Rad animal behaviors in the news [Links]

This week's links are dedicated to Paul, the psychic octopus, who died last week.

Scicurious explains how a parasite can turn rats into cat-loving zombies.

How butterfly fish use their swim bladder to croak like a frog

Read The Curious Case of Dogs, especially the part about how feral dogs in Russia have learned to ride the subway.

Someone photographed an epic battle between a spider and a millipede.

Ed Yong had a bunch of awesome links posted this week, here I have stolen five cool ones regarding animal behavior:

The Thoughtful Animal covers robot lizard push-ups

Clever crows go to tool school?

Humans are animals too! Neuroanthropology discusses how cooking contributed to human evolution.

This one is a little creepy. Russian bears are starting to eat corpses out of graveyards.

King cobras at the NYTimes.

And here are some more awesome stories I have read recently, copied and pasted straight from my bookmarks menu:

Wine-scented flower draws in fruit flies with yeasty tones | Not Exactly Rocket Science | Discover Magazine

Study: A “Pessimistic” Dog Is More Likely to Destroy Your Slippers | 80beats | Discover Magazine

Wolf Nannies Shorten Sex Lives of Male Pups | Wired Science | Wired.com

Evolutionary arms race turns ants into babysitters for Alcon blue butterflies | Not Exactly Rocket Science | Discover Magazine

Untitled Vanity Project: Scientists Create Fearless Zebra Fish

Forget Elephants; Sea Lions Never Forget! : The Thoughtful Animal

Mucus for dinner

The proud parents and their mucus eating fry.

Cichlids are great parents. All cichlid species contribute some degree of parental care, with many extreme examples, such as the mouthbrooders who forgo eating for several weeks while their eggs develop in their mouth.

The Amazonian cichlids known as discus fish (pictured below) secrete mucus from their bodies for their baby discus fish to eat. I wonder what it tastes like?


Journal of Experimental Biology has a new paper on them entitled "Biparental mucus feeding: a unique example of parental care in an Amazonian cichlid" that you can check out if you're interested. Or read the short press release here.

Is your fish a lefty or a righty?

You probably know that the right and left half of your brain do slightly different things. This is called lateralization of brain function, and it turns out fish have it too!

How do we know? Behold, the amazing detour test:

My drawing of the detour test, featuring Klaus.

So you make a fish detour around a striped clear barrier towards something on the other side, and whether it turns left or right can tell you about which side it prefers to view specific stimuli. This works because fish have monocular vision, with each eye on a different side of their head they they see totally different things with their left eye versus their right eye.

There have been a bunch of cool studies using this detour test that suggests that there is lateralization for aggression in a cichlid (which also depends on sex!) and in some other fish, sexual behavior, predator avoidance behavior, and much more.

One of my favorites is titled "Sex differences in the cerebral lateralization of a cichlid fish when detouring to view emotionally conditioned stimuli" (Reddon and Hurd 2009). Even though they didn't find that many significant results (only one), I found this study awesome in its design. I mean, they were emotionally conditioning fish! How do you get a fish emotional? Show it a fishstick?

Here's how they did it. They conditioned convict cichlids to associate an object with either food (positive emotional valence) or a chemical alarm cue (negative emotional valence). The objects they used were probably just lying around the lab, but they seemed to work well for their purpose: a blue pipette tip box and a yellow tennis ball.

The conditioned stimuli. 

Then they gave the fish a detour test with the emotionally conditioned stimulus on the other side of the barrier. Their fish didn't seem to have a preferred side overall, regardless of whether the stimulus was positive or negative. However they did find an interaction between sex and emotional valence on lateralization: males were more lateralized in response to the negative stimulus while females were more lateralized in response to the positive stimulus. However, whether the lateralization was to the left or the right depended on the individual.

So unlike other fish, where lateralization is consistent within a population and is genetically based, it looks like convict cichlids are lateralized at the individual level. The authors don't come up with an explanation for the sex differences that they found, although they do mention that convict cichlids are biparental and males and females typically have sex-specific parental roles. The males primarily defend the offspring from intruders will the females stay close to the offspring and nurture them. Perhaps males have a specialized center on one side of their brain that responds to alarm cues, in order to respond better to attacks from predators?

Picky pipefish dads and the problem with correlations

A pipefish paper made a big splash when it first came out, but how convincing is the evidence? Here is my take.

Love is a battlefield. For some animals, the battle goes on even after love has been made.

I'm talking about post-copulatory sexual selection. Sexual selection after mating is a lot like sexual selection before mating, except whereas before mating, males compete with other males and females choose which male to mate with, after mating it is the sperm that compete with other sperm and the females reproductive tract that choose which sperm to use to fertilize eggs. The later phenomenon is known as cryptic female choice because you can't see it happening unless you do a paternity analysis on the offspring [1].

The stereotypical competitive male and choosy female are products of differences in the potential reproductive rate for males and females, and are not necessarily a result of having testes or ovaries. Sex-role reversed species such as syngnathids illustrate this point quite nicely.

This pregnant male seahorse is a syngnathid.

In syngnathids, the males "get pregnant": the females lays her eggs into the male's pouch and he carries them around until they hatch. This male pregnancy lowers the male potential reproductive rate below that of females. As a result, it is the females that compete with each other for access to males, and it is the males who are more choosy about who they mate with [2].

A recent paper published in Nature by Pazcolt & Jones [3] claims that in one syngnathid, the Gulf pipefish, males practice cryptic male choice after sex by favoring eggs from "attractive" females and aborting eggs from "unattractive" females.

The Nature News coverage of this article was titled "Male pipefish abort embryos of ugly mothers" which at first might makes you wonder how such subjective concepts like "ugly" and "beautiful" were assigned to pipefish by human observers. But actually it is just a catchy headline, in the original paper, attractiveness simply equals female size, based on the fact that male pipefish are known to prefer large females.

When it first came out, the paper was covered in several blogs (including by Ed Yong and grrlscientist). However, since then the papers conclusions have been challenged by some big names in the field of sex-role reversal. Gywnne et al. [4] claimed that the results of Pazcolt & Jones could be explained entirely by larger females having higher quality eggs. Pazcolt & Jones replied [5], defending their original conclusions.

Let's dive into the experiment and see what conclusions we can make for ourselves:

Fruit bat sex! Now with more licking!

Fruit bat has tongue, can use it. Image Oregon Zoo

I read about bat fellatio on The Thoughtful Animal when the paper about it by Tan et al. first came out earlier this year. So I was really excited when I saw it for myself at the Oregon Zoo just a few weeks ago:

Now the original paper has won the Ig Nobel prize in Biology!

Interestingly, the bats that I recorded were a different species of fruit bat (straw-colored fruit bat Eidolon helvum) than the original paper described (short-nosed fruit bat Cynopterus sphinx).

Bats practice fellatio during sex (which seems to prolong intercourse) and also lick their genitals after sex (potentially to protect against STDs due to the antibiotic properties of saliva). You can see both happening in the video.


Tan, M., Jones, G., Zhu, G., Ye, J., Hong, T., Zhou, S., Zhang, S., and Zhang, L. 2010. Fellatio by Fruit Bats Prolongs Copulation Time. PLoS ONE, 4 (10): e7595. Link

Cool animal behaviors in the news! [Links]

BFFs of the week. Image www.suryiaandroscoe.com

Here are some sweet animal behavior stories that I have found in the last month or so!

Orangutan with a pet dog? Momma cat adopts a squirrel? SUPER CUTE videos of interspecies BFF's at Wired.

The sea walnut (jellyfish) sucks in prey without them knowing it. With video.

Female snails change the way they smell, male snails become confused.

Tool use in dolphins! New Scientist calles him "William the Concherer"

This is a cool example of how copying can be advantageous or not depending on the situation, but mostly I just love the title. When Male Stickleback Fish Refuse to Ask for Directions

Here is another interspecies BFF, the ant and the acacia tree

The farmed foxes experiment will never get old. Tame foxes help answer the question did dogs gain their social intelligence by accident?