original: The only known communal roost contained only four individuals.
simplifications: The only known communal roost had only four individuals. The gathering area had only four individuals. Four individuals made up the communal roost. The only communal roost had just four individuals. The only known communal roost had only four people. Only four individuals lived in the known group roost. The only know communal roost consist of only four individuals The were four people in the only known communal roost. There were only four individuals in the only known communal roost. The only known communal settlement contained only four individuals.