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:

• Rangifer tarandus tarandus (semi-domesticated) 1.0% (Ringberg J M 1981 Body growth and carcass composition of lean reindeer (Rangifer tarandus tarandus L.) from birth to sexual maturity. Can J Zool 59: 1040-1044)
• Dama dama 0.95% (n = 19 female individuals, https://www.mdpi.com/2076-2615/13/6/1082)
• Antilocapra americana 0.95% (https://www.sciencedirect.com/science/article/abs/pii/0034568774900668)
• Eudorcas thomsonii thomsonii 0.94% (my own data, Wildlife Ranching and Research, Athi-Kapiti plains, Kenya)
• Odocoileus virginianus 0.9% (https://pubmed.ncbi.nlm.nih.gov/7380330/)
• Damaliscus pygargus phillipsi 0.845% (n = 8 adolescent individuals, https://www.researchgate.net/profile/Liana-Maree/publication/326460201_Physical_and_chemical_carcass_composition_of_springbok_Antidorcas_marsupialis_blesbok_Damaliscus_dorcas_phillipsi_and_impala_Aepyceros_melampus/links/5b4ec4efa6fdcc8dae27b55c/Physical-and-chemical-carcass-composition-of-springbok-Antidorcas-marsupialis-blesbok-Damaliscus-dorcas-phillipsi-and-impala-Aepyceros-melampus.pdf)
• Pantholops hodgsonii 0.84% (n = 9 adult males, https://avmajournals.avma.org/view/journals/ajvr/73/6/ajvr.73.6.809.xml)
• Aepyceros melampus 0.82% (n = 16 adult females, Hoffman L C, Kritzinger B, and Ferreira A V 2002 The effects of sex and region on the carcass yield and chemical composition of impala (Aepyceros melampus), being Chapter 3, pp.70-89 in Kritzinger B 2002 Meat quality parameters of the impala (Aepyceros melampus) MSc Thesis, University of Stellenbosch)
• Nanger granti granti adult females 0.80% (my own data)
• Litocranius walleri adult males 0.77% (n = 5, N S Smith, Galana Ranch, Kenya, 13-19 February 1964)
• Capricornis crispus adult males 0.75% (n = 34, https://www.jstor.org/stable/3801288?origin=crossref and https://link.springer.com/chapter/10.1007/978-94-011-8030-6_33)
• Antidorcas marsupialis marsupialis 0.71% (n = 8 adult individuals, https://www.researchgate.net/profile/Liana-Maree/publication/326460201_Physical_and_chemical_carcass_composition_of_springbok_Antidorcas_marsupialis_blesbok_Damaliscus_dorcas_phillipsi_and_impala_Aepyceros_melampus/links/5b4ec4efa6fdcc8dae27b55c/Physical-and-chemical-carcass-composition-of-springbok-Antidorcas-marsupialis-blesbok-Damaliscus-dorcas-phillipsi-and-impala-Aepyceros-melampus.pdf)
• Capricornis crispus adult females 0.67% (n = 25, https://www.jstor.org/stable/3801288?origin=crossref and https://link.springer.com/chapter/10.1007/978-94-011-8030-6_33)
• Nanger granti granti adult males 0.65% (my own data)
• Capra hircus 0.50% (https://www.sciencedirect.com/science/article/abs/pii/0034568774900668)
• Ovis aries Tibetan breed 0.48% (https://avmajournals.avma.org/view/journals/ajvr/73/6/ajvr.73.6.809.xml)
• Ovis aries fat-tailed breed in Java 0.42% after adipose tissues subtracted from body mass (Hasanah U et al. 2019 Carcass composition of fat tailed sheep at different slaughter weight, IOP Conference Series: Earth and Environmental Science 260)
• Ovis aries adult males 0.29% (large sample in Crile and Quiring 1940, with mean body mass 100 kg, including adipose tissues)

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