Social behaviour of the crested porcupine in urban and rural areas

Abstract The social behaviour of rodents has captivated scientists for decades, offering valuable insights into the evolution of mammalian sociality. One of the main critical gaps in understanding rodent sociality is the role of subadult individuals prolonging their stay with parents and younger siblings, particularly in nocturnal and elusive species. Moreover, urban environments are known to elicit changes in the social behaviour of mammals, leading to altered patterns of sociality. Yet, little is known on how rodent societies may change in altered environments. Thus, we aimed at investigating the social behaviour of the crested porcupine Hystrix cristata in central Italy, with a particular focus on group composition and on the prolonged occurrence of subadult individuals within family groups. We also tested the potential effects of natural and urban environments. We combined marking of free-ranging individuals with camera trapping campaigns across three ecologically contrasting areas, and showed a pair-living social system for adult crested porcupines. Most videos captured either single young individuals or pairs of adults. Subadult marked females were observed together with adults during the birth season in the year following their birth, suggesting a potential helping role. Conversely, subadult marked males were rarely observed, presumably dispersing. Groups exceeding two individuals ranged between three and five, and were typically observed following reproductive events, with porcupines commuting in line, parents positioned at head and tail of the row. Urban environments showed a slightly different pattern, with occasional aggregations of subadults. We highlight the importance of understanding subadult behaviour in crested porcupines, as well as of testing the effects of urban ecosystems upon mammalian social systems. These findings contribute to a broader understanding of social behaviour and evolutionary adaptations in rodents and, more in general, of mammals.