A standardized osteometric method for identifying Iberian raptors from skeletal remains

Abstract

Raptors suffer high mortality rates due to anthropogenic threats, such as electrocution from power lines or lead poisoning, so the specific identification of skeletal remains is essential for establishing monitoring and protection programmes. This study developed and validated a standardized osteometric method for measuring long bones and craniopelvic bones from skeletal remains to identify raptor species. A database of 26 species of Iberian raptors (n = 853) was developed based on 11 measurements of 9 bones, including the ulna, sternum, femur, humerus, tarsometatarsus, tibiotarsus, and radius, as well as the synsacrum length and postacetabular ilium width and length and width of the skull. Missing values were estimated using multiple linear regression, and canonical discriminant analysis was applied to correct and modify the databases. Cross-validation was added to this analysis. Additionally, the obtained model was verified using external radiographs. The highest percentage of success was obtained with the tarsometatarsus-ulna combination (94.53%), followed by tarsometatarsus-radius (94.05%) and tarsometatarsus-humerus (93.02%), when two bone lengths were combined. When a third measurement was incorporated, the tarsometatarsus-ulna-femur combination achieved a 99.45% correct classification rate. In blind verification testing, the radiographs of 15 individuals, the tarsometatarsus-ulna model correctly classified all samples, achieving a 100% success rate. These results show that the study method provides a simple and replicable protocol for identifying raptor species from incomplete skeletal remains. This optimizes the monitoring of mortality and supporting conservation measures.