The Reproductive and Anatomical Characteristics of the Invasive Nutria (Myocastor coypus M.) in a Central European Population.

The nutria or coypu (Myocastor coypus M.) is endemic to South America. However, this species invaded Central Europe in the 19th century. The rapid spread of the invasive nutria across Central Europe triggered countless ecological conflicts with the local species. In the current research, we surveyed two populations in Slovakia and compared the reproductive performance of this species to its reproductive performance in other countries, where it is native. A total of 69 nutria were harvested from the wild in 2022-2024. The result of the postmortem analysis reveals no intersexual differences in the body weight and length. A visual inspection of the uterus among 25 female specimens confirmed that 16 (64%) were pregnant, including 3 individuals with the body size characteristics of young nutrias. The pregnancy rate was estimated at 90% (9 out of 10) in spring and 47% (7 out of 15) in autumn. The average number of embryos per individual was 6.94 ± 2.22 for all females, and it was 6.27 ± 2.05 in spring and 8.8 ± 1.64 in autumn, with no significant difference between seasons (p > 0.05). No clear relationship between the Body Mass Index (BMI) and the fertility of females, i.e., the number of embryos, was observed. Our results highlight the crucial need to raise public awareness about the invasive characteristics of the species and contribute to the establishment of an effective intervention techniques, including the establishment of the necessary legal framework for eradicating emerging populations across Central European habitats.