[ **up: [[Vertebrates]]** ] --- # South American grass mice ## Diverse sex determination system (Fertile XY females) [[2025-0313. 'In mammals, there are indeed a few natural exceptions to the standard XX-XY sex determination system.'|’In mammals, there are indeed a few natural exceptions to the standard XX/XY sex determination system (SDS). For example, fertile XY females are found in natural populations of … South American grass mice species …’]][^1] [^1]: P. A. Saunders, et al., ‘[[Saunders, et al. ‘Masculinised behaviour of XY females in mammal with naturally occurring sex reversal’, 2016.|Masculinised behaviour of XY females in a mammal with naturally occurring sex reversal]]’, *Scientific Reports*, vol. 6 (11 March 2016), p. 1.