Table 1.

Species showing social flexibility.

species	male tactics	female tactics	social organizations	fluctuation in population density?	importance of intraspecific competition	references
burying beetle, Nicrophorus vespilloides	—attract females via pheromones —attract females to carcass —satellite	—single breeding —communal breeding —parasite	—solitary —pair-living —one male, multi-female	yes	carrion size determines number of females that can breed together	[50–52]
pied kingfisher, Ceryle rudis	—breeder —non-reproducing helper —reproducing helper	breeder	—pair-living —family group —two males, one female	yes	availability of good nesting sites influences whether unrelated helpers are accepted	[53,54]
prairie vole, Microtus ochrogaster	—philopatric helper —solitary wanderer —breeder	—philopatric helper —single breeder —communal breeder	—solitary —pair-living —multi-male, multi-female	yes (breeding seasons versus winter)	Female–female competition in communally breeding groups: higher reproductive success if only one female breeds per group	[55–58]
house mouse, Mus musculus	—philopatric helper —solitary roamer —breeder	—philopatric helper —single breeder —communal breeder	—solitary —pair-living —multi-male, multi-female	yes	—intrasexual aggression —female infanticide	[59,60]
striped mouse, Rhabdomys pumilio	—philopatric helper —solitary roamer —breeder	—philopatric helper —single breeder —communal breeder	—solitary —pair-living —multi-male, multi-female	yes	—intrasexual aggression —female infanticide —male reproductive suppression	[45,46,48,61]