Flickr.com is a photography website I regularly use for nature and animal photography.

It helps to first try to find specific names of ecosystems, parks, in a general wiki search before going into a deep dive! For instance I may search for ONSEN-> then browse specific ONSEN located in mountain regions-> discover 'Towa-Hachimantai National Park' & be able to seek photos of that specific park.

I may search for 'peat bog'-> discover 'Shropshire Wildlife Trust'-> find a whole list of specific reserves under that trust's umbrella I can browse for reference of specific environments!

inaturalist is also valuable for unique new photos of unusual, rare animals.

I like searching animal names in Japanese on twitter, as a lot of photographers and zoos tag their photography on twitter via hashtags! Then you can browse their RTs, or who they follow.

for information on size/weight I utilize a combination of dimensions.com & animalia.bio

and of course youtube is an IMMENSE resource; many zoos, sanctuary, aviary, post endless resources or longform content on whatever animal your looking for. Stable Horse Training is for instance my favorite for horse body language and herd dynamics! Kingsdown Ferrets has loads of beautiful wonderful Ferret footage! Creek Valley Critters has delightful mouse footage!