[seekingcharlie]

I've worked with several people like this (at multiple companies) & I would recommend you to try & think of the both of you as a team working together towards a common goal, even if you're in different departments.

People naturally go into "defence mode" when they feel they are under threat. Do what you can to communicate in a way that is for the team vs for yourself as a silo (& thinking of him as a silo). Something as simple as asking if you can help him in any way, can change a dynamic entirely.