In this paper we report our ongoing work with evolving biohybrid societies. We develop robots that will be integrated in an animal society and will be accepted as a conspecific. Moreover, we want our robots to affect the behaviour of animals. We are using evolutionary algorithms to optimise robot controllers, where fitness is evaluated via measuring the effect a robot controller has on the animals. Several issues have to be considered: if the animals do not have a homogeneous behaviour several evaluations are needed to rule out outliers, and yet evaluating animal behaviour is a time consuming task. Besides the time it takes to record their behaviour, we have to take into account animal resting time, stimulus habituation, and feeding periods. Another factor that increases the task difficulty is robot heterogeneity, which is similar to the so called reality gap problem that occurs in evolving robot controllers in simulation. In our case, if we want a robust robot controller, we have to evaluate it in different robots. Overall, we found that doing online on-board evolutionary computation with robotic devices and animals is extremely challenging and we provide clues to avoid its major pitfalls.