We reviewed the distribution of Robertsonian (Rb) races of Mus musculus domesticus in central and southern Italy. This Rb system is called the Apennine system and includes four races (Cittaducale, ICDE, 2n=22; Ancarano, IACR, 2n=24; Campobasso, ICBO, 2n=22; Colfiorito, ICOL, 2n=33–34) surrounded by standard populations with karyotype 2n=40. Here we evaluate the relationships between the altitudinal distribution of races, and the indoor vs. outdoor behaviour of populations, inferred from literature data on the diet of the barn owl Tyto alba. We assume that a higher prevalence of mice in owl pellets reflects a higher outdoor occurrence of mice. The IACR and ICDE races were found at higher altitudes than the standard populations, while the ICBO race is present at lower altitudes like the standard race. The standard race has indoor and outdoor populations; in all the Rb races an indoor life has been suggested by our data. This behaviour is only partly due to altitude, since the ICBO race also lives at sea level. We speculated that indoor life is an intrinsic characteristic of the ICBO race irrespective of the environment. This pattern reinforces the idea that indoor life, through its population dynamics, has played a significant role in the evolutionary history of Rb races.
The diet of the barn owl from three localities in Thessaly, Central Greece, was studied in the breeding and non breeding seasons over one year. A total of 420 pellets with 1.013 prey items were analyzed. Twelve small mammalian species were taken (94.9% by number and 96.1% by biomass), although Mus domesticus (26.3%), Crocidura spp. (25.3%) and Apodemus spp. (18.4%) were the main species predated by number. Rats (Rattus spp.), showed the highest frequency (11%) and biomass percentages observed to date in Greece, and their presence in the barn owl diet is also among the highest in the Mediterranean Europe. Birds (Passer spp. and Carduelis spp.) and insects (Acrididae) were also present (3.9% and 1.2%, respectively). Ecological niche values, seasonal and geographical differences were tested, the results pointing to the opportunistic feeding behavior of the barn owl in the croplands of central Greece.