mane is fully erect, and (3) ears are almost fully depressed." "While in pursuit the [territorial male] depressed his ears, erected his mane, median gland, and on 13 occasions the upper 1/3 of his rump patch (Fig. 9)." "Fig. 12. This is the typical alarm posture with the rump patch and mane fully erect and the ears in a neutral position. The median gland is normally erect in this posture."

Excerpt from my notes: The exclusively male dark patch at the masseter is clearly associated with a masculine gland, in a position unusual among ungulates. This is perhaps the prime example, in all the ungulates, of a skin-gland unambiguously associated with gross-scale display of dark/pale contrast in the pelage. Apart from relatively large horns, this dark patch is the most sexually dimorphic feature of A. antilocapra, first appearing in infants. Its anatomical position is surprising (different from other ungulates) and the visual emphasis is surprisingly strong, the dark patch in maturity being so large and so tonally contrasting that it is visible at distance and from various perspectives. In this feature, no other ruminant is similar to the pronghorn, a species in which all the dark features (including forehead and horns) are on or near the head.

Certain spp. of Oryx have dark markings on the tract passing from the crook-of-throat to the masseter (https://www.shutterstock.com/da/image-photo/oryx-closeup-627303404 and https://www.shutterstock.com/da/image-photo/east-african-oryx-beisa-known-species-1302873655 and https://www.dreamstime.com/beautiful-close-up-oryx-head-magnificent-horns-gemsbok-against-pale-blue-clear-sky-image257816498 and https://www.masterfile.com/image/en/841-03507691/gemsbok-south-african-oryx-oryx and https://www.masterfile.com/image/en/700-02887439/oryx-buffalo-springs-national-reserve-kenya and https://www.agefotostock.com/age/en/details-photo/side-profile-of-an-oryx-in-the-kalagadi-transfrontier-park-south-africa/ESY-054018317 and https://www.shutterstock.com/da/image-photo/gemsbok-oryx-30641182?utm_campaign=image&utm_medium=googleimages&utm_source=schema and https://www.gettyimages.co.uk/detail/photo/oryx-antilope-leaks-minerals-kgalagadi-royalty-free-image/1215316063?phrase=gemsbok+face&adppopup=true and https://www.gettyimages.co.uk/detail/photo/gemsbok-drinking-water-royalty-free-image/121329915?phrase=gemsbok+face&adppopup=true).

However, these lack glands.

SEASONAL CHANGES

A noteworthy feature of Antilocapra americana is that it retains the same colouration throughout the seasonal cycle, despite having structurally/texturally distinct winter pelage.

Requiring investigation is the possibility of seasonal change in the colouration of the nape. In some photos, there is striking dark/pale contrast, partly owing to posteriorward extension of pale from the crown down each side of the dark mane.

In its seasonal uniformity in colouration, A. americana differs from sympatric cervids and possibly Bison bison.

The seasonal relative darkness of the cervids of snowy climates in the Northern Hemisphere tends to make them conspicuous in winter, even if they are inconspicuous in summer.

In its lack of seasonal change, A. americana resembles North American bovids (Ovis, Oreamnos) rather than cervids. However, A. americana tends to be particularly gregarious in winter (when females and males run together), so that conspicuousness may be enhanced by numbers and movement.

LEGS

The legs of Antilocapra americana are pale, and fairly uniformly so. There is no pedal flag. The ground-colour of the legs is paler than that of the palest parts of the torso, neck, and face.

On close scrutiny, the following features can be discerned:

  • the hooves, like the horns, are blackish, producing a nominal dark/pale contrast with the pasterns and fetlocks. Note that false hooves/dewclaws are absent;
  • whitish extends from the ventral surface of the torso to parts of the upper legs, on the posterior surface of the forelegs but the anterior surface of the hindlegs;
  • the elbow is white (https://www.nps.gov/articles/pronghorn.htm and https://www.sportsmansguide.com/article/twenty-pronghorn-pointers?id=2470), which can be thought of as an extension of the pale flank-band; the knee is also white, but less noticeably so.

The white tracts on the inner surfaces of the upper legs end with oblique borders, in opposite orientations on fore vs hind. However, the inner surfaces of the legs are such a pale tone of fawn that this pattern is easily overlooked.

Task: compare the patterns with Aepyceros and Antilope.

BACK-OF-HEAD PATTERN

There is a complex pattern on the posterior surface of the head in Antilocapra americana, extending to the nape and ear pinnae.

This consists of

  • pale pelage on the posterior of the crown, extended on to the nape at each side (left and right) of the mid-line, and
  • the dark pelage of the erectile mane of the nape.

The mane does not extend on to the crown, or even the occipital area of the skull.

The dark/pale contrast in this pattern is moderate, because the pale aspects are not white, while the dark aspects are brown rather than black. Furthermore, the display depends partly on the erection of the mane, which is narrow and inconspicuous when folded.

Then fairly pale posterior surfaces of the ear pinnae add to the display. However, this is rather ambivalent because

  • the paleness on the back-of-ear is not nearly white, and lacks any dark tip, and
  • one of the two ears is often turned inconspicuously backwards while the animal faces forward.

There is some analogy in display between the front and the back of the head. Both are complex and subtle, and subject to variation according to ontogeny/sex/subspecies. The mane differs in prominence between juveniles and adult males, and between e.g. subspecies mexicana and subspecies americana.

The dark mane, which seems most prominent in juveniles, may enhance the conspicuousness of the acetabulo-ischiopygal bleeze when viewed directly from behind. The dark mane adds tonal contrast despite being relatively far from the observer.

I have the following note in my files:

"Video on the Web, viewed June 2020, shows two adult male individuals of Antilocapra americana in winter pelage, with the horns reduced to dark spikes, shorter than the ear pinnae. This footage shows that A. americana does indeed have a kind of back-of-ear display, with enough dark/pale contrast to be noteworthy. The posterior surfaces of the ear pinnae are pale, with a tone similar to that of the lower legs. There is no dark tip on the ears, on either front or back. The main pale feature in the display is the whitish at the base of the ears. The main dark feature is the mane, which is narrow (not erect) in this view. The pale descending from the back-of-crown partway down each side of the mane is disjunct from the pale at the ear-bases. This back-of-ear/back-of-head/'nape' display is seen against the mainly dark-looking back and neck of the animal."

MANE

The mane is associated with masculinity in various mammals, which makes sense because it can enhance the apparent size of mature males in masculine rivalry.

As in giraffids, Antilocapra americana has a 'hyperprecocial' pattern, in which the mane is largest in and most conspicuous, relative to body size, in juveniles and females.

Then displaying if the mane is complex and subtle in A. americana. However, it is noteworthy that the mane is - unlike the dark subauricular patch of males and the piloerectile acetabulo-ischiopygal bleeze - not known to be glandular.

Another peculiarity of the mane is that it ends abruptly, well-short of the base of the neck. When the head is held up, the mane seems to reach the base of the neck; however, when the bead is lowered to forage, the real shortfall becomes apparent. Either way, the mane certainly fails to reach the withers.

LACK OF GLOSS

Antilocapra americana does not have any gloss on its pelage, at any season. This is a point of difference from e.g. Nanger and Eudorcas, as well as alcelaphin bovids.

Even the horns are hardly glossy, being blackish but more-or-less matt.

The lack of gloss in A. americana is associated with the structure/texture of the pelage, which resembles that of e.g. Oreotragus and Hydropotes. This resemblance includes easy detachability, which is

  • presumably an anti-predator adaptation,
  • borne out by discussion among taxidermists on the Web, and
  • possibly greatest in winter pelage.

POSSIBLE CAUDAL FLAG

The tail of Antilocapra americana is grojnd-colour (fawn) on its upper (dorsal) surface, and white on its lower (ventral) surface. There is a narrow fawn-coloured midline separating the left from the right half of the acetabulo-ischiopygal bleeze; this mid-dorsal 'stripe' ends in the tail.

The tail is often lifted to a horizontal position during fleeing, making it a slightly noticeable feature by virtue of its (slight) projection.

The tai is displayed more than in Ovis canadensis, Ovis dalli, Oreamnos americanus, Alces alces, or Cervus canadensis, but less than in Odocoileus hemionus (check) and Rangifer tarandus. The latter erects the tail habitually, altering the silhouette more than in A. americana, despite the similarities of the tails.

It is noteworthy that, although males of A. americana have a (unpaired) median gland, exposed by erectile pelage, this is located not on the tail or at its base, but instead on the sacrum, anterior to the acetabulo-ischiopygal bleeze.

It is possible that Antilocapra americana possesses a caudal flag. This is despite the fact that the tail is small, and seemingly insignificant relative to the bleeze on the hindquarters.

The tail is sometimes erected and moved, gleaming white, without piloerection of the acetabulo-ischiopygal bleeze - which in its quiescent state is pale but not white. In other words, the tail - viewed in profile - sometimes flashes white as it is wagged. Each bout of wagging consists of a brief (split-second) series of a few rapid wags.

However, it is unlikely that any caudal flag in A. americana is deployed vs predators; its activation seems to be purely social/intraspecific.

Antilocapra americana does not erect the tail when piloerecting the acetabulo-ischiopygal bleeze. In this way it differs from Rangifer tarandus, which habitually raises the tail but does not seem able to piloerect the (small) patch of white pelage on the buttocks (https://churchillwild.com/caribou-antlers-and-their-growth/ and https://www.theguardian.com/world/2024/apr/23/wolf-culls-canada-caribou-saving-endangered-mountain-caribou).

The tail of A. americana is not inert, because it is

  • often raised to horizontal during running, and
  • sometimes flicked (flashing white) during standing.

However, the main function of the tail (and its base) in terms of display is to provide a fawn dividing line between the two 'hemispheres' of the acetabulo-ischiopygal bleeze, somewhat punctuating the whitish expanse of this bleeze.

Overall, the following summary pertains:

  • The tail of A. americana is sometimes hard to distinguish from an adjacent ruff of pelage at the edge of each half of the acetabulo-ischiopygal bleeze.
  • More than in any other ungulate, A. americana has specialised on emphasis by piloerection of an extensive, discrete, disc-like, white bleeze on the hindquarters.
  • This 'piloerectile emphasis' makes the tail relatively insignificant, even though the tail itself is actually similar to that of Rangifer, in which it is a major feature of the display on the hindquarters.
  • The tail of A. americana is far shorter than that if any antilopin bovid (check), fawn on the proximal dorsal surface and white on the ventral surface and the tip (which cannot be called a tassel).

Most of the ungulates of North America have short tails.

POSSIBLE ANTERIOLATERAL FLAG

https://www.jasonsavagephotography.com/tag/pronghorn/

SUBSPECIES PENINSULARIS (based on photos from the breeding programme in Los Angeles Zoo).

The main difference from the nominate subspecies seems to be a reduced pattern of dark/pale contrast on the cheeks. The pale patch of the cheek, typical in the nominate ssp., is longitudinally divided by fawn in ssp. peninsularis (https://animalworld.tumblr.com/post/188640547595/peninsular-pronghorn-antilocapra-americana). This is individually variable.

Other points noted for ssp. peninsularis:

  • The orbits of the skull also seem to be less prominent than in the nominate ssp.
  • The forehead of adult males is dark.
  • The pelage on the rump is slightly sexually dimorphic in that the vicinity of the 'caudal' gland in males.
  • The horns of males are short and forward-directed, with a 'ruff' of pale pelage at the bases, with a narrow strip of fawn separating the horn-bases from the whitish pelage of the ear-bases and posterior crown. The latter whitish is, in turn, more-or-less separated from the white of the facial streak posterior to the subauricular gland.
  • There is a whitish band, in both sexes, transversely across the crown, just anterior to the ear-bases.

ONTOGENY

None of the conspicuous features of colouration is fully-developed in infants of Antilocapra americana. However, all are incipient (partly visible) shortly after birth.

Infants possess the dark/pale contrast at the nose/mouth, with the rest of the malar flag developing only later in life. The pelage of the subauricular gland starts to darken in juveniles (i.e. its colouration is precocial). However, the dark spot is initially small. It gradually spreads as adulthood and maternity are reached.

The conspicuous pale feature on the flanks is particularly dim in infants, becoming fully-developed in juveniles.

The acetabulo-ischiopygal bleeze is functional already in infants, in the sense that it can be piloerected to show conspicuous white. However, without such piloerection the feature is inconspicuous in infants, because

  • the superficial hairs of the bleeze are pale fawn rather than white, and
  • the hindquarters are so poorly-developed in infants that the expanse of the feature is limited.

Overall, the colouration of infants is certainly adapted for concealment. Infants possess a functionally (dependent on piloerection) conspicuous feature only on the hindquarters, and not on the flanks or the cheeks.

Infants of A. americana are less precocial in colouration than are gazelles. The most similar gazelle in this respect is Antidorcas marsupialis. This is partly because its infants lack the facial pattern of juveniles and adults.

COMPARISON WITH GAZELLES

The adult body mass of Antilocapra americana is about double that in Gazella-Eudorcas, and intermediate between those of Antidorcas marsupialis and Damaliscus pygargus.

Antilocapra americana resembles gazelles in that its adaptive colouration is a subtle combination of conspicuous and inconspicuous features, at various scales. Because it is larger-bodied than most gazelles, it tends to be less able to hide in open environments.

If it were the case that A. americana were as unambivalently conspicuous as Antidorcas marsupialis, then

  • the whitish pelage would be white, and
  • there would be dark features on both the hindquarters and the flanks.

The erectile bleeze is not frequently activated in earnest in A. marsupialis. By contrast, the erectile bleeze of A. americana is frequently activated, flashing pure white, almost as a 'contingent substitute' for the whole-figure conspicuousness of A. marsupialis.

I.e. while there is analogy in the erectile bleezes of the two spp., another way of looking at it is that A. americana

  • is less committed to conspicuousness than is A. marsupialis, and
  • boosts its conspicuousness more readily - by means of 'flareing' - than does A. marsupialis.

In any collection of about 100 photos of A. americana, one will find many inadvertent depictions of its erectile bleeze. By contrast, in any 100 photos if A. marsupialis, I would not expect to see any depictions of its erectile bleeze, especially if one specifies displays in earnest rather than in play. The ratio could be about 10:1.

Antidorcas marsupialis possesses a lateral bleeze, whereas A. americana does not. In the latter, the whitish on the flank has high clearance, thus catching the light. However, this feature is not necessarily white, and it cannot be whitened by 'flareing' in the manner of the bleeze on the hindquarters. Furthermore, the bold pattern in the flanks is precocial in A. marsupialis, but not in A. americana.

Just as the colouration on the faces of most spp. of gazelles (Gazella and Eudorcas) is disruptive, so the patterns on the face and anterior surface of the neck of A. americana are disruptive.

Posted on May 1, 2024 02:08 AM by milewski milewski | 12 comments | Leave a comment

April 29, 2024

A puzzling case of the Australian raven (Corvus coronoides) ignoring the shingleback lizard (Tiliqua rugosa)

@davidsando @max_tibby @joshuagsmith @thebeachcomber @jadonald @bmduggan

On 28 April 2024, at about 14h00, I encountered an individual of Tiliqua rugosa rugosa (https://animaldiversity.org/accounts/Tiliqua_rugosa/ and https://www.inaturalist.org/observations?taxon_id=37460) by the side of a road in Karrakatta Cemetery (https://www.mcb.wa.gov.au/our-cemeteries/karrakatta-cemetery/) in the Perth Metropolitan area (https://en.wikipedia.org/wiki/Perth).

The autumn weather was fine, sunny, and warm, with no wind. The ambient temperature was 26 degrees Celsius.

The lizard was fully sunlit, away from any cover. I approached it to within one meter, and it remained stationary and passive, not reacting to my presence. It seemed unperturbed, despite being completely exposed and vulnerable.

Tiliqua rugosa has camouflage-colouration. This individual, which was probably a large juvenile (estimated body mass about 0.5 kilograms) rather than fully-grown, remained inanimate, not even flicking its tongue. However, its presence was obvious because it was out in the open.

The individual was in normal condition apart from its tail, which was noticeably shrivelled and scruffy. This was probably the result of its store of fat having been used up in this dry season - which has been exceptionally warm and rainless (https://business.weatherzone.com.au/climate/second-hottest-summer-days-on-record-in-perth/ and https://www.abc.net.au/news/2024-03-09/wa-summer-weather-wrap-autumn-outlook/103541460), and prolonged past mid-autumn.

After a moment, I walked on.

I paused after 10 meters to see how the lizard was reacting to my departure. Looking back, I noted an adult individual of the Australian raven (Corvus coronoides, https://ro.ecu.edu.au/cgi/viewcontent.cgi?article=1294&context=theses_hons and https://en.wikipedia.org/wiki/Australian_raven and https://australian.museum/learn/animals/birds/australian-raven/), perched about 7 meters high in a eucalypt tree, about 5 metres beyond the lizard. The body mass of the bird was probably about 650 grams.

This individual had been vocalizing, rather softly and querulously, before I noticed it, and it continued to do so as I watched to see what the lizard did once I was no longer close to it. The vocalisation of the bird did not attract any other individuals of its species.

After about 10 seconds the lizard started to crawl towards the road, intermittently flicking its tongue in the typical manner of its species. The lizard had been in plain view of the bird from the start, and was now even more obvious owing to its slow movement.

I was curious to see whether the bird would fly down from its perch to investigate or attack the lizard. Tiliqua rugosa is, after all, something of a 'sitting duck', with its slow movement and modest armour of reinforced scales.

In this suburban neighbourhood, the Australian raven is unpopular owing to its habitual predation on nestling birds (https://westernweb.net/2015/11/17/are-urban-ravens-really-thugs-and-murderers/). The species is known to be capable of killing juveniles (up to 400 g, https://www.alamy.com/stock-photo-juvenile-european-wild-rabbit-oryctolagus-cuniculus-uk-47511065.html) of the feral rabbit (Oryctolagus cuniculus, https://www.tandfonline.com/doi/pdf/10.1071/MU959041).

A congener, namely Corvus ruficollis (https://www.inaturalist.org/observations?place_id=any&subview=map&taxon_id=8034) is known to be a predator on another large, slow-moving lizard, namely Uromastyx aegyptia (https://www.inaturalist.org/observations?taxon_id=31332).
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8388000/8388073.stm and https://www.researchgate.net/publication/225220613_Cooperative_hunting_in_Brown-Necked_Raven_Corvus_rufficollis_on_Egyptian_Mastigure_Uromastyx_aegyptius and https://cris.bgu.ac.il/en/publications/cooperative-hunting-in-brown-necked-raven-corvus-rufficollis-on-e).

However, this individual of C. coronoides showed no interest in the lizard, simply continuing to vocalise (in a way I have not heard previously) until it flew off after about three minutes. By this time the lizard, locomoting in a leisurely and unconcerned way, had partly crossed the road.

The whole incident left me with the impression that the bird 'knew something I did not' about the unsuitability of T. rugosa as prey.

What could this possibly be? Why did the Australian raven not muster up a group, to collectively attack the lizard?

While walking at this same location several years previously, I had experienced a 'funeral' congregation (https://corvidresearch.blog/tag/crow-funeral/ and https://birdoftheweek.home.blog/2020/09/19/bird-152-australian-raven/ and https://www.scienceabc.com/nature/animals/do-crows-mourn-their-dead.html) of the Australian raven - testimony to the ability of the species to muster a large group by means of vocalisation.

I had encountered as many as 50 individuals - constituting the entire population of the suburb where I live - congregated in and among the trees above, calling excitedly and alternately flying and perching. I had then observed a freshly dead individual of C. coronoides on the ground near the same road.

The attendant group had followed me fairly cohesively as I walked past, over a distance of several tens of meters, as if 'mobbing' me (https://en.wikipedia.org/wiki/Mobbing_(animal_behavior)) in emotional association with the death of their conspecific.

Returning in time to the incident at hand:
If a mere fraction of such congregation were mustered in response to the spotting of potential prey in the form of a vulnerable individual of T. rugosa, the lizard could potentially have been overcome and eaten.

Posted on April 29, 2024 03:34 AM by milewski milewski | 17 comments | Leave a comment

April 26, 2024

Polygonaceae and Plumbaginaceae as biogeographical outliers in the Cape Flora of South Africa

In both South Africa and Australia, large regions of nutrient-poor substrates have distinctive floras, dominated by sclerophyllous or semi-sclerophyllous, fire-prone shrubs.

These are 'heathlands' in a loose sense (https://link.springer.com/chapter/10.1007/978-3-642-68935-2_2 and https://search.worldcat.org/title/ecosystems-of-the-world-9b-heathlands-and-related-shrublands-analytical-studies/oclc/1003129176 and https://ui.adsabs.harvard.edu/abs/1982JEcol..70..922G/abstract).

The families Polygonaceae (https://en.wikipedia.org/wiki/Polygonaceae) and Plumbaginaceae (https://en.wikipedia.org/wiki/Plumbaginaceae) would not seem to belong in these ecosystems.

This is because these two closely-related dicotyledonous families are mainly

  • herbaceous, and
  • associated with nutrient-rich - or in the case of Plumbaginaceae sodic or even saline - substrates in the Northern Hemisphere.

So, Polygonaceae and Plumbaginaceae seem remote from the 'southern heathland' floras, both geographically and ecologically.

However, these families have managed to defy the general pattern in a limited way, which tends to pass under the radar for botanists whose interest is centred on fynbos (https://en.wikipedia.org/wiki/Fynbos) in South Africa and/or kwongan (https://en.wikipedia.org/wiki/Kwongan) in Australia.

What are easy to overlook are that

  • both the genus Polygonum and a particular genus in the Plumbaginaceae have somehow found their way to the southernmost reaches of South Africa, where they have speciated into 'narrow endemics' in the Cape Flora (https://link.springer.com/article/10.1023/A:1018360607299), and
  • one genus of Polygonaceae, namely Muehlenbeckia (https://en.wikipedia.org/wiki/Muehlenbeckia), has penetrated southwestern Australia, where it grows as an unobtrusive but anomalous liane at the edges of what is the most extreme example of 'heathland' on Earth.

The species to which I refer are as follows:

  • Polygonum undulatum, a biogeographically remarkable but fully indigenous 'misfit' in 'renosterveld' South Africa
  • a set of about ten species of Limonium, all restricted to low-lying plains under a mediterranean-type climate in the southwestern Cape of South Africa
  • Muehlenbeckia adpressa, a small liane, widespread in southernmost, mesic Australia and present on nutrient-poor substrates the South-West Botanical Province (https://en.wikipedia.org/wiki/Botanical_Provinces_of_Western_Australia).

Polygonum undulatum is remarkable partly because it has undergone some degree of evolutionary convergence with the 'ericoid' growth-form (https://www.inaturalist.org/observations?verifiable=true&taxon_id=592411). I refer to the following features

  • perennial and somewhat woody,
  • evergreen and perhaps semi-sclerophyllous.

Most species of the same genus (https://en.wikipedia.org/wiki/Polygonum), which occur in the Northern Hemisphere, are herbaceous and deciduous (including annuals). Many are weedy/ruderal (https://www.wswa.org.au/western_weeds/polygonaceae.htm), and some are so thoroughly domesticated that they have become important in agriculture.

Limonium kraussianum (https://www.inaturalist.org/taxa/589185-Limonium-kraussianum)
Limonium peregrinum (https://www.inaturalist.org/taxa/589189-Limonium-peregrinum)
Lumonium purpuratum (https://www.inaturalist.org/taxa/589190-Limonium-purpuratum)
Limonium longifolium (https://www.inaturalist.org/taxa/589187-Limonium-longifolium)
Limonium capense (https://www.inaturalist.org/taxa/589179-Limonium-capense)
Limonium anthericoides (https://www.inaturalist.org/taxa/589178-Limonium-anthericoides)
Limonium acuminatum (https://www.inaturalist.org/taxa/589176-Limonium-acuminatum)
Lumonium equisetinum (https://www.inaturalist.org/taxa/589184-Limonium-equisetinum)
Limonium sp. nov. (https://www.researchgate.net/profile/Ladislav-Mucina/publication/46888924_Syntaxonomy_and_zonation_patterns_in_coastal_salt_marshes_of_the_Uilkraals_Estuary/links/590e9c83a6fdccad7b10e0ee/Syntaxonomy-and-zonation-patterns-in-coastal-salt-marshes-of-the-Uilkraals-Estuary.pdf)

https://en.wikipedia.org/wiki/Muehlenbeckia_adpressa

https://www.inaturalist.org/observations/105053325 and https://exploreparks.dbca.wa.gov.au/site/hellfire-bay and https://stock.adobe.com/images/hellfire-bay-is-a-popular-beach-in-the-cape-le-grand-national-park-west-of-esperance-western-australia-australia/275286283 and https://www.alltrails.com/trail/australia/western-australia/hellfire-bay-trail

Posted on April 26, 2024 10:07 PM by milewski milewski | 13 comments | Leave a comment

April 24, 2024

Life-history strategy of the pronghorn (Antilocapra americana): short-lived but with long gestation compared to real antelopes

@ptexis @tonyrebelo @jeremygilmore @matthewinabinett @paradoxornithidae @jwidness @tandala @oviscanadensis_connerties @davidbygott @simontonge @beartracker @variani18 @aguilita

See https://www.inaturalist.org/journal/milewski/93100-an-index-to-my-posts-about-the-pronghorn-antilocapra-americana#

The maximum lifespan of the pronghorn (Antilocapridae: Antilocapra americana) is said to be 16 years (https://animaldiversity.org/accounts/Antilocapra_americana/ and https://eol.org/pages/328661/articles).

The mean body mass of adult females is about 45 kilograms (https://ielc.libguides.com/sdzg/factsheets/pronghorn).

How does this compare with other ruminants?

The maximum lifespan of *bovids (Bovidae) and cervids (Cervidae) of comparable body mass is as follows, in order of decreasing lifespan:

  • Cervus nippon (40 kg) 25.4 years
  • Dama dama (45 kg) 25 years
  • *Pseudois (40 kg) 24 years
  • *Ovis (about 50 kg) 24 years
  • *Rupicapra (about 40 kg) 22 years
  • *Capra ibex (40 kg) 22 years
  • *Hemitragus (36 kg) 22 years
  • Ozotoceros bezoarticus (30 kg) 22 years
  • *Capricornis crispus (40 kg) 22 years
  • *Capra hircus (20-60 kg) 21 years
  • Axis axis (40 kg) 21 years
  • Axis porcinus (40 kg) 20 years
  • Rusa timorensis (about 50 kg) 20 years
  • Odocoileus (about 50 kg) 20 years
  • *Nanger dama (37.5 kg) 19 years
  • *Antidorcas (30 kg) 19 years
  • *Redunca (30-48 kg) 18 years
  • *Oreamnos (about 65 kg) 18 years
  • *Naemorhedus (27.5 kg) 17.6 years
  • Muntiacus muntjak (20 kg) 17.6 years
  • *Aepyceros (45 kg) 17.4 years
  • Capreolus capreolus (25 kg) 17 years
  • *Gazella (15-30 kg) 17 years
  • Mazama americana (30 kg) 16 years
  • *Ourebia (17 kg) 14 years

The above data show that the maximum lifespan of the pronghorn is shorter than expected for similar body mass in

  • *bovids (by 1.4-8 years), and
  • cervids (by 4-9.4 years).

However, gestation periods ('lifespan in utero') do not necessarily conform to the above trend.

The pronghorn gestates for 8.2 months, http://placentation.ucsd.edu/prong.html).

This is long, relative to certain like-size

  • *bovids, e.g. Capra (which gestates for only 5-6 months) and Pseudois (which gestates for only 4-5.3 months), and
  • cervids, e.g. the white-tailed deer (Odocoileus virginianus), which gestates for 6.6 months.

In general, most species, similar in body mass to the pronghorn,

  • in *bovids gestate for 5-7.5 months, differing from the antilocaprid by 0.7-3.2 months, and
  • in cervids gestate for 7-8 months, differing from the antilocaprid by 0.2-1.2 months.

At adult female body mass of about 50 kg, gestation in bovids tends to be about one month less than in cervids. The bovid genus Redunca (three species, varying in adult female body mass from 30 kg to 70 kg) is an exception, with gestation about as long as in the pronghorn.

The above data therefore show, overall, that the pronghorn has an anomalously short lifespan, but an anomalously long gestation.

DISCUSSION

Pace of life is the rate at which a species metabolises, grows, and reproduces, relative to adult body mass.

Organisms with slow pace of life tend to live long, whereas those with rapid pace of life tend to live briefly.

Pace of life varies among species, even within ruminants.

Forms living in environments where resources are scarce, and predators are few, can be expected to have relatively slow pace of life. Such environments include islands, high mountains, and dense forests.

By contrast, forms living in nutrient-rich, low vegetation on plains, able to migrate annually in search of rich resources, can be expected to have relatively rapid pace of life.

Slow pace of life - within the context of ruminants - is exemplified by Bubalus depressicornis (adult female body mass > 90 kg), of Sulawesi in Indonesia. This bovid has maximum lifespan of 31 years (https://animaldiversity.org/accounts/Bubalus_depressicornis/), nearly double that of the pronghorn.

Comparisons must take into account body size, because we can expect large-bodied forms to live and gestate longer than small-bodied forms. For example, Giraffa (adult female body mass 800 kg) has rapid pace of life, but has a maximum lifespan of 27 years (https://animaldiversity.org/accounts/Giraffa_camelopardalis/).

However, there is no simple correlation between lifespan and pace of life on one hand, and gestation periods on the other, in ruminants.

The following species seem noteworthy in having both slow pace of life and long gestation:

The above camelid happens to have similar body mass to the pronghorn.

This shows that in the pronghorn relative to Vicugna vicugna, both parameters are much shorter, viz.

  • maximum lifespan (by nearly 9 years), and
  • gestation period (by 3.3 months).

What emerges for the pronghorn is that

  • lifespan is short for the body size, relative to bovids, and
  • gestation period, although much shorter than in a like-size camelid, is much longer than in bovids that are like-size with a similarly rapid pace of life.

The rapid pace of life, hence short lifespan, of the pronghorn can possibly be explained by its particularly nutrient-rich - albeit generally dry - habitat, and mainly dicotyledonous diet (https://www.inaturalist.org/journal/milewski/93032-a-new-explanation-for-the-hypercursoriality-of-the-pronghorn-antilocapra-americana-selenium-as-a-crucial-micronutrient#).

The anomalously long gestation of the pronghorn is not necessarily incongruous with rapid pace of life. However, how it fits into the life-history strategy remains to be explained.

Perhaps the first clue to investigate is Pantholops hodgsonii (26 kg), which occupies a comparable niche in Asia. This pantholopin is said to gestate for 7-8 months (https://animaldiversity.org/accounts/Pantholops_hodgsonii/) - which, if true, is anomalously long for a bovid.

Posted on April 24, 2024 03:25 PM by milewski milewski | 13 comments | Leave a comment

April 23, 2024

An index to my Posts about the pronghorn (Antilocapra americana)

https://www.inaturalist.org/journal/milewski/93729-sundry-aspects-of-the-adaptive-colouration-of-the-pronghorn-antilocapra-americana#

https://www.inaturalist.org/journal/milewski/93148-life-history-strategy-of-the-pronghorn-antilocapra-americana-short-lived-but-with-long-gestation-compared-to-real-antelopes#

https://www.inaturalist.org/journal/milewski/93032-a-new-explanation-for-the-hypercursoriality-of-the-pronghorn-antilocapra-americana-selenium-as-a-crucial-micronutrient#

https://www.inaturalist.org/journal/milewski/92855-is-there-subtle-sexual-dimorphism-in-the-colouration-of-the-ear-pinna-in-the-pronghorn-antilocapra-americana#

https://www.inaturalist.org/journal/milewski/92356-illustrations-of-the-walking-and-stotting-gaits-of-the-pronghorn-antilocapra-americana#

https://www.inaturalist.org/journal/milewski/52136-the-mane-as-a-little-known-aspect-of-the-erectile-bleeze-of-the-pronghorn-antilocapra-americana#

https://www.inaturalist.org/posts/52201-the-peculiar-showiness-of-the-subauricular-gland-of-the-pronghorn-antilocapra-americana#

https://www.inaturalist.org/posts/52221-why-the-pronghorn-antilocapra-americana-has-a-striped-neck#

https://www.inaturalist.org/journal/milewski/52296-interpreting-the-buccal-semet-of-the-pronghorn-antilocapra-americana#

https://www.inaturalist.org/journal/milewski/52840-regional-interspecies-mimicry-in-conspicuous-colouration-of-ruminants#

Posted on April 23, 2024 11:03 PM by milewski milewski | 2 comments | Leave a comment

A new explanation for the hypercursoriality of the pronghorn (Antilocapra americana): selenium as a crucial micronutrient

The pronghorn (Antilocapridae: Antilocapra americana) is renowned for its extreme speed and endurance when running (https://www.youtube.com/watch?v=jR18k9c3MsE).

It is widely accepted that no animal on Earth exceeds the pronghorn in this combination.

Skeptical readers may perhaps suspect that the performance of the pronghorn my perhaps have been exaggerated.

However, the claims of speed and endurance are consistent with several other exceptional/extreme features, viz.

  • extremely large heart and lungs,
  • a consistent habit of opening the mouth while galloping,
  • long-range visual vigilance,
  • long-distance signalling by means of 'semaphoric' pale patches on the pelage, and
  • a lack - relative to other forms of 'plains game' - of displays of individual fitness to scanning predators.

All of the above add up to a syndrome of apparent 'hypercursoriality' in the pronghorn.

This syndrome seems incongruous, because the predatory regime in which the pronghorn lives is less, not more, intense than that pertaining to 'plains game' in Africa and Eurasia.

https://www.perplexity.ai/search/Compare-the-maximum-RVcPX3W1Q5GD5EbGMHJ5Vw

The long-range visual vigilance of the pronghorn is indicated partly by fully lateral placement of the eyes on the head, permitting the pronghorn to scan the horizon behind it as well as in front and to the sides.

However, this in itself hardly differs from 'plains game' in Africa and Eurasia.

What distinguishes the pronghorn are

  • extremely large eyeballs, both absolutely for a mammal and relative to body size, and
  • bony orbits that protrude from the skull laterally, to a degree possibly exceeding that in any other ungulate.

The long-distance signalling of the pronghorn is indicated partly by a conspicuously pale patch on the hindquarters (https://www.inaturalist.org/observations/211220855 and https://www.flickr.com/photos/189038430@N06/53350736417/in/faves-58287925@N05/ and https://pngtree.com/freebackground/pronghorn-antelope-buck-antlers-hunting-pronghorn-nature-photo_4107882.html).

However, various other forms of 'plains game' have comparable features of colouration.

What is extreme in the case of the pronghorn is

The limited incidence of displays of individual fitness in the pronghorn is not categorically different from various 'plains game' in Africa. For example, Damaliscus spp. tend not to stot, despite being extremely cursorial among Bovidae.

However, what is odd in the case of the pronghorn is that

  • stotting, to the extent that it occurs among adults, is displayed mainly sociosexually, rather than to potential predators,
  • 'style-trotting' is rather poorly-developed, and
  • neither stotting nor proud-trotting occur in juveniles, even while playing.

This raises the question:

Selenium:

https://www.horizons-mag.ch/2017/04/03/the-world-map-of-a-trace-element/

https://www.researchgate.net/figure/Selenium-distribution-and-availability-in-regions-of-the-continental-United-Sates-Panel_fig3_228832815

https://extension.uga.edu/publications/detail.html?number=B1390&title=selenium-in-georgia-soils-and-forages-importance-in-the-livestock-industry

https://drkhorsesense.wordpress.com/2021/03/11/lose-your-fear-of-selenium/

https://poisonousplants.ansci.cornell.edu/toxicagents/selenium_map.html

https://pubs.usgs.gov/publication/70006713

https://meridian.allenpress.com/jwd/article/32/1/9/121989/TOXICOLOGIC-EVALUATION-OF-A-HIGH-SELENIUM-HAY-DIET

https://customequinenutrition.com/blogs/nutrients/selenium-101

https://www.researchgate.net/figure/Indicators-of-environmental-selenium-status-for-the-USA-Selenium-rich-environments_fig2_40455792

https://bioone.org/journals/journal-of-zoo-and-wildlife-medicine/volume-32/issue-3/1042-7260_2001_032_0373_PCDIHR_2.0.CO_2/PRESUMPTIVE-COPPER-DEFICIENCY-IN-HAND-REARED-CAPTIVE-PRONGHORN-ANTILOCAPRA-AMERICANA/10.1638/1042-7260(2001)032[0373:PCDIHR]2.0.CO;2.short

https://link.springer.com/article/10.1007/s10344-012-0645-z

https://www.pharmanord.com/history-of-selenium-research

Posted on April 23, 2024 03:45 AM by milewski milewski | 31 comments | Leave a comment

April 21, 2024

Additional illustrations of the differences in the ear pinnae of the two species of klipspringers (Oreotragus)

@variani18 @ludwig_muller

Please see

There are two species of klipspringer, not one.

Oreotragus oreotragus occurs in South Africa (Drakensberg, Karoo, Western Cape, Northern Cape, Namibia as far north as Windhoek).

Oreotragus saltatrixoides occurs in the rest of Africa, including Mpumalanga, Limpopo, and Northwest provinces of South Africa, and northwestern Namibia.

OREOTRAGUS OREOTRAGUS

Orientation of ear pinnae vertical
Pattern on front-of-ear inconspicuous (= not qualifying as an auricular flag)

https://critterfacts.com/klipspringer/?doing_wp_cron=1713667813.4174098968505859375000

https://mostlybirding.files.wordpress.com/2019/01/pick-2018-48.jpg

OREOTRAGUS SALTATRIXOIDES

Orientation of ear pinnae horizontal
Pattern on front-of-ear conspicuous (= qualifying as an auricular flag)

https://www.gettyimages.co.uk/detail/photo/klipspringer-male-kruger-national-park-south-africa-royalty-free-image/685029237

https://www.gettyimages.co.uk/detail/photo/klipspinger-male-royalty-free-image/524447344

https://www.dreamstime.com/klipspringer-oreotragus-brookfield-zoo-illinois-march-image141868490

https://www.dreamstime.com/stock-photo-klipspringer-closeup-portrait-oreotragus-oreotragus-small-african-antelope-image44207213 and https://www.alamy.com/stock-image-klipspringer-oreotragus-oreotragus-or-small-african-antelope-164226024.html

https://www.dreamstime.com/stock-photo-klipspringer-closeup-portrait-oreotragus-oreotragus-small-african-antelope-image44207351

Posted on April 21, 2024 02:52 AM by milewski milewski | 8 comments | Leave a comment

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