Please help identify another old horror movie...?

Ok, I remember seeing this movie as a child. I think it is from the 60's or 70's and features some kind of creatures that feed on humans and maybe animals. I only remember images from various scenes. The creature is about the size of a very large armored turkey, with no legs and crawls or slides along the ground. It has a shell and, I think, one tentacle / head. If it gets a hold of a person or animal it starts sucking out their blood / guts or both with a large sucking sound similar to that of trying to finish the last remnants of a chocolate shake through a straw. I think they first discovered the creature existed by finding the remains of cows they had eaten. I remember one scene where the people were running through the woods and one of these creatures dropped out of a tree onto a guy's chest. He was toast. In another scene the creature had one of the characters by the wrist with the tentacle / head and another character had to chop off the guy's hand with a hatchet. He didn't want to do it, but the guy despairingly said, "You must!" as he held out his hand and awaited amputation..." Even as a child I wondered why he didn't just chop the tentacle, but I think the creatures had like a bulletproof / hatchet proof armor. I think I remember one of the characters attempting to shoot one of the creatures and the bullet just ricocheted off the armored shell. In another scene, one of the creatures was reproducing (I think) and it had split itself in half. During this process it was helpless and there was quite a bit of slimy goo between the two halves of the dividing creature... The humans came upon it, observed it discussed it and left without killing it. Don't really understand why they didn't do anything, but hey, I didn't write the movie... In the final scene of the movie, the people were holed up in some building or room or something and dozens of these creatures were after them. The creatures were breaking windows and doing whatever they could to get to the humans because they were starving. The humans won by holding out long enough to starve all the creatures to death. All help is appreciated! Thank you!