Archivos de diario de mayo 2024

01 de mayo de 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.

Publicado el mayo 1, 2024 02:08 MAÑANA por milewski milewski | 12 comentarios | Deja un comentario

06 de mayo de 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

Publicado el mayo 6, 2024 01:59 TARDE por milewski milewski | 8 comentarios | Deja un comentario

07 de mayo de 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.

Publicado el mayo 7, 2024 12:18 MAÑANA por milewski milewski | 12 comentarios | Deja un comentario

08 de mayo de 2024

10 de mayo de 2024

Contrary to popular belief, the pronghorn (Antilocapra americana) does not have a particularly large heart

@tonyrebelo @jeremygilmore @ludwig_muller @variani18 @ptexis @oviscanadensis_connerties @tandala @davidbygott @zarek @maxallen @dinofelis @capracornelius @dejong @beartracker @matthewinabinett @jwidness @aguilita @paradoxornithidae

Everyone knows that the pronghorn (Antilocapra americana) is extremely speedy and enduring when running (https://www.nature.com/articles/353748a0).

Also generally accepted is that this capacity to perform is owing partly to the large heart of the pronghorn relative to body size (https://en.wikipedia.org/wiki/Pronghorn and https://lewis-clark.org/sciences/mammals/pronghorn/ and https://ielc.libguides.com/sdzg/factsheets/pronghorn/characteristics and https://www.facebook.com/migrationinitiative/photos/a.1555355961349673/2764556360429621/?type=3).

No skeptical scientist seems to have questioned the implication of an uniquely large heart in this, the only surviving member on Earth of the family Antilocapridae.

It may therefore surprise readers to hear that the reputation of a massive heart in the pronghorn is exaggerated.

Somewhat like the continually repeated fallacy that reedbucks (Redunca) raise the tail in alarm (https://www.inaturalist.org/posts/39738-contrary-to-field-guide-books-reedbucks-redunca-spp-do-not-flag-the-tail-in-alarm#), this seems to be a case of a tenuous 'fact' being passed unquestioningly from one semi-popular author to another.

It is true - as originally asserted by McKean and Walker half a century ago (1974: (https://www.sciencedirect.com/science/article/abs/pii/0034568774900668) - that the heart of the pronghorn is significantly larger, proportionately, that that of a domestic caprin bovid (Capra hircus).

However, their reported value of 0.95% - referring to the mass of the heart as a percentage of body mass in adults of the pronghorn - turns out to be unexceptional compared with various other ruminants of similar body size.

My collation of the data is as follows, for ruminants of adult body mass 20-80 kg. The order is that of decreasing proportional mass of the heart:

Further data for Rangifer tarandus platyrhynchus may possibly be found in Krog J, Wika M, Lund-Larsen T, Nordfjell J, and Myrnes I (1976) Spitzbergen reindeer, Rangifer tarandus playrhynchus Vrolik: Morphology, fat storage and organ weights in the late winter season. Norwegian Journal of Zoology 24: 407-417.

In adults of Homo sapiens, the mass of the adult heart (about 310 grams) is about 0.45% of body mass (https://hypertextbook.com/facts/2006/StephanieGambino.shtml and https://pubmed.ncbi.nlm.nih.gov/22182983/ and https://bionumbers.hms.harvard.edu/bionumber.aspx?id=115099&s=n&v=1 and https://pubmed.ncbi.nlm.nih.gov/26153896/).

For comparison, in adults of thoroughbreds of Equus caballus, the heart is about 0.9% of body mass (see details in comment below).

The heart is hardly more massive, relative to body mass, in domestic caprin bovids (C. hircus and O. aries) than in humans. This is probably the result of an anthropogenic process of diminution, resulting inadvertently from selective breeding in domestication.

This means that the original finding, viz. that the heart of the pronghorn is far more massive than that of C. hircus, was misleading in comparing a fully wild species with a fully domesticated species.

In this Post, I have corrected the unintended exaggeration that has followed this initial mistake.

However, my collation raises a new puzzle, as follows.

Gazelles are remarkably heterogeneous, among genera and - in the case of Nanger granti granti - between the sexes, in terms of the mass of the heart relative to body mass.

I refer to

  • Eudorcas thomsonii thomsonii (0.94% with scant sexual difference),
  • Litocranius walleri walleri (males 0.77%),
  • Antidorcas marsupialis marsupialis (0.71% with no evidence yet of sexual difference), and
  • N. g. granti (females 0.8%, males 0.65%).

A result is that adult males of N. g. granti (https://www.inaturalist.org/observations?taxon_id=601873), which resemble the pronghorn in body size and colouration, are indeed inferior to the antilocaprid in the mass of the heart relative to body mass. The values are respectively 0.65% and 0.95%.

Publicado el mayo 10, 2024 08:08 TARDE por milewski milewski | 20 comentarios | Deja un comentario

11 de mayo de 2024

13 de mayo de 2024

'Prodigousness', a new - and suitably objective - term for apparent extravagance in Nature

THE PROBLEM

Various organisms seem unnecessarily extravagant - even wasteful - in their allocation of resources to certain structures and functions of life.

This constitutes a scientific - i.e. biological as opposed to philosophical - puzzle.

By resources, I mean materials, energy, and opportunities in the sense of 'opportunity costs' (https://en.wikipedia.org/wiki/Opportunity_cost).

A classic example is the masculine tail of the Indian peafowl (Pavo cristatus, https://www.inaturalist.org/taxa/1204-Pavo-cristatus, https://archive.nytimes.com/www.nytimes.com/books/98/12/06/specials/cronin-ant.html).

However, an even more puzzling anatomical example is the large antlers (https://en.wikipedia.org/wiki/Antler) of various spp. of Cervidae.

These annually shed-and-regrown bony structures consume orders of magnitude more phosphorus and other nutrients than are devoted to the permanent - and relatively small - head adornments of comparable Bovidae (https://en.wikipedia.org/wiki/Bovidae).

An example in the realm of energetics, rather than anatomy as such, is the stotting gaits (https://en.wikipedia.org/wiki/Stotting) of herbivores such as the Rocky Mountain mule deer (Odocoileus hemionus hemionus, https://www.youtube.com/watch?v=h8DweS5Z684 and https://www.inaturalist.org/observations?taxon_id=143865)

In scientific enquiry and rigorous thinking, it is important to use words as precisely as possible.

For this reason, neither 'extravagant' nor its various synonyms are apt in a purely biological context.

All of them - including 'prodigal' (https://en.wikipedia.org/wiki/Parable_of_the_Prodigal_Son) - have moral overtones (https://www.merriam-webster.com/thesaurus/extravagant).

More particularly, the moral implication of the existing words tends to be one of 'wantonness', or even sinfulness.

A SOLUTION

What is ideally needed is a word combining

  • unambiguousness,
  • precision in meaning, and
  • scientific objectivity.

For the above reasons, I have invented a new term, while taking care to adhere to sound etymological principles.

The word 'prodigal' (https://www.youtube.com/watch?v=Nttqb8GvneU) derives from the Latin adjective 'prodigus', meaning 'lavish'.

This same word-root can easily be rendered to 'prodigous' instead of 'prodigal' (https://www.youtube.com/watch?v=QrmWACALQcU).

The only difference is '-ous' instead of '-al'. Please see https://www.perplexity.ai/search/In-the-English-XWU6c7epTLOzcbiT3IAFNA.

Please note that the word 'prodigious', spelt with an 'i' after a 'soft g', has

I thus introduce to Biology two new words, namely the adjective 'prodigous' (pronounced with a hard 'g'), and its corresponding abstract noun 'prodigousness'.

An example of how to use 'prodigous' is as follows:

"The head adornments of the extinct deer Megaloceros (https://en.wikipedia.org/wiki/Megaloceros) are so prodigous that they may seem to have been maladaptive. However, what are needed are rigorous analyses of costs vs benefits, to reveal the real adaptive values of extreme sexual dimorphism in the context of natural selection in a past environmental regime in the Pleistocene".

Publicado el mayo 13, 2024 09:17 MAÑANA por milewski milewski | 3 comentarios | Deja un comentario

14 de mayo de 2024

A comparison of organ sizes between the common warthog (Phacochoerus africanus) and the domestic pig (Sus scrofa)

INTRODUCTION

The common warthog (Phacochoerus africanus, https://www.inaturalist.org/taxa/42122-Phacochoerus-africanus) is extreme, among Suidae (https://en.wikipedia.org/wiki/Suidae), for its adaptation to African savannas.

This is based on a combination of

  • specialisation on a staple diet of grass,
  • dependence on burrows for refuge and shelter, and
  • diurnal, not nocturnal, activity.

The most obvious morphological adaptation in the common warthog is in dentition (https://www.instagram.com/p/y7u1rDsXp6/ and https://www.vin.com/apputil/content/defaultadv1.aspx?pId=26439&catId=159991&id=10047368&ind=32&objTypeID=17#:~:text=The%20premolars%20and%20molars%20are,tubules%20may%20have%20single%20roots.).

The teeth are extremely modified for grinding fibrous and gritty items, mainly the rhizomes of grasses.

I was, therefore, curious to see how the internal organs of the common warthog differ in proportional size from those of the domestic pig (Sus scrofa, https://www.inaturalist.org/observations?taxon_id=324492).

METHODS

Sources:

Common warthog: data collected in Uganda by H P Ledger and N S Smith (authors of https://www.jstor.org/stable/3798800 and https://www.semanticscholar.org/paper/The-Carcass-and-Body-Composition-of-the-Uganda-Kob-Ledger-Smith/c891d40fecc1cb23ead94a137421e929870c1df3 and https://kalrorepository.kalro.org/items/eab259a5-ccd3-44ab-8e84-872dc179970d) for

  • n = 10 adult females, and
  • n = 11 adult males.

Domestic pig: various references (all referring to sexually mature subadults of both sexes that have not yet attained full body mass), including https://www.scielo.cl/scielo.php?pid=S0718-16202009000200002&script=sci_arttext and https://www.jstage.jst.go.jp/article/jvms/60/5/60_5_545/_pdf and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9863662/ and https://www.perplexity.ai/search/Give-lengths-of-7EadhvLkRVyTwb1r31OJPg.

RESULTS (all values are means)

Body masses:
Common warthog 71 kg, domestic pig 112 kg.

This indicates a two-fold difference in full maturity, probably owing partly to the mass of adipose tissues in the domestic pig.

The contents of the large intestine, including the caecum, are much more massive, relative to body mass, in the common warthog (10.3%) than in the domestic pig (2.2%).

The small intestine is remarkably short, both absolutely and relatively to body mass, in the common warthog (7.2 m) compared to the domestic pig (17.0 m).

The following are absolutely similar between the two spp.:

  • mass of empty stomach,
  • length of large intestine (5.1 m for common warthog, 4.8 m for domestic pig),
  • mass of heart, and
  • mass of spleen.

The following are similar in mass, relative to body mass:

  • empty stomach (common warthog 0.53% of body mass, domestic pig 0.48%),
  • empty small intestine (common warthog 0.78%, domestic pig 0.93%)
  • liver (common warthog 1.35%, domestic pig 1.07%).

The following organs are somewhat more massive, relative to body mass, in the common warthog than in the domestic pig:

  • empty large intestine, including caecum (common warthog 2.0%, domestic pig 1.15%)
  • mass of heart (common warthog 0.38%, domestic pig 0.26%),
  • mass of lungs (common warthog 0.87% including trachea, domestic pig 0.24%)
  • mass of spleen (common warthog 0.2%, domestic pig 0.12%).

The following are nebulously/slightly more massive in the common warthog than in the domestic pig, relative to body mass:

  • stomach (0.53% cf 0.48%), and
  • liver (1.35% cf 1.07%).

DISCUSSION

The comparison is complicated by the differences

  • in mature in body masses between the two spp., and
  • the different ontogenetic stages of the individuals sampled for each species.

Slight differences in the relative sizes of certain organs may possibly be explained by the domestic pig having been selectively bred for fattiness.

However, the most striking difference is that the large intestine (including the caecum) of the common warthog is clearly more filled - absolutely as well as relatively - than that of the domestic pig. Consistent with this is that the small intestine of the common warthog is shorter than that of the domestic pig.

These salient differences may be explained by the fibrous diet of mainly grass of the common warthog, compared to the omnivory of the domestic pig.

The main differences between the common warthog and the domestic pig relate to gastrointestinal fermentation (in the hindgut). Any differences relating to cursoriality (heart and lungs) are minor.

Perhaps the crucial difference in this whole comparison is that - in conjunction with modification of the dentition - the contents of the large intestine are far more massive than those of the domestic pig.

This reflects the grazing specialisation of the common warthog, and its dependence on volatile fatty acids generated by microbes in the colon and caecum. In this way, the common warthog is somewhat convergent with Equidae.

Note: The small intestine of the common warthog happens to be absolutely similar in length to that of the coexisting ostrich (Struthio camelus). I plan to Post on this topic soon...

Publicado el mayo 14, 2024 02:42 TARDE por milewski milewski | 1 comentario | Deja un comentario

15 de mayo de 2024

Food values of sundry plants in East Africa

Most recent: Calculation of silica content in diet of ostrich

See

https://www.jstor.org/stable/1940401

https://pubmed.ncbi.nlm.nih.gov/16578767/ and https://europepmc.org/article/med/16578767

https://www.researchgate.net/publication/355163451_Forage_quality_in_tundra_grasslands_under_herbivory_Silicon-based_defences_nutrients_and_their_ratios_in_grasses

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317429/

https://eprints.nwisrl.ars.usda.gov/id/eprint/510/1/673.pdf

https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.00438/full

https://www.researchgate.net/publication/267292612_Silica_as_a_plant_defense_against_herbivorous_insects

https://api.research-repository.uwa.edu.au/ws/portalfiles/portal/106649226/AAM_A_shift_from_phenol_to_silica_based.pdf

https://www.researchgate.net/publication/6432754_Herbivore_specific_induction_of_silica-based_plant_defences

https://esajournals.onlinelibrary.wiley.com/doi/am-pdf/10.1002/ecy.3250

In each case, the first value is % of diet, and the second value is silica %

Asteraceae 15.6% 8.0% 124.8
Malvaceae 18.6% 4.0% 74.4
Commelinaceae 12.8% 8.5% 108.8
Fabaceae 8.1% 0.7% 5.67
Balanitaceae 5.4% 0.2% 1.08
Solanaceae 5.4% 0.1% 0.54
Acanthaceae 0.8% 7.0% 5.6
Convolvulaceae trace 3.0% 0.03
Poaceae 18.0% 4.8% 86.4
seed capsules 4.0% 0.3% 1.2
inflorescences 3.5% 0.2% 0.7
pods of legumes 2.0% 0.3% 0.6
succulents 1.5% 0.4% 0.6
fib st 0.8% 0.2% 0.16
faeces 1.0% 4.0% 4
fleshy fruits 0.5% 0.2% 0.1
invertebrates trace 0% 0
other 2.0% 1.0% 2.0

Total = 416.68
Mean = 4.2% silica content

Solanum fruits rival grass leaves in crude fibre: 30% (Field 1975)

Ratios of condensed tannins to crude protein:
Vachellja drepanolobium 5.9/21=0.28
Vachellia seyal 1.7/15.5=0.11
Vachellia xanthophloea (Wrangham and Waterman 1981 and Altman et al.) about 0.09
Aspilia mossambicensis 0.7/15= 0.046
Hibiscus flavifolius 0.8/15= 0.053
So, ratios of condensed tannins to crude protein in Vachellia spp. (about 0.1-0.3) seem double those of staples in the diet of the ostrich, viz. Aspilia and Hibiscus.

Look up Dougall and Sheldrick (1964), who record Melhania ovata crude protein in stem and leaf 11.8%

Wilson and Bredon (1963) record crude protein of Pavonia patens as 19.1%

Ratios of silica to crude fibre
Dougall (1963a):
grasses 4.11/30.28=0.135
herbaceous legumes 1.18/21.9=0.054
leguminous browse (woody plants) 0.59/30.32=0.019
non-leguminous browse 1.6/28.78=0.056
Bredon and Wilson:
whole plants of grasses in Zone I, Karamoja:
6.29/27.74=0.23
6.48/31.49=0.21
7.33/33.02=0.22
8.75/34.88=0.25
7.77/35.86=0.22
13.66/27.63=0.49
9.19/32=0.29
7.45/34.04=0.22
5.47/34.86=0.16
6.57/30.91=0.21
Mean = 0.25

Dougall (1963a) found that, in general,

  • grasses have ratios of silica to crude fibre 7-fold those of leguminous browse plants such as Vachellia,
  • herbaceous legumes showed intermediate ratios, and
  • ratios in leguminous browse are less than half those in herbaceous legumes.

From Wilson and Bredon (1963), New nutrient analyses to feed into my calculations:
Commelina cp 7.1-14.4% cf 19.8-28.3% si 5.3-15.3% with mean 9.65%, making a new overall mean of 8.5%
Justicia exigua si 5.99% (!!!)
Heliotropium rather calcium-rich si 5.3% (!)
Ipomoea spp. si range 0.74-5.13 mean 2.96
Crossandra cp 10.9% cf 24.3% si 11.5% (!!!)
Hibiscus 8-14.7%
Monechma cp 18.2% cf 26.5% si 1.6%
Pavonia cp 19.1% cf 16.3% si 11.9% (!!!)

CHEMICAL DEFENCES

There is a definite link between woodiness and tannin content. Acacias are particularly rich in tannins, the leaves varying with age in tannin content.

Acanthaceae

  • are bitter-tasting, rather than spicy
  • contain flavonoids
  • are poor in tannins
  • contain compounds of nitrogen; in some cases fairly toxic with alkaloids (not as much as in Solanum), including iridoids, quiniline alkaloids, and quinaziline alkaloids

Capparidaceae (Boscia and Capparis are well-known, Maerua is not)

  • usually spicy (amides or glucosinolates)
  • Boscia known to have glucosinolates (mustard)
  • some (probably excluding Maerua) have cyanogenic glycosides
  • Maerua contains small pepperidine alkaloids, as in Salvadora; tastes spicy like pepper; Maerua and Salvadora probably contain less tannin than do acacias
  • condensed tannin content unknown

Salvadoraceae

  • contain calcium oxalate and potassium salts, but not potassium oxalate
  • silica-rich (evergreen rough leaves in Dobera)
  • Salvadora persica contains small nitrogenous molecules and is stringy, and perhaps antibacterial substances (mildly antiseptic)

Grass leaves do sometimes contain oxalates (typically associated with succulents). Birds may be preadapted to deal with oxalates.

Euphorbia (including forbs)

  • nasty latex
  • diterpenes in foliage and fruit
  • heterochroma

Celtis leaves silica-rich, according to Waterman

Balanites

  • seed largely non-toxic, containing oil and simple, common triterpenes
  • fleshy fruit-pulp is very palatable
  • probably poor in tannins

Zygophyllaceae

  • peculiar chemically
  • leaves of Tribulus relatively innocuous
  • seeds contain alkaloids

Cucumis

  • well-known for bitter principles
  • few alkaloids, as in Cucurbitaceae generally
  • cucurbitacins
  • not phenolic
  • triterpenes (containing no nitrogen, which is true also for diterpenes)

Achyranthes, Achyropsis

  • seem fairly innocuous
  • poorly-known

Boraginaceae, particularly Heliotropium

  • tend to be rather toxic
  • alkaloids of quinilidine type, as in Senecio
  • no tannins

Echium and Echinops

  • various defences, including small alkaloids

Similarities among Salvadora, Maerua, and Acanthaceae:

  • small, non-aromatic nitrogenous compounds (e.g. azomin, carpane)
  • 2-methylpepperidines, which taste peppery but lack antimicrobial activity
Publicado el mayo 15, 2024 09:37 MAÑANA por milewski milewski | 6 comentarios | Deja un comentario

Diet of the Maasai ostrich (Struthio camelus massaicus) on the Athi-Kapiti plains, Kenya

Struthio camelus massaicus (https://www.inaturalist.org/observations?taxon_id=322201)

STUDY AREA AND METHODS

Location:
Wildlife Ranching and Research, which was later renamed Swara Plains Conservancy (https://www.perplexity.ai/search/What-is-the-UV5KdNn1SCaEOGLoyrCChw), and was recently incorporated into Nairobi National Park.

Time of fieldwork:

Intermittently during 1987-1989

RESULTS

The following are the genera recorded eaten by the Maasai ostrich, either found in adult stomachs (n = 10 individuals) or observed in 17 foraging bouts by one habituated adult individual.

Percentages refer to mass eaten in the first instance, and incidence in stomachs in the second instance.

Asterisks (*) indicate those families also recorded to be eaten frequently during the direct observations.

All families were recorded in the diet of this population of the Maasai ostrich in both the dry and rainy seasons, except Balanitaceae (eaten mainly in the dry season), and Cyperaceae and Acanthaceae (eaten mainly in the green season).

  • *Asteraceae (Aspilia, Galinsoga, Tagetes, Bidens) 23.0% (0-90); 60%
  • *Malvaceae (Hibiscus, Pavonia, Melhania,?Abutilon) 17.6% (5-40); 90%
  • *Poaceae (Sporobolus, Cynodon, Eragrostis) 15.7% (0-75); 80%
  • *Commelinaceae (Commelina) 14.5% (0.1-60); 100%
  • *Fabaceae (Indigofera, Crotalaria, Dolichos, Trifolium) 6.8% (0-30); 20%
  • Solanaceae (Solanum) 5.2% (0-20); 50%
  • Balanitaceae (Balanites) 5.2% (0.1-22); 90%
  • Mimosaceae (??Vachellia) 2.7% (0-20); 50%
  • Asphodelaceae and Asparagaceae (Aloe, ?Albuca) 1.8% (0-6); 40%
  • Euphorbiaceae (Euphorbia) <0.5% (0-2); 30%
  • Cucurbitaceae <0.1% (0-0.5); 10%
  • Cyperaceae <0.1% (0-0.1); 10%
  • Lamiaceae (?Plectranthus, ?Ocimum) <0.1% (0-0.1); -
  • Tiliaceae (Grewia) <0.1% (0-0.2); 10%
  • Convolvulaceae (Ipomoea) <0.1% (0-0.1); -
  • Acanthaceae (Justicia, Crossandra) <0.1% (0-0.1); -
  • Polygonaceae (Oxygonum) -
  • Amaranthaceae (Achyranthes) -
  • unidentified 6.8% (0-25); 100%

Aspilia mossambicensis:
https://www.inaturalist.org/taxa/147342-Aspilia-mossambicensis

Galinsoga parviflora:
https://www.inaturalist.org/taxa/48178-Galinsoga-parviflora

Tagetes minuta:
https://www.inaturalist.org/taxa/79313-Tagetes-minuta

Bidens pilosa:
https://www.inaturalist.org/taxa/50203-Bidens-pilosa

Hibiscus flavifolius:
https://www.inaturalist.org/taxa/343058-Hibiscus-flavifolius

Pavonia:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=52356&view=species

Abutilon:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=53864

Commelina:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=52893

Indigofera:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=83365&view=species

Crotalaria:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=123472&view=species

Dolichos:
https://www.inaturalist.org/observations?place_id=56881&subview=map&taxon_id=139262&view=species

Trifolium:
https://www.inaturalist.org/taxa/55745-Trifolium-repens

Solanum:
https://www.inaturalist.org/observations/215986766

Balanites glabra:
https://en.wikipedia.org/wiki/Balanites_glabra

Grewia:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=68716&view=species

Ipomoea:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=52346&view=species

Justicia:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=50152

Crossandra:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=201316&view=species

Melhania:
https://www.inaturalist.org/observations?place_id=7042&subview=map&taxon_id=185886&view=species

Oxygonum:
https://www.inaturalist.org/observations?place_id=7042&subview=map&taxon_id=553830&view=species

Achyranthes:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=142081

Albuca:
https://www.inaturalist.org/observations?place_id=7042&subview=map&taxon_id=119218

Aloe:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=71956

Plectranthus:
https://www.inaturalist.org/taxa/430498-Plectranthus-fruticosus

Ocimum:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=61399&view=species

Silica content in diet of ostrich

As at 1 May 1989: at least one-third of the non-grass genera in the diet are rich in silica.

Rich in silica:
Aspilia, Justicia, Crossandra, Commelina, Pavonia, Cucumis, all grasses, Salvadora

Moderately rich in silica:
Galinsoga, Ipomoea, Hibiscus, Heliotropium

Poor in silica:
Balanites, Euphorbia, Solanum, Vachellia, Monechma

Unknown as yet:
Melhania, Indigofera

Publicado el mayo 15, 2024 10:49 TARDE por milewski milewski | 4 comentarios | Deja un comentario