To understand the function and origins of sleep, sleep needs to be studied across many different species. Although it is well conserved throughout mammals, 95% of papers are restricted to just three species, Homo sapiens, Mus musculus, and Rattus norvegicus. We aimed to characterize sleep and wake in a Murid rodent Acomys cahirinus in greater detail alongside the well-studied laboratory house mouse (Mus musculus) and wild M. musculus using a well validated, non-invasive, piezoelectric system for sleep and activity monitoring. We confirmed A. cahirinus, M. musculus, and wild M. musculus to be primarily nocturnal, but with clearly distinct behavioral patterns. Specifically, the activity of A. cahirinus sharply increases right at dark onset, which is common in nocturnal species, but surprisingly, decreases sharply just one hour later. Using infra-red camera recordings in single and group cage conditions, we found that A. cahirinus is more active early in the night period than late night period in single and group cages, and this decreased activity in the latter half of the night is much greater compared to M. musculus. In order to better understand these differences in activity, we investigated the sleep architecture of A. cahirinus using electroencephalogram (EEG) recordings. Our data show that A. cahirinus have a few key differences in sleep from M. musculus. A. cahirinus have significantly longer daily sleep periods and exhibit a much higher amount of REM sleep. A. cahirinus are awake at dark onset, but sleep more than M. musculus after the middle of the night. Most strikingly, A. cahirinus do not close their eyes virtually at all while sleeping, day or night. In order to test whether the sleep patterns of A. cahirinus are affected by or responsive to different light input, we set up a light flashing experiment during the daytime. While sleep amount did not change significantly during light flashing, A. cahirinus spent significantly less time in REM compared to baseline. In contrast, M. musculus had no difference in REM sleep percentage. Histological studies showed A. cahirinus have thinner retinal layers, but much thicker corneas than M. musculus. Electroretinography (ERG) results, specifically b-wave amplitudes, are significantly different between these two species. While eye closure and sleep have not been systematically studied across mammals, our observation is clearly a rare behavior. This raises further questions about A. cahirinus sleep architecture, the adaptive value of eyes open sleep to A. cahirius and whether they may have limited visual processing even during normal sleep.

Reproductive behaviour and aspects of group dynamics in the genus Acomys were studied in the respect to the individuals? physical condition, life history traits and social environment. Three of the presented studies reveal the important effect of social environment on the behaviour of group members to the new-coming male and reproductive behaviour of females (sex ratio of the pups and litter size). The other two studies investigate the costs associated with group living and cooperative breeding in Sinai spiny mice and the factors influencing alloparental behaviour. Results of this Ph.D. thesis reveal several aspects of social and reproductive behaviour of group-living mammals and contribute to the understanding of the formation and maintenance of the societies in general.