A lot of the animals in the game will be active both day and night, so trying to choose 'nocturnal' ones can be quite tricky. For example, these are all the animals already present in Planet Zoo that are kept in the Night Safari in Singapore (which is only open after dark):
- Aardvark
- African buffalo
- African lion
- Asian small-clawed otter
- Asiatic black bear (basically identical to the Formosan)
- Babirusa
- Bengal tiger (Night Safari actually has Malayan tigers, but they are very similar to the Bengal)
- Binturong
- Bongo
- Clouded leopard
- Dhole
- Gharial
- Giant anteater
- Giant forest scorpion
- Greater flamingo
- Hippopotamus
- Indian elephant
- Indian rhinoceros
- Malayan tapir
- Mexican redknee tarantula
- Spotted hyena
Information all comes from the map:
www.mandai.com
Elsewhere, these are other animals I have heard of being kept in indoor nocturnal houses:
- American alligator
- American beaver
- Boa constrictor
- Chinese pangolin
- Cuvier's dwarf caiman
- European badger
- Fennec fox
- Gila monster
- Platypus
- Spectacled caiman
There are many others I expect would work, especially among exhibit animals (most of the frogs and invertebrates and all the snakes bar the Eastern brown).
I would love to see a pack of nocturnal animals - there are so many options to choose from:
- Marsupials (most of them are nocturnal, including wallabies, possums, tree kangaroos, quolls and bilbies)
- Rodents (crested porcupines are the most obvious but most rodents are nocturnal - some I would love include the springhare, giant cloud rat and giant flying squirrel)
- Nocturnal primates (several equal in size or larger than ring-tailed lemurs include aye-ayes, slow lorises, mongoose lemurs, owl monkeys and greater galagos)
- Small carnivores (civets are my favourite - especially the Owston's - but other options could include small cats, kinkajous and mustelids)
- Small ungulates (chevrotains have been kept in nocturnal houses and I have read of bay duikers being kept in them as well)
- Oddball mammals (armadillos and sloths are two fairly obvious candidates here; others that could be considered are hedgehogs, tree hyraxes and the common tenrec)
- Ground-based night birds (kiwi is the most obvious, but night herons, thick-knees and the white-winged duck are also nocturnal)
- Larger nocturnal species (if a 'Night' pack was made instead of a 'Nocturnal House' pack, then it could include a couple of larger mostly nocturnal species such as the striped hyena, maned wolf or even go all out and put in either the black or Sumatran rhinoceros.
An exhibit animal for a nocturnal pack could either be a 'standard' nocturnal animal or perhaps a cave-dwelling species. Some of my favoured options include the headlight beetle (a nocturnal beetle that can be bred in captivity that produces glowing spots of light), blind cave fish or a species of gecko.