Thanks for all the great comments on this Tree Yelper!
Thats the first I've ever seen out of hippo ivory. Might be a first. Nice to see new creations.... 
This is my first (Tree Yelper) Trumpet that I turned out of Hippo Ivory. I am sure it is not the first call ever made out of Hippo Ivory! Hippo Ivory has a hard outer layer (husk) which has to be remove prior to being able to turn it. Hippo Tusks are usually much shorter and have a more severe curve thatn Elephant Tusks. This makes it difficult to get a Blank that is large enough to make a Full Size Trumpet Call out of!