Highly specialized fossorial mammals, such as moles, may be important to understand the role of light as a zeitgeber of rhythms, both for the limited exposure to light and the regression of some of the structures apt to perceive it. Moreover, entrainment of circadian rhythms in subterranean animals is a particularly interesting task, as other environmental cues in addition to light could play an important role in the synchronization of organisms with the external periodic cycles. The search for an endogenous circadian rhythm of rest and activity has to be run in controlled conditions. However, it relies on a good knowledge of activity patterns in natural conditions. Here we describe two different approaches and techniques for investigating mole activity rhythms in the lab and in the field.

During lab studies moles must be housed in separate cages. Each cage consists of a nest box, a food box and a vertical box with plexiglass walls and earth inside. Different parts of the cage are connected with net or plain plastic runs. A program under MS-DOS written in JPI Modula-2 has been developed to monitor mole activity. The program interfaces to a hardware system which uses infrared (IR) barriers placed in couples along the paths and contact microphones which detect sounds coming from the soil in the mole cage. Both IR barriers and microphones outputs come to a microcontroller operated interface where signals are digitally converted and sent to the personal computer in the form of serial codes. The program continuously checks data from the serial RS-232 port and generates four files (one for each cage monitored) with raw data of IR barriers and microphones activation along with exact times of events generated. Sequential activation of IR barriers allows us to define movement direction and animal location. Activity state is determined by information coming both from location data and microphones activation. If a LED malfunctions this is reported by the program. This simple structure allows recording of rest/activity patterns of lab animals without the use of invasive techniques, can be run in dark conditions and with complicate settings.

Field studies on activity patterns of fossorial insectivores are limited by the impossibility of direct observations, absence of a distinct neck for radio-collars, lack of adequate implantable micro-transmitters and of anaesthetic protocols. Moreover radio-tracking techniques often require exhausting schedules that cannot be protracted continuously for more than a few days, while a rigorous study on activity rhythms requires data logging over an extended period of time. We tested different kinds of implantable micro-transmitters and we used automatic recording of field data by means of an event recorder connected to a receiver positioned over mole nests. Preliminary results are briefly discussed.