One of the marvelous things about living now is the technology. We have access to resources we didn't before. You can take drawing classes via internet - there are free ones on Youtube- and the web is full of pictures of humans, animals, plants, architecture, and what not. Compare that to a library book with small, musty pictures...
I saw and interview of Jordorowsky. He couldn't find the money to film Dune, but he made it into a comic. It was drawn by Moebius. He, was an artist who could draw anything in a second. Good drawers draw from model, until the forms are ingrained in them. I can't draw most of the animals from memory because I don't have an exact enough a memory of them. But when I draw from a model, it is no problem.
Live drawing is more difficult, and different, and I do recommend it. But animals are easier to draw from a still picture, and if you can't draw something live, use the internet, look, look, look, and draw.
A squirrel, pencil, about 14cm in height - from a hilarious video on Youtube: