The Biology and Evolution of Fierce Females (Moles and Hyenas) Jiménez Medina, Rafael Burgos Poyatos, Miguel Barrionuevo Jiménez, Francisco Javier Talpid mole Spotted hyena Female masculinization Talpid moles and spotted hyenas have become the paradigms of anatomical and behavioral female masculinization. Females of many mole species develop ovotestes that produce testosterone, show external genitalia that resemble that of males, and close their vaginal orifice after every estrus, and female spotted hyenas lack an external vaginal orifice and develop a pseudoscrotum and a large pseudopenis through which they urinate, mate, and give birth. We review current knowledge about several significant aspects of the biology and evolution of these females, including (a) their specific study methods; (b) their unique anatomical features, and how these peculiarities influence certain physiological functions; and (c) the role that steroid hormones as well as genetic and environmental factors may have in urogenital system development, aggressive behavior, and social dominance. Nevertheless, both mole and hyena females are exceptionally efficient mothers, so their peculiar genitalia should not call into question their femininity. 2025-12-04T12:02:54Z 2025-12-04T12:02:54Z 2023-02 journal article Jiménez, R., Burgos, M., & Barrionuevo, F. J. (2023). The biology and evolution of fierce females (moles and hyenas). Annual Review of Animal Biosciences, 11, 141–162. https://doi.org/10.1146/annurev-animal-050622-043424 https://hdl.handle.net/10481/108592 10.1146/annurev-animal-050622-043424 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional Annual Reviews