I just figured I would see if anyone here is familiar with the Zoo Cougar and how to tie this fly.
I know how often sparse is the rule of thumb when trying to imitate baitfish in the salt but this being a fresh water fly I cant seem to find just how much calf tail to add under the Mallard flank as well as what the calf tail is trying to accomplish on this fly. I assume it creates excellent motion while in watrer but would love to hear what if anything else this material is accomplishing.

I am also interested if this is representative of a specific bait fish or is it an attractor... I always thought it looked like a juvenile brown trout. If any has tied this fly with any substitutions or variations I would be glad to hear of them. Kelly Gallop makes reference to substituting a spun head with a wool head in his book Modern day streamer techniques for trophy trout but that is all the substitutions I have heard of.