Exotic lenses are not slow.

Modern cameras can shoot at much higher ISOs without objectionable grain than they ever have before. Couple that with long telephotos that are faster (sure they’re not f/1.8 or f/2 that you see in shorter lenses) lenses and you’re filling the frame at a distance with a usable ISO and shutter speed.

Daylight generally provides enough light for the job.

Additionally, depending upon the animal you’re taking pictures of, shutter speed likely doesn’t need to be above 1000/1500. Most animals are not moving around at full speed all the time.

For birds in flight even, I shoot around 1/1250 or so. Exceptions would be hummingbirds if I want to stop wing movement, that’s at least 1/2500 or a bit higher.

And equipment can make a big difference. For serious professional shooters, they may have a fixed aperture of say f/4 or f/5.6, which is excellent. A budget lens can be several stops more which would cause challenges, particularly at dusk/daybreak.

Looking for the right light. Fast lenses. High ISO. Lots of waiting and taking a lot of shots that don’t turn out.

The wildlife photographers I know will use whatever iso is required to get the photo. Better to have some noise in the photo then no photo. You can also clean the noise up in post.

Just let that ISO climb and clean it later. Topaz denoise, DxO, LR C Denoise all work wonders for making an ISO 10000 shot look decent.

Since lens with high focal distance are generally not that fast

Cheap lenses aren’t that fast. Here’s a 400mm 2.8 lens for $12,000 And if that’s not enough here’s a 200-500mm 2.8 for over $20,000

Even if you add a 2X extender that’s still 5.6 at 800 or 1,000mm. That’s not that bad when you’re shooting in good daylight conditions.

And of course that’s assuming you’re shooting from a long distance. This is just one option to shoot wildlife. Another is to turn into a hunter. Camo, scents, lures, bait, blinds, etc. Combined with enough time and patience these people will get wildlife pretty close to them so they can use wider lenses.

Crank that ISO baby. 12800 is acceptable for me on a full frame body. You can always clean it up in post.

Obviously, limit your shutter speed if possible.

With DxO DeepPrime, noise is getting close to being irrelevant.

how do they get light without addind too much gain an grain ?

With the giant ball of plasma in the sky you can shoot at 1/3200ths, f/5.6, ISO 400 - or 1/800ths and ISO 100.

I don’t see what the problem with either of those would be?

With enough money you can get lenses that are long and fast. Otherwise, you seek out good light; one of the biggest tips for beginner wildlife photographers is to go out at the right time of day. Direct sunlight an hour or so after dawn is more than sufficient to freeze motion with minimal noise, even at a reduced aperture on an APS-C camera body (400mm, f8, 1/2000s, ISO400).

Flashes used to be common - early digital/film era wildlife photography books I’ve read suggest that a flash is a necessary tool - but seem to be dwindling. Use of denoising software is also common.

F4 is pretty fast and there are fast telephoto lenses like the 600mm f4. They cost an arm and leg but professional photographers rent them, or their work pays for them.

During the day there is a lot of light. At f4 during the day at ISO 400 shooting at 1/200th of a second is possible.

Noise also seems to be a bogey man with people complaining about noise even at ISO 100 at times which I think is confusion over what ISO related noise is.

Once you take a 20mp+ and either resize for web or print it most noise is not visible to anyone but pixel peeping photographers even at IS 3200 or higher as long as the image was properly exposed.

Lastly with modern AI denoising tools even very high ISO images can look very clean.

Let me know if you want some real world examples of ISO 3200+ images that I think look very clean when resized for web at sizes larger than IG allows.

Rent your own elephant and bring it back to the studio where the big big Lights are

/s

Everyone here is going on about fast lenses but, while I’m no professional, I literally use a kit lens. At 250mm its biggest is 5.6. When I’m shooting birds or animals I just go auto iso on manual setting and don’t go above 1600 iso on my canon rebel t7.

I’m not getting anything that’s far away and needs a lot of crop, but outside of that it’s not really an issue.

Enjoy the hunt, your skills will get better over time. Just put your camera into manual with auto ISO and forget about it. Clean up in post.