“Society of the den”: Identifying patterns of denning behaviour in Upper Pleistocene hyena populations

In this study, we examine patterns for identifying spotted hyena dens in the fossil record through mortality profiles and discuss their ethological significance as a tool for understanding how this taxon occupied cavities in the past. We analysed the age structure of the spotted hyena from the Upper Pleistocene site of Cueva del Camino (Pinilla del Valle, Madrid) and compared it with other sites as well as with a modern hyena population. We interpret the mortality profile obtained at Cueva del Camino as indicative of a spotted hyena den, specifically a communal den, due to the scarcity of neonates and the high percentage of juveniles in the communal denning period. In the comparative analysis, we found a pattern in spotted hyena mortality profiles that can help classify denning behaviour in the fossil record: the composition of communal denning populations should comprise more than seventy percent juveniles, and the proportion of adults should be lower than that of older adults. Furthermore, for the first time, we can also statistically discriminate between den and non-den occupations. However, one of the main issues that arise with statistics is that when the sample size is low, confidence is reduced, which can lead to misinterpretations of the type of occupation. As an alternative approach, we followed the method of Discamps and Costamagno to adapt the ternary diagram demarcation to the spotted hyena, based on species-specific age class boundaries. Based on this method, we propose that: (I) the JOP zone could be associated with sites used as communal dens by hyenas, (II) the JPO zone could be designated for sites where a clan, including cubs, used the cave for living, and (III) the O and P zones could be related to sporadic occupations by hyenas.