Nowadays detectives can use DNA analysis to help catch a killer. But what happens when a crime scene has been exposed to the elements for thousands of years? DNA does not always stay intact that long—so for a paleontologist trying to figure out what kind of predator killed a long-dead fossil animal, the case often goes cold.
But a new method promises to help researchers identify these ancient killers. It relies on the fact that when a predator gulps down the bones of its prey—say, when a swooping owl snatches and eats a small rodent in the night—the diner's stomach juices leave behind microscopic etchings on the surface of the victim's bones.
These etchings occur in patterns that are unique to the type of predator that did the deed, making them a bit like fingerprints that scientists can use to crack unsolved cases, explains Rebecca Terry, a paleontologist at Oregon State University, who led the team that studied the etchings. This technique, she adds, will help researchers paint pictures of what kinds of predators were active in long-vanished ecosystems, particularly in areas where fossils are scarce. “It's really powerful,” she says.
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Terry and her team used a scanning electron microscope to examine the leftover bones that modern predatory birds regurgitate as pellets after a meal. They also looked at the feces of carnivorous mammals. “A bone that passes into and out of a nocturnal owl is clearly distinguishable from bones that have been eaten by diurnal raptors” or mammals, Terry says. Patterns etched on bones inside an owl's stomach tend to be relatively short and close together; those from the stomach of a hawk or mammal tend to be longer and more widely spaced, according to the study, which was published last November in PALAIOS. And the patterns left by the modern-day owls and mammals, Terry adds, were “indistinguishable” from those found on fossil bones digested by similar predators long ago.
These findings will help answer one of paleontologists' most basic questions about the fossils of animals they suspect were killed and eaten: “Whodunit?” As Joshua Miller, a paleobiologist at the University of Cincinnati, who was not involved in the new research, says, “You can actually look at an individual bone and get some perspective on why that bone is where you found it. And that's really neat.”