Tag Archives: tortoise

Episode 223: The Elephantnose Fish and the Burmese Star Tortoise

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This week let’s learn about an amazing little fish and an awesome tortoise! All the pictures here were taken by ME at the Tennessee Aquarium in Chattanooga!

Further Reading:

Star tortoise makes meteoric comeback

The astonishing elephantnose fish:

Burmese star tortoises:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. I’m fully vaccinated now so I’m able to go out and about cautiously, still wearing a mask of course, and this weekend I went to the Tennessee Aquarium in Chattanooga. I had a fantastic time and saw lots and lots of amazing fish and other animals! If you ever get a chance to visit, it’s definitely worth it.

When I got home, I kept thinking about one particular fish. I wanted to learn more about it. So I decided to make an episode about that fish and another animal I saw at the aquarium.

The fish that captivated me so much is called the elephantnose fish. I’d never seen anything like it. The one I saw was about the length of my hand, dark gray or black in color, and looked like a pretty ordinary fish except for the proboscis that gives it its name. The fish has a flexible projection from its nose that it was using to probe around in the gravel at the bottom of its river habitat.

I should mention that the Tennessee Aquarium has enormous displays, beautifully designed to mimic the animals’ natural habitat and give them plenty of room to move around. There’s one tidal animals display in the ocean side of the aquarium where the water sloshes through and around rocks to mimic the tide. It’s fascinating to watch the fish in that exhibit stay pretty much motionless despite the water’s movement, because that’s what they’re adapted for. So there’s plenty of opportunities to see an animal’s behavior.

Anyway, I took lots of pictures of the elephantnose fish and when I got home, I started researching it. It turns out that it’s way more interesting even than I thought!

It lives in rivers and other freshwater in central Africa and grows up to 9 inches long, or 23 cm. That’s according to the info display next to the exhibit. The display also said the fish was a species called Peter’s elephantnose fish, although it’s possible they have more than one species on display. There are a lot of elephantnose fish, more properly called mormyrids or freshwater elephantfish, and many of them have this interesting proboscis.

The proboscis isn’t actually a nose like an elephant’s trunk. It’s technically a modified chin and mouth, called the Schnauzenorgan. The elephantnose fish mostly eats small worms and insect larvae, and it especially loves mosquito larvae.

The elephantnose fish uses electroreception to navigate the muddy waters where it lives and find food. Its whole body, and especially its Schnauzenorgan, is covered with electrocyte cells that can detect tiny electrical pulses. If you remember way back in episode ten, about electric animals, many animals can sense the weak bioelectrical fields that other animals generate in their nerves and muscles. It’s especially common in fish since water conducts electricity much better than air does. But the elephantnose fish also generates a stronger electric field of its own, which it uses as a sort of sonar. It generates the field in special electric organs in its tail, and as it moves around in the water, the electric field comes in contact with other things—plants, rocks, other fish, and so on. It’s not strong enough to give an animal a shock, but it’s strong enough for the elephantnose fish to easily sense changes in its environment. The fish can tell what it’s near because its electrical field interacts differently with different things. A rock, for instance, doesn’t conduct electricity so the fish probably senses it as a blank spot in its electrical field, while a plant may conduct electricity even better than water and therefore changes the shape of the fish’s electrical field in a particular way. But it doesn’t generate its bioelectric field all the time. It can control when it discharges pulses of electricity the same way a dolphin can control when it sends out pulses of sound. If the fish feels threatened, maybe by another elephantnose fish nosing in on its territory, it will pulse much faster so it can keep tabs on what the other fish is doing—plus, of course, the other elephantnose fish can sense its pulses and can interpret how aggressive the first fish is. Female elephantnose fish generate a slightly different electrical field than males, which allows males and females to find each other to spawn.

You may be thinking about all this and wondering how the elephantnose fish can sense the tiny bioelectric charges of its tiny prey over its own electric field. Its electric field is much stronger than that of a teensy worm hiding in the mud, after all. It would be like trying to hear a bird chirping outside through a closed window while someone is playing music really loudly in the room you’re in. It turns out that the elephantnose fish is able to filter out its own electrical field so it can sense other things—but at the same time it’s still able to navigate using its electrical field.

The elephantnose fish needs a large brain to interpret all these complicated bioelectrical signals, and it has a brain to body size ratio equivalent to birds and possibly equivalent to primates. It’s not a social fish, and intelligence seems to develop from complex social interactions, although the fish is considered pretty intelligent. I mean, generally fish are not masterminds, so it’s not hard to be considered an intelligent fish, but the elephantnose fish has the brainpower to pull it off.

The elephantnose fish lives along the bottom of rivers and ponds, usually murky ones, and is mostly nocturnal. For a long time researchers thought it probably couldn’t see very well. It turns out, though, that it sees extremely well. Its retina is made up of cup-shaped cells that act like tiny mirrors, reflecting light and concentrating it so it can see better even in low light.

The elephantnose fish is a popular pet, but it is hard to keep. You have to really know what you’re doing and have a really big aquarium that’s set up just right. The males are aggressive toward each other and while the fish isn’t threatened in the wild, from what I could find out it has never bred in captivity.

Speaking of breeding in captivity, our other animal this week isn’t a fish but a reptile. It’s called the Burmese star tortoise and unlike the elephantnose fish, it’s critically threatened in the wild. It also doesn’t have a Schauzenorgan and instead just has a short little snub nose and lives on land in dry forests in Myanmar. It’s basically the opposite of the elephantnose fish.

It gets the name star tortoise because of its pretty shell markings that look sort of like stars. It can grow up to a foot long, or 30 cm, and eats grass, fruit, and other plant material, but will also eat mushrooms, insects, and snails. It has a steeply domed carapace, the proper name for its shell, with big bumps on it. It lives in central Myanmar in south Asia, but by the late 1990s it was almost extinct in the wild. The tortoise was eaten by locals, but mostly it was captured and sold as a pet or as a medicine ingredient even though it’s a tortoise, not a medicine. This was despite the tortoise being a protected species in the country.

Conservationists realized they had to act fast before this lovely tortoise went extinct. In 2004, authorities caught smugglers with 175 of the tortoises, so Myanmar’s conservation group created tortoise breeding facilities within three of the country’s wildlife sanctuaries. They consulted zoo veterinarians and tortoise experts from all over the world to make sure the rescued tortoises were as happy and healthy as possible. The first captive-bred Burmese star tortoise babies had only been hatched the year before, since it’s hard to breed in captivity.

Each sanctuary has guards that protect it from anyone who wants to sneak in and steal the animals to sell, and 150 of the tortoises have little radio trackers attached to their shells so conservationists can keep an eye on exactly where they are. They go out and check on the tagged tortoises every other week.

Since 2004, over 16,000 Burmese star tortoises have hatched in captivity and about a thousand have been returned to the wild. They’d release more into the wild, but the conservationists are worried that poachers would collect them to sell. The country of Myanmar is in a long-running civil war, unfortunately, and that makes it hard for the people living there to concentrate on conservation. Their main goal is just to stay safe. Hopefully things will get better soon for the people of Myanmar, and when they do, the tortoises will be waiting.

You can find Strange Animals Podcast at strangeanimalspodcast.blubrry.net. That’s blueberry without any E’s. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or Podchaser, or just tell a friend. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us that way.

Thanks for listening!

Episode 095: Giant Tortoises

This week let’s learn about giant tortoises! What’s the difference between a turtle and a tortoise? The most basic difference is that the turtle lives in water and the tortoise lives on land. And there are some really, really big tortoises in the world!

A Galapagos tortoise:

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This episode was supposed to be about strange reptiles, with more awesome suggestions from listeners. I was going to include some information about a couple of giant tortoises…but the more I researched, the longer that part of the episode became, until it just took over. So here’s an episode about giant tortoises, and we’ll have the strange reptiles episode in a couple of weeks instead. I’m going to give a shout-out to listeners Leo and Finn, who have been waiting patiently to hear their suggestions. Sorry you’ll have to wait a little bit longer.

The biggest tortoise in the world is the Galapagos Tortoise, which as you probably know, or can guess from the name, lives in the Galapagos Islands off the coast of Ecuador. In fact, the islands were named after the tortoises. Galapago means tortoise in Old Spanish. There are eleven species of Galapagos tortoise alive today, but there used to be 15. The others were mostly eaten to extinction by sailors who would stop by the Galapagos Islands, capture tortoises, and sail away with them to eat later.

The biggest individual Galapagos tortoise ever measured was a male named Goliath. When he died in 2002, Goliath was 4.5 feet long, or 1.36 meters, 2 feet three inches high, or 68.5 cm, and weighed 919 pounds, or 417 kg. He was only 42 years old when he died, but Galapagos tortoises frequently live for more than 150 years. Adult tortoises have no predators except humans. They’re just too big, too heavy, too strong, and have too tough a shell for other predators to bother with.

The Galapagos tortoise eats plants, including grass, leaves, fruit, and even cacti. Its neck is long, which allows it to reach plants that are farther away, since it can’t exactly climb trees. It can survive up to six months without water, getting most of its moisture from the plants it eats, but some tortoises on more arid islands will lick dew from rocks to get moisture. Some of the boulders have been licked by tortoises so much over the centuries that they have deep grooves worn in the surface from turtle tongues.

As I’ve mentioned before in other episodes, sometimes herbivores will eat meat when they can get it. The Galapagos tortoise does this too on occasion. There’s a type of finch on the Galapagos that cleans parasites off the tortoises, and to help the finch reach as much of its skin as possible, the tortoise will stand up straight with its legs extended. The finches hop underneath and clean ticks and other parasites from the tortoise’s legs, neck, and the skin between the carapace, or upper shell, and the plastron, the lower shell. But occasionally a tortoise will suddenly pull its legs into its shell and drop, smashing the finches flat. Then it stands up and eats the squashed birds. This is not cool, tortoise. Those birds are trying to help you.

Galapagos tortoises lay round, hard-shelled eggs. The female digs a hole in the dirt that’s about a foot deep, or 30 cm, and lays about a dozen eggs in it. She covers the eggs with dirt, tamps it down with her plastron, and leaves. When the babies hatch, they have to dig their way out of the hole. This can take weeks, but fortunately the babies still have yolk sacs attached that keep them from starving.

One of the Galapagos tortoise species that went extinct recently was the Pinta Island tortoise. The last known individual was called Lonesome George. He was found in 1971 on Pinta Island and taken to the Charles Darwin Research Station on Santa Cruz Island. Although researchers tried to find more Pinta Island tortoises, even offering $10,000 if someone found a female, George turned out to be the very last one. He lived with two females of another Galapagos giant tortoise species, in hopes that they were closely related enough to produce babies, but none of the eggs the females laid ever hatched. Lonesome George died in 2012.

Since then, in 2015, DNA testing on a population of tortoises living on Santa Cruz Island showed that they are a subspecies of their own, and closely related to the Pinta Island tortoises. This had to be an “if only we’d known” moment for the conservationists, who could have paired George with females from that population to produce offspring that were genetically close to the Pinta Island tortoise.

Other Galapagos tortoise species were luckier. The Española Island tortoise was down to only 14 individuals in the wild in 1963. They were all taken to the research station on Santa Cruz Island, joined a few years later by another Española tortoise that had been living in the San Diego Zoo. The breeding program was successful and these days there are over a thousand Española tortoises on the island. Similarly, rats introduced to Pinzón Island in the late 19th century nearly drove that island’s species of tortoise to extinction by eating their eggs and hatchlings. By 1965 there were fewer than 200 adults left alive, and no babies had survived for the better part of a century. Scientists started collecting eggs to incubate in safety at the research station, and rear in captivity until they were big enough to survive rat attacks. By 2012, all the rats had been removed from the island and tortoise nests started to hatch naturally in the wild again.

But the Galapagos tortoise isn’t the only giant tortoise alive. The Aldabra giant tortoise is from the Aldabra Atoll in the Seychelles [pronounced say-SHELZ], a collection of 115 islands off the coast of East Africa. It’s about the same size as the Galapagos tortoise and looks similar, but it’s not closely related. Females lay leathery-shelled eggs in shallow nests. In hot weather, some Aldabra giant tortoises will dig burrows to shelter from the heat. It eats plants and has a long neck like the Galapagos tortoise to reach branches, but unlike the Galapagos tortoise it will sometimes rear up on its hind legs to reach leaves. This is dangerous for a tortoise, because if it topples over on its back, it might not be able to right itself and can die.

Like the Galapagos tortoise, some species of Aldabra giant tortoise have gone extinct in the recent past, and for the same reasons. This included Arnold’s giant tortoise, which lived on one of the central Seychelles islands.

In 1995, the Nature Protection Trust of Seychelles was told about two unusual tortoises in a hotel garden. A couple of scientists went to investigate. The tortoises were both male, extremely old, and appeared to fit the description of Arnold’s giant tortoise, which had supposedly gone extinct over a hundred years before. Where had they come from?

It turns out that the hotel had recently bought the tortoises from a very old local man. They had been in the man’s family for longer than anyone alive could remember. Originally there had been three tortoises, but one had died only a matter of months before the scientists discovered them. They were able to get the dead tortoise’s skeleton for study, which proved that these weren’t just regular old Aldabra giant tortoises, they were Arnold’s giant tortoises—possibly the last two alive in the world.

But the researchers weren’t going to give up that easily. They started digging into reports of other unusual tortoises on the islands. Not only did they eventually find a handful of other Arnold’s giant tortoises, they found a second subspecies that had supposedly gone extinct in 1840, referred to as hololissa after its scientific name, Aldabrachelys hololissa.

As if that wasn’t awesome enough, after all this excitement in the tortoise studying community, the Blackpool Zoo in England took a closer look at the Aldabra giant tortoise that had been living there for the last 25 years, named Darwin. It turns out that Darwin was a hololissa tortoise all along. After that, other zoos brought in experts to examine their giant tortoises, and more hololissa and Arnold’s individuals turned up. The problem is that these tortoises all look pretty much alike except to experts. The tortoises have been placed in a successful captive breeding program in the Seychelles.

Researchers used to think that giant tortoises grew so big due to island gigantism, where a species isolated on an island evolves to become larger. In addition to the Seychelles and the Galapagos, giant tortoises used to live on the Canary Islands and the Mascarene islands, including on Mauritius. You know, where the dodo used to live.

But giant tortoises used to be common all over the world, not just on islands where they mostly live today. Big as these living tortoises are, there used to be giant tortoises even bigger.

The biggest known giant tortoise lived in what is now India and Pakistan, and probably in other places too. It lived around two million years ago and may have only gone extinct about 100,000 years ago, or maybe even more recently. It was twice the size of the Galapagos tortoise, possibly as much as nine feet long, or 2.7 meters, and six feet high, or 1.8 meters.

The giant land tortoise, Hesperotestudo crassiscutata, lived even more recently in North and Central America. It was a little bit larger than the Galapagos tortoise, maybe six feet long, or 1.8 meters, but it went extinct only 12,000 years ago. Researchers think humans may have played a part in driving that tortoise to extinction too, by eating it and its eggs. Since I’m recording this episode on Thanksgiving day in the United States, I’m feeling a little guilty about eating so much turkey. Fortunately, turkeys, unlike giant tortoises, are not endangered.

I’m thankful that some species of giant tortoises have survived until today. They’re awesome animals.

You can find Strange Animals Podcast online at strangeanimalspodcast.com. We’re on Twitter at strangebeasties and have a facebook page at facebook.com/strangeanimalspodcast. If you have questions, comments, or suggestions for future episodes, email us at strangeanimalspodcast@gmail.com. If you like the podcast and want to help us out, leave us a rating and review on Apple Podcasts or whatever platform you listen on. We also have a Patreon if you’d like to support us that way.

Thanks for listening!