Which animal scavenged bones in Madagascar?

(writing in progress)

Which animal or animals scavenged bones in Madagascar (https://en.wikipedia.org/wiki/Madagascar)?

In Africa, there is a diverse guild of bone-eaters of body mass 5 kg or more, including

• three genera of Hyaenidae,
• Gypaetus barbatus (https://en.wikipedia.org/wiki/Bearded_vulture), and
• Hystrix spp. (https://en.wikipedia.org/wiki/Cape_porcupine and https://en.wikipedia.org/wiki/Crested_porcupine).

In Australia, the bone-eating guild was rudimentary. The main scavenger was Sarcophilus harrisii (https://en.wikipedia.org/wiki/Tasmanian_devil). This raccoon-size marsupial has disproportionately large jaws, but is otherwise unremarkable in body form for a dasyurid (https://en.wikipedia.org/wiki/Dasyuridae).

Sarcophilus is the closest thing Australia has ever produced to a hyena. However, even the extinct forms of Sarcophilus were smaller than any bone-eating extant hyena.

I explain the difference between Africa and Australia by invoking the limited productivity of the particularly nutrient-poor soils of the latter continent. There never has been a niche for a large, specialised bone-eating tetrapod in Australasia, and Sarcophilus can be considered a ‘half-hyena’, as it were. However, Sarcophilus does at least nominally represent the guild in question.

In the case of Madagascar, I suggest that extinct hippos (https://twitter.com/RomanUchytel/status/1493644709557850125/photo/1 and https://en.wikipedia.org/wiki/Malagasy_hippopotamus) of Madagascar were the main bone-crunching scavengers.

My rationale is as follows:
 
A landmass the size of Madagascar should be able to support some sort of animal, of body mass more than 5 kg, able to consume bones, albeit as a minor component of its diet.
 
The largest carnivore in Madagascar, namely Cryptoprocta ferox (https://en.wikipedia.org/wiki/Fossa_(animal)), has been observed cracking the adult pelvis of the domestic pig (Sus scrofa), swallowing the pieces along with the attached muscle (Steve Goodman, personal communication). It is probably able to crush bone to a limited extent, but inferior to Sarcophilus in this way. The two species are similar in body mass (about 7 kg), but the head of C. ferox (https://www.alamy.com/wild-fossa-in-kirindy-forest-western-madagascar-full-body-view-image429129826.html) is far smaller than that of S. harrisii (http://www.oceanwideimages.com/Large-Image.asp?pID=7220&cID=200&rp=categories%2Easp%3FcID%3D200%26p%3D1).

A recently extinct relative, Cryptoprocta spelea, had distinctly larger molars than the extant species, indicating a greater capacity for bone-crushing (https://d1wqtxts1xzle7.cloudfront.net/82177950/source-libre.pdf?1647331623=&response-content-disposition=inline%3B+filename%3DOn_the_specific_identification_of_subfos.pdf&Expires=1656199889&Signature=c6WKzK9L34Nf0QNsEvTim5rZ55fsakAXNPYx~w51IFX8gjceWnplNPM-69WVDC~Nv8GMDWUj8haw8fX5jkAIU3PZJSG9jC06imJq9Fk20Fmr0j2jYAzYQZUr7zo2EZM-PCEQVxIaKdojuHwu87oM1nEpIcCP5bxi4FwDBs8Z0L4rbG4wrwToOIa~UwLmuOeGgxjdg~G3IEob8BvQO2m4AT3g-Jd2Nt2ls2AWSlEG8gv22wCCIPmNVUdCTdIZuAu0PBhlgttRlRFJc5rRLtjoe01egiIfm38iRcayK1xsTGp3GKQ~ppRm06opBPL~kidUv1SiLiF9h80mhZrS44n5fw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA).

Unlike South America, Madagascar lacks a proliferation of potentially bone-gnawing rodents to fill in for the lack of a semi-specialised, large scavenger. There is a considerable diversity of indigenous rodents, most living in forest situations, in Madagascar. These include nesomyine rodents weighing more than 1 kg (https://en.wikipedia.org/wiki/Nesomyinae). However, this cannot emulate the role of rodents in Africa or South America.
  
There seems to be nothing in the dentition of the extinct large lemurs to invoke this kind of scavenging. There is no evidence for bone-eating in the work on stable isotopes in the subfossil bones of lemurs (https://scholarworks.gsu.edu/cgi/viewcontent.cgi?article=1117&context=anthro_theses and https://royalsocietypublishing.org/doi/abs/10.1098/rsbl.2022.0094 and https://link.springer.com/article/10.1007/s10764-005-5325-3 and https://www.pnas.org/doi/10.1073/pnas.2022117118 and https://www.researchgate.net/publication/41762655_A_glance_to_the_past_Subfossils_stable_isotopes_seed_dispersal_and_lemur_species_loss_in_Southern_Madagascar and https://www.academia.edu/851657/A_glance_to_the_past_subfossils_stable_isotopes_seed_dispersal_and_lemur_species_loss_in_southern_Madagascar and https://www.frontiersin.org/articles/10.3389/fevo.2019.00490/full).
 
The elephant bird (Aepyornis maximus, https://prehistoric-fauna.com/Aepyornis-maximus and https://en.wikipedia.org/wiki/Elephant_bird) could potentially swallow whole bones of considerable size. In Africa, the ostrich (Struthio camelus) is known to swallow bones in the wild, despite the small size of its mouth, and by virtue of the elasticity of its throat. However, it seems reasonable to assume that any such role would have been limited.

Potamochoerus larvatus (https://en.wikipedia.org/wiki/Bushpig) certainly has jaws and teeth strong enough to crush bones. However, it does not qualify because it is not strictly indigenous to Madagascar (https://www.nature.com/articles/s41598-020-77279-5#:~:text=The%20bushpig%20(Potamochoerus%20larvatus%3B%20Suidae,tenth%20to%20thirteenth%20centuries7.).
 
Hippos have strong enough jaws and durable-enough teeth to consume bones (https://houseofwhitley.com/product/hippopotamus-lemerlei-fossil-skull/ and https://upload.wikimedia.org/wikipedia/commons/f/fa/Hippopotamus_lemerlei_skull.jpg and https://www.lot-art.com/auction-lots/Extinct-Malagasy-Hippopotamus-Skull-Hippopotamus-lemerlei-460x330x260-mm/47908219-extinct_malagasy-23.5.21-catawiki and https://www.barnebys.it/aste/lotto/malagasy-hippopotamus-skull-hippopotamus-lemerlei-44-33-28-cm-mbm9knu-uy). The extant hippopotamus (https://en.wikipedia.org/wiki/Hippopotamus) in Africa is indeed known to accept large animals as food from time to time despite its grazing specialisation.

Hippos are in a sense preadapted to bone-crunching because they combine large bodies (indeed the largest of all animal bodies in the fauna of Madagascar) with proportionately large heads. Although the extinct hippos of Madagascar were associated with forest and water, and probably absent from relatively dry environments, are they not the likeliest candidates?

Also see https://www.inaturalist.org/journal/milewski/69604-spectacular-counterpart-of-hyenas-in-south-america#.

(writing in progress)

Posted on June 25, 2022 10:30 PM by milewski