**3. Conclusions**

The caution implied in our title refers to the danger of not considering a study species' natural behaviour and the ecological conditions under which it evolved when designing experimental procedures under often highly artificial laboratory conditions and in interpreting the results obtained from these within highly reductionist frameworks. In the present case of the rabbit's unusual daily pattern of nursing, this has arguably involved jumping too quickly to assume that this and associated patterns of behaviour and physiological and neural functions, including in the young, to have a circadian basis, and then investing considerable time and money to explore underlying physiological, neural and molecular mechanisms based on these possibly erroneous assumptions. At times, it has also involved an important confusion in the use of terminology between circadian and diurnal processes in article titles and abstracts, and thus in the interpretation of results. If our above historical analysis of the case of the rabbit's nursing rhythm is correct, it raises the question that in how many other models of "circadian" function, including in humans, might such bias also be the case? In mammalian studies, and in contrast to studies in invertebrates, the adaptive advantages of flexible hourglass processes, set to start and stop by immediate environmental events, have been little considered in contrast to the benefits but also costs of the inertia, the lag in adjustment, of circadian processes (review in [62]). Speculatively, in the human case, one can think of the ease (and pleasure) with which many of us transition from workday routines to often very different weekend or holiday schedules. And to complicate things, since we are dealing with the regulation of biological functions in complex organisms leading complex lives, perhaps we need to consider that diurnal functions may be regulated by a combination of circadian and hourglass processes working in tandem?

*Circadian Synchrony between Mothers and Young in the European Rabbit: Or Not? A Cautionary… DOI: http://dx.doi.org/10.5772/intechopen.101922*
