Currently there is quite a few posts on backfilling and this is my take on potential backfilling
Hirschfelden- Sika deer, Chamois?, European Mouflon, Mallard, European badger, Gray partridge, Raccoon dog
Layton lakes- Bighorn sheep, Mountain goat, Mountain lion, Wood duck, Dusky grouse
Med-ved- Mountain hare, Taiga bean goose, Snow sheep?
Vurhonga savannah- Egyptian goose, Burchell's zebra, Helmeted guineafowl, Greater kudu, Spotted hyena
Parque fernando- Chiloe wigeon, Pere David's deer, Gray fox, Iberian mouflon, fallow deer
Yukon valley- Dall sheep, Willow and/or Rock ptarmigan, Spruce grouse, Coyote, Mountain goat, Sitka blacktail deer, Snow goose
Cuatro- Red fox, Fallow deer, Chamois?, Red-legged partridge, Tufted duck
SRP: American badger, bobcat, White-tailed ptarmigan, Brant goose, White-tail jackrabbit
Te- Tahr, Rocky mountain elk, Sambar, Rusa, Red necked wallaby, Californian quail
Rancho- Plains bison, Mountain lion, Black bear, Mexican duck (Desert mule deer and Desert bighorn sheep)
Mississippi acres- Mallard, Red fox?, American black duck
Revontuli coast: N/A
EC- Feral cat, Feral dogs/Dingo, Feral donkey, Feral camel, Water buffalo
Sundarpatan- Himalayan snowcock, Himalayan monal, Indian Peafowl, Sloth bear, Himalayan black bear, Axis deer?, Sambar