Grails - Multiple Drop Down Boxes Values

Hey I am learning Grails. I've been playing with it for a while but nothing too serious. And let's say I have two drop down boxes, one with the type of animal and the second with the breed. How do I give the second box the values?? For example, If I select dog, it should only show me dog breeds, not the cat ones.

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Thanks in advance.

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One way is to use AJAX to do this (if you don't mind making a server call each time you change the selection on the first dropdown). Take a look here:

http://www.grails.org/AJAX-Driven+SELECTs+in+GSP