The limits of dogs' smelling ability

Ok I saw this thing on a documentary the other night where they were showing off a dog’s ability to find something via smell. They dropped a container of something (I don’t think they said what, but it’s obviously something with a strong smell) to the bottom of a lake around 20 feet deep, which then was buried under a few feet of mud/dirt. They marked the location with GPS.

Then they took the dog out on a boat and rode around the surface of the lake in a grid pattern. Seemed like a good size lake. The dog was filmed at the front of the boat sniffing the air. I think they said something about there being wind on the lake (I’m sure there was some). Eventually the dog barked and they circled in to a certain location and sure enough, the GPS indicated it was the correct spot. A diver went down and picked up the canister from the lake bottom, under the dirt. Score one for the dog.

I know dogs have amazing senses of smell, and I’ve seen dogs do impressive things with that ability, but this just doesn’t seem possible. It wasn’t clear whether or not the people driving the boat knew where the canister was placed before they left, however they were able to see the correct location on the GPS screen. So I was thinking this could have been due to the “Clever Hans” effect. The dog was watching the people for a sign of when the boat was at the right location, and he then barked to signal the correct spot.

However, they did briefly film the dog leaning forward at the front of the boat looking and sniffing out front, not looking at the humans driving the boat behind him.

Realistically, how many molecules of whatever was in that sealed canister can make it out the canister, up through a few feet of mud and 20 feet of water, and then make it into a dog’s nose at the surface of a big, windy lake? I’d say the chances even one molecule made it into the dog’s nose would be pretty slim.

Am I right for calling bs on this, or are dogs ability to smell things even that much better than I can conceive?

The police use cadaver dogs to find underwater corpses, which is similar to what’s described here. I don’t know how accurately they can pinpoint the target - the odor molecules must diffuse through the water so that the smell covers an area. How close did they say the dog got? Was in within a few feet? Several yards?

Undoubtedly this.

This would only be relevant if (A) the dog was shown to be spending the whole time not looking at the humans, and (B) it was deaf.

How many molecules could be anywhere from zero upwards, depending on how well the thing was sealed, but it is not really to the point. First of all, the stuff would disperse widely in the water before reaching the surface, and then it wold be blown away from wherever it reached the surface by the wind, thus even if the dog cold smell it, which is possible, it would not be able to localize it at all well.

Dogs have more sensitive noses than we humans do, but they do not have a magical ability to localize smells just by experiencing them. They localize the sources of smells on the ground by systematically sniffing back and forth over the area where they have smelt something of interest to see where the scent is strongest and in which directions it fades away. A dog on a boat on a lake, even without the confounding factor of wind, is not in a position to do this. He can only sniff where the boat carries him to.

The only reasonable conclusion is that this an example of the “Clever Hans” effect. The “experiment” was either very poorly (not to say ignorantly) designed, or outright fraudulent.

They actually said this dog was trained as a cadaver dog, which could find dead bodies in the water. But 20 feet deep buried under mud? Even a stinking rotting corpse would be too much for me to believe.

njtt: Yea obviously I have no idea where the dog was the entire time. This was a serious documentary though.

Documentary filmmakers are not generally well versed in experimental design.

About 30 years ago I had a German Shepherd which followed me everywhere, it wouldn’t let me out of his sight. One evening (when it was dark) I asked my wife to hold the dog for a couple of minutes while I went outside and hid behind one of the bushes in the garden. when she released it the dog ran into the garden and was obviously looking for me. A few minutes went by and I eventually jumped out from behind the bush and frightened the life out of the dog. I have always been very skeptical about how good their noses are after that.

Well, how much time elapsed between heaving the canister overboard and the dog patrolling the surface? Is it possible scent from the (contaminated) outside of the canister lingered on the water’s surface and the dog found that? Their sense of smell is fantastically acute. Here’s an interesting excerpt from a much longer NOVA article:

On a windy day, when both the air and the surface water of the lake would have been moving? :dubious:

The acuity of a dog’s sense of smell is not in question. What is in question here is a dog’s (or anything’s) ability to accurately locate the source of a smell, under the conditions described. Many factors, including the wind and the dog’s inability to range freely over the search area as it sniffed (due to its being confined to a boat) suggest this would be impossible, even if (as may or may not have been the case) the dog was able to detect the smell.

On the other hand, the dog in question was with a bunch of humans who were apparently actively tracking how close they were to the target with a GPS, and if there is one thing that dogs are better at than smelling, it is picking up and responding to subtle behavioral cues from humans.

I think they have to be trained to focus and process that information. Your dog was probably freaked out by you being gone, and also excited to be outside, and not aware that he should be looking for you, and not able to focus on it.

I play games with my dog where I hide treats around the house while she’s outside, then when she comes in I have her find them. She is sooooooooooooooooo excited, she will walk right over treats without picking them up. I know she can smell them, she just can’t focus because of the excitement.

On the flip side, if we’re in the front yard and someone has visited within 2 days, you can see her smelling the driveway where their car was, and then following their footsteps down the front walk. This always amazes me.

Anyway, my observation is that clearly all dogs have an extremely powerful sense of smell but most of the time it’s over-powered by their sense of dumb.

I’m glad Sailboat posted that stuff, I was going to add some of the same. Dogs are pretty darn amazing when it comes to their sense of smell.

Consider: they can smell the ground where someone walked or ran and pick up their scent. The dog’s nose is so sensitive that it can smell 2 adjacent footprints that a person made, fractions of a second apart. The dog can EASILY distinguish which one is fresher and therefore determine which direction the person is walking.

We had a beagle when I was a kid, and observed him come across a set of (my father’s) footprints in the snow. They were about 30 minutes old at the time. This was New Brunswick, it was deep snow, and also snowing at the time. He stuck his entire head in 2 holes and took a breath before he knew which direction to go in.

That just blew my mind. He could smell snow that someone touched for a split second and know who it was and which direction he was walking in.

Humans can not even conceive of how sensitive (some) dogs are to scent. Beagles and other hounds are known for this. When outside, our dog was sniffing the ground 100% of the time. He would choke himself on his leash.

While I think that Shepherds and other dogs also have acute senses of smell, I don’t think they are as instictively attuned with them as the hounds, which the German Shepherd antecdote above tends to suggest.

If there was peanut butter in that canister, I am quite sure my dog could find it in seconds.

Dogs are amazing, and I love them and I’m not questioning their ability to smell a helluva lot better than us (it can be parts per trillion). I’m only questioning the scenario described.

Someone asked how long the container had been there before they arrived w/ the dog. I don’t know but it was implied the container was placed in the lake before they took off in the boat. At most I’d suspect a few hours. We don’t know how long it took crisscrossing the lake for the dog to signal, but this wasn’t on the great lakes or anything. Seemed to be a relatively small lake, not a pond or anything like that though. They were on a standard small recreational ski/fishing lake boat thing (what, like 12-15 feet or so).

I’m not sure just any dog could find a canister of scent at the bottom of a lake, but it’s entirely possible that a trained cadaver dog with boat experience and a competent handler can and does do just that, not just for documentary films, but in training scenarios and in finding real bodies or just parts that are in the water.

Water, wind, currents and whatever else can do weird things to the scent pool, but the smell of decomp does come up through the water, so while the dog may hit on target odour, it may not be exactly above the location, but it will give a good starting place to look.

If the constant babble about UFO sightings has taught us anything, it’s that swamp gases do indeed come up through water.

Methane bubbles do come up from a lake bottom, even people can smell that. There were no bubbles coming up from this sealed canister.

Let’s also not forget that anecdotes of exceptional performance aren’t data. We usually never hear about the six times the dog insisted a spot was a melanoma and it turned up cancer-free, or the time the dog sniffed two footprints and ran the wrong direction.

No, I would rephrase that to say that "dogs have an extremely powerful sense of smell but most of the time it’s over-powered by their sense of fun – of their innate feeling that life should be joyful, and not consist of the mundane tracking of stupid smells. I say this in my capacity as a human who is so close to dogs that I’m sort of an honorary canine myself. :smiley:

It does sound like the documentary makers fudged their “findings.”

Useless piece of trivia: a bloodhound can track an odor the size of a pinch of paint pigment in an area of air the size of Manhattan Island; that does sound like parts per trillion.

Avalanche dogs can find someone buried under 6.8 metric shit-tons of snow.

I doubt that they can in a high wind.

Anyway, snow, after an avalanche, stays relatively still compared to water, and a dog can range freely over the surface of it, quartering back and forth as he sniffs to locate where the scent is strongest. He can’t do that in a boat.