Echidnas: Electro-Senses

Ten Things I Like About... Podcast

Summary: Some echidna senses don’t make much sense, but they’re really cool! Join Kiersten as she discusses echidna senses.

For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean

“Functional Diversity and Evolution of Bitter Taste Receptors in Egg-Laying Mammals,” by Akihito Itoigawa, Akashi Hayakawa, Yang Zhou, Adrian D. Manning, Goujie Zhang, Frank Grutzner, Hire Imai. Molecular Biology and Evolution, Volume 39, Issue 6, June 2022. https://doi.org/10.1093/molbev/msac107

“Distortion product otoacoustic emission and auditory brainstem responses in the echidna(Tachyglossus aculeatus),” by D M Mills and R K Shepard. J Assoc Res Otolaryngol. 2001 Jun; 2(2): 130-46.

“Color vision evolution in egg-laying mammals: insights from visual photoreceptors and daily activities of Australian echidnas,” by Shiina Sakamoto, Yuka Matsushita, Akihiro Itoigawa, Takumi Ezawa, Takeshi Fujitani, Kenichiro Takakura, Yang Zhou, Goujie Zhang, Frank Grutzner, Shoji Kawamura, and Akashi Hayakawa. Zoological Letters, 2024; 10: 2.

Music written and performed by Katherine Camp

Transcript

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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

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Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

This episode continues echidnas and the ninth thing I like about these incredible animals is their senses. Just like most mammals echidnas have eyes, ears, a nose, and a tongue which covers four of the five senses. We know they use their eyes to see, their ears to hear, and their nose to smell and we’re going to talk about all of these things in this episode. Whether they use their tongue to taste, I’m not sure, but we’ll try and find out an answer. I do know they use their nose for more than just smelling. Let’s get started.

We’ll begin with vision. Echidnas are often described as nocturnal, as I said in previous episodes, but some researchers and zookeepers have seen them active during the day. What does this have to do with their vision? Whether an animal is diurnal or nocturnal can, evolutionarily speaking, influence the development of color vision. Not many controlled studies have been done to truly determine the daily behaviors of the echidna, but scientists have been able to determine that echidnas do have some color vision. Since reports say echidnas are active both day and night it does stand to reason they have at least some color vision opsins.

Their distance vision is nothing to write home about. In other words, not great, but they are excellent at discerning shapes. They can distinguish a human shape from other forms, so that means they can probably distinguish other animal and plant forms, as well. They don’t rely on vision too much, but it is helpful during the daylight hours when and if they are active.

Hearing is a sense that many animals with poor vision will depend on to survive. Echidnas are no expiation to this rule. They do have ears with which to hear, but the do not have external pinnae. The fleshly part of the ear that sticks out from the side of the head is called the pinna. We have them, dogs, and cat’s have them, many mammals have them, but not echidnas. They have a large slit behind their eyes, often hidden in their fur and spines. This opening connects to their auditory canal and allows them to hear.

A study published in 2001, determined that echidna hearing is as sensitive as other mammals such as gerbils and rabbits but it is a much narrower frequency range. They did establish that echidnas have some sort of cochlear amplifier inside the structure of the ear but it is not the same as other mammals. Echidnas can hear frequencies above 20 kHz which is higher than typical bird or reptile hearing but lower than typical mammal hearing.

Let’s take a quick lick, oh sorry, look at the sense of taste. The echidna has taste buds at the base of the tongue. The presence of taste buds implies that they can taste something. But what can they taste? A study published in 2022, looked at the bitter taste in the echidna. Bitter taste receptors are typically thought to help identify toxic chemicals in plants and invertebrates. This would be very important for an animal that eats invertebrates. This research concluded that echidnas do have just enough bitter taste buds to help keep them safe while foraging for food. More research will need to be done to find out if they have any other taste profiles.

The nose. This is where we get to the really cool stuff. Echidnas have an excellent sense of smell. Their nose is located at the end of their long snout. They rely on their sense of smell to find food underground. Their keen sense of smell allows them to find termites, ants, earthworms and other soft bodied larvae in the ground. This isn’t unusual or the truly exciting thing about their noses.

The really cool thing about their noses is that they can sense electrical currents with it. That’s pretty cool. I’m going to read you a paragraph from the Nature Comes Standard website that explains how this works. Quoting from the article entitled E.S.P: Echidna Sensory Perception, “The snout senses vibrations via both electrical and mechanical signals. A prey’s movement creates a vibration that reaches the snout, acting upon a nanoscale column of cells like a combustion engine’s push-rod. The push-rod transfers the signal to a nerve ending, creating an electric signal, and a mechanoreceptor creating a similar sensation as a humans fingertip. This information is processed to sense the presence and motion of prey. Like counting the time delay between a lightning flash and a thunder boom, the echidna can sense a prey’s distance and speed.” End quote.

That, I think, is quite a cool nose. There are even scientists studying how this works to improve human navigation and develop new methods of scanning objects. I love it when we take the time to learn from Nature.

That’s it for echidna senses, and I have a feeling that you found it just as interesting as I did because it’s my ninth favorite thing about them.

If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.

Join me next week for the final episode about echidnas.

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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.