Males are simultaneously polygynous, females are serially polyandrous. As such, polygamous relationships can be polygynous, polyandrous or polygynandrous. Strongly polygynous or monogamous species display increased female-female aggression. Similarly, scientists disagree whether Lower Paleolithic humans were largely monogamous or polygynous. An explanation for why polygynous systems persist is explained by the polygyny threshold model. Organisms with polygynous mating systems are controlled by one dominant male. Wrasses exhibit three different mating systems&colon; polygynous, lek-like, and promiscuous mating systems. Male dispersal is more common in mammals with cooperative breeding and polygynous systems. Usually males, mainly in polygynous species, have shorter lifespans than females. This might have been due to the past prevalence of polygynous relations and female hypergamy. Sea otters are polygynous&colon; males have multiple female partners. Infanticide is common in polygynous species such as gray langurs and gorillas. Women who are part of polygynous marriages generally experience higher rates of domestic violence. In polygynous species, males will try to monopolize and mate with multiple females. The red-winged blackbird are territorial, polygynous, gregarious and migratory birds of short distance .