Those have a snap strap on the back, I also have a few with double straps. My hunting packs all have MOLLE webbing so I just weave them on, I also use a bottle bag set up with MOLLE webbing instead of a pack sometimes. If you don't have any MOLLE or straps on your hunting pack you can always sew a piece of nylon on. Just make sure you measure your tubes or w/e to be sure they fit in the pouch.
Anything with MOLLE webbing is great for hunting as it allows a lot of versatility in adding and removing stuff.
Last year for Spring turkey hunting this was my set up for the entire season:
That rig carried extra ammo, my thermos and a cup, calls, TP, spare knife, and some snacks. Lighter and easier then a backpack.