How Do Animals Keep from Getting Lost? | Hacker News Reader

How Do Animals Keep from Getting Lost?

newyorker.com

74 pointsjonbaer20 comments

1) Using a combination of mechanisms.

Dead reckoning using only a compass does you little good if you integrate over days (or more: for migrating animals, integration period would be months), more so if you are moving through water or air that itself moves in varying directions at varying speeds that you cannot measure reliably (example: human sailors sailing from the north coast of Spain into the English Channel sometimes managed to end up west of Land's End (https://en.m.wikipedia.org/wiki/Scilly_naval_disaster_of_170...)

Homing pigeons, for example, are better at finding their home if they have had time to fly around in its wider neighborhood. That way, if their imperfect navigation methods bring them somewhere 30 miles from home, they recognize the location and get home from there.

For homing pigeons, smell also has been mentioned as something they use to get home.

It also wouldn't surprise me if homing pigeons living near the center of Paris became better at getting home after the Eiffel Tower was built.

2) using the law of large numbers. Not all animals need to return for migration to be a success for the species.

1) The article claims, the conference thinks you're wrong.

"This marked a change from previous years, Richard Nissen, a member of the Institute, told me, when a range of other navigation aids were part of the discussion: landmarks, olfactory cues, memory, genetics, polarized light, celestial objects. “Everyone now seems completely sold on the idea that animal navigation is based on magnetism,” Nissen said. Human-centric as it sounds, most of the conference’s attendees believe that animals possess a kind of compass."

When humans get lost it's only memory and random walking, it's a good theory animals only have one more enhancement, small memory cues, magnetic and randomness.

My father had a pretty good innate sense of direction. He just said it was a feeling, and he could cross-check with the sun, etc., if available- but could do pretty well without it. He said he was pretty old when he realized that not everybody could do that. Perhaps it's not totally gone from humans.

"one more enhancement" is not the same as "only use their compass", and "small memory cues" is what is called a mental map (those do not have to be complete, and can be very sketchy) in the literature.

It's hard to get lost if you don't have anywhere you need to be.

Thousands of HN readers prove this statement wrong every day.

Side note: Two weeks ago, a friend told me that dogs turn their bodies to poop in a north-south axis. I couldn't believe it and couldn't believe that I hadn't noticed before. So this was a timely read.

The article begged the question for me: Does the biocompass come into play for humans? Does anyone know of any examples of cultural/tribal traditions/oral histories that suggest that humans can improve their wellbeing by being aware of Earth's magnetic fields for various tasks?

I read that article and starting watching my dog, who tends to do his business while walking. It's not true for my dog at least. There really is no rhyme or reason though he will tend to go parallel to a path if there is one.

So I'm not convinced on the north/south axis thing, and not just because of my anecdata, but because it sounds like one of those internet facts like duck quacks don't echo.

It's a bit off topic, but having raised ducks, I think I know the reason for that "fact."

Duck quacks have an odd sound sometimes, almost like an echo in itself. I've only noticed it when they're on the ground; in the air they seem to quack differently. Anyway, with a quack that already sounds a bit like an echo, I could see a case where the quack was actually echoing against a hard surface, but not sounding any different from the "normal" quack.

My ducks flew away years ago, so I can't do any scientific testing now...

My uncle works with desert tortoises in the Mojave. On some projects they find all the animals in a certain area, attach radio transmitters, and translocate them to another valley.

How they respond varies. Some make take up residence in the new area while others make a bee line towards home.

Not sure if science or performance art.

Has anyone tried slapping a magnet on these migratory animals and testing whether or not they get hopelessly lost?

From the article:

In the early nineteen-sixties, a German graduate student named Wolfgang Wiltschko began conducting experiments with European robins, which he thought might find their way by picking up radio waves that emanated from the stars. Instead, Wiltschko discovered that if he put the robins in cages equipped with a Helmholtz coil—a device for creating a uniform magnetic field—the birds would change their orientation when he switched the direction of north.

It's been done more recently than that too. Here's one experiment with sea turtles: http://jeb.biologists.org/content/199/1/73

Here's a great read about homing pigeons where they do that sort of test [1]. The answer appears to be that they use multiple cues so it's hard to isolate them.

This seems likely to me, since there just doesn't seem to be enough information in knowing the magnetic field at your location to determine your home location, which the this article claims they do (they don't need information from the trip out to find home, and they fly roughly straight home so they must know the home direction immediately upon start). Interestingly, they can't return home if you knock out their sense of smell. But maybe that accidentally knocks out 'compass sense' as well.

This article has some great snippits: "Older pigeons transported to the release site inside sealed metal containers, supplied with bottled air, anesthetized and placed on rotating turntables, all of which should make it hard for them to keep track of their outward journey, still home."

They can home from 1800km away! And after being away for 7 years! They can home even if they never left the home loft (presumably until being sedated and carried away to test their homing ability), though the success rate is low.

Edit: more directly to your question is this quote: "Keeton reasoned that if his pigeons were well oriented under overcast they must be using a cue other than the sun compass.He found that pigeons with magnets fastened on their backs were often disoriented when released under overcast."

and "Under a sunny sky, the coils, whatever their polarity, only deﬂect the pigeon’s vanishing bearings by a few degrees. If a pigeon wearing an NUP coil starts its homeward journey under overcast, it will head away from the release point in the direction away from home. Should the sun appear, even if only momentarily, through a hole in the clouds, it will reverse course and head directly for home."

[1] https://www.researchgate.net/publication/13905901_Pigeon_Hom...

You can teach yourself to see polarised light using the naked eye by exploiting polarisation effects in the lens of your eyeball.

https://www.polarization.com/haidinger/haidinger.html

I've never seen this myself, however. Also, I don't know how useful this would be for direction finding. I can see that the effect would be useful for figuring out the direction of the sun on a cloudy day, but accounts indicate that the Haidinger's Brush effect is pretty small and easy to miss.

But if humans can see it, more or less by accident, it's not much of a stretch to imagine than animals are much more sensitive to it.

They have:

http://blogs.discovermagazine.com/notrocketscience/2012/04/2...

A few miles from where I live is a eucalyptus grove where monarchs overwinter. There are other similar eucalyptus groves nearby without butterflies. Not only do they make it to Mexico, they stop over at this exact grove year-after-year.

As an absolute novice in genetics I wonder if you couldn't use CRISPR to supress the expression of this MagR protein and see if the animals can still find their way. If not, why not?

I wonder what happens when the Earth's magnetic poles reverse, like they have in the past. On average, it happens every 200k - 300k years, so animals have experienced this many times.

I'm guessing there's a lot of initial confusion, but that they become accustomed to the new orientation, once they associate a direction with whatever sense they have of the magnetic field.

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