Some Fish Eggs Can Hatch After Being Pooped Out by Swans

iStock/olaser
iStock/olaser

A question that’s often baffled scientists is how certain species of fish can sometimes appear—and even proliferate—in isolated bodies of water not previously known to harbor them. A new study has demonstrated that the most unlikely explanation might actually be correct: It’s possible they fell from the sky.

Specifically, from the rear end of a swan.

A study in the journal Ecology by researchers at the Unisinos University in Brazil found that killifish eggs can, in rare cases, survive being swallowed by swans, enduring a journey through their digestive tracts before being excreted out. This kind of fecal public transportation system explains how killifish can pop up in ponds, flood waters, and other water bodies that would seem an unlikely place for species to suddenly appear.

After discovering that some plants could survive being ingested and then flourish in swan poop, researchers took notice of a killifish egg present in a frozen fecal sample. They set about mixing two species of killifish eggs into the food supply of coscoroba swans living in a zoo. After waiting a day, they collected the poop and dug in looking for the eggs.

Of the 650 eggs they estimated to have been ingested by the swans, about five were left intact. Of those, three continued to develop. Two died of a fungal infection, but one survived, enduring 30 hours in the gut and hatching 49 days after being excreted.

Because killifish eggs have a thick outer membrane, or chorion, they stand a chance of coming through the digestive tract of an animal intact. Not all of what a swan ingests will be absorbed; their stomachs are built to extract nutrients quickly and get rid of the whatever's left so the birds can eat again. In rare cases, that can mean an egg that can go on to prosper.

Not all fish eggs are so durable, and not all fish are quite like the killifish. Dubbed the "most extreme" fish on Earth by the BBC, killifish have adapted to popping up in strange environments where water may eventually dry up. They typically live for a year and deposit eggs that can survive in soil, delaying their development until conditions—say, not being inside a swan—are optimal. One species, the mangrove killifish, can even breathe through its skin. When water recedes, they can survive on land for over two months, waddling on their bellies or using their tails to "jump" and eat insects. A fish that can survive on dry land probably doesn't sweat having to live in poop.

The researchers plan to study carp eggs next to see if they, too, can go through a lot of crap to get to where they’re going.

[h/t The New York Times]

9 Tiny Facts About the Chevrotain

Dave Curtis, Flickr // CC BY-NC-ND 2.0
Dave Curtis, Flickr // CC BY-NC-ND 2.0

With a round body, spindly legs, and long fangs, this odd creature gives the platypus a run for its money. Also known as the mouse deer, chevrotains are shy and mysterious, and not much is known about them. But here's what we do know.

1. Chevrotains are not mice, nor are they deer.

Lesser mouse deer or chevrotain
BirdHunter591/iStock via Getty Images

At first glance, these animals look like a weird mash-up of a deer, a mouse, and a pig. Mouse deer share a suborder with deer (Ruminantia) but are not considered “true deer.” They have their own family, Tragulidae.

2. Chevrotain species vary by weight.

Mouse deer in Thailand
MonthiraYodtiwong/iStock via Getty Images

These creatures are way smaller than any deer. Depending on the species, a chevrotain can weigh anywhere from 4 to 33 pounds. The smallest species is the lesser Malay, while the largest is the water chevrotain. No species gets any larger than a small dog.

3. There are a lot of different kinds of chevrotains.

Mouse deer
aee_werawan/iStock via Getty Images

This tiny animal comes in many variations. The family has been classified into two genera: true chevrotains (Hyemoschus) and the mouse deer (Tragulus). The spotted mouse deer are still very mysterious, so scientists have placed them in their own genus called Moschiola. Despite being categorized in different genera, they all share a similar look.

4. Chevrotain fangs are fiercer than Dracula's.

Chevrotain in a woodland
BirdHunter591/iStock via Getty Images

Open up a chevrotain’s mouth and you’ll find two long fangs. They're especially elongated in males, which use the needle-like canines to stab each other. Thanks to an extra thick coat and robust muscles around the neck and rump, these adorable fighters are protected from bites during combat.

5. Some consider the chevrotain a living fossil.

Chevrotain sticking its tongue out
Josh More, Flickr // CC BY-NC-ND 2.0

Chevrotains are the most primitive of ruminants. Like deer and similar hoofed animals, they have even-toed hooves and a multi-chambered stomach. But unlike deer, chevrotains have a three-chambered stomach instead of four, and they lack horns or antlers. They haven't changed or evolved much during their time on Earth. Scientists see them as an evolutionary link between ruminants and non-ruminants.

6. Taking a dip is the water chevrotain's best defense.

The water chevrotain is known for its ability to dive underwater when it senses a predator nearby. The miniature swimmers scrunch up and walk on the bottom of rivers and streams to prevent being picked up by the current. If there are any reeds or plants around, the animals will grab them to stay tethered. Chevrotains are able to hold their breath for about four minutes.

While hiding from hungry predators, the water chevrotain can reemerge to get some air before diving back down. Still, the animal tires easily, and can only swim for short periods of time.

7. Childbirth is an expedited experience for chevrotains.

Chevrotain in a woodland
aee_werawan/iStock via Getty Images

After getting pregnant, a female chevrotain will carry the offspring for five to nine months, depending on the species. The baby can usually stand on its own within one hour of being born. Mothers will visit their young periodically for feedings and stand on three legs while nursing.

Chevrotains are known for their ability to be almost continuously pregnant—greater and lesser Malay mouse deer can mate again only a few hours after giving birth.

8. Chevrotains are shy wallflowers.

Chevrotain in a woodland
cowboy5437/iStock via Getty Images

Due to their small size, chevrotains are preyed upon by many different animals. Lacking antlers or horns for protection, the tiny animals are forced to lead secluded lives. Some species are nocturnal and very rarely seen. Chevrotains are very shy and often graze alone, only coming together to mate. They communicate with a series of smells and noises; this timid behavior makes it difficult for scientists to study them.

9. Chevrotain hooves make a lot of noise.

Chevrotain in a woodland
asxsoonxas/iStock via Getty Images

Although normally peaceful, a male will angrily beat his hooves when agitated—they can stomp around four to seven times a second. This “drum roll” technique wards off predators and warns other chevrotains in the area that there’s danger.

Additional sources: "Water Chevrotain," Amazing Animals of the World; "Chevrotains (Tragulidae)," Grzimek's Animal Life Encyclopedia; Mammals IV, Gale Virtual Reference Library

'Lost Species' of Tiny, Rabbit-Sized Deer Photographed in Vietnam for the First Time in 30 Years

Global Wildlife Conservation
Global Wildlife Conservation

The silver-backed chevrotain, also called the Vietnamese mouse-deer, is elusive. It's so elusive that scientists had feared it was extinct after none had been photographed for decades. But as The Washington Post reports, the first images taken of the mammal in nearly 30 years prove that the species is still alive in the woods of Vietnam.

No larger than small dogs, chevrotains are the tiniest ungulates, or hoofed animals, on Earth. They have vampire-like fangs and skinny legs that support their bodies. Silver-backed chevrotains are characterized by the silver sheen of their tawny coat.

The tiny population native to Vietnam has been devastated by poachers in recent decades. That, and the animal's natural shyness, make it incredibly difficult to study. Before this most recent sighting, the last time scientists had recorded one was in 1990.

Global Wildlife Conservation, the Southern Institute of Ecology, and the Leibniz Institute for Zoo and Wildlife Research teamed up in hopes of documenting the lost species. Researchers interviewed residents and government forest rangers in the Vietnamese city of Nha Trang about the silver-backed chevrotain, looking for tips on where to find one. Residents said that while populations had been hit hard by hunting, the animals were still around.

Based on this local ecological knowledge, scientists set up three camera traps in the Vietnamese woods. In just five months, they captured 275 photographs of the little mouse-deer. They then installed 29 additional cameras and snapped 1881 new images in that same length of time.

“For so long this species has seemingly only existed as part of our imagination," Global Wildlife Conservation associate conservation scientist An Nguyen said in a statement. "Discovering that it is, indeed, still out there, is the first step in ensuring we don’t lose it again, and we’re moving quickly now to figure out how best to protect it.”

Now that a silver-backed chevrotain population has been located, researchers plan to conduct the first-ever comprehensive survey of the species. Once the data is collected, it will be used to build a plan for the species' survival.

[h/t The Washington Post]

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