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

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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

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Publicado por milewski hace 2 meses

Heart size in Taurotragus oryx pattersonianus (https://www.inaturalist.org/observations?taxon_id=948191):

Needham et al. (2022, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9659003/) report on a sample size of n = 10 adolescent male individuals, with mean body mass 271 kg. The mean mass of the heart, relative to body mass, in this sample was 0.45%.

In 1986-1988, I recorded the following on Wildlife Ranching and Research, on the Athi-Kapiti plains, Kenya:
Adult females n = 9, mean body mass 342 kg, mean mass of heart 1.93 kg. The mean mass of the heart, relative to body mass, in this sample was 0.564%.
Adult males n = 4, mean body mass 537.5 kg, mean mass of heart 3.025 kg. The mass of the heart, relative to body mass, was 0.563%.

My commentary:
The above data, from two sources, indicate 0.45% in adolescent males and 0.56% in adult males, and 0.56% in adult females.

Overall, what emerges is that the value for adults of T. o. pattersonianus is about 0.56%, which is much less than in the pronghorn and alcelaphin bovids.

Publicado por milewski hace 2 meses
Publicado por milewski hace 2 meses

ALCELAPHINS AND CERVUS

My own data, collected in 1986-1988 at Wildlife Ranching and Research, on the Athi-Kapiti plains in Kenya, produced the following results.

Heart size in juveniles (mean body mass 111 kg) of Connochaetes albojubatus: 0.806% (https://www.inaturalist.org/journal/milewski/94562-the-ostrich-as-a-quasi-ungulate-part-2-proportional-sizes-of-organs-in-ostrich-size-yearling-juveniles-of-the-eastern-white-bearded-wildebeest-connochaetes-albojubatus-near-nairobi-kenya#)

Heart size in Alcelaphus cokii (https://www.inaturalist.org/observations?taxon_id=132649 ):

Adult females:

Sample size n = 50
Mean body mass 124.3 kg
Mean mass of heart 0.83 kg
Mass of heart relative to body mass 0.67%

Adult males:

Sample size n = 68
Mean body mass 136.0 kg
Mean mass of heart 0.80 kg
Mass of heart relative to body mass 0.59%

For comparison, the value for Cervus elaphus (https://www.inaturalist.org/taxa/204113-Cervus-elaphus) is reported to be 0.925% (https://www.perplexity.ai/search/There-is-a-4cWbATSgRDycYfb_Xg5yHg).

This difference would be puzzling, because Alcelaphus is reputed to run with particular speed and endurance, among ruminants.

However, a different source for C. elaphus (adults of both sexes, mean body mass 109 kg) gives the mass of the heart as 0.75% of body mass, which is more similar to the values for A. cokii.

Publicado por milewski hace 2 meses

HEART SIZE IN CAPYBARA (Hydrochoerus hydrochaeris):

Mean about 0.4%, based on 200 g relative to adult body mass 50 kg (https://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i0076-3519-264-01-0001.pdf).

In 1989, Rodrigo Parra (an author in https://www.semanticscholar.org/paper/Digestion-in-the-capybara-(-Hydrochoerus-)-Baldiz%C3%A1n-Dixon/4ed734ca38effc8f8aa6c3527bc3d906b19c5cc3) told me that the heart of the capybara is 13% less massive, relative to adult body mass, than the average for mammals.

Publicado por milewski hace 2 meses

In 1990, I calculated the allometry of heart mass relative to adult body mass for ungulates. For each species, I compared the actual values with those predicted by the regression, in order to assess whether the species in question was larger- or smaller-hearted than expected for its body mass. *Asterisks indicate one sample only.

The results were as follows:

equids +0.35
gazelles/impala/giraffe +0.21
alcelaphins +0.09
rhino * +0.28
deer* +0.27
tragelaphin +0.14
tragelaphin/reduncin/hippotragin +0.04
Oryx -0.06
dwarf antelope -0.02
bovin -0.14
domestic sheep -0.42
pig -0.47

A later analysis for the heart:
Equus caballus +0.7
Taurotragus oryx +0.3
Cervus elaphus +0.3
rhinos +0.3
Aepyceros melampus +0.2
Giraffa +0.2
elephants +0.2
Lepus europaeus +0.2
gazelles +0.2
alcelaphins +0.1
Reduncini +0.03
Equus quagga 0
Strepsiceros strepsiceros -0.1
Oryx -0.1
neotragins -0.1
Syncerus caffer (small sample) -0.1
Bos taurus -0.2
Ovis aries -0.4
Phacochoerus africanus -0.4
Sus scrofa domestica -0.5

The corresponding ranking for the lungs (the pair combined) are as follows:

Cervus elaphus +0.4
Equus caballus +0.2
gazelles +0.2
Syncerus caffer (small sample) +0.2
elephants +0.15
Oryx +0.1
alcelaphins +0.1
rhino +0.1
Giraffa +0.1
Lepus europaeus +0.1
Equus quagga 0
Taurotragus oryx 0
Aepyceros melampus 0
reduncins -0.05
neotragins -0.1
Strepsiceros strepsiceros -0.3
Phacochoerus africanus -0.3
Bos taurus -0.3
Ovis aries -0.4

Publicado por milewski hace 2 meses

Heart size in Kobus kob thomasi (https://kalrorepository.kalro.org/server/api/core/bitstreams/0f43f621-40cc-42c2-bb47-ce0c915c3cc1/content ):

Mature males (n = 10)
Mean body mass 96.7 kg
Mass of heart relative to body mass 0.6%

Adult females (n = 10)
Mean body mass 62.1 kg
Mass of heart relative to body mass 0.6%

Publicado por milewski hace 2 meses

HEART SIZE IN DOMESTICATED EQUIDS

Heart size in Equus caballus (thoroughbred, in Kentucky, USA):

Source: Crile and Quiring (1940)

Adult females >3 years old, n= 10
Mean body mass 443.4 kg
Mean mass of heart 3663 g
0.83%

Adult males >3 years old, n = 5
Mean body mass 485.3 kg
Mean mass of heart 4688 g
0.97%

Adult castrated males >3 years old, n = 4
Mean body mass 446.6 kg
Mean mass of heart 3531 g
0.79%

Heart size in Equus asinus:

Sources:
Crile and Quiring (1940) n = 2 adult males
Spector n = 1 adult female

0.644%

Publicado por milewski hace 2 meses

Quotients of spleen mass relative to body mass, according to deviations from the allometric regression:

Equus caballus +2.1
neotragin bovids +1.5
Phacochoerus africanus +0.9
Cervus elaphus +0.7
Equus quagga +0.4
Taurotragus oryx +0.3
gazelles (Eudorcas thomsoni and Nanger granti) +0.3
Diceros bicornis +0.3
Aepyceros melampus +0.3
reduncin bovids +0.2
alcelaphin bovids including Connochaetes +0.1
Oryx 0
tragelaphin bovids -0.2
Giraffa tippelskirchi -0.3
elephantids -0.4
Ovis aries -0.5
Bos taurus -0.5?
Sus scrofa domesticus -0.6
Lepus europaeus -0.9

DATA

Cervus elaphus 0.54% of 109 kg
Kobus leche & K. kob 0.30%
Ovis aries 0.10% of 100 kg
Alcelaphus cokii 0.40% of 124 kg
Sus scrofa domestica 0.13% of 102 kg
Equus asinus 0.28% of 127.6 kg

Publicado por milewski hace 2 meses

HEART SIZE IN GREYHOUND

A remarkable and well-documented fact is that the heart weighs 1.25% of adult body mass in the greyhound breed of Canis familiaris (https://pubmed.ncbi.nlm.nih.gov/7785814/).

This is proportionately far more massive than in the pronghorn.

It is worth noting that the relative mass of the heart is nearly threefold greater in the greyhound than in the human athlete.

https://www.perplexity.ai/search/What-is-heart-XOICu_zlRd6m6.yLCCoc8g

Publicado por milewski hace alrededor de 2 meses

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