“…In contrast to this, indicate that they have detected a 'phylogenetic signal' in mammalian sleep, perhaps indicating some predictability of this state across species. Detailed sleep studies in rodents have been examined in the rat [Alfoldi et al, 1990], mouse [Richardson et al, 1985;Ayala-Guerrero et al, 1998;Tang and Sanford, 2002], Djungarian hamster [Deboer et al, 1994], Syrian hamster [Tobler and Jaggi, 1987], chipmunk [Estep et al, 1978;Dijk and Daan, 1989], gerbil [Kastaniotis and Kaplan, 1976;Susic and Masirevic, 1986;Ambrosini et al, 1994], guinea pig [Tobler et al, 1993;Tobler and Franken, 1994], squirrel [Folk, 1963;Chepkasov, 1980], Octodon degus [Kas and Edgar, 1998] and the blind mole rat Spalax [Tobler and Deboer, 2001]. …”