Osteological data from harpy eagle's nests

The goal of this study is to provide a taphonomic analysis of bone fragments found in harpy eagle nests in the Brazilian Amazonia, utilizing the largest sample collected to date. Harpy eagle kill samples were collected from nine nests between June 2016 and December 2020 in Mato Grosso, Brazil. We identified the specimens and calculated the number of identified specimens (NISP) and the minimum number of individuals (MNI). These metrics were used to estimate bone survivability and fragmentation. A total of 1661 specimens (NISP) were collected, representing at least 234 individuals (MNI). We identified at least nine species of primates, which represent 63.8% of the individuals in the kill sample. Harpy eagles preyed mostly on the medium-sized capuchin and bearded saki monkeys (28.2% of the MNI) and two-toed sloths (17.7% of the MNI). Four distinct patterns of bone survivability were found, one characterizing bird prey, another characterizing xenarthrans, a third typical of medium-sized monkeys, and a fourth common to woolly monkeys and porcupines. The large sample size analyzed in this study provides a unique opportunity to better understand harpy eagle behavior and prey selection in the wild. We conclude that harpy eagle predation leaves a unique signature on the prey that is specific to each taxon. The inter-taxon variations observed in the taphonomic signatures of harpy eagle kills should be taken into account when evaluating the potential influence of these raptors as accumulators of bone material in both paleontological and neontological assemblages.

Methods
We collected harpy eagle kill samples from nine nests between June 2016 and December 2020 (Table 1). The nests are located in the southern Amazonia of Mato Grosso state, Brazil, on the right and left banks of Rio Juruena, and between the Juruena and Teles Pires rivers (Figure 1). The climate in this region is classified as a “tropical wet climate” (Alvares et al., 2013). Annual rainfall averages 2350 mm, and annual ambient temperature averages 24.5 °C (Radam-Brasil, 1983).

Bone, hair, eggshell, and feathers were collected by EBPM and colleagues in the nests and on the ground below the nest tree. To access the nests, raptor-specific tree-climbing protocols were employed (Miranda et al., 2021; Pagel & Thorstrom, 2007; Rosenfield et al., 2007). Permits to work in the area were provided by the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio), Brazilian Ministry of the Environment (SISBIO process No. 58533).

Every attempt was made to ensure that all bones produced by the nests were collected. The presence of small teeth, isolated vertebrae, and podials in our sample suggests that the sample reflects the kill accumulation from the nests. The following was noted for each osteological specimen: taxon, skeletal element, side, greatest length, age class, association with other elements, and damage.