Seasonal patterns of circadian rhythmicity of colonic and body surface temperatures in adult Rouen ducks (Anas platyrhynchos domesticus) under natural light/day cycles in a tropical savannah

Abstract

ABSTRACT The effects of cold-dry (harmattan) and hot-dry seasons on the circadian rhythms of colonic (CT) and body surface (BST) temperatures in 20 adult male Rouen ducks (Anas platyrhynchos domesticus) were investigated under natural light/day cycles in tropical conditions. Air temperature (AT), relative humidity, CT and BST were recorded bihourly for a period of 72 h during both hot-dry and harmattan seasons. Colonic temperature and BST exhibited rhythmic cycles during the hot-dry and harmattan seasons; however, the amplitude of the CT was higher (P < 0.05) during the hot-dry (0.6 ± 0.05°C) compared to that of the harmattan season (0.2 ± 0.02°C), while the amplitude of BST ranged from 8°C to 10°C in both seasons. The mesor of CT did not differ (P > 0.05) between seasons; however, that of BST was higher (P < 0.05) during the hot-dry than harmattan season. The acrophases for CT (14:00 h) and BST (12:00–14:00 h) were observed during the photophase in both seasons. The present study provided base-line reference values of CT and BST for the Rouen ducks under natural photoperiod in a tropical savannah zone, which until now have not been reported in the available literature.