Elephant sculptures in the city

I have noticed elephant sculptures in the city a few times lately and have been wondering why they are around. Then I met a friend at Federation Square last week and we saw two of them.
I especially liked this one with the wrinkled, knitted skin.

They are around the city in various spots to celebrate the 150th anniversary of the Melbourne Zoo.  You can find a link to a map here.  They will be on display around the city till September 21st.  I will have to take my camera with me when I go to the city and try to see some others.