Moles are small mammals and they live in areas that have soil so they can dig tunnels underground. Although they spend most of their time underground they still must be able to protect themselves most of them have claws but for female moles through evolution obtained high levels of male hormone testosterone. Which makes these females have stronger muscles for digging, foraging, and defence. Most of the year they are like this but during mating season testosterone levels drop and the mating cycle occurs.
Male development in humans and other mammals is determined by chromosomes. In XY embryos a gene called SRY is able to turn on testis genes and turn off ovary genes to transform cells into a testis. In XX embryos the pathway is different it makes an ovary instead that allows oestrogen. Embryonic tissue become either an ovary or a testis but in female moles its different they develop a patch of tetis within their ovaries. But instead of making ovaries they make ovotestes which means one end of the tissue is ovarian and the other is testicular tissue. This explains why female moles have male like genitalia and are muscular and aggressive, because outside of breeding the testicular tissue expands more than the ovarian end.
The question is though is how does a female mole able to form a testis without the SRY gene? Scientist had to sequenced the entire mole genome to figure out how this was possible. They found something on the gene FGF9 this gene switches on testis growth in XY embryos and inhibits genes that determine ovarian development but in female moles this stay on even with the absence of the SRY gene. A gene CYP17A1 is another gene for the reason why female moles have male-like hormones/genitals, this gene is the key increasing testosterone so in female moles they have two copies of this gene. I think this study is very important because now we know that the development of testis or ovary development in embryo development are just not about a on/off switch in the depending if there is SRY gene or not, its a much more complex network. We can also use this study to figure out how it is possible in other mammals the females are able to much more bigger than a male such as the hyenas.