Earthdog = fun :-) I know more than you will ever want to know about it! I will try and keep it short lols.
The two most commen places to play is the AWTA (American Working Terrier Association) http://www.dirt-dog.com/awta/
and AKC - http://www.akc.org/events/earthdog/
Earthdog is for terriers and dachunds that can fit down a 9" by 9" tunnel. The first level - Junior Earthdog - the tunnel is 30' long with two 90 degree turns with a caged rat at the end.
The rat is very safe and most of the rats are very used to dogs and know that the dog can not get to them.
This is a typical layout for the tunnels
The owner is allowd to walk up to the tunnels so far and must not go beyond a marked point - put the dog down - then you have to stand there and be quiet - the dog must go into the tunnel by it's self and does everything on it's own (on the one hand that is the cool thing about it for the owner - you just stand there and the dog does all the work). The dog has a set amount of time it must go though the tunnels. Then it must bark, dig, etc. at the rat for so many seconds. It takes two legs to get a Junior Earthdog title. Then once you have your JE you got for your Senior Earthdog then you Master Earthdog - each level gets harder.
Off the AKC website on the breeds that are elegible to play in AKC. (AWTA - if your dog can fit down the tunnel you can play)
All dogs six months of age or older from the following breeds are eligible to participate in Earthdog Events.
AKC Recognized Breeds
•Dandie Dinmont Terrier
•Glen of Imaal Terrier
•Miniature Bull Terrier
•Parson Russell Terrier
•Smooth Fox Terrier
•West Highland White Terrier
•Wire Fox Terrier
Foundation Stock Service Breeds
•Dogs of these breeds recorded with the Purebred Alternative Listing Program/Indefinite Listing Privilege (PAL/ILP) or dogs with Conditional registration are eligible to participate.
•Spayed and neutered dogs are eligible to participate.
•Monorchid or cryptorchid males are eligible to participate.
•Bitches in season are not eligible to participate.
•Blind and/or deaf dogs may not participate.
•Dogs with Limited Registration are eligible to participate.