| Abstract: | The activity patterns of two closely related echimyid rodents (spiny rats) of the Brazilian Caatinga were studied. One species, Proechimys Trinomys] yonenagae , is a fossorial dweller of fixed sand dunes. P. T.] albispinus , inhabits remnants of the Atlantic rainforest areas. A third species, Trichomys apereoides , collected in granite formations in the Caatinga was also studied. The animals were kept individually in cages under controlled conditions and light-dark cycle of 12:12 h. Data were collect by Scan sampling every 2 h, over 3 days, and were analyzed by Cosinor method. All species were nocturnal. P. yonenagae showed a regular pattern of circadian activity and restricted its activity to subjective night. P. albispinus showed an intermittent pattern of activity, especially in the dark phase. T. apereoides showed a bimodal pattern with high crepuscular peaks of activity. A high level of synchrony was found in the activity among individual P. yonenagae . No sex differences were found in behavioral patterns of either P. yonenagae or P. albispinus . Since the two species of Proechimys share a common ancestor, the differences that were found stress the importance of external selection over circadian rhythmicity. |
