# Scent threshold - upper issue



## NancyJ (Jun 15, 2003)

Renee - you mentioned that there are now articles (I was trying to dig that out of the testimony but it was too all over the place for me) that a dog trained in low levels of a substance without proper exposure to high levels may not indicate, may not even notice, or may fringe alert on larger quantiites.

Other than common knowledge (and I acknowledgethis effect -though what I don't have is the fringe alert, but difficulty working out the scent pool) are there published and available articles on this that you know of?


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## ladylaw203 (May 18, 2001)

I will look for Dr. Furton's later. I also assisted in research with regard to this for Texas A and M which is soon to be published

Basically, Furton discovered what myself and some others have been preaching for years because we learned it working narcotic detector dogs. Amounts produce a different scent signature to a dog due to their scent discrimination ability. Now, do some dogs generalize better than others and work it out? Yes. I have done my own experiments with odor over 20 years because it fascinates me. I also have seen this putting on seminars for years. The dog trained on tiny amounts will most probably struggle when presented with a full set of remains above ground,shallow or in shallow water. In other words he will fringe or not go to source,but stay in the amount of odor that he is used to working. 
The diversity of aids is important as well.


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## NancyJ (Jun 15, 2003)

Would love notification on the article when it comes out! I assume you will post when it goes to press.

Looking forward to the May seminar in Culowhee at the FOREST - with another opportunity to work full body decomp.

I put the question here because I know it relates to ALL kinds of detection work, not specifically HR.


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## NancyJ (Jun 15, 2003)

Oh, and because these forums are public. The remains, out for scientific studies, are not directly accessible to the dog but in a chain link fenced area which is also in another fenced area - I will be happy to get within 10 feet of a source this size.

What I gather is different than Knoxville is that area is way off in the woods so an actual "search" for it, can be done.


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## ladylaw203 (May 18, 2001)

Yes. ALL of these studies etc impact all scent detector dogs. that is why I spend so much time trying to educate civilian handlers to keep abreast of current trends in the courtroom,studies etc. We are just recently seeing cadaver dogs addressed in the courtroom and naturally,they use the narcotic dogs as a yardstick.
10 feet will be fine. also note the age of the HR.


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## NancyJ (Jun 15, 2003)

We have been fortunate to have a few big exposures .... but I completely understand than when a body is found it has to be taped off and processed and they don't need dogs and handlers in the middle of the scene. Spectrum being another big challenge, particularly with HR.


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## DFrost (Oct 29, 2006)

As a trainer, it's important to recognize that a threshold can shift. For example, as has been discussed, a dog encountering an unusually large amount of odor can have trouble responding. After having been exposed to that large amount of odor, one must also recognize a dog would have trouble detecting a smaller odor for a period of time after encountering the larger odor. That is "threshold shift". A dog determines "source" by looking for the next higher concentration. when the dog has reached a point of saturation, it can no longer detect a weaker or stronger odor. At that point, the dog is stymied and must be removed from the situation until it (the dog) returns to normal. I think the military did a great job of teaching this with the odor spectrum. 

DFrost


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## ladylaw203 (May 18, 2001)

jocoyn said:


> Oh, and because these forums are public. The remains, out for scientific studies, are not directly accessible to the dog but in a chain link fenced area which is also in another fenced area - I will be happy to get within 10 feet of a source this size.
> 
> What I gather is different than Knoxville is that area is way off in the woods so an actual "search" for it, can be done.


my understanding is that the area is about the size of a small backyard there.

I would not reward my dog at the fence due to the fact that one would be rewarding for a final trained response NOT at source. I would praise and take the dog to another source that I could reward at source. Just something to ponder


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## ladylaw203 (May 18, 2001)

DFrost said:


> As a trainer, it's important to recognize that a threshold can shift. For example, as has been discussed, a dog encountering an unusually large amount of odor can have trouble responding. After having been exposed to that large amount of odor, one must also recognize a dog would have trouble detecting a smaller odor for a period of time after encountering the larger odor.
> DFrost


 
Exactly. Problem is that many cadaver dog handlers do not have realistic amounts of HR to train on so their dog's thresholds are low. They fringe when presented with a realistic amount . I see a lot of dogs fringing in shallow water search because of that for example.  hard for them to get training aids and many do not understand the threshold issue and realize what their dog might be doing.


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## NancyJ (Jun 15, 2003)

We did learn a way around the fringing issue when you have a breeze ..... work those with the wind at your back helps a lot with pinpointing.


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## ladylaw203 (May 18, 2001)

Well, in the real world,you probably would not know to do that because you would probably start the search using the wind to the dog's advantage  Also, that would depend on what is out, how much, and how long it had been there along with the temp. A full set of remains,above ground in high temps and the dog can smell it from the car. The dog trained on tiny amounts with a low threshold is going to have problems most probably working that odor to point of origin.


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## NancyJ (Jun 15, 2003)

Well, actually we would have known in that case - we knew we were on day 3 of a water search in summer in shallow water (but too much trees on the bottom for planes and side scan) after two days of divers coming up blank. 

What happened there was my teammate pinpointed the location the night before.

I came in the next morning because they thought she was wrong, because she put the body a good 200 yards from where they were diving and where the eyewitness accounts were, but when we hit scent it was so all over the place we could not pinpoint.

An hour after I got out of the boat and my area matched hers (I worked it absolutely blind) but I could not pinpoint he came up exactly where she said. 

Since then we learned a number of folks work with the wind at their back and then make the hook to work into it. Only if you have a good steady wind though.


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## ladylaw203 (May 18, 2001)

I was referring to land. The threshold issue in water really comes into play in shallow water. The deeper the water,the better the lower threshold dog's accuracy. 

Also, eyewitness accounts are generally worth 0. Folks are upset and are usually not accurate


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## NancyJ (Jun 15, 2003)

Yes, just about all of our whole body searches are in the water; usually within a few hours - 3 days was an anomaly for us. Much easier to pinpoint a 3 hour old drowning in 75 feet than 3 days in 15 feet in the summer! 

As I understand we have NO natural lakes in the state-they are all damned streams and full of trees and buidlings and whatever else was at the bottom when the land was flooded. A divers nightmare given the lack of visibility at the bottom.

The overwhelming majority of our land calls are disarticulated and old (hunter finds bones) or speculative shallow graves...both of which are low level and tedious.


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## ladylaw203 (May 18, 2001)

huh. I wonder why no natural lakes? Interesting. at least you have streams. we have no streams. canals,puddles. no streams....


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## NancyJ (Jun 15, 2003)

Hmm well I guess there have got to be some small natural lakes closer to the coast. But all the big lakes are manmade as is every lake or pond I have ever seen.

We have more streams and rivers than you can shake a stick at though.


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## ladylaw203 (May 18, 2001)

do you have to deal with hydraulics?


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## NancyJ (Jun 15, 2003)

There are a lot of lowhead dams so, yes. Also a LOT of strainers. . If we have to go anywhere near a dam that is controlled, our DNR and power copanies are very good about adjusting the schedule or stopping outflow all together.

Most of what we do get are people drinking on the lakes though and not swimming or fishing in the rivers...not too much in the rivers. And we are not going to risk our life or a dogs life to find a dead person. And we don't go into the danger zone near a dam.


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## ladylaw203 (May 18, 2001)

yep here too 4 Bs bubba with beer in a bass boat..............


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## NancyJ (Jun 15, 2003)

Or a party pontoon. It almost always seems to involve young men and beer.


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