Complex sentence: It may be that the forager expects reciprocal altruism--where the unsuccessful members could provide food knowledge to the successful forager in the future--but given the size and mobility of roosts, this is unlikely to be the case.
Split into simpler sentences: It may be that the forager expects reciprocal altruism, where the unsuccessful members could provide food knowledge to the successful forager in the future. But given the size and mobility of roosts, this is unlikely to be the case.