DIEL ACTIVITY RHYTHMS IN THE LEVANT VOLE, MICROTUS GUENTHERI

ABSTRACT

Activity rhythm of the Levant vole (Microtus guentheri) was studied using an actograph in a dark test room at 20–22°C, where sexually inexperienced voles (3♂♂, 3 ♀♀) were singly caged. The test room was lit by fluorescent lamps according to 11 different L: D regimes, photophase duration being altered from test to test by 2 h, ranging from 4 to 24 h (4,6,8… 24 L: 20, 18, 16… OD). Activity was significantly reduced when photo-phases were <6 h or >18 h. The voles exhibited diurnal/nocturnal shifts, according to photophase. They were diurnal when photophases were 6 or 8 h long, and nocturnal when they were 10–18 h long. The Levant vole should therefore be regarded as predominantly nocturnal in Israel, where day lengths range between 10 and 14.5 h. Activity patterns showed short-term bouts of activity occurring during the 24 h cycle in intervals of about 3 h, and long-term bouts, of up to 7 h, occurring mainly during activity-onset and activity-cessation. Activity-onset was less accurate and less dependent on the L: D timing than activity-cessation.