
Pets up for adoption rotates on a 3 day cycle unless the player adopts one, which will then be temporarily shortened to 1 day.
Normally pets aren't quite worth their hefty 600 batteries (or 600 gems) price tag as they need roughly 600 days until the increased comfort when deployed in dorms pay off the cost.
This won't, of course, stop pet lovers from adopting them when they have spare batteries. Pets are an excellent dormitory decoration item as well.
The whole paradigm of pet costs are however changing in older servers soon. Players will be sending dolls out in expeditions into random terrain (urban zones, snowy plains, forests, and wastelands) and pets may be sent along with them to aid in their scavenging search.
Enough talk, let's go over the pet station costs and unlocks. I've crammed everything in one image so that folks can pass around just this one if needed:

Click to get a bigger view!
It takes 2955 batteries to fully upgrade one category of pet housing and 4435 batteries for full upgrade of work bench, total of whopping 16,255 batteries for full upgrade of rescue station facility. 30,055 if including cost to adopt all pets.
Below is a full visual list of adoptable pets:
--- Dogs:







--- Cats:






--- Birds:





--- Misc pets:





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