To be fair, with their mindset, they are probably right to view everyone else as competition. They clearly feel the clock ticking down to their termination, and management is probably trying to replace them as we speak.

A developer with no leadership or social skills is very replaceable. Unlike software development, those are the skills you can't develop alone in the bedroom.

People who can actually get work done and do the hard things are hard to come by, unfortunately. You can be quite an asshole if you deliver and there's no one else around competent enough to take over.

It is not uncommon that the people seeking to be mentored are lazy to put any effort into learning. It is also not uncommon for a lazy manager to put an effort to see how much this senior programmer is mentoring other. It is also not uncommon that this senior person might have learnt all his/her skills from books/discussions forums etc. Some of these senior programmers put their personal time because they are passionate about their craft. Please don't make assumptions that anybody who is not so pleased about sharing his skills is not a team player. Oftentimes, a lazy manager pits team members against each others. You sound like that horrible manager to work with. If I were your team member, I would find another manager.