Shepherd snakes

so the basic idea here is that a group of snakey creatures has developed herding behaviours of their prey, meaning they care for limited groups of livestock before eating them, usually only the appropriately sized individuals and in periodic batches. the snakes have a limited sense of sustainability so they might end up eating all their livestock and running into problems; therefore it's beneficial for them to keep smaller animals that reproduce and grow rapidly, and likewise this offers an additional pressure for animals around these snakes. a shepherd snake without a flock might get increasingly desperate and start gnawing on carcasses (esp. bones) or even rocks instead. they're quite vulnerable in this respect as they're rubbish ambush hunters, and also haven't developed the digestive skillz for an omnivorous or herbivorous diet. maintaining ranges for the snakes where they can keep their flocks without escapes or human intervention is crucial for maintaining their populations.

one convenient coincidence is that many of these snakes carry infectious diseases which among other things cause degradation of hosts' parathyroidal glands, leading to hypercalcemia. shepherd snakes themselves are not immune to this, but benefit from it as they are a subgroup of rocky snakes. this means the increased calcium levels benefits them during their quite frequent molting cycles, since their scales require a high uptake of various mineral substances. inducing the disease in their prey and letting it progress over some time is also beneficial to the snakes, as this means the stuff they eat also accumulates more calcium before consumption. the disease itself is believed to be the main pressure having led to the snakes adopting herding behaviours (~"wow that creature I failed to munch and then ate later was better for me than eating it straight, maybe I should keep my prey around?"), not the other way around.

shepherd snakes are generally not a danger to humans, as they are quite friendly and immunization programmes for the diseases some of them carry are widely available. transfer primarily happens through the snakes' saliva, most typically through behaviours where they hold their livestock in their mouths. i.e. if you don't kiss them on the mouth or be small and thin-skinned enough for them to grab you, you're probably not even exposed. particularly smaller kinds of shepherd snakes are quite popular as pets due to their generally friendly demeanor; they can quite easily be made to think their human owners are part of, or the entirety of, their flocks, while they rarely move on to trying to actually eat the humans because they're too big. strains used as pets are also typically disease-free, but require very particular diets to compensate for this on top of usually not having their wild diets in the first place.

they were also used for some early sedative medications as they also do chemically sedate their flocks to an extent, but this has since become deprecated.