Johannesburg - A prehistoric predator that lurked in caves and stalked the night is helping scientists understand the future of climate change.
That prehistoric predator can still be heard and seen today, often silhouetted against suburban night skies.
What it was is the barn owl.
Wonderwerk cave in the Northern Cape has an amazing collection of small animal fossils that date to two million years ago. What wasn’t known was what left those remains.
Through analysis scientists from the Universidad Complutense de Madrid (UCM) and the Spanish National Museum of Natural Sciences have been able to demonstrate that the formations of small animal fossils were mainly left by the barn owl. This allowed them to conduct a weather check two million years ago.
“Given the absence of changes of predators over the sequence, we can confirm that any possible changes in the composition of the assemblage of micro-mammals are not the result of a predator’s preferences, but environmental changes,” explained Sara García Morato, a researcher at the Department of Geodynamics, Stratigraphy and Palaeontology at UCM and MNCN, in a statement.
Their research was recently published in the journal Quaternary International.
In the field of palaeontology small mammals like mice are seen as good indicators of environmental and climatic change. The reason for this is that they respond quickly to changes in their surroundings.
The team first had to work out what the predator was that left this fossil assemblage. They did this by looking at the skeletal remains and examining the damage to the bones caused by the predator’s digestion process.
These results were then compared to a line up of possible suspects, including both nocturnal and diurnal birds of prey and other carnivores.
“Each predator produces its distinctive signature on the prey that it ingests,” explained Yolanda Fernández Jalvo, a researcher at MNCN, in a statement.
The traces left on the bone fitted the profile of the barn owl.
Owls regurgitate pellets that contain undigested fur and bones.
“In the case of the South African deposit, this lengthy continuation of the same type of predator guarantees that palaeo-ecological interpretations of the site are providing us with reliable paleo-environmental results over the course of almost 2 million years, which is quite outstanding,” added Morato.
By understanding past climates, explains Wits university palaeoanthropologist Dr Lee Berger, scientists can get a better handle on what we can expect with future climate change. However the problem with using micro fauna fossil assemblages is that it has its advantages and disadvantages.
“The big plus is that you get large numbers of animals collected but there are two negatives,” says Berger, who was not involved in the study. “One is the very limited distance that barn owls collect from, which is about four kilometres.
“So you are very much talking about the immediate environment, and not necessarily the environment, that things like the hominids that may have occupied at any given time. The second thing with barn owls is they are nocturnal, so you are only getting one side of the ecological picture.”
What those past meals of generations of barn owls tell about the climate around Wonderwerk cave is that it was wetter two million years ago than today.
The team noted the presence of manganese oxides on the bones, which is usually deposited when conditions are humid.
“The presence of manganese oxides declines the more modern the era that the fossils correspond to, allowing us to confirm a climatic trend towards greater aridity in the region," added Fernández Jalvo.