Heart of Conservation podcast. EP#28 Show notes (Edited)
Hi there, I’m Lalitha Krishnan and you’re listening to Season 4, Episode 28 of Heart of Conservation. I bring you stories from the wild that keep us all connected to our natural world.
We hear of people following the butterfly trail, or kids chasing frogs and catching worms, but beetle watching isn’t a thing as far as I know. But my guest on this episode is passionate about the real dung beetles so much so it was the topic of her PhD research. Three new species of dung beetles have been discovered and named by her. I’m speaking to Seena Narayanan, a Senior Research Associate & Assistant Museum Curator at ATREE. She has prepared species pages for the Scarabaeine dung beetles of the Indian subcontinent and manages a growing insect collection at the ATREE Insect Museum in Bangalore. Seena thank you so much for joining me on Heart of Conservation.
Seena Narayanan: It’s a pleasure. Thank you, Lalitha.
Lalitha Krishnan: Now, according to Wikipedia, there are 400,000 beetle species which constitute 40% of all described insects and except for the sea and polar regions they can be found anywhere on earth. And yet, we know so little about them. Seena could you start with defining a dung beetle? So, what makes it different from other beetle species?
Seena Narayanan: The beetles are the largest order among all insects. They belong to the order Coleoptera. ‘Coleos’ means sheath-like and ‘tera’ defines wings. It’s Greek. So, for most of the insect orders, you’ll find ‘tera’ in their names. Why beetles are successful, why they are in such huge numbers is because of elytra which are the forewings which protect their transparent underwing or their body as a whole. Around the world, we find 6000 species of dung beetles. They’re different from other beetle species because they mostly feed on dung. We’re talking about Scarabaeinae today which are True dung beetles. Scarabaeinae is a subfamily of beetles and they belong to the family Scarabaeidae. This Scarabaeidae family has many subfamilies. Scarabaeinae is one among many subfamilies.
Lalitha Krishnan: How many species of dung beetles can we find in India?
Seena Narayanan: In India, we’ll find around 500 species of the 6000 species of beetles worldwide. When I say 500 species, I am particularly talking about Scarabaeinae, the True dung beetles. So, in North-east India, we recently published a paper and we have recorded around 206 species. All over India, there are around 500 species.
Lalitha Krishnan: You discovered three species and named them. So, tell us about those.
Seena Narayanan: As the name indicates, these were mostly found in dung. They will provision their young ones also with dung but some beetles were found on other resources. I was studying these dung beetles which were found on millipedes and some mushrooms. Most of the species I discovered were from these millipedes. We got two species from the Western Ghats and one from Northeast India which was found feeding on a dead snail. These were from Onthophagus which is the most specio genus—‘Specio’ means most of the species are found under this genus. So one is called Onthophagus jwalae and the other, Onthophagus pithankithae. These two were found on millipedes and Onthophagus tharalithae which were found on snails.
Lalitha Krishnan: When you say, they are feeding on millipedes, are they feeding on dead insects or latching themselves to live ones?
Seena Narayanan: There was this particular species that was found running behind a live millipede which we found in the forest of Southern India. So, it need not only be dead millipedes that dung beetles feed on. It can even feed on the tissue of a live one. So when we got that millipede to the lab we saw that one adult was inside the body of a millipede which was alive. There are many predatory dung beetle species. Even though these millipedes produce defensive chemicals, it’s found that these dung beetles are attracted to these defensive chemicals because of the smell. The smell attracts them from far away and they come to the site.
Lalitha Krishnan: What is the dung beetle dance? I’ve read about it…
Seena Narayanan: Prof Marcus Byrne and Dr Mary Dacke were doing a series of experiments on Roller beetles. They saw these beetles rolling away from the dung balls. Let me explain. These dung beetles have different functional groups. Some of them will roll away the dung balls. These are the Roller beetles. Some will tunnel under the dung pat; these are the Tunnelers and some will just dwell in the dung pat. So, in this process, they will take away the resources to avoid competition from other beetles. Among the dung rollers, (Prof Marcus Byrne and Dr Mary Dacke) did some experiments in Africa and they saw that the Dung beetle, each time they roll a dung ball, it will climb on top of this dung ball and they will turn around and orient itself. What they’re doing in this dance is they are looking for the sun. According to that, they will orient themselves and push the ball in a straight line. They also saw that there is some kind of thermoregulation. They will rub their face in between while on top of the dung ball. This is to keep themselves cool on that hot sand. The way they orient themselves on the dung ball is called the dung beetle dance.
Lalitha Krishnan: Lalitha Krishnan: You did mention how they nest? But could you elaborate a little more?
Seena Narayanan: As I said, this nesting is different for different functional groups. There are these tunnelers; among the tunnelers themselves, the sizes will vary. There are large tunnelers and small tunnelers. The smallest one might take the dung into the soil just under the dung pat, just some centimetres down. The largest ones like the Heliocopris dominus, the Elephant dung beetle can take the dung a meter deep. In the case of tunnelers, they take the dung under the dung pat and they tunnel under the soil. So, there can be different branches in that tunnel and what they do is they nest at the end of these branches-the tunnels. So, they will make many brood balls inside and the male and female will mate inside this tunnel and lay eggs inside these brood balls. That’s how they provide for the young ones.
And in the case of the rollers, they will just roll the dung ball some metres or feet away from the main resource and again, they will tunnel under the soil and bury these dung balls.
In the case of dwellers, what they do is, lay brood balls in the dung pat itself and lay eggs in these dungballs.
And young ones are called grubs.
Lalitha Krishnan: Grubs. Of course. Birds love them.
Seena Narayanan: They feed and change instars and pupate.
Lalitha Krishnan: What are instars?
Seena Narayanan: Instars are the different stages. So, in the end, they will produce a pupa and the adult will emerge from that. After the summer showers, once the soil gets a little wet, they will emerge. This is the time, starting of June when they start to emerge.
Lalitha Krishnan: This is also the season when birds are still feeding their young with grub for instance. You know you mentioned dung beetles feed on millipede apart from the dung of course but what else constitutes a dung beetle’s diet?
Seena Narayanan: True Dung beetles; because they provide their brood also with dung and also they feed on dung, they’re called ‘True dung beetles’- Scarabaeinae subfamily. The adults can take in the liquid form of dung; their mouthparts are modified for even tiny particles of dung. And grubs can feed on solid dung material also. Other than that they also feed on—as I said before—the tissues of millipedes, snails, dead decaying substances and also on decaying fruits.
Lalitha Krishnan: Interesting. Earlier you had spoken about the beetle dance but I just want the audience to know that even in Egyptian mythology, the dung rolling beetle was associated with the god of the rising sun who was believed to roll the disk of the morning sun at daybreak. Scientifically, it has been proven that migratory birds, seals and other creatures too navigate by the stars. But that’s also been said of the dung beetles. Is it true?
Seena Narayanan: Yes. The experiments which Prof. Marcus Byrne and Dr Mary Dacke had done–were awarded the Noble Prize for this work. There are diurnal beetles and nocturnal beetles also, so, it’s not just in the daytime you find beetles, they’re active during the night also. You’ll find some species rolling the dungballs at night. When there is no sun, what they do is, follow the stars. That’s what the experiment results prove. They will follow the light of the milky way/stars.
Lalitha Krishnan: That’s amazing. And, like birds, do you think they get disoriented by street/building lights?
Seena Narayanan: So, even on cloudy nights, they get disoriented according to the experiment results. When they spot the polarised lights they will get attracted to the light and keep moving. They can be some effect of street lighting etc which is very bright.
Lalitha Krishnan: What threats do dung beetles face?
Seena Narayanan: So, most of the threats are anthropogenic. There is deforestation and habitat loss. There are species-specific dung beetles like the elephant dung beetle I was talking about earlier. These specifically feed on elephant dung. As mammals reduce in number, it affects the population of dung beetles also. They have to find the resources. So, when there are lots of trees cut down, deforestation happening, and lots of buildings coming up, there is no pasture lands for cattle to graze. All these things affect dung beetles.
Lalitha Krishnan: True. We see birds care for their young and other animals do the same of course but when it comes to insects, we don’t know much about their parental care. Perhaps, because we don’t see them too much or we don’t observe them too much. How do beetles care for their young?
Seena Narayanan: In the insect world there are many insects which give parental care like the Giant water bug which carries its eggs on its body to protect them. The Spittlebug produce spittle which protects the eggs kept inside. Similarly, the dung beetle provides their young ones with dung. In some species, like the largest species which lay eggs only once a year, the female will protect the young ones for a while. They stay around the nest, near their brood balls. So, in the case of larger species like the dung beetles, you’ll find some parental care.
15:24 Alright. Now Seena, would you like to tell us something about your current role at the Insect museum?
Seena Narayanan: The collections at ATREE Insect Museum are curated according to the projects and according to the insect groups the PhD students are working on. Whatever we collect from these projects and their fieldwork are part of the collections at the ATREE Insect Museum. Insects are named, labelled according to which place they are collected from, and curated. We create a database. Right now, we have two projects that are DBT funded projects for monitoring the diversity of ants and dung beetles of Northeast India and another is for edible insects of Northeast India. We have collections from most states. The second phase of the project will be coming in a couple of months. The recent collections we have are of ants, dung beetles and edible insects of North East India.
We also have parasitic wasps i.e. these wasps which belong to the Hymenoptera order. We have many new species being described.
Lalitha Krishnan: Are these from the Northeast?
Seena Narayanan: All over India. We have collections from the Western ghats. The person who recently joined our lab is working on those collections from the Western Ghats and from Northeast India.
Lalitha Krishnan: How many of you work at the Insect lab?
Seena Narayanan: Currently we have two Research Associates and four JRFs.
Lalitha Krishnan: Could you share a word or concept that will improve our understanding of dung beetles?
Seena Narayanan: As beetles are very important to the ecosystem, and they help in many services, I would say it is ‘Eco-system Services’. Through the process of relocating dung and burying them, they help in nutrient cycling and bioturbation which means the porosity of the soil increases. Then there is this secondary seed dispersal—whatever seeds are present in the dung are dispersed. And, there are some parasites which get suppressed and beetles also help increase nutrients in the soil. So, many ecosystem services are provided by dung beetles even reducing greenhouse gas emissions.
Lalitha Krishnan: Thank you so much, Seena. What you do is so important and so interesting. And I love all the stories about dung beetles.
Seena Narayanan: Thank you Lalitha. Each insect has its own story.
Lalitha Krishnan: I hope you enjoyed listening to Seena and hearing all about dung beetles. Do check out the ATREE website. Heart of Conservation is available on several platforms. Do subscribe and watch out for more episodes and please spread the word. Bye for now.