Repopulation Times Per Species

Balrogs are Immortal - if killed, the spirit goes back to Valar
Bats losses can be restored the following year
Crebain losses can be restored the following year
Dead are Immortal - if killed, the spirit goes back to Valar
Dragons losses can be restored every 50 years
Dwarves losses can be restored every 5 years
Eagles are Immortal - if killed, the spirit goes back to Valar
Elven losses can be restored every 20 years
Ents there will be no new generation ever seen again
Hobbits losses can be restored every 4 years
Huorns losses can be restored every 30 years
Istari are Immortal - if killed, the spirit goes back to Valar
Human losses can be restored every 5 years
Human/Orc Hybrids losses can be restored every 7 years
Orcs losses can be restored every 5 years
Skin Changers losses can be restored every 15 years
Spiders losses can be restored every 20 years
Trolls losses can be restored every 10 years