Daily rhythmicity of behavioral responses in donkeys of different age groups during the cold-dry (harmattan) and hot-dry seasons in a tropical savannah

The aim of the study was to evaluate the daily rhythms of behavioral activities of adult, yearling, and foal donkeys during the cold-dry (harmattan) and hot-dry seasons in a tropical savannah. Thirty, clinically healthy free-ranging donkeys, divided into 3 groups of 10 donkeys each according to their age, served as experimental subjects. Behavioral activities of donkeys were monitored bihourly from 06:00 to 06:00 h (GMT +1) during the cold-dry and hot-dry seasons. Application of single cosinor procedure showed that behavioral activities exhibited varying levels of daily rhythmicity in both seasons. Behavioral activities of adult, yearling, and foal donkeys peaked during the afternoon period (13:11-14:45 h) of the photophase of the light-dark cycle during the cold-dry and hot-dry seasons. The diurnal index of activity rhythm showed that donkeys are mostly diurnal animals. During the study period, the percentage time spent on feeding during the harmattan season was higher (P < 0.05) than during the hot-dry season in adults (37.38 ± 1.57% vs 30.72 ± 1.29%), yearlings (33.20 ± 1.43% vs 27.00 ± 1.25%), and foals (16.79 ± 0.82% vs 14.38 ± 0.65%). The percentage time spent dozing during the hot-dry season by adults (28.21 ± 1.59%), yearlings (29.31 ± 1.60%), and foals (37.64 ± 1.48%) was higher (P < 0.05), when compared with the corresponding values (23.75 ± 1.55%, 26.43 ± 1.59% and 42.42 ± 1.40%, respectively) obtained during the harmattan season. In conclusion, daily rhythmicity of behavioral activities in donkeys, kept under natural light-dark cycle, was similar in both seasons, although the intensity of activity was higher in the cold-dry than the hot-dry season. This finding may be useful in the management, improvement of productivity, and welfare of working donkeys under different thermal environmental conditions.