we used them in south africa to track clients kills.
one actually got taken by a python, but they managed to wrestle him from the snakes jaws- and let the ol' snake go unharmed. and the dog " Diesel" was a lot wiser for it.
they were great- high energy tracking dogs- but since i have had a Teckel, i think i would take a teckel over any other dog for tracking for my situation.
they are easy enough to train- Like Pat says, they can all be trained to track- they all do it naturally, they just need to do it on command- but most JRT's come with the auditory/ brain nerve connector either dysfunctional or completely absent
but they will track, quite well in fact!