Torresian crows have learned how to make a meal of cane toads | Hacker News Reader

Torresian crows have learned how to make a meal of cane toads

australiangeographic.com.au

115 pointsfern1249 comments

Crows are a constant source of amazement. The last couple of years, we have watched our local population take up the practice of crushing walnuts under moving carwheels. I know this trick is performed with high levels of sophistication in many parts of the world - nevertheless, it has been fascinating to see this new behavior take hold and spread among the many, many crows in the region. It's hard not to fancy a pair of disapproving corvid eyes boring into you whenever you've let your instinct take over and have swerved.

Actually, I'm getting more and more into the habit of not swerving. For everyone else, absolutely, but not really for the crows. They have my vector to any number of decimal points, and will nonchalantly hop out of harms way at the last possible moment - often into the opposite lane, if no oncoming traffic is seen there. We never see them as roadkill. Pheasants, gulls, sparrows, what have you, but never the crows.

I imagine Aussies could make a bigger dent in their cane toad problem by giving some smart folks a budget to teach classes and produce educational videos specifically for crows.

Spread the knowledge on how to safely eat cane toads to every corvid on the continent, much faster than that information could spread naturally.

Some crows have a concept of death and mortality, and the ability to make causal associations. It is certainly possible to teach them a skill by literal demonstration, and may be possible to teach via symbolic representation.

Catch a bunch of cane toads. Prepare the edible parts from some as motivational snacks to attract interested crows. Use a crow puppet to naively eat a model cane toad, and make it "die". Then use another crow puppet to manipulate and eat a model toad avoiding the poison glands. Give a live cane toad to a crow known to have the skill, so it can demonstrate. Then release some live toads for novices to try it out.

Then attempt an experiment to show a video of that demonstration to an ignorant flock, and see if they can acquire the skill that way.

That is happening in a sense -- for quolls. See the linked story in the article.

Scientists make sausages out of toad meat and add a nauseating agent. Quolls are learning to avoid toads. Might take a few generations.

It'd be a very interesting experiment to figure out how to effectively teach wild crows new skills.

Clever crows, but a real shame other predators are being killed off because of their unfamiliarity with an invasive species. I wonder if any naturally immune individuals will rise up from the loss of their main populations.

More likely some of those predators will learn to avoid them rather than become immune to their poison. Hopefully they will learn that before they are reduced to unsustainable levels.

Do most animals have that ability though? How do you learn from something when you're dead from it nearly instantly? I don't think snakes have knowledge outside of instinct. That's the point of this crow article.

You get snake-phobia and survive.

You get a addictive behaviour and slowly immunize yourself with microdoses of poison.

You hunt your prey in a poison diluting or neutralizing environment.

You set the plains on fire with dryd grass to interrupt the feeding cycle of the plague and eat the denatured poisonous creatures.

There are a lot of different strategies. One must admire the crows for eating the fugu though.

We're talking snakes here, and another animals that aren't really sentient. They aren't microdosing themselves with poison or setting fires.

https://pickle.nine.com.au/2018/01/10/08/46/australian-birds...

There are sources for addiction regarding animals on the web. Its quite interesting what horses and goats do for some weeds.

https://en.wikipedia.org/wiki/Colorado_River_toad#Drug_use_o...

The war on Horse-Drugs should have priority. Give the DEAs some hoes to whack out the danger.

Pretty cool link on the Colorado River toad. Apparently raccoons use the same strategy as these crows, turning the toad over on its back and eating the belly.

Perhaps you mean sapient. Snakes and other animals are definitely sentient.

Those actions can still be done unintentionally. For example, a particular kind of snake can prefer to eat some particular kind of fruit when they are young, which also happens to be the favourite plant for a cane toad to rub on to get rid of itchy bottoms.

I know sentience is an abused word, but for almost any of its practical definitions that's a false statement.

Sentience is the ability for subjective experience, which applies to any of the animals being discussed here. If you're thinking of something like self-awareness (a totally separate quality), you're probably correct. But that has nothing to do with the ability to learn.

I think the author of the comment you're replying to conflated sentience with sapience.

Since we're discussing snakes, wouldn't that be 'serpience'?

Natural variation and selection. (Biological) Evolution changes populations, not individuals.

Suppose there's one snake that is genetically disposed not to eat toad-shaped things, frogs, cane toads, anything like that, the same way I don't like nuts. They're not toxic to me, I could eat them, but I don't. Previously toads weren't toxic to snakes, but that snake didn't eat them.

Normally that snake has a small disadvantage, other snakes eat toads and it goes without. Too bad. But now it won't get poisoned. This means it's slightly more likely to survive to adulthood, breed and produce more snakes.

Further genetic changes to avoid toads will also be selected for in the same fashion.

This process is very slow in multi-cellular creatures, but it does exist. It may not be fast enough to adapt to the cane toad of course.

Appreciate your comment. It always impresses me how many people misunderstand the (what I feel to be) basic concepts of evolution. I'm not educated on the matter either, mind you - I'm sure I'm very ignorant on many aspects of it.

Regardless, it always makes me wonder how much the anti-evolution "movement" would be affected if people simply had a better grasp of it.

Quite a bit of the provided possible outcome rests on likelihood of certain genetic factors and, relative size of snake population, and how quickly cane toads spread.

The actual values of these variables (and a few more I'm sure) can change whether one population dies out or not and how quickly. Just because evolution provides a solution to the general problem, doesn't mean there's a solution that saves the population when the specific problem is looked at in detail. Invasive species cause local extinctions all the time.

We're not talking about natural selection, we're talking about actual learning(crow article), and discussing if other animals have that ability. I understand how evolution works.

I believe the commenter you were responding to was referring to the "learning" traits of populations by means of selection.

I don't think so, the commenter was saying that a snake that avoided toads by way of its genetics, would be more fit, and thus reproduce more snakes that avoid toads. Genetics can affect instincts so this is not far fetched. But yes, learning genes would be much more apt and effective over a larger obstacle course. It is tough to see how a snake is going to develop a neocortex though.

http://www.pnas.org/content/101/49/17150

They’re not learning, but they are evolving to cope.

It called instinct. It’s why cats know to go in litter boxes, why many animals are afraid of snakes, and why dogs bark.

Which is what they DO NOT have, because predator populations are being wiped out. Does anyone read the discussion prior to commenting?

How do you think animals develop instinct?

natural selection: the ones that don't eat will survive, and the ones that do will die

Not in one individual, but animals that die from eating them will self select themselves out of the gene pool (if done before they get a chance to mate), over time only leaving those that avoid it. The more generations that survive this the more it becomes an instinct.

Guys, again, I understand natural selection. We're talking about learning(and indirectly teaching).

Article contains a link to a story about how conservationists are trying to 'teach' quolls (Australian native marsupial) by negative association with toad-meat sausages laced with a nausea inducing compoound : http://www.australiangeographic.com.au/topics/wildlife/2017/...

I recommend this excellent and hilarious documentary if you'd like to find out more about cane toads:

> Cane Toads: An Unnatural History

https://imdb.com/title/tt0130529/

(I have found versions of this on YouTube, but unsure how legal they may be)

In some respects, if human development followed the cane toad, we would become virtually indestructible. As children, we would use them as cricket balls and some would still hop away afterwards. We found that inserting lit penny bungers into them was an effective way of terminating. Freezing them was also effective, but your mother tended to object to them being in the freezer.

What was disturbing about them was the size that some would grow to. I personally have seen one that was about 20 cm (8 inches) high. I have heard of them being much larger.

I feel bad for those frogs. Imagine being eaten/beaten for 40 minutes by a crow. Probably left to slowly die after it is done eating you.

And the crows friends are watching the whole time too.

To be fair, the frogs are the ones making it more difficult than it has to be.

Cane toads are an ecosystem destroying highly invasive introduced species.

The crows are doing our work for us. The method might be messy, but cane toads should be exterminated in non-native habitats as expediently as possible.

Instead of feeling bad for them, why don't you feel bad about the species they have almost wiped out?

For those that aren't aware, here's a good summary of the problems with cane toads in Australia. https://en.wikipedia.org/wiki/Cane_toads_in_Australia

You can feel bad for the toads and the species they are wiping out. It's not like they are consciously deciding to be an invasive species.

I feel bad for the native species. Cane toads are prolific throughout the world, and they've driven many species to near extinction.

At some point you have to decide what your priorities are and start culling. E.g. Australia wants to kill 2 million feral cats over a decade, as there are 30 million of them, and each one kills 3-20 native animals a day. [0] At some point you have to make decisions and decide which is more important. If you could teach crows how to eat cats, Australia would like to have a word.

[0] https://news.vice.com/article/feline-massacre-australia-unve...

It's OK to kill an animal and feel bad for it at the same time.

crying onto my bacon.

I love cats, I have two (both indoor cats, I love Cats but they are furry little killing machines even when well fed) and I still think the plan is reasonable if sad, it's sad for the cats and sad for the indigenous animals that are suffering predation from an invasive very effective predator.

Yeah well, nature. On the flip side, we are (probably) one of the few species to have evolved a sense of existential dread.

These frogs are really strange - usually poisonous animals have some way of clearly showing not to mess with them: bright colors, smell, sounds they make...

They’re stealthy hunters, so bright aposomatic coloration would be counterproductive. I also believe that there is some aposomstic scent markers and behavior in the case of cane toads, it’s just that native Australian fauna has taken time to adapt.

http://www.pnas.org/content/101/49/17150

They’re not “learning” to avoid, but selection pressures are having the same end result.

Reminds me if this joke from QI, the UK TV show:

"Australians have a big problem with cane toads. They have a foul odour and spread like wildfire. And they have a big problem with cane toads."

Seems to be a handful of videos on YouTube of this phenomenon. A bit in the gruesome direction as a warning to others https://www.youtube.com/watch?v=7lWX5x0Kmgs There's a few videos posting about the phenomena from 6-7 years ago so apparently they've learned this trick for some time.

"During much of this process other crows stood and watched."

  EXT. A FIELD OUTSIDE BRISBANE - DAY

  CROW 1: I dare you to eat that poisonous frog.

  CROW 2: Hold my beer.

I'm from Brisbane, I'm going to start paying more attention to Colin the Crow who frequents my back yard with a little more care.

At this present moment he's helping my house mates chicken finish her breakfast.

Day 1 Colin seems to be a chicken in disguise

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