Does Shikamaru have a summoning animal? What is the summoning of Shikamaru? 

And also, can I get some explanation of his chakra nature? I don't get it, as Kakashi skips it during Naruto's training for rasen-shuriken.
It is nowhere mentioned the summoning animal of Shikamaru Nara.



A mythological mosnter called "Inoshkacho" had the body of a boar, a deer's antlers, and butterfly wings.

So it could be assumed that
Ino = Boar
Shikamaru = Deer
Chouji = Butterfly

The Nara clan's forest is located on the outskirts of Konoha, it is a unique forest within the Land of Fire. Many deer reside here as the clan looks after them and often times use their antlers in medicines