They are very territorial but there can be multiple bigger pike in an area. In the summer when there is heavy cover, they aren't exactly snuggling up to each other, they pick a spot and set up for ambush. When something goes by, they whack it. Because they hunker down in such thick cover they are a pita to target.
In the spring you can find them packed in pretty tight groups and it's not uncommon to see many larger pike near one another.
In the fall they seem to roam around actively feeding in areas with bait and get really aggressive - they are so much fun at this time and a lot easier to target.
It has been my experience that if you can see them, the odds are pretty low of you catching them...but go back to that area later and if you can't see them that is a good sign you can catch them - they are still there and waiting to ambush.
Now the truly female behemoth pike are a different animal all together and they don't always pattern like the others so usually hang out where they can feed easily and expend as little energy as possible. They are known to eat dead bait because it is an easy meal. They are vastly solitary creatures so targeting them means lots of time on the water and very few to no bites...a lot of times you will see them in open water right at the thermocline.