Seasonality of daily surface activity patterns in a subterranean rodent, the tuco-tuco

Author(s)

Milene Gomes Jannetti

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2018-10-11

Examining board members

Gisele Akemi Oda; Silvia Cristina Ribeiro de Souza

• Advisor: Gisele Akemi Oda; Verônica Sandra Valentinuzzi

Abstract

Biological rhythms and their synchronization by environmental cycles are generally studied in rodents, inside laboratory. Our group studies activity/rest rhythms of South American subterranean rodents known as tuco-tucos (Ctenomys aff. knighti), in laboratory and field. In nature, it is known that tuco-tucos emerge daily to the surface, in brief episodes. Short records of tuco-tucos\' individual surface activity, previously collected by our group, had suggested that daily temporal pattern of emergence varied seasonally, being crepuscular in summer and concentrated around midday in winter. The same seasonal pattern was observed in populations of other desert rodents and was attributed to daily variations of environmental temperature, in summer and winter. At the same time, seasonality of activity patterns of various species of mammals and birds can be explained by daily synchronization of the activity rhythm by different photoperiods. Our aim is to characterize seasonal variation of daily activity rhythms of tuco-tucos, using bio-logging, and to verify the contribution of environmental factors in the seasonality of these patterns. Throughout the year, accelerometers and luximeters were tied to 29 freshly caught animals (15 females and 14 males). Each animal was kept inside semi natural enclosures for one month. Environmental variables were recorded simultaneously. Other 18 animals (9 females and 9 males) were kept inside laboratory, exposed to natural photoperiod, in a room with constant temperature. We confirmed the seasonality of temporal pattern of surface activity of tuco-tucos. The accelerometers resulted to be more precise and sensitive to small body movements than telemetry records found in literature. They also revealed nocturnal and subterranean activity patterns inside the enclosures. During summer, daily surface activity of tuco-tucos was better predicted by time of day (endogenous factor) than by environmental temperature (exogenous factor). During winter season, however, environmental temperature has a stronger contribution on the emergence pattern in tuco-tucos, indicating complex contributions of endogenous and exogenous factors that outline activity patterns (AU)

• FAPESP's process: 16/25058-0 - Seasonality of daily surface activity patterns on a subterranean rodent, the tuco-tuco
• Grantee: Milene Gomes Jannetti
• Support Opportunities: Scholarships in Brazil - Master