Abstract:
We investigated locomotor activity rhythms in the little-studied wild-caught
eastern rock sengi (Elephantulus myurus) from Goro Game Reserve, Limpopo
Province, South Africa. To assess whether locomotor activity is endogenously
entrained by the light–dark cycle, animals (n = 13) were subjected to three different
light-cycle regimes: a 12 h light/12 h darkness (LD) cycle, a total darkness (DD)
cycle and an inverse of the LD cycle (DL). Ten animals exhibited strong light
entrainment under LD1 with the total percentage of activity during the light phase
(56.5% 11.9%) significantly higher than during the dark phase (43.5% 11.9%).
Eleven animals expressed distinct endogenous free-running rhythms under DD
(mean t = 23.6 h 0.6 h; range: 22.9 h–24.5 h), with significant inter-individual
variation. Under DL, the total percentage of activity was approximately equal
during the light (50.4% 7.8%) and dark phase (49.6% 7.8%). E. myurus was on
average active 25% of the 24-h day with a nocturnal–diurnal ratio of 0.8 under
LD1 and exhibited locomotor activity under controlled conditions similar to that
of closely related species in the wild. In 62% of the animals, activity was highest
around dawn, lowest during the afternoon and intermittently expressed throughout
the night. Little quantitative data are available on the daily locomotor activity
rhythms of sengis particularly in response to the light–dark cycle. This study
provides valuable quantitative data on locomotor activity rhythms in E. myurus.
