Because gray-brown mouse lemurs are nocturnal, their days actually start at dusk, when they wake up from their sleeping spots to search for food. Like many mouse lemur species, gray-brown mouse lemurs live in dispersed social groups, where individuals will share or overlap in their home range, but will not always be found together within that range. Females are philopatric, meaning they stay in the range they were born in with their mothers and sisters through life, and males will disperse from their birth range when ready to find a mate. Similar to other lemurs, females are dominant to males and will often win in agonistic interactions between the sexes — although these occurrences are rare, males are typically okay with the females having the better food. Being dominant allows females greater access to the resources they need to raise their young. At the end of the night, they’ll find a place to curl up and sleep for the day, often in a tree fork or in tangled vegetation. They’ll sometimes sleep in small groups or pairs. Because all of the known predators of gray-brown mouse lemurs hunt during the night when they’re active, and individuals are not always seen sleeping huddled together, researchers believe these sleeping groups are to facilitate social bonds rather than provide protection from predation or for temperature regulation.

While the gray-brown mouse lemurs can be found in much dryer habitats than other mouse lemur species, they do overlap with the gray mouse lemur in some regions, and have been known to hybridize.