Both our labs are 2 and went through the snake avoidance class last year with SnakeBreaker and were highly scared of the snakes and learned their lesson! Soooo glad we signed up and took the course! Highly recommend taking yoUr dogs to it!!! However we have a few lizards under the carport at the ranch and both dogs go crazy watching for them and chasing them. Do dogs know the difference between a lizard and a snake?

Sounds like it....

Might find a rat snake to test them....

Sounds like they obviously do know the difference.

I’ve always been told that snakes have an odor, and that is one of the reasons a dog that has gone through snake avoidance keeps the learned behavior to stay away from them.

I have had dogs that were snake broke avoid rattlers but go after non venomous snakes.
BTW dogs should really be snake broke two or three times.
Reinforcing the lesson makes a big difference.
Here is the score on my snake broke dogs.
Dogs that turned away from a visible or heard snake 5
Dogs called back from a visible snake 2
Dogs bitten by a snake 1
I believe most bird dogs in the field on a regular basis in south texas encounter one or two snakes a year that we do not see.

Rattlers stink. Even I can smell them. Dogs can smell 300 times better than me.

yes, pit vipers smell different than other snakes.

Yes they can tell the difference. I tell every client to get it done at least once a year. Do it until you can't even throw that dog on a snake. There is no set rule so far as effectiveness of the training. My yellow male needed it twice a year. I did my black bitch once 13 years ago and to this day she will climb over you to get away from a snake. Both ends of the spectrum, there is no way to know where a dog will wind up on that spectrum.