Zoologists follow many lines of evidence - folklore, reports by local hunters, the finding of physical evidence (always the goal, but sometimes this just happens out of the blue (Dr. Alan Rabinowitz found at least one new species after seeing horns on display in a hunter's home in Laos)) , Ancillary evidence like footprints can also be involved, although not by itself definitive (when Dr. Grover Krantz described sasquatch as a known fossil species, Gigantopithecues blacki, very few of his fellow scientists saw value in it: he named, based only on footprints, a species of which we had no fossils except jaws and teeth.)
The hardest things to evaluate are stories told by individuals. Anecdotal evidence can't support a paper in NATURE describing a new species. But that doesn't mean anecdotal evidence has no value.
An individual's story (whether fresh or handed down) can be important to the search for unknown animals in two ways: 1) Stories can point to an animal that might be discovered if physical evidence is searched for as a result of the stories: Rabinowitz found evidence for some animals that way, and so did Dr. Marc van Roosmalen when he found the largest new species of land mammal of the 21st century so far, Roosmalen's tapir. . 2) On the other hand, if an animal is reported in a given area, if there are NO stories about it by indigenous people, that is highly suspicious and important negative evidence. It's the reason the chupacabra can be rejected out of hand - the animal just sort of appeared in the 1990s, Attempts to dig out old, fragmentary, and vague stories that might refer to it are unconvincing.
So listen to stories. Or lack of stories. Either might be important .
Dr. Marcus van Roosmalen, who has found several new monkeys as well as his tapir by using local stories as the starting point for a search.