An new study conducted in Doñana National Park explores how vertebrate remains fossilize in a Mediterranean environment. The research, published in PLOS One, provides new insights into bone weathering processes, a crucial variable for understanding the formation of fossil deposits. This is the first experimental calibration of bone weathering in a Mediterranean climate—an ecologically and climatologically significant setting given the abundance of fossil-rich sites in the region.

The research team was led by Marcos Pizarro-Monzo and M. Soledad Domingo from the Complutense University of Madrid, with contributions from the Doñana Biological Station (CSIC), the National Museum of Natural Sciences (CSIC), the Catalan Institute of Human Paleoecology and Social Evolution (IPHES), the University of Alcalá, and the University of California, Santa Cruz.

“Doñana National Park is an exceptional natural laboratory for studying fossilization processes,” explains M. Soledad Domingo, professor at the Faculty of Geological Sciences and co-author of the study. “Its wide variety of environments—marshes, ponds, and dunes—provides conditions similar to the depositional settings where continental vertebrate fossils are often found. Moreover, the park’s protected status and restricted access allow us to conduct long-term controlled experiments.”

The main focus of the study is bone weathering, a variable used by paleontologists and zooarchaeologists to estimate how long skeletal remains stay exposed before burial. “Until now, the most widely used weathering scale was the one developed in Amboseli National Park, Kenya, under a semi-arid tropical climate,” notes Marcos Pizarro-Monzo, PhD candidate at the Faculty of Geological Sciences and lead author of the study. “However, climate conditions play a fundamental role in the rate of weathering, so it was essential to establish a scale adapted to the Mediterranean climate—where fossil sites are particularly common.”

To conduct this research, the team placed skeletal remains from four of Doñana’s main ungulate species—red deer (Cervus elaphus), fallow deer (Dama dama), wild boar (Sus scrofa), and horse (Equus ferus)—in a protected area of the park in 2018. The bones were left directly on the ground, exposed to the ecosystem’s natural conditions. Since then, the researchers have carried out regular visits to document bone deterioration and record environmental variables such as temperature, humidity, rainfall, and solar radiation, while also analyzing meteorological data provided by ICTS Doñana.

“We’ve tracked the evolution of these bones for nearly six years and already see clear differences between species and bone types,” says Pizarro-Monzo. “Bones from larger animals, like horses, degrade more slowly than those from smaller species, and bone surfaces shielded from sunlight show almost no deterioration. Our results indicate that bone weathering in the Mediterranean climate progresses at an intermediate rate between tropical savannas and temperate environments.”

Implications for Paleontology and Beyond

The study’s findings provide a crucial reference for interpreting the processes that affect bone remains before burial, helping to better understand how fossil sites form in Mediterranean climates. Beyond its importance for paleontology and archaeology, the research also has potential applications in forensic science, where estimating the exposure time of skeletal remains is vital.

“This work is part of a broader taphonomic project called LiveDeadFossil, which we are carrying out throughout Doñana National Park,” explains Domingo. “Monitoring modern skeletal remains not only helps us understand how fossil deposits form but also provides valuable information for ecologists and conservation biologists on habitat preferences, resource use, and mortality patterns over time in animal communities.”

This advancement in taphonomic research within a Mediterranean context opens new pathways for studying fossils and the natural processes that preserve them, offering a more comprehensive view of Earth’s biological history.

Reference

Pizarro-Monzo, M., Domingo, L., Negro, J.J., Cantero, E., Martín-Perea, D.M., & Domingo, M.S. (2025). Bone Weathering in a Mediterranean Climate Region: An Experimental Case Study from Doñana National Park (Spain). PLOS One. DOI: https://doi.org/10.1371/journal.pone.0335508