Logically, therefore, behaviour timing should be recorded relative to these events. Yet, in the field, recording the timing of behaviour is much less difficult with a clock, which is often deemed a suitable common proxy. In this paper, we assess the potential methodological problems associated with analyzing behaviours on the basis of clock time rather than with the actual position of the sun. To demonstrate the important difference between these methods of analysis, we first simulated a behaviour set at sunrise and compared the time of occurrence with the two methods. We then used a dataset, based on a long-term

monitoring of hunting behaviour of African wild dogs, Lycaon pictus, to BMS-777607 chemical structure reveal how using clock

time can result in erroneous assumptions about behaviour. Finally, we investigated the occurrence of sun time www.selleckchem.com/products/poziotinib-hm781-36b.html records in published field studies. As a majority of them did not take into account the relevance of astronomical events, it is probable that many result in faulty behavioural timings. The model presented can change clock-recorded time into actual deviation from astronomical events to assist current protocols as well as correct the already recorded datasets. Daily events are classically positioned in time with a clock on a 24-h period. The sun’s position in the celestial sphere, recorded at the same ‘time of day’ (hereafter referred to as ‘clock time’), changes on successive days throughout the year. These differences are due to the earth’s tilt on its axis (23.5°) and Tolmetin its elliptical orbit around the sun.

This change is plotted on what is known as an analemma. Many studies of diel activities highlight the importance of the moment of the day in regulating animals’ daily behavioural cycles (Aschoff, 1966; Daan & Aschoff, 1974; Boulos, Macchi & Terman, 1996; Semenov, Ramousse & Le Berre, 2000; Metcalfe & Steele, 2001). Numerous animal activities are likely to be a function of either light intensity or ambient temperature and thus of the sun’s position in the sky: time of sunrise, zenith or sunset, or more generally ‘sun time’ rather than ‘clock time’. Lunar events are also of biological importance. The ‘clock time’ of sunrises (zenith or sunsets, hereafter referred to as ‘sun time’) differs according to the latitude, longitude and date of the year. Consequently, observations of behaviours lasting months should take into account the variation of daylight length. In fact, patterns of behaviour may appear to differ if analyzed by clock time rather than by the deviation from sun time. Moreover, the tilt of the earth on its axis generates a difference in annual variation of sun time according to latitude. Consequently, the difference between clock time and sun time will be greater at high latitudes. Although the difference between clock time and sun time is known, clock time is much easier to record when logging behaviours in the field.