Hi!

You could use cardboard of chicken wire for the framework. Unless you have an aircraft hanger to build it in, it might be a idea to make it in several pieces that can be easily transported then placed together. Just bear in mind the width of each piece and make sure that you can get it through your door - it seems obvious but it is easy to forget things like this when you get carried away with the mache!

To get the basic shape that you want, study pictures of elephants in different poses and decide first if you want an African or an Indian elephant as there is a considerable difference in the size of their ears.

Impossible to estimate, but where weight is an issue, you could build it out of chunks of polystyrene. It is a bit fiddly to get the pieces to stick together (you  can use masking tape) but once it is covered by a  couple of layers of papier mache, it will all hold together well.

Good luck with it - and hope we all get to see the finished result!?