Why do echidnas lay eggs

Echidnas, as well as platypuses, have an almost sixth sense. These animals are electroreceptive! The snouts of echidnas are packed with receptor cells that help them track movements as well as the subtitle electric fields produced by their prey.

Scientists estimate that echidnas have about to 2, electroreceptor cells in their snout. Did you know that Echidnas are toothless animals? Echidnas eat a diet full of insects such as ants, termites, and worms, but how do they eat them if they do not have teeth? Echidnas have slender snouts and very strong claws that they use to open ant hills, logs, and more.

Then, they use their sticky tongs to get the insects they eat. And these tongues are very long — they are almost half a foot long! Lastly, they use tough pads on the roof of their mouths to break down their food. Their spines are actually just long, hollow, and tough hair follicles. Echidnas use their spines as their main defense against predators such as cats, dogs, foxes, and goannas. When an echidna needs to protect itself from a predator, they will roll up into a ball with their spines sticking out and protecting them and then they will dig themselves into a burrow to stay safe.

The mystery then is why any monotremes survived. Now Phillips and his colleagues suggest that platypuses and echidnas lived on because their ancestors sought refuge where marsupials could not follow — the water.

Platypuses are amphibious creatures, while echidnas — the anteaters — are terrestrial. However, new genetic evidence and comparisons with fossil monotremes suggests that echidnas only diverged from platypuses 19 to 48 million years ago.

This means echidnas recently had semi-aquatic predecessors and only later recolonized the land. A number of aspects of echidna biology are consistent with an amphibious platypus-like ancestor — a streamlined body, rearward-jutting hind limbs that could act as rudders, and the contours of a duck-like bill during embryonic development. It was thought that the much shorter fossil record for echidnas, from about 13 million years ago, was just due to the patchy nature of the fossil record," Phillips said.

Their new findings suggest "the lack of early echidna fossils was in fact because they simply had not evolved yet. The researchers conjecture that marsupials could not afford a substantial invasion of aquatic environments because when they are born, they need to suckle milk constantly for weeks; newborn marsupials could drown if their mothers ever had to venture into the water.

Not only that, but paper suggests that the change from a platypus-like body form to an echidna-like body form appears to have happened surprisingly quickly, in less than 15 to 25 million years.

That such a major change in overall morphology could happen so quickly is intriguing. See Subscription Options. Discover World-Changing Science. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Create Account See Subscription Options. Continue reading with a Scientific American subscription.