when the sun goes down, the Night Stalkers come out to hunt. No pony knows were they came from, or how they came about, but every pony knows to stay out of their territory. The rattlesnake coyote hybrids form large and loosely organized packs that together take down prey for bigger then themselves, or lots of smaller critters. They jump in to bight their prey, injecting their neurotoxin venom, then running off to wait for the prey to collapse. Once the prey is vulnerable, the pack rushes in to drag off, and eat their prey.
 
A pack of Night Stalkers is more of a mob with similar goals, having almost no social structure, just banning together out of safety, and easier access to food. they have exelent hearing, and like a snake, have heat vision, but their eyesight is poor.
 
Though though a rumor, there has been stories of night stalkers that can turn invisible, and if true, it is speculated that it is possible that a pack of them killed and ate a blue alicorn, possibly gaining the monsters power.