Those got around. I saw one in, "South African Panorama" many years ago. Some old Afrikaner used it out in the bush for snakes and small game.I think he cited .22 ammo costs as a factor in his choice.

I suppose it worked okay on true rabbits.

Another South African whom I knew said his Ruger .22 auto pistol fared badly on rock rabbits, technically hyraxes, which were quite tough to kill with a .22. He did kill a puff adder with the Ruger.

That man's Ruger was the scarce model with 5.25-inch barrel of medium weight. It would surely have generated as much velocity as a K-22 or one of those Parker-Hale conversions. Writer Skeeter Skelton clocked .22 ammo from a Walther PPK going as fast as from a longer K-22.

I don't think a .22 is enough gun for Nile or savanna monitor lizards. But I can affirm that the little green anole lizards of North America are easily killed with a .22, if you really feel a need for that. I hit one with a Hi-Standard Field King pistol and the shot blew the lizard several feet away. Maybe some muscle contraction applied? I was astounded at the power of a .22 on a lizard that size.