WINTER CIRCADIAN ACTIVITY PATTERN OF FREE-RANGING COYPUS IN THE PARANA RIVER DELTA, EASTERN ARGENTINA

During August 1990, 3 male and 3 female coypus Myocastor coypus (Molin a, 1782) were radiotracked for 42 24-h periods at the Delta of Parana River, Argentina. Coypus were mainly nocturnal, with activity peaks ar ound one hour after sunset and two hours before sunrise. Movement rate peaked between 02.00 and 04.00 o'clock. This pattern is similar to th at observed in captive individuals and introduced feral populations. A mong 7 environmental factors (day period, temperature, wind, cloud cov er, and presence or absence of moon, fog, and rain) only period of day and rainfall during daylight were found significantly related to coyp u activity, but no environmental factor influenced coypu nocturnal rat e of movement.