The urban environment is hostile to many mammalian species, yet some are recognised as ‘urban adaptors’. Research tends to focus on these species and their adaptations to urban habitats, which can arise through behavioural plasticity or microevolutionary change. Far less attention has been given to traits showing inertia at behavioural or evolutionary scales. We examined one such trait, sexual segregation, and evaluated its impact on sex-specific survival of eastern grey kangaroos (Macropus giganteus) in the seaside town of Anglesea, southern Australia. We captured and marked over 500 individual kangaroos at a golf course on the edge of town, where the population was concentrated. This population had the three precursors of sexual segregation: sexual dimorphism, seasonal breeding and polygynous mating. Median body mass of adult females was 27 kg (range 17–34 kg); median male mass was 46 kg (range 22–73 kg). Mating was concentrated in the austral spring and summer, followed by a birth peak in December, with 80% of births from November to February. Each year, at least 43% of adult males sired 1.7 offspring on average (range 1–9). Sexual segregation was strong in the non-mating season: most adult females remained on the golf course and properties nearby, whereas most adult males left the course and ranged throughout the town and adjacent native bushland in autumn and winter. Males were thus at greater risk of road-kill, which caused 50% of deaths versus 20% of females. Given the intensity of selection on this behavioural trait, we predict that sexual segregation will diminish in this urban kangaroo population.