The part most relevant to this blog:
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A Ranger’s Best Friend
We’ve had a lot of internal discussions about improving ranger pets for a while. The difficult question wasn’t what was wrong with ranger pets, it was how to fix them. Well, that answer is finally here.
Slotting and Swapping Pets
Rangers now have a total of two terrestrial and two aquatic pet slots. Amphibious pets are able to occupy either terrestrial or aquatic slots. Rangers can now use F4 to swap between the two valid pet slots during combat. This mechanic works even when your current active pet is defeated, allowing a ranger to quickly adapt when a pet is downed or when a situation arises that calls for a new pet. Swapping pets has a cooldown associated with it, and this cooldown is longer if the active pet was downed when the swap took place. A downed pet that was swapped out will be at full health when he is swapped back in. We’ve done a lot of work to make each ranger pet more unique and fill a particular role, which fits perfectly with the fluid, adaptable nature of combat in Guild Wars 2.
Pet Controls
Pets now have two stances: active and passive. In the active stance, if your pet is doing nothing and you engage in combat, your pet will attack your opponent. In the passive stance, your pet will follow you and not to attack unless explicitly ordered to do so. You’ll be able to toggle between these stances by pressing F3.
Ranger pets can be ordered to attack a specific enemy by selecting a target and hitting F1. This action will temporarily overwrite your pet’s current behavior, giving you more direct control over your pet’s actions in complicated combat situations.

Species and Families
Pets no longer evolve. Instead, they are set to the level of the ranger, and their stats and abilities are determined by their species. Each pet belongs to a species and each species belongs to a family. For example, a snow leopard is a species belonging to the feline family of pets. Charming a species unlocks that species for you, allowing you to equip that species into any pet slot whenever you are out of combat. In Guild Wars 2, a single ranger can collect and use every type of pet in the game without having to worry about stables or leveling the pets from scratch.
Each family has three basic skills that define that family. For example, bears are hard to kill, drakes do AoE damage, devourers use ranged attacks, etc. These skills are automatically used by the pet. Each species within a family has a unique skill. For example, polar bears have an icy roar that freezes enemies, while brown bears have a roar that removes conditions. This family skill has a cooldown and is activated by the ranger by hitting F2.”