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Egg-eating Snake (Dasypeltis fasciata) photo by Bill Bouton

To continue “egg week” we encounter a creature which not only reproduces through laying eggs, it lives entirely by eating them!  Meet Dasypeltis,  a genus of colubrid snakes of Africa.  There are 12 recognized species of Dasypeltis snakes ranging across the great continent (they are non-venomous, by the way).  These serpents are all oophagous , which is to say they eat eggs…  In fact they are exclusively oophagous—they eat nothing but eggs! Gosh!

The adult snakes range in size from 30-100 cm (12-39 inches) in length and come in a variety of unobtrusive colors.  They have ridiculous jaws of vast flexibility which can expand to many times the diameter of their head so that they can eat eggs which are much wider than their bodies.   This leads to some disturbing-yet-amazing-photographs which would make even the greatest champion-eater envious. Egg-eating snakes have a highly developed sense of smell–they are capable of telling if an egg has gone off, or if it has developed past a point where it is easily digestible.


Photo by David A. Northcott

These egg-eating snakes do not have teeth as such; instead they have hard ridges on their spine which allow the snakes to break open the eggs after swallowing them.  So once the egg is safely inside the snake’s gullet, the hungry creature breaks it into pieces inside itself and sucks the nutrients out (whereupon it regurgitates all the shell fragments).  This strikes me as an insane way to get nutrients, but it apparently works surprisingly well:  snake nutritionists (?) calculate that “snakes are remarkably efficient and waste very little of the contents of an egg.”  Because of the way egg-eating works in the wild–where one tends to discover a lot of eggs at once or none at all—the snakes can eat a number of eggs in one uh…sitting (can I say “sitting” in this context?). They then go semi-dormant during the wet season (all of which means that distraught reptile enthusiasts sometimes force feed quail eggs to their pet egg-eating snakes—which also strikes me as insane).

Dasypeltis 022Photo by Jonathan Brecko


Obdurodon--A Miocene Platypus which flourished 15 to 20 million years ago

Ferrebeekeeper has an abiding interest in monotremes including both the poisonous platypus and the enigmatic echidnas (with their advanced frontal cortex).  But sadly that is about it as far as it goes for the extant egg-laying mammals: there are only two living families of monotremes (with a scanty total of five species split between them).  To learn more about these animals one must turn to paleontology.  Unfortunately even in the fossil record, monotremes are extremely rare.

Based on genetic evidence, biologists believe that the first monotremes made their advent in the history of life about 220 million years ago during the Triassic era; however the earliest known fossil monotreme so far discovered was a fossil jaw from the early Cretacious era about 120 million years ago.  The bones belonged to Steropodon galmani, which seems to have been a beaked swimmer about 50 cm (20 inches) long which lived in Australia.  Steropodon was apparently a giant among Cretacious mammals–most of which seem to have been shrew-sized (so as to better avoid attention from their contemporaries, the dinosaurs). Reconstructions of Steropodon all seem to resemble the platypus, and most paleantologists would probably concede that it was a sort of platypus—as apparently were other Mesozoic fossil monotremes such as  Kollikodon and Teinolophos (platypuses and these platypus-like forbears are called the Ornithorhynchida).  During the Cretaceous era, the land which is now Australia was in the South Polar regions of the world (approximately where Antarctica is today).  Although temperatures were much warmer during the Cretaceous, monotremes must still have been able to deal with terrible cold: it is believed that the extremely efficient temperature control and the deep hibernation mechanism which these animals continue to display first evolved during that time.

An artist's reconstruction of Steropodon

The only monotreme fossil which was not found in Australia was from another platypus-like creature named Monotrematus sudamericanum.  The creature’s remains were found in a Patagonian rock formation from the Paleocene era (the era just after the fall of the dinosaurs). Monotremes probably flourished across South America and Antarctica, as well as on Australia, but evidence is still scarce. There are most likely many interesting monotreme fossils throughout Antarctica, but, for some reason, paleontologists have not yet discovered them. Additionally, unlike the marsupials (which still quietly flourish throughout South America), the poor monotremes were wiped out on that continent.

Another artist's vision of Steropodon galmani--Notice how peeved the poor creature looks!

Last week I wrote about the Eocene era and the great proliferation of mammalian types which took place during that warm and fecund time.  Although most families of mammals alive today first appeared on the scene during the Eocene, obviously the monotremes were already incredibly ancient.  The Eocene does however seem to have been significant time for the monotreme order: the aquatic platypuses were apparently the ancestral monotremes, and echidnas (the Tachyglossidae) probably split off from them during the Eocene.  Unfortunately we have no Eocene monotreme fossils so this conclusion is based on genetic evidence and on the suffusion of Miocene monotremes which include representatives of both Ornithorhynchida and  Tachyglossidae.  Some of these latter creatures are spectacular, like Zaglossus hacketti the giant echidna from the Pleistocene which was about the size of a ram! As Australia dried up so did the monotremes and now there is only one species of platypus left…

The Giant Echidna (Zaglossus hacketti) which lived until 20,000 years ago...

Well, that’s a cursory history of the monotremes based on what we know.  I wish I could tell you more but unfortunately there is no fossil evidence concerning the first half of the order.  Sometimes I like to imagine the first monotremes—which were probably clunky, furry platypus-looking characters with an extra hint of iguana thrown in. These creatures fished in the alien rivers of the Triassic world in a time when dinosaurs and pterosaurs were also still evolving.

Ye Olde Ferrebeekeeper Archives

July 2022