Going only on what I have seen, I'd say ... by: ScooterMama
Hello, Going on what I have only witnessed, you will know by the time they are between 4 and 6 weeks old. Some more and some less depending upon the JRT or the PRT.
Hope this helps--- Oh, and I forgot to say that some are smooth coats, broken coats and rough coats. One dog can also have 2 different kinds on the coat.