Rambouillet X Polypay lambs, averaging 45, 62 and 90 days of age, were penned with 8-9-month-old heifers for 60 days. Following 30 and 60 days of pen confinement, the treated and control lamb-heifer groups were observed in a 120-ha paddock for interspecific and intraspecific aggregation or dispersion; i.e. cross species bonding. Interspecies distances averaged  ≤ 20 m in the treated groups vs. 600-1000 m in controls. Interspecific distance was not different between 45 and 90-day-old lambs. Treated lambs followed any heifer(s) which tolerated sheep. Bonding was poorly developed (lambs and heifers were widely separated) within the 62-day-old lamb-heifer group, possibly because two heifers periodically physically abused the lambs by butting and kicking them. It was concluded that 45 90-day-old lambs can be successfully bonded to cattle by penning the two animal species together for a period as short as 30 days.