Tag Archives: animal behavior

Why These Fish Bully Other Fish–Into Breathing Air

[Two Clarias gariepinus catfish caught near Bogor, West Java in Indonesia. Image by W.A. Djatmiko via Wikimedia Commons and CC-BY-SA-3.0] 

There’s one in every school. These aggressive individuals go around pushing and biting their neighbors, goading them into risky behaviors–like breathing.

Several species of catfish, including the African sharptooth catfish (Clarias gariepinus), have both gills that take in oxygen from water and an organ called the “labyrinth” or “dendritic organ” that allows the fish to “breathe” air.

These catfish evolved to survive in warm, humid rivers–where oxygen levels in the water can drop dangerously low at night.  So while they breathe through their gills most of the time, the fish also have the option of swimming to the surface and taking a big gulp of air.

But, oddly enough, low oxygen levels don’t fully explain catfish’s breathing choices. For one thing, they tend to surface in groups.

Behavioral ecologist Shaun Killen of the University of Glasgow  wondered whether something in the social lives of catfish might be driving them to the river surface, so he teamed with catfish researchers at the Federal University of Sāo Carlos in Brazil to find out more.  

In the experiment, the scientists assigned the catfish to groups of four per tank and counted the number of air-breaths. They repeated the test at several different dissolved oxygen levels and then compared the group counts to how often the fish air-breathed while alone.

They found that fish breathed air more frequently when other fish are around, even when there was plenty of oxygen in the water.

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Dolphins (probably) can’t recognize each other’s voices

[Above: Two bottlenose dolphins swimming around. Image via Max Pixel and Creative Commons CC0 license.]

Human speaking voices come in a dizzying array of tones. They can be raspy or reedy, lilting or monotone, chirpy or sonorous, nasal or throaty, breathy or booming, and that’s before we even start describing accents.

Most mammals, including humans, use their vocal tracts to make noise, and so slight variations in the anatomies of our voice boxes, throats, mouths, and nasal passages give our voices unique timbres.

Perhaps, not surprisingly, we can use variation in vocal qualities to tell people apart. (Some people have a lot more acuity at this than others, but most of us can recognize our favorite singers, even on songs we haven’t heard before and distinguish our dog’s bark from the neighbors’ dog’s yapping.)

Animals do the same. Mother bats can recognize their babies’ voices.  (Anyone else remember Stellaluna?) So can fur seals, rhesus monkeys, and sheep.

“If you answer the phone, and it’s someone you know very well, you know the voice, and they don’t have to tell you their name,” explains behavioral biologist Laela Sayigh of Hampshire College. “That’s how really every other mammal that has ever been studied identifies each other.”

With one notable exception–dolphins.

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The Case of the Hot-Blooded Lizard

[Photo of a black and white tegu lizard (Salvator merianae) by Wagon16 via Flickr & Creative Commons]

“Pitch Imperfect” is a series of blog posts where I highlight stories that I pitched but didn’t quite sell and discuss why it was tough to sell them. The goal is to share both interesting research stories and some of the obstacles in getting them into the news cycle.

Proposed Headlines:

–Hot-blooded lizards may hold clues to mammals’ evolution
–(shorter alternative) How mammals evolved their heat

Proposed Dek:

–Cold-blooded Tegu lizards can turn up their own body heat during their breeding season, says Brazilian-Canadian study

The Pitch:

Nine months out of the year, Argentine giant tegu lizards split their time between basking in the sun to recharge their cold-blooded bodies, digging the underground burrows where they sleep at night, and hunting insects. However, when their mating season begins, these cold-blooded creatures warm up. And stay warm, even while sequestered in their sunless burrows.

Researchers only discovered this temperature increase when they used surgical implants to monitor the lizards’ heart and breathing rates, said Brock University biologist Glenn Tattersall. When they dug deeper into previous research on warm-bloodedness, they realized their evidence lined up with an evolutionary hypothesis about how mammals and birds got their heat.

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The Case of the Looming Octopus

[Photo  courtesy of David Scheel via Current Biology]

“Pitch Imperfect” is a series of blog posts where I highlight stories that I pitched but didn’t quite sell and discuss why it was tough to sell them. The goal is to share both interesting research stories and some of the obstacles in getting them into the news cycle.

Proposed Headline:

How Octopuses Communicate through their Color-Changing Skin

Proposed Dek (aka “the sub-headline” or  “social media blurb”)

Turning dark and “looming” is a warning; white with black splotches means surrender.

The Pitch

When a philosopher and a marine biologist set up cameras to record octopus’s mating behavior, they saw something they didn’t expect.

Octopuses- which many biologists describe as solitary, cannibalistic predators- appear to use their skin to send each other signals, according to their study in Current Biology.

The marine biologist, David Scheel, describes one example from their footage: “The first octopus comes up from the back, being very dramatic– standing tall and turning very dark. Then it tussles with the other octopus for a minute, until that octopus turns pale.”

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