Episode 363: The Dodo and Friends

Thanks to Wilmer and Carson for suggesting we revisit the dodo!

Further reading:

Dodos and spotted green pigeons are descendants of an island-hopping bird

On the possible vernacular name and origin of the extinct Spotted Green Pigeon Caloenus maculata

Giant, fruit-gulping pigeon eaten into extinction on Pacific islands

A taxidermied dodo:

The Nicobar pigeon, happily still alive [photo by Devin Morris – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=110541928]:

The 1823 illustration of the spotted green pigeon:

Show transcript:

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

This week we’re going to revisit a bird that everyone’s heard of but no one has seen alive, because it’s famously extinct. We talked about the dodo way back in episode 19, so it’s definitely time we talked about it again. Thanks to Wilmer and Carson for suggesting it! We’re also going to learn about some of the close relations of the dodo.

The first report of a dodo was in 1598 by Dutch sailors who stopped by the island of Mauritius in the Indian Ocean. Mauritius is east of Madagascar, which is off the eastern coast of Africa. The last known sighting of a dodo was in 1662, just 64 years later. The dodo went extinct so quickly, and was so little known, that for a couple of centuries afterwards many people assumed it was just a sailor’s story. But there were remains of dodos, and in the 19th century scientists gathered up everything they could find to study the birds. More remains were found on Mauritius.

In the wild, the dodo was a sleek bird that could run quite fast. It may have eaten crabs and other small animals as well as roots, nuts, seeds, and fruit. It was also probably pretty smart. People only thought it was dumb because it didn’t run away from sailors—but it had no predators on Mauritius so never had to worry about anything more dangerous than an occasional egg-stealing crab before.

When humans arrived on Mauritius, they killed and ate dodos and their eggs. What the sailors didn’t eat, the animals they brought with them did, like pigs and rats. It was a stark and clear picture of human-caused extinction, shocking to the Victorian naturalists who studied it.

A lot of the drawings and paintings we have of dodos were made from badly taxidermied birds or from overfed captive birds. At least eleven live dodos were brought to Europe and Asia, some bound for menageries, some intended as pets. The last known captive dodo was sent to Japan in 1647.

The dodo grew over three feet tall, or almost a meter, with brown or gray feathers, a floofy tuft of gray feathers as a tail, big yellow feet, and a weird head. The feathers stopped around the forehead, making it look sort of like it was wearing a hood. Its face was bare and the bill was large, bulbous at the end with a hook, and was black, yellow, and green. The dodo looks, in fact, a lot like what you might expect pigeons to evolve into if pigeons lived on an island with no predators, and that’s exactly what happened.

The dodo’s closest living relation is the Nicobar pigeon, which can grow 16 inches long, or over 40 cm. Like other pigeons, the dodo’s feathers probably had at least some iridescence, but the Nicobar pigeon is extra colorful. Its head is gray with long feathers around its shoulders like a fancy collar, and the rest of its body is metallic blue, green, and bronze with a short white tail. Zoos love to have these pigeons on display because they’re so pretty. It’s a protected animal, but unfortunately it’s still captured for sale on the pet black market or just hunted for food. It only lays one egg a year so it doesn’t reproduce very quickly, and all this combined with habitat loss make it an increasingly threatened bird. Scientists are trying to learn more about it so it can be better protected.

The Nicobar pigeon lives on a number of islands in the South Pacific and it can fly. Sometimes an errant individual is discovered in Australia, often after storms. Imagine going into your back yard one day and seeing a 40-centimeter-long bird whose feathers shine like jewels! The Nicobar pigeon lives in small flocks and eats seeds, fruit, and other plant material.

An even closer relative to the dodo is also the most mysterious. We don’t even know for sure if it’s extinct, although that’s very likely. It’s the spotted green pigeon and we only have one specimen–and we don’t even know where it was collected, just that it was an island somewhere in the South Pacific. There used to be two specimens, but no one knows what happened to the second one.

For a long time researchers weren’t even sure the spotted green pigeon was a distinct species or just a Nicobar pigeon with weird-colored feathers, but in 2014, DNA testing on two of the remaining specimen’s feathers showed it was indeed a separate species. Researchers think the spotted green pigeon, the dodo, and another extinct bird, the Rodrigues solitaire, all descended from an unknown pigeon ancestor that liked to island hop. Sometimes some of those pigeons would decide they liked a particular island and would stay, ultimately evolving into birds more suited to the habitat.

The specimen we have of the spotted green pigeon is 13 inches long, or 32 cm. Its feathers are dark brown with green iridescence and it has long neck feathers like the Nicobar pigeon. It also has little yellowish spots on its wings and a yellow tip to its bill. Researchers think it was probably a fruit-eating bird that lived in treetops.

The only reason we know there were once two specimens of this mystery bird is from a book about birds published in 1783, where the author mentions having seen two specimens. There was also an 1823 book about birds with an illustration of the spotted green pigeon that differs from the known specimen in some details. Researchers think the illustration might have been painted from the now-missing specimen.

There’s more to this mystery, though, because in 2020 an ornithologist studied a 1928 book about Tahiti that mentioned a bird that sounds a lot like the spotted green pigeon. It was even called a pigeon in the book. Since the author of that book had drawn on studies made by her grandfather almost a hundred years before, and since her grandfather had interviewed Tahitians about their history and traditions and they told him about the pigeon, the ornithologist suggested the spotted green pigeon might actually be from Tahiti. Now that scientists have a clue about where to start looking for remains of the bird, we might learn more about it soon.

Also in 2020, a study was published about another pigeon from the Pacific Islands. Fossils of it were found on the island of Tonga, and the scientists determined that the bird probably went extinct soon after humans first arrived on the island 2,850 years ago. The pigeon has been named Tongoenas burleyi. It grew about 20 inches long, or 50 cm, not counting its tail. It could fly and probably spent a lot of its time in trees, eating fruit. There are lots of different trees on the island that produce really big fruit, some of it as big as a tennis ball. Scientists think the pigeon was adapted to swallow these huge fruits whole, digest them, and poop out the seeds. The trees still exist but they’re in decline and scientists think it may be because no birds remain on the island that can spread their seeds effectively.

We don’t have any feathers from the newly described pigeon, but it was probably colorful. We do have a lot of bones, because many charred bones have been discovered in cooking pits excavated by archaeologists.

We don’t know yet how or if Tongoenas is related to the dodo. The Pacific islands are home to at least 90 living species of pigeon, and many of them we don’t know much about. There are undoubtedly many more waiting to be discovered by scientists, whether living or extinct.

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. We also have a Patreon at patreon.com/strangeanimalspodcast if you’d like to support us for as little as one dollar a month and get monthly bonus episodes.

Thanks for listening!

Episode 138: City Animals

This week we’re going to learn about some animals that have made their homes in cities alongside humans. Thanks to Corianne who suggested this amazing topic!

Further reading:

The BBC’s Urban Fox FAQ

Toronto vs. Raccoons

The urban fox has a favorite coffee shop and knows where to find parking downtown:

The urban raccoon’s apartment is really small but it’s in a great location:

The urban (rock) pigeon can walk to work in good weather:

Show transcript:

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

This week we’re going to look at animals that live in cities. This is a great suggestion by Corianne, who especially suggested the pigeon. But pigeons aren’t the only animals that live in cities alongside people. In fact, in 2018 a large-scale camera trap study of animals in Washington DC and Raleigh, NC concluded that just as many mammal species live in cities as live in the countryside. That’s only mammals, though. There aren’t as many species of other animals in cities.

Different animals hang out in cities in different parts of the world. In parts of Africa and Asia, local monkeys have moved into cities and cause mischief by stealing food from markets and tourists. Gulls are also thieves of food, sometimes getting so bold as to snatch a sandwich from a person’s hands while they’re eating it, even in cities nowhere near the ocean. City parks attract squirrels and deer, decorative fountains and ponds attract geese and ducks as well as alligators, peregrine falcons move in to feast on pigeons, rats, and other small animals, and some cities have to deal with the occasional bear or leopard, wild boars, even penguins. But today we’re going to focus on three really common city dwellers, both because they’re interesting and because there are so many misconceptions out there about them.

We’ll start with urban foxes. We talked about foxes in episode 106, but while urban foxes are plain old red foxes and not a separate species or subspecies, they’ve adapted to city life easily since they’re omnivores and agile animals that can climb obstacles like fences.

Many cities throughout the world have urban foxes, but they’re especially common in the UK. They eat out of trash cans for some of their diet, but they also hunt rats and other small animals that live in cities too, along with earthworms, insects, and even plants. They especially like fruit and acorns. When a fox finds some food, it will often run off with it and bury it somewhere, then come back later to eat it.

Because an urban fox doesn’t have to worry about predators as much as ordinary countryside foxes do, it can grow larger on average than its country cousins. But it’s also in more danger of being hit by cars or infected with diseases common to dogs and other canids, like mange and distemper.

Urban foxes have a bad reputation for biting, attacking pets, and in general being a nuisance. But the fox is just being a fox and doing the best it can. In many parts of the world, the red fox’s natural habitat is fragmented more every year as cities grow larger and farmland and woodland is turned into houses. Besides, foxes have been reported in cities for a long time—over a century in London, England, where foxes are relatively common. They especially like areas with parks, or where people have gardens or lawns.

The biggest problem with urban foxes is people who treat them like they’re dogs. They’re wild animals, so while it’s okay to leave food out for them, don’t try to touch one or get too close to it. Foxes who get too used to people can become aggressive. Foxes usually don’t bother animals as large as cats, either, and they avoid dogs, but don’t leave small pets like guinea pigs or rabbits outside, especially at night, because that is just asking for trouble.

The urban fox doesn’t always live only in the city, though. One fox, nicknamed Fleet, was tagged by researchers in 2014 and tracked to see where he spent his time. To their surprise, Fleet lived up to his name and traveled from the city of Hove into the countryside across England. In 21 days he traveled 195 miles, or 314 km, and probably went farther but his GPS tracker stopped working so we don’t know how far.

This is what a fox sounds like:

[fox sound]

In the UK, foxes are frequent city animals, but in North America it’s much more common for raccoons to fill the same ecological niche. The raccoon is native to North and Central America although it’s been introduced in parts of Europe as a fur animal and briefly to Japan as a pet. The raccoon makes a really bad pet, by the way. It’s not domesticated and will tear your house up.

The raccoon is mostly gray or gray-brown with some lighter areas of fur, black rings on its bushy tail, and black markings over its eyes. It grows a little over two feet long, or around 70 cm, not counting its tail. Its legs are relatively short and it scurries instead of really running, although it can swim well. The raccoon is a great climber and can even climb down trees headfirst by turning its hind feet so that they point backwards, which gives it a better grip. It has sharp claws too, and dexterous hands although they don’t have opposable thumbs. The raccoon’s front paws have as many sensory receptors as human hands, which means it can learn a lot by just touching something. Like, for instance, how to unlock a trash bin.

The raccoon is well-known for getting into trash no matter what kind of bin it’s in. This is because raccoons are remarkably intelligent. By now you probably know that intelligence and social complexity are linked, but raccoons have a much different society than other intelligent animals. Groups of related females generally occupy the same territory and come together to eat and rest, while males usually live in small groups that are mostly separate from females.

Like the fox, the raccoon is an omnivore. It eats insects and worms, fruit and nuts as well as other plant material, bird and reptile eggs, frogs, fish, crustaceans, and other small animals. Raccoons in captivity are known to wash their food by dipping it in water, but this behavior hasn’t actually been documented in wild raccoons. Some researchers think the raccoons aren’t actually trying to clean the food, but are mimicking the motion of catching food in water, while others suggest the raccoons are stimulating the nerve endings in their hands with water to learn more about the food they’re touching.

Raccoons prefer open forests near water, since they like to catch fish and frogs. But they will eat pretty much anything, which means they raid trash bins. For years, the city of Toronto in Canada had trouble with raccoons getting into people’s trash bins. The bins were designed to be picked up and emptied by city trucks, but the raccoons had learned to break the locks. In 2015 the city redesigned the bins to be raccoon resistant, and in 2016 after extensive testing the new bins were distributed to residents. Before long the raccoons had figured out how to open them.

Researchers think that the daily puzzles urban raccoons solve to find food actually make them smarter. Since they’re pretty smart to start with, that’s kind of scary.

Like urban foxes, urban raccoons can get too used to humans. They’re rarely dangerous to people or pets, but they can cause a real mess if they get into your house and will bite if they feel threatened.

This is what a raccoon sounds like:

[raccoon sound]

We’ll finish with the ubiquitous city bird, the pigeon. It’s properly called the rock pigeon or rock dove and is native to parts of Eurasia and Africa. But these days it’s spread throughout much of the world, especially in cities.

Most people are familiar with the pigeon. It’s usually gray or brownish-gray with a white patch on its rump and two broad stripes of black on its wings. Both males and females have iridescent feathers on the neck that shine green and purple in sunlight, but the iridescence in males is much more pronounced. Pigeons with other markings are either feral domesticated pigeons or have feral domesticated pigeons in their ancestry. The domesticated pigeon was actually developed from the rock pigeon and it’s probable that most city pigeons are actually mostly feral domesticated pigeons.

The pigeon is a fairly large bird, up to 15 inches long, or 37 cm, with a wingspan over two feet, or 72 cm. It mostly eats seeds and other plant material, but will also eat small insects. City pigeons will eat bread and other foods too, but they would be happier with whole grains. Like many other birds, the pigeon stores food in its crop after swallowing it, which allows it to eat more food than it would otherwise be able to hold. The crop is a chamber at the bottom of the esophagus.

Not only do pigeons have a crop, which not all birds have, pigeon parents produce a food called crop milk or pigeon milk that they feed to babies. It’s not milk at all, of course, but the nutrient-rich lining of the crop that it sheds and regurgitates to feed its babies, which are called squabs. Both parents produce crop milk, which sort of looks like cottage cheese. The babies can’t digest anything except crop milk for the first week of life, so the parents may actually not eat anything during the first days after the eggs hatch to make sure there aren’t any seeds mixed in with the crop milk. After a few days the parents mix in food that’s been softened in the crop.

Pigeons and doves are almost the only birds that produce crop milk. The flamingo and the male emperor penguin do too, even though they aren’t related to pigeons. But that’s it, as far as we know. So if anyone asks you what the flamingo, the emperor penguin, and the pigeon have in common, now you know. Also, they’re all birds.

Pigeons live in flocks, although the flock may break up into smaller groups or pairs during part of the day. At night the birds usually roost together except for pairs who have eggs or babies in a nest. Pigeons mate for life and both parents take care of the eggs and squabs. Flock leaders find food and lead the rest of the birds to it, whether the food comes from plants growing in a park or from a person scattering birdseed.

Pigeons are actually clean animals when they have access to water. They like to bathe and preen to keep their feathers clean. If you’ve ever watched a typical bird drink water, maybe at a puddle or a birdbath, you might have noticed that the bird dips some water into its beak, then tilts its head back so the water runs down its throat. This is because most birds can’t actually swallow water the way most mammals can. I mean, if you had to you could drink water while you were upside down, although you might choke or get it in your sinuses. But some of the water at least would get into your stomach. Birds couldn’t. Except for the pigeon, which can actually drink like a mammal, keeping its head down as it swallows. The pigeon and its close relatives are the only birds known who can do this.

No one thinks of pigeons as especially smart birds, but guess what. They’re actually pretty bright. Pigeons can easily memorize images, even hundreds of them, and retain those memories for years. They not only recognize individual humans, they can learn to understand what human expressions mean. They also have keen vision and can differentiate between very similar items or pictures, which leads to pigeons being trained to do something unexpected. Wait for it. You’re not going to believe this. Pigeons can learn to identify malignant breast tissue in mammograms at least as well as humans can. Researchers train birds to identify the differences in mammogram slides, then use four birds in a team. The team can be 99% accurate in identifying malignancies that need to be treated. So pigeons can save human lives!

Not only that, but researchers can find sources of lead pollution by taking blood samples from sick or dead pigeons found in cities. Since city pigeons generally have small territories that only encompass a few blocks, researchers can measure the level of lead found in birds and know roughly where the lead exposure occurred. That helps the city find and clean up sources of lead pollution.

Pigeons are actually quite healthy birds, despite their reputation as diseased. They’re surprisingly resistant to a lot of bird diseases, including bird flu. Many people think of pigeons as dirty scavengers, but like other urban animals, they’re just living out their lives in an environment humans made. And if they’re scavengers, just think about where that food is coming from. People are dropping it on the ground, that’s where. Maybe people are the dirty ones, throwing food around. Pigeons are just cleaning it up for us.

This is what a pigeon sounds like:

[pigeon sound]

You can find Strange Animals Podcast online 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. We also have a Patreon if you’d like to support us that way.

Thanks for listening!