Call it the Sarlacc Pit of the Late Miocene: A recent study by Spanish paleontologists has shown how a nasty cave entrance gobbled-up a disproportionate number of carnivores for an extended period over 9 million years ago.
The cave, dubbed Batallones-1 (or Bat-1 for short), was discovered back in 1991, and it has produced a tremendous number of fossils.
Typically, digs like this one produce a consistent ratio of herbivores to carnivores, a figure that usually settles around 10:1. But Bat-1’s lower level was dominated by the remains of carnivores — accounting for nearly 98% of the fossils — a list of creatures that included (especially) saber-toothed cats, hyenas, ancestors of the red panda, an extinct ‘bear-dog’, and many others.
Image: The skeleton of the hyena Protictitherium crassum. Credit: Domingo MS, Alberdi MT, Azanza B, Silva PG, Morales J (2013).
What’s more, analysis of the fossil record indicated that the remains settled at the bottom of the cave over a protracted period of time, and that the remains were highly isolated in time (meaning that the carnivores didn’t accumulate in the pit by virtue of mass events). The paleontologists also ruled out the possibility that the animals accidentally fell into the cave, or that they were brought there by other animals or flushed into the cave by flooding waters.
Rather, it appears that the carnivores intentionally entered into the cave — only to be trapped forever. The researchers theorize that the cave entrance was enticing to predators who were inexperienced, desperate, or overly adventurous as they sought an easy meal or drink of water.
“In modern ecosystems, mortality among prime adult individuals is not rare and is related to their proneness to search for resources in dangerous locations mainly during [stressful periods],” write the researchers in their study, which now appears in PLOS.
Image: (A) Carnivores intentionally enter the cave, (B) Regular floods fill the cave and bury the remains; carnivores continue to enter into the cave over time, (C) Final stages of the filling of the chamber, but it’s not a carnivore trap anymore. D) Deposition of elements from the upper level assemblage. Art by Mauricio Antón, Israel M. Sánchez and M. Soledad Domingo.
The researchers believe that the animals deliberately entered the cave of their own free will owing to the dearth of herbivore remains. The top of the cave was very visible and avoided by most herbivores; most falls were accidental, but not entirely uncommon — as witnessed by the remains of an unfortunate rhino (Aceratherium incisivum).
It’s not entirely clear if the carnivores died as a result of their fall into the pit, or if they remained alive for some time, eventually dying after progressive weakening. But the skeletal remains weren’t altered very much, and they didn’t have any trampling marks on them — a possible indication of instantaneous death. But the researchers say they’re simply not sure.
“Carnivores could be struggling for getting resources but it is unlikely that they risked their [lives] in the jump,” they wrote. “Most probably, carnivores got trapped and remained alive for some time.”