Geza Vastagh (Hungarian 1866-1919) sketched lions from life. This study is in pastel.
Many of his best studies were done at the zoos in Hamburg, Leipzig, and Berlin. He also sketched and photographed in Africa in 1898.
One of the challenges is deciding which moment to capture. A snarling pose like this passes so quickly. It's a lot easier to capture an animal in a sleeping pose.
More samples of Geza Vastagh on Wikimedia Commons
Thanks to R.D.