Using natural light
Just because you don’t have a spotlight or a flash, doesn’t mean you can’t take photos of wildlife during twilight. If you choose good settings, you’ll still end up with respectable photos.
Twilight photos that aren’t lit with an external light source usually come out underexposed (very dark). To capture detail in the shadows, you have to let more light in when you take your shots. In Aperture Priority (A/Av), choose a low f-value (f/4 or f/5.6), increase your ISO value slightly (if you were on 400, go to 800), and then overexpose the photo with the help of the exposure compensation function. Do it in small increments – one third at a time – until you capture enough detail.
Remember, if the animal is in a tree you may end up with a washed out background, but in this case it doesn’t bother me – I’d rather see the leopards clearly than have them silhouetted against a dull sky.