I'm on a deserted island. How can I tell which plants are poisonous? | Hacker News Reader

I'm on a deserted island. How can I tell which plants are poisonous?

straightdope.com

104 pointsyanowitz62 comments

My all time favorite answer for this question is from a book I read in Brazil. It was a jungle-survival guide from a Brazilian military:

First of all, find a monkey. Follow the monkey, and eat everything the monkey eats. If possible, eat the monkey too.

There are of course variations of this trick. If you can't find a monkey, either a quail or a toucan will do just fine. I have some friends who were in a military survival training mission in the Amazon.. For many days all they were able to find was swamp cabbage (palmito). Then they found a toucan... The monkey trick didn't work because the trees are very very tall.

I guess one common variation is the monkey eating you...

They're in the Amazon, not Soviet Russia.

Energetically, I bet you'd spend more calories following the bird than any calories you'd gain from food you collect. On the other hand, I've been told that toucan is quite tasty.

Although, once you found the locations you could remember them or map them and then later trips would be more efficient.

Yes, but that probably isn't enough of a savings. We don't have a toucan's digestive system, and can't process large amounts of fruit quickly through our digestive tract like they can. It's a case of starving with a full stomach.

I saw a show on monkeys once where a species of monkeys discovered that by eating the wood charcoal from nearby villages they could eat more of a plant that was normally somewhat toxic to them, the charcoal acting as a filter for the toxin.

I wonder why they spend so much time eating nasty things like larvae in these courses. There's lots of fish in the Amazon. Snakes and lizards are quite tasty too. I guess it must be the easiest thing to catch.

This seems like a really bad idea to me (except for the last part).

I've seen capuchin monkeys eat the fruit of Strychnos, the genus that strychnine comes from. That could be a fairly risky thing for a human being to consume, especially if you happen to eat any of the seeds, then all bets are off.

Many monkey species, especially those that eat leaves (these would be the most common species you'd encounter, at least in the new world) walk a very fine line between eating enough of a given plant to satisfy their energy budget and eating too much and poisoning themselves. A human following their example is likely to end of with a stomach full of undigestible fiber, get sick, or worse. Energetically, you'd probably spend more calories following the monkeys around than you'd gain from any food you'd collect.

Now eating the monkeys, that might be a good idea, but the primates you'd most likely encounter would be in social groups, and once you kill one of them, it will be very hard to kill another from the same group.

The simple rule I was taught that if you can find anything that moves, cook and eat it before eating unknown plants. Your odds are generally much better with animals than plants -- you can probably find dozens of examples of inedible or poisonous plants on your back yard alone, while poisonous (as opposed to venomous) animals whose poison is still dangerous after being cooked are quite rare.

An even simpler rule is to start with anthills -- ants live almost everywhere, and while many ant species use poison as a weapon, none are poisonous after cooking.

A caution here is that some fish, especially in tropical areas, are poisonous. Any mammal or bird can be eaten, some reptiles are poisonous though - box turtles, for example, can retain poisons absorbed from their food.

"Any mammal or bird can be eaten"

http://en.wikipedia.org/wiki/Venomous_mammals

...some birds are poisonous to eat or touch, such as the pitohui, the ifrita,

I love how this guy clearly has no idea what he's talking about, relies primarily on a single source (US Army Survival Manual) that's based on decades of research and experience in these kinds of life-and-death situations, then proceeds to disagree with the source on multiple points. So much for fighting ignorance...

Cecil does know what he's talking about. The Straight Dope is a website based on people submitting questions to Cecil who, in turn, does the research and presents the findings for you along with some of his trademark witticism. It's been a wildly successful website.

The readers know the premise - that Cecil, not an expert but definitely a pretty smart guy - is doing the work for you. And given the wealth of information presented in such a digestible form, I'd say that's fighting ignorance indeed.

The Straight Dope is a website based on people submitting questions to Cecil who, in turn, does the research and presents the findings for you along with some of his trademark witticism. It's been a wildly successful website.

That's exactly my point: he did a little research, found one primary source upon which to rely, and then proceeds to disagree with that source, based solely (as far as I can tell) on his opinion. Why wouldn't I just listen to that source directly, which is based on actual expertise?

And its success is completely irrelevant to whether he knows what he's talking about.

There's a show on the Discovery Channel about people who get lost in the wilderness. One thing I've noticed is that they spend all their energy and time trying to get back to civilisation, so they very rapidly get worn down.

I think a good strategy when you are lost in the wild is to immediately start keeping an eye out for shelter, food, and water. The article gives some good tips, but they take time if you want to be reasonably sure of what you are going to eat.

There is a saying that, "you can travel across the land or live off the land but not both."

You may be able to improve your chances over the short term by concentrating on finding food but if you want to survive long term your best chance may be to get back to civilisation and get back quick.

Having said that as with most situations the optimal strategy is probably somewhere between the two extremes.

If you have no idea how to get back to civilization, your best strategy is to wait for search and rescue. Wandering aimlessly is the worst thing you can do.

Also, you want to try and make a signal to any rescuers or passers by.

Try chopping down trees in a pattern so planes can see the pattern. Have a bonfire ready that can be lit in less than a minute if you hear a plane or helicopter, or see a boat. A mirror too can be reflected out to people.

Yes, the universal symbol is to make an X in an open area with branches or something. A smoky fire is also a good idea.

You are correct, there is a doctrine that prioritizes those things, immediate survival is more important than eventual rescue.

One thing not mentioned is what you're looking to avoid when you're conducting the UET.

When testing skin contact beware of:

* Rash

* Hypersensitivity (to touch or light)

When testing by contact with the lips and chewing beware of:

* Numbness or pain

* Spicy flavour, heat or burning sensation

* Any hint of a taste of almonds (as mentioned: Cyanide. Not a good idea)

This is by no means complete, the 'SAS Survival Guide' has some good info on this topic, though other parts of that book should be taken with a grain of salt...

Don't forget to wait. Poison ivy might not show up till the next day.

Okay, someone a bit more intelligent than me should correct me on this:

Are most poisonous plants not bitter or foul tasting? Also, apart from mushrooms, don't they usually signal their poison?

Why does a plant develop poison if not to discourage animals from eating it : and if it does not signal through taste or look, how would an animal know?

I know nothing about this topic, I'm actually curious.

The problem is actually that lots of things that you can eat taste horrible. And you won't find much ripe fruit in the wild anyway, because they're eaten right away.

http://en.wikipedia.org/wiki/Bitter_melon

Yeah, Goya looks like and tastes like something you should definitely not eat but is a great food when cooked, despite it's bitter taste.

It's also used as a natural insulin substitute.

Many wild plants are bitter while being perfectly edible - pokeweed, for example, is widely eaten despite being rather bitter without preparation (it is still edible even raw, I've munched on it often when hiking as a teen). Others are perfectly tasty while being poison, some will just make you sick, but wild almonds are supposed to taste like domestic ones, but have enough cyanide to kill a child outright.

All other sources I have found suggest that mature poke leaves are poisonous until cooked. I'm not sure if Bill is a troll, wrong, or just of solid constitution, but please do your own research before taking his advice on wild edibles.

ps. I've also seen no one else claim that "wild almonds" taste like domestic almonds: "not even the most ardent nut lover among us will eat wild almonds; their lousy taste keeps us away" http://discovermagazine.com/1994/sep/biologyandmedici422

I've seen claims both ways on leaves - poisonous and not - I've only eaten them cooked and don't particularly like them. The young stalks are the only part universally agreed not to be poison, that is the part I have eaten often (older stems gain poison later - rule of thumb is not to eat them after they start turning purple, though I have eaten them up until they started getting woody without problems). Some sources claim the berries are poisonous some claim not, but I grew up being told they were poison and have never tried them. And the root is universally agreed to be seriously poison.

As I understand it, poisonous things are often orange. But, then, plenty of things that aren't poisonous are also orange. If you can mimic a poisonous thing and convince other things to not eat you, bonus! Producing poison is actually rather costly, so just being a scam artist is a cheaper way to survive. Of course, this only works if actual poisonous stuff outnumbers scam artist plants/critters. If the percentage relationship is reversed, the whole thing falls apart because other things conclude that "You're probably safe to eat, since most other things that look like you have proven to be safe".

Even with a survival manual it's easy enough to get one harmless food source mixed up with another look-alike harmful one.

It's widely speculated that this happened to Chris McCandless aka Alexander Supertramp, who hiked into the Alaskan wilderness back in the 90s to get away from it all but ended up dying from either starvation or eating something poisonous which contributed to his starvation..

I guess the point is get ready to kill some small animals and go fishing. The idea that a couple of "Castor bean seeds" could be fatal is enough for me to consider all plant life poisonous unless I'm 99% positive it's a lemon or an apple or something like that, something well known...

Wiki page on McCandless: http://en.wikipedia.org/wiki/Christopher_McCandless The speculation is that he died either from eating http://en.wikipedia.org/wiki/Hedysarum or Hedysarum with "Black Patch Desease" fungus : http://en.wikipedia.org/wiki/Rhizoctonia_leguminicola

I just watched the movie about him "Into The Wild" -- pretty interesting.

He died in the Denali National Park:

"Wild blueberries and soap berries thrive in this landscape, and provide the bears of Denali with the main part of their diets. Over 450 species of flowering plants fill the park, and can be viewed in bloom throughout summer.

Unfortunately, the spring and summer months are short."

http://en.wikipedia.org/wiki/Denali_National_Park_and_Preser...

Edit: his journal was called "Beautiful Blueberries."

Look for the plants that other animals are eating, use them as bait, eat the other animals.

Reminds me of a theory I came up with awhile ago. Why do little humans have such a strong propensity for sticking everything in their mouths? Well, way back when in the stone age, infant mortality was high. Mortality among the newborn is high for many species. As a result, low tech-level human communities don't invest in a little individual until they make it in the world for awhile. In fact, the little buggers haven't really had that many physical resources devoted to them. It takes a lot of food to make a baby. But that's peanuts to the resources invested in an adult over 2 decades of life. So who should be the food taster? Who should try things out to see if they're safe to eat? That's right, all those little ones!

It actually makes evolutionary sense for little humans to want to stick random things in their mouths and so become unwitting food tasters. It's better for the community, overall.

(Also, it puts pressure on mothers to be attentive! Another benefit to the community.)

Lots of female friends of mine absolutely hate this theory. I can understand why. But nature isn't always so nice.

(And yes, this theory is actually testable!)

The theory may very well be true, but it isn't very helpful. Firstly, you probably won't have an infant around when you get to that deserted island and secondly, if you do, it's probably your own and you'd rather die yourself than watch your child die. Of course the latter is stupid, because the child will die if you die, but humans aren't rational beings.

The theory may very well be true, but it isn't very helpful.

Theory is a tangential discussion of food tasting and not meant to be applied to this specific context. Applying it so would be not too smart. I hope you're not making conclusions by projecting your own thought processes.

My understanding is that babies stick things in their mouths because their other senses aren't well developed, so their tongue is the best "scanner" they have. They are just trying to learn about their world in spite of having poor vision, poor tactile information, etc.

Boil it, if you've got the means. The army disparages this practice, saying boiling doesn't destroy all toxins. Maybe not, but it'll destroy some toxins, and at the same time get rid of the tannins that render foods like acorns unpalatable.

Boiling doesn't get rid of tannins. Native Americans poured boiling water over ground acorns to leach out some of the tannins.

Another useful rule is that all grasses (and their seeds) are edible. Not particularly tasty or nutritious, but they won't kill you.

Hmm, nobody mentions eating the insects or digging for grubs but I've seen this done on "Man vs. Wild".

Water is more important than food. A person can go a long time without food, but will die without water in just a few days time.

I would observe what the local animals seem to be eating.

Another trick is to take a sample and rub a bit of it on of your skin. If it causes irritation, its probably bad.

Depending on climate either shelter or water is the most urgent. Most people can go weeks to months without food if they must.

If you find yourself behind enemy lines, you need ammo, especially if they are hunting you down. Otherwise keep it for emergencies.

Here's an unpleasant thought; what are the rules for drinking your own urine? Some apparently do this for fun, but what about for survival situations?

If you're able to find enough edible plants (via watching other animals), it might also be worth trying to cultivate them, but this depends on your broader circumstances.

Don't expect to stave off dehydration by drinking urine. Your body expels salts (and other substances) through urine. Thus you'll die from hypernatremia drinking urine or seawater, just as happens if you don't drink water at all.

Apparently blood and alcohol are also bad. They are processed as food, which requires large amounts of water from your body. Thus while they're both fluids, they result in a net loss of water.

Fish apparently have a column of fresh water near their spine. You can cut them open and drink from this. You can also suck fresh water from their eyes.

Edit: Oh, hey, a citation:

http://en.wikipedia.org/wiki/Urophagia#Attempting_survival

Everything else is from "Complete Survival Manual," Michael Sweeney.

I got myself a copy of the SAS survival handbook sometime last year. It covers this topic and many others: http://www.amazon.com/SAS-Survival-Handbook-Revised-Situatio...

There are a lot of books with this advice in them. It could even have been cribbed from my Boy Scout Handbook from back in the 1970s.

I would collect everything an animal might want to eat, place them in distinct piles and watch what comes around and what is eaten. You can then form a strategy based on the animals sited or just eat what they do, working up from very small portions.

Not about survival as such, but the "Plants for a Future" project catalogues 7000 "rare and unusual plants, particularly those which have edible, medicinal or other uses."

http://www.pfaf.org/

One tip I learned for berries was that if the birds don't eat them, you shouldn't either because they're almost certainly poisonous. The reverse is not true: birds can eat things you can't.

Yeah birds and other animals (even some people) can eat poison ivy. Most of us would die.

Bottom line: If there's any there, it's not safe to eat it. If they're all gone, then they would have been safe.

Next chapter, how to test for witches by the flotation method.

>If they're all gone, then they would have been safe.

WRONG. Birds can eat a lot of things that would make you very sick.

How do I know what I should eat and what I should feed to my mother-in-law?

I haven't seen this point addressed, neither in the article nor in this discussion. But does it sound to anyone else like he is implying that he wants to live but would like to poison his mother-in-law? (I know it's cliche, but the phrasing sounded odd to me. Maybe it was intended humorously.)

Apparently you have an Internet connection. Look it up on Wikipedia.

If you must eat plants and can't watch the animals then:

Spread a bit on your skin, wait a while to see if there's a rash. Touch some to your lips and tongue, again waiting a while to see if there's a reaction. Eat a tiny bit, wait a while. Eat a larger bit and then wait. Continue upping the dose.

This is from memory from the SAS survival guide. Should take days and isn't very safe but may be the best you've got.

This sounds vaguely familiar... like I just read an article with this advice, or something...

Ah, yeah I should have read the article. Oops.

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