Urban females experience better reproductive conditions than rural females in Eurasian red squirrels

Abstract Urbanization has a negative impact on ecosystems and threatens the existence of wildlife; however, it also provides alternative habitats for wildlife. Man-made structures and anthropogenic resources contribute to urban wildlife by providing nest sites and food. In particular, supplemental feeding, such as garden bird feeding, has been considered to contribute strongly to urban wildlife by providing a high-energy food, possibly increasing reproductive success. However, it remains unclear whether, and to what extent, supplemental feeding boosts reproduction, particularly in mammals. Here, we studied the multiple aspects of reproductive conditions of female Eurasian red squirrels Sciurus vulgaris , living in the rural and urban areas which differed mainly in supplemental feeding, in Obihiro City, Hokkaido, Japan. From the individual-based daily observation, we found that the urban population had a significantly 24% higher pregnancy rate and a one-month earlier breeding season than the rural population. Urban females were one year earlier/older for each initial/latest reproductive bout (at one and five years old) than rural females (two and four years old, respectively). The number of weaned young from single litter were on average 3.0 young for urban and 1.5 young for rural areas. In addition, although rural females did not attend multiple breeding, 40% of urban females did so. Our results suggest that urban squirrels have better reproductive conditions than rural squirrels.