27 de mayo de 2024

Ecology of termite mounds in Kruger National Park

Publicado el mayo 27, 2024 11:13 TARDE por milewski milewski | 0 comentarios | Deja un comentario

Portulacaria afra

Publicado el mayo 27, 2024 10:29 TARDE por milewski milewski | 0 comentarios | Deja un comentario

Ecological differences between lookalike species of Zosterops in southwestern Australia and southwestern southern Africa

@tonyrebelo @jeremygilmore @ludwig_muller

Only five genera of passerine birds are indigenous to both southwestern Western Australia (https://en.wikipedia.org/wiki/Southwest_Australia) and the climatically and latitudinally similar southwestern Cape of South Africa (https://en.wikipedia.org/wiki/Western_Cape).

These are, in alphabetical order

In this Post I compare, ecologically, the following taxa:

The two taxa seem virtually identical in size and shape.

Furthermore, both of them eat fruit-pulp and nectar.

However, the emphasis/reliance seems different.

Zosterops v. capensis differs from its southwestern Australian congener in several ways.

Firstly, it relies on indigenous fleshy fruit-pulp (https://www.projectnoah.org/spottings/10432262), rather than the indigenous nectar with which Z. l. chloronotus is mainly associated (https://library.dbca.wa.gov.au/static/Journals/082168/082168-25.pdf).

Secondly, it is perennially resident, rather than migrating from temperate latitudes to the subtropics each winter.

In western South Africa, the subtropics are perennially occupied by a different species, viz. Zosterops pallidus (https://www.inaturalist.org/taxa/472771-Zosterops-pallidus).

Thirdly, Z. v. capensis seems particularly suited to dispersing and sowing the relatively small, arillate diaspores of Celastraceae, particularly

These plants lack counterparts in the flora of southwestern Australia.

Fourthly, Z. v. capensis lacks a certain mutualistic relationship with plants, as follows.

Zosterops lateralis pollinates various spp. of Acacia, indigenous to Australia, by being attracted to extrafloral nectaries, located on the foliage.

The bird pollinates the plants despite having a short beak. This is by virtue of accidentally rubbing against the yellowish pom-prom inflorescences - which do not produce nectar - as it moves through the shrub from one nectar-bearing leaf or phyllode to another (Sargent O H 1928 Reactions between birds and plants, Emu 27: 185-192 and https://www.researchgate.net/publication/253953794_Birds_as_pollinators_of_Australian_plants).

The above comparison raises two questions about Zosterops in the southwestern Cape of South Afirca, as follows.

  • Is any indigenous plant in the Cape Floristic Region (https://en.wikipedia.org/wiki/Cape_Floristic_Region) naturally pollinated by Z. v. capensis? and
  • Has Z. v. capensis taken to visiting the extrafloral nectaries of the various spp. of Acacia introduced anthropogenically to South Africa, thus helping to pollinate these plants?

Also please see https://www.inaturalist.org/journal/milewski/91030-extreme-seasonal-incidence-of-the-silvereye-zosterops-lateralis-chloronotus-in-autumn-of-2024-in-the-perth-metropolitan-area-western-australia-in-response-to-heat-and-drought#

Publicado el mayo 27, 2024 01:35 MAÑANA por milewski milewski | 15 comentarios | Deja un comentario

26 de mayo de 2024

Pictures worth a thousand words

Publicado el mayo 26, 2024 02:54 TARDE por milewski milewski | 0 comentarios | Deja un comentario

The ostrich (Struthio camelus) as a quasi-ungulate, part 7

https://navlovesm.pics/product_details/36430434.html

https://navlovesm.pics/product_details/36430429.html

https://navlovesm.pics/product_details/36430433.html

https://navlovesm.pics/product_details/40147153.html

https://www.dreamstime.com/here-photo-see-very-beautiful-ostrich-antelopes-drink-water-beautiful-ostrich-antelopes-africa-image168615862

https://www.flickr.com/photos/chajoha/49006831467

https://www.pond5.com/stock-footage/item/87606070-ostriches-and-springbok-antelope-shimmering-heat-wave-kalaha

https://www.dreamstime.com/here-photo-see-very-beautiful-ostrich-antelopes-drink-water-beautiful-ostrich-antelopes-africa-image168615896

https://navlovesm.pics/product_details/40147153.html

https://www.dreamstime.com/here-photo-see-large-ostrich-hot-africa-near-antelope-beautiful-ostrich-hot-africa-nearby-antelope-image168487062

https://www.dreamstime.com/here-photo-see-very-beautiful-ostrich-antelopes-drink-water-beautiful-ostrich-antelopes-africa-image168615879

https://x.com/catersmediagrp/status/984113857189765121

https://www.pond5.com/stock-footage/item/87606070-ostriches-and-springbok-antelope-shimmering-heat-wave-kalaha

https://navlovesm.pics/product_details/47232595.html

The following is a list of all the ungulates potentially coexisting with the ostrich, with their body masses (adult females) and metabolic body masses (https://www.perplexity.ai/search/Explain-the-concept-OzTlv1FeQ92LIlZ07kQsaw), both expressed in kg

** = true coexistors

Struthio camelus 110 27

Hippopotamus amphibius 1200 204
**Diceros bicornis 800 150
**Giraffa tippelskirchi 800 150
**Giraffa giraffa 800 150
**Giraffa camelopardalis 800 150
**Giraffa reticulata 800 150
**Syncerus caffer 400 89
Camelus dromedarius 350 81
**Equus grevyi 350 81
**Taurotragus oryx 300? 72? https://www.alamy.com/an-eland-bull-and-an-ostrich-sharing-a-watering-hole-in-southern-african-savanna-image235462173.html
**Equus quagga quagga & burchellii 290? https://www.african-safari-pictures.com/ostrich-pictures.html
Equus kiang 300?
**Equus hartmannae 275?
Equus somaliensis 250 63
Equus zebra 250 63
**Equus quagga boehmi 250 63 https://www.gettyimages.com.au/detail/photo/tanzania-zebra-herd-royalty-free-image/583742292?phrase=struthio+camelus+massaicus&adppopup=true
**Kobus ellipsiprymnus & defassa 240 61
Hippotragus equinus 220 57
**Strepsiceros strepsiceros 210 55
Equus hemionus kulan 200?
**Connochaetes albojubatus 180 49
**Connochaetes taurinus 180 49
Equus hemionus hemionus 150?
**Oryx gazella 150 43 https://www.flickr.com/photos/gridarendal/31282852533 and https://www.alamy.com/gemsbok-or-orix-antelope-and-an-ostrich-at-a-waterhole-kgalagadi-transfontier-park-south-africa-image448482611.html and https://pixabay.com/photos/ostrich-bird-antelope-oryx-running-63360/
**Oryx dammah 150 43
**Connochaetes mearnsi 140?
Hippotragus niger 140 41
**Alcelaphus caama 140 41
Alcelaphus buselaphus
**Alcelaphus cokii 125? 35
Alcelaphus lelwel
**Damaliscus lunatus 120 36
**Oryx beisa & callotis 120 36 https://navlovesm.pics/product_details/36430425.html
**Beatragus hunteri 100 32
Cervus elaphus 100 32
Addax nasomaculatus 100 32 taken as mf
**Connochaetes gnou 90 29
Hylochoerus meinertzhageni 85 28
**Ammelaphus imberbis 80 27
METABOLIC BODY MASS OF OSTRICH FITS IN HERE
**Oryx leucoryx 80 27
**Damaliscus pygargus 70 24
Tragelaphus spekii & gratus 70 24 mf
Potamochoerus larvatus 50 19
Redunca arundinum 50 19
Ammotragus lervia 50 19
**Phacochoerus africanus 45 17
**Phacochoerus aethiopicus 45 17
**Aepyceros melampus 45 17
Dama dama 45 17
**Nanger granti 45 17 https://www.gettyimages.com.au/detail/news-photo/kenya-africa-medium-view-of-an-ostrich-near-an-antelope-in-news-photo/947611476?adppopup=true and https://www.flickr.com/photos/gridarendal/31282852533 and https://navlovesm.pics/product_details/47232597.html and https://navlovesm.pics/product_details/47232593.html
Nanger dama
**Nanger soemmeringi 40 16
**Redunca redunca 40 16
Capra nubiana 40 16
Arabitragus jayakari 40 16
Tragelaphus scriptus 35 14
Tragelaphus sylvaticus 35 14
**Litocranius walleri 35 14
Ammodorcas clarkei 35 14
Redunca fulvorufula 30 13
Antidorcas marsupialis 30 13 https://navlovesm.pics/product_details/47232591.html
Gazella leptoceros 25
**Eudorcas rufifrons 20 9
**Eudorcas thomsonii 20 9 https://navlovesm.pics/product_details/47232592.html and https://navlovesm.pics/product_details/36430428.html and https://www.gettyimages.com.au/detail/news-photo/kenya-africa-medium-view-of-an-ostriches-grouping-in-the-news-photo/947611526?adppopup=true
**Gazella 20 9
**Sylvicapra grimmia grimmia & steinhardti 20 9
**Gazella dorcas 15 8
**Sylvicapra grimmia caffra & & orbicularis 15 8
Ourebia ourebi 15 8 mf
Ourebia montana 15 8 mf
Sylvicapra grimmia campbelliae & hindei & madoqua & coronata & 10 6
**Raphicerus campestris 10 6 cs
Raphicerus melanotis & sharpei 8 5 Cs
Neotragus moschatus 5 3
**Madoqua 5 3
**Madoqua 4 3
Madoqua 3 2

Publicado el mayo 26, 2024 01:37 MAÑANA por milewski milewski | 26 comentarios | Deja un comentario

24 de mayo de 2024

An extinct canid ('Canis rubronegrus') hiding in plain sight in the domestic dog (Canis familiaris)? part 2

@ludwig_muller @ptexis

...continued from https://www.inaturalist.org/posts/56803-an-extinct-canid-canis-rubronegrus-hiding-in-plain-sight-in-the-domestic-dog-canis-familiaris-part-1#

I have just read Smith et al. (2017, https://www.publish.csiro.au/zo/zo17040), which contains important data and analyses.

Please note that the terms 'braininess' and 'EQ', as I use them in this Post, are not synonymous.

This is mainly because EQ (encephalisation quotient)

  • was designed as a species-specific index of braininess relative to the allometric expectations from body mass, and
  • is poorly applicable to the domestic dog (Canis familiaris), with its extreme range of breeds.

EQ in canids tends to complicate rather than to clarify the picture of relative braininess. This is because the domestic dog varies so much in body mass (according to breed) that the ancestral body mass is obscure.

Despite the above complications, Smith et al. (2017) found that

  • the wolf (Canis lupus) is indeed brainier than the domestic dog, with no overlap,
  • the coyote (Canis latrans) and the Eurasian jackal (Canis aureus) seem brainier than the wolf, notwithstanding the fact that the former two spp. are about three-fold smaller-bodied (about 10 kg) than the latter (30 kg), and
  • the black-backed jackal (Lupulella mesomelas) and particularly the side-striped jackal (Lupulella adusta) - despite being 'jackals' - are less brainy than like-size, wild spp. of Canis.

I have reshuffled the data in Smith et al. (2017) as follows, to list all those spp./breeds with body mass about 10 kg, in decreasing order of EQ:

  • Boston terrier 8 kg EQ 164
  • pug 8 kg EQ 158
  • coyote (Canis latrans) 10.5 kg EQ 153
  • miniature schnauzer 7 kg EQ 152.5
  • dachshund 8 kg EQ 145
  • miniature poodle 8 kg EQ 145
  • fox terrier 8 kg EQ 144
  • Eurasian jackal (Canis aureus) 9 kg EQ 142
  • dingo 13 kg, EQ 137
  • wirehaired fox terrier 9 kg EQ 135
  • standard schnauzer 8 kg EQ 135
  • New Guinea singing dog (Canis hallstromi) 11 kg EQ 124.5
  • black-backed jackal (Lupulella mesomelas) 8 kg EQ 121.5
  • short-eared dog (Atelocynus microtis, wild canid of South America) 9 kg EQ 119
  • beagle 14.5 kg EQ 117.5
  • cocker spaniel 13 kg EQ 116
  • bush dog (Speothos venaticus, wild canid of South America) 6 kg EQ 102
  • side-striped jackal (Lupulella adusta) 11 kg EQ 86

How do we interpret the fact that EQ in various breeds of the domestic dog exceeds that in various like-size wild canids? Part of the answer is that EQ was originally conceived as a species-specific quotient.

When applied to breeds within a species, EQ becomes subject to interpretation because of the uncertainty of 'typical' body mass, as follows: EQ exaggerates braininess in small-bodied breeds, and understates braininess in large-bodied breeds.

I assume that the EQ corresponding with the 'real' species-specific EQ of the domestic dog is about 1.0, corresponding to body mass about 20 kg.

Please bear in mind that the point of Smith et al (2017) was the braininess of the dingo relative to the domestic dog; all wild canid spp. were ancillary to their study.

On the above basis, the following picture emerges from Smith et al. (2017).

The domestic dog (excluding the dingo) is less brainy than both the wolf and the Eurasian jackal (C. aureus). It is true that the difference is greater relative to the wolf than relative to the Eurasian jackal. However, relating this to the question of the real main wild ancestor of the domestic dog is rather subjective.

It seems likely that 'Canis rubronegrus' would likewise have been brainier than the domestic dog, based on the finding that all three extant wild spp. of Canis (wolf, coyote, and Eurasian jackal) are brainier than the domestic dog.

So, the data analysed by Smith et al. (2017) do not necessarily undermine the possibility that the domestic dog, with its anthropogenic decephalisation, was mainly derived from an extinct jackal-like (relatively omnivorous, non-gregarious) species rather than the specialised carnivore that is the wolf.

However, the data do suggest that my hypothetical ancestral species, 'Canis rubronegrus', was larger-bodied (about 20 kg) than extant jackals (about 10 kg).

The kelpie breed, with its wild-type conformation and colouration, has body mass 11-20 kg (https://www.perplexity.ai/search/What-is-the-ToObfrkBRw2sKkYuQVAdLg).

The wild ancestor must have been somewhat large-bodied, on average, than the kelpie, if we are to make sense of the EQ values of jackal-size (about 10 kg) breeds of the domestic dog.

In other words, I suggest that 'Canis rubronegrus' was jackal-like in diet and sociality, more than in body size. This would be consistent with Bergmann's rule (https://en.wikipedia.org/wiki/Bergmann%27s_rule), if the ancestral species lived at the northern limit of the vegetated landscape in the Ice Age.

Publicado el mayo 24, 2024 05:17 TARDE por milewski milewski | 2 comentarios | Deja un comentario

The ostrich (Struthio camelus) as a quasi-ungulate, part 6

The only ungulates rivalling the ostrich in length of leg and neck, and diminution of the head, are giraffes (Giraffa) and certain spp. of gazelles. However, all of these use this configuration to reach high rather than to walk far.

The ostrich resembles like-size ungulates in the size of the gastrointestinal tract and other organs, and presumably also digestive power and total metabolic costs.

Among ungulates, body size is associated with ecological separation among spp. of roughly similar shapes.

This is partly because

  • large-bodied forms forage less selectively, and eat poorer foods, than is true for small-bodied forms, while potentially digesting their food more thoroughly, and
  • there are associated differences in height of foraging (Owen-Smith 1985).

Large ungulates with long legs and necks, and small heads with fine muzzles, can potentially coexist with a wide variety of spp., by being more selective (and thus requiring lesser gastrointestinal volumes) than like-size forms, and foraging higher than small-bodied forms.

The ostrich, like e.g. giraffes, seems to maximise selectivity without compromising its mobility. It is potentially able to forage delicately over a wide vertical and horizontal range, thus rivalling ungulates a fraction of its size in the quality of food economically selected.

However, height effectively provides little separation between the ostrich and ungulates, particularly in the sparsest vegetation, where the few shrubs are apparently browsed by gazelles rather than the ostrich. This suggests that horizontal mobility is critical for a bird forced to compete with ungulates for the forbs on which it depends.

In well-vegetated areas, this presumably allows the ostrich to be extremely selective. In barren areas, it may allow the bird to find a sufficient quantity of any food available.

In addition, the ostrich potentially enjoys the flexibility of variable passage rate, since theoretically then food passage in monogastric spp. is independent of fermentation rate (in turn partly a function of food quality). At the same time, it may be able to digest its food more thoroughly than can a gazelle, which it matches in degree of comminution of food and exceeds in fermentation volume, retention time, and gastrointestinal surface area (while requiring scarcely more bulk of food).

If giraffes can be described as tree-specialists of open vegetation, then perhaps the ostrich will be found to be a forb-specialist of open vegetation.

The ostrich, like certain ruminants, is able to survive on a limited quantity of good quality.

The ostrich may use retarded rate of passage of finely-ground food to achieve particularly thorough digestion of limited quantities of food where necessary, rather than processing large quantities of food very superficially as equids potentially do.

This would suit the ostrich to extremely arid areas where the very sparse available vegetation is generally nutrient-rich.

The monogastric competitors of the ostrich are apparently limited by their dependence on

  • drinking water,
  • local, reliable concentrates (suids), and
  • large quantities of food (equids).

Ruminant competitors are limited in ways that favour the ostrich particularly in arid climates. These limitations are in

  • body size,
  • mobility, and
  • digestive power.

The ostrich and equids both coexist with ruminants, but forage with different ratios of quantity to quality. The ostrichnhas the grinding power of ruminants, the fermenting power of equids, and a particularly large area for absorption in the hindgut.

While the ruminant digestive system is specialised for a certain regime of intake rate and fermentation rate, the monogastric/hindgut fermentation system is relatively flexible to variation in quality and quantity of food. Caecal and colonic fermentation capitalise on microbial breakdown of cellulose without the costs of blocking the system (e.g. via an omasal filter) to variable throughput rate. Where grinding is performed by the stomach, it also avoids the costs to foraging time from which cud-chewers suffer - leaving the beak free to keep selecting.

Publicado el mayo 24, 2024 01:54 MAÑANA por milewski milewski | 6 comentarios | Deja un comentario

23 de mayo de 2024

The ostrich (Struthio camelus) as a quasi-ungulate, part 5

Trophic limitations potentially imposed on any homeothermic herbivorous species (non-coprophagous) of a given body size, and the alternative adaptive strategies of digestion available to the animal.

Limitation:
poor quality of food

Responses:

  • increased intake, with the effect of substitution of quantity for quality
  • prolonged retention and fermentation of fine fraction (while passing the coarse fraction), which requires sacculation in diverticula rather than the main canal, and has the effect of compensating for limitations on gut-fill, or reliance on body-mobility
  • prolonged retention and fermentation of all food, including coarse fraction, with the effect of microbial production of energy and protein from cellulose

Limitation:
poor quantity of food

Responses:

  • fine comminution of food, with the effect of boosting the surface area for microbial and enzymatic digestion
  • prolonged retention and fermentation, with the effect of extending the duration of microbial and enzymatic digestion

Limitation:
wide variation in quality of food

Responses:

  • enlargement of hindgut rather than foregut, with the effect of avoiding wastage by fermentation of available digestible protein
  • sacculation in diverticula, rather than main canal of gastrointestinal tract, with the effect of promoting the speed of passage of food when the rate of fermentation falls below a critical threshold (i.e. in response to a decrease in quality of food)

Limitation:
poverty of energy, rather than protein, in food

Responses:

  • enlargement of hindgut rather than foregut, with the effect of provision for final assimilation in the small intestine

Limitation:
lack of moisture in food

Responses:

  • fine comminution, with the effect of retrieval of water from faeces before defecation
  • enlargement of hindgut rather than foregut, with the effect of retrieval of water from faeces before defecation
Publicado el mayo 23, 2024 11:57 TARDE por milewski milewski | 0 comentarios | Deja un comentario

Scaling (allometry) of organ mass in Felidae: how big cats are more - and less - than small cats

Please see

Also see https://academic.oup.com/jeb/article-abstract/28/8/1516/7381326?login=false.

Most of my Posts report some original observation, contribute terminologically, or make some original interpretation.

This Post is not original, because it merely rehashes material in the literature.

However, the topic is of such interest that it deserves to be aired again, more than six decades after the original publication by Davis (1962, https://www.semanticscholar.org/paper/ALLOMETRIC-RELATIONSHIPS-IN-LIONS-VS.-DOMESTIC-CATS-Davis/fcae1e3094e1b6d96bdabd1efabea516bdf6efcc).

Everyone knows that the lion (Panthera leo) is essentially a scaled-up version of the domestic cat (Felis catus).

However, it is also obvious that the eyes are proportionately far smaller in the former felid than in the latter felid.

Please compare

https://www.pinterest.com.au/pin/manny-the-selfie-cat-and-his-selfiecat-security--777433954432445959/

This differential scaling, in which the various organs are not commensurate, is called allometry (https://en.wikipedia.org/wiki/Allometry).

More particularly, eyeballs exemplify negative allometry (= hypoallometry). Negative because, as we go from small-bodied spp. to large-bodied spp., the organ in question gets proportionately smaller.

So, how do the various other organs scale, in the small-cat-writ-large that is the genus Panthera?

Comparison of Felis catus with Panthera leo:

Values are percentages of adult body mass, based on Davis (1962). The first value is for F. catus, the second is for P. leo, and the third is the ratio.

https://www.mun.ca/biology/scarr/Allomteric_Equation.html

Eyeballs 0.4% 0.04% -10.0 (negative allometry)
Brain 1.1% 0.2% -5.5
Pancreas 0.25% 0.1% -2.5
Kidneys 0.7% 0.5% -1.4
Bladder and urethra 0.1% 0.07% -1.4
Liver 3.5% 3.0% -1.2
Gastrointestinal tract 5.0% 5.0% 1.0 (isometry)
Skeleton 13.5% 13.0% 1.0 (isometry)
Muscles 50.0% 59.0% +1.2
Heart 0.4% 0.6% +1.5
Adrenals 0.01% 0.02% +2.0
Spleen 0.25% 0.5% +2.0
Respiratory 1.0% 2.0% +2.0 (positive allometry)

We can fill in the comparison by looking at the leopard (Panthera pardus), as follows from different sources.

Body composition (percentages of adult body mass), and allometric exponent (https://www.researchgate.net/figure/The-allometric-scaling-exponent-b-ie-the-slope-describes-how-the-parameter-of_fig1_263705401#:~:text=Jim%20E%20Riviere-,The%20allometric%20scaling%20exponent%20b%20(i.e.%2C%20the%20slope)%20describes,%C3%82%20Wb%20as%20an%20example.).

The first value refers to Panthera leo, the second to Panthera pardus, and the third to Felis catus.

Please note that

  • negative allometry means an exponent of <1,
  • positive allometry (= hyperallometry) means an exponent >1, and
  • proportional constancy (= isometry) means an exponent of 1.

Eyeballs 0.04% 0.07% 0.38% 0.43
Brain 0.21% 0.41% 1.1% 0.61
Liver 2.8% 3.7% 3.6% 0.89
Kidneys 0.55% 0.55% 0.71% 0.94
Gastrointestinal tract 4.8% 3.1% 4.85% 0.98
Skin 12% - 13.2% 0.99
Skeleton 13% 12.2% 13.6% 0.99
Muscles 59% - 50% 1.03
Heart 0.6% 0.5% 0.4% 1.03
Spleen 0.52% 0.26% 0.24% 1.14
Respiratory 2.2% 1.0% 1.1% 1.19

What emerges is that there is no organ in felids that is the positive counterpart of the negative allometry seen in eyeballs and brain.

Publicado el mayo 23, 2024 12:25 MAÑANA por milewski milewski | 7 comentarios | Deja un comentario

22 de mayo de 2024

The ostrich (Struthio camelus) as a quasi-ungulate, part 4: avian advantages of mobility in arid climates

Which morphological differences permit the ostrich to compete with ecologically similar ungulates, particularly under arid climates?

Birds tend to be extremely mobile, exploiting resources too patchy in space and time for like-size, like-diet mammals. This hypothetically applies even to flightless birds, for subtle reasons.

The ostrich may exceed ungulates in certain aspects of mobility, partly by virtue of its concentration of mass near the centre of gravity (e.g. gizzard replaces Jaws, tongue, and teeth).

Greater mobility would help to explain the following:

  • why all like-size ungulates coexisting with the ostrich, whether dependent on drinking (Equus asinus) or not (Oryx), depend on grass rather than forbs; the foraging selectivity of the bird follows from aspects of mobility (including light, dexterous head); and
  • why - contrary to their respective body-heights - the ostrich apparently prefers forbs while gazelles prefer woody plants, since long legs and neck allow horizontal as well as vertical mobility.

Giraffa is not only the largest-bodied of extant ruminants, but also remarkably arid-adapted. The ostrich and Giraffa are similar in

  • diurnal foraging,
  • horizontal mobility, and
  • selectivity in foraging.

Morphologically, the ostrich resembles Giraffa in its

  • small head,
  • large eyeballs,
  • long neck, and
  • long feet.

Furthermore, I predict that, consistent with the relative mobility in the ostrich, its proportional allocation of body mass should differ from that of ungulates in being

  • greater for organs of vision, performance, and thermoregulation,
  • smaller for ingesta and urine,
  • smaller for the head (including the brain), and
  • smaller for offspring and maternal tissues.

In line with monogastric ungulates which share its limited digestion of food in the stomach, the ostrich has

  • a short small intestine, and
  • heavy caecum and large intestine,

The ostrich differs from most ungulates, and all monogastric ungulates, in having

  • a longer caecum and large intestine, and
  • additional partitioning inside these chambers.

This suggests greater assimilation efficiency of food and water than in hindgut-fermenter ungulates, particularly considering the finer grinding of food in the ostrich and the fluid nature of its caecum contents, relative to e.g. equids.

The observed ability of the ostrich to maintain itself on limited water fits adaptation to aridity, in which quantity of food is more limiting than its quality.

The ostrich seems to be capable of extraordinary water economy, judging from

  • the large size of its kidneys (loop of Henle; uric acid),
  • the presence of a bladder-like coprodaeum,
  • the mobility of feathers and wings, and
  • the likely large ratio of skin mass to surface area.

A small spleen possibly reflects high body temperatures, for immunological reasons.

The ostrich has a small brain. However, it produces far more offspring per breeding attempt, and particularly per lifetime, than is true for ungulates sharing the bird's predators.

In short, the ostrich has

  • the gastrointestinal tract (and presumably the flexibility of throughput rates) of an ungulate hindgut-fermenter, and
  • the gracile build, fine comminution of food, and thorough fecal water-retrieval of a ruminant concentrate-selector.

The ostrich has the potential for efficient digestion of starch, fat, and animal protein, and the rapid reproduction, of an equid, while the opposite of equids in its mobility (and precociality of offspring) and tolerance of thermal extremes on exposed plains.

In body composition and ecology, the ostrich has little in common with hippos (maybe contrast body composition of ostrich with that if pygmy hippo of similar body mass and dietary quality), except for foraging selectivity despite being inactive for half of each day.

The ostrich, in arid climates, fills the niches of

  • ruminant concentrate-selectors, and
  • pigs.

This is because the ostrich has

  • greater flexibility of food quality and quantity, and
  • greater mobility than either of these types of ungulates. (Relate back to bird themes...)

The quality of the diet of the ostrich resembles that of ruminant 'concentrate selectors', none of which penetrates flat, arid zones, except camel, which a is big enough to fall back on woody tissues, and b relaxes the inflexibility of the omasal filter of other cud-chewers.

The ostrich combines the digestive efficiency and water-retention of ruminants (heavy gut-walls and fine grinding by stones) with the flexibility of monogastric ungulates (no obligate limitation to throughput rates nor wasteful fermentation of animal protein), with a degree of selectivity greater than in either type of ungulate.

Long neck, small head, long limbs, combined with large body mass and efficient digestion, allow the ostrich to be a concentrate selector in extremely sparse vegetation, where quantity is even more limiting than quality.

This parallels

  • Giraffa in how coexistence with a wide variety of ungulates is achieved, and
  • Camelus (unique water economy and reduced bulk needs) in penetrating arid climates beyond most ungulate competitors.

However, the ostrich differs from both Giraffa and Camelus in potential fecundity, in keeping with the particularly ephemeral resource in arid climates.

So, mobility is a crucial element in the strategy of the ostrich, but mainly in terms of food selection, penetration of arid climates, and emancipation from parental ties.

Publicado el mayo 22, 2024 03:23 TARDE por milewski milewski | 2 comentarios | Deja un comentario