Why be diurnal? Or, why not be cathemeral?

摘要: As a behavioural strategy, cathemerality is thought to confer considerable advantages by allowing animals extend activity flexibly into either the diurnal or nocturnal phase in response prevailing ecological conditions. Factors such as temperature, access food sources and minimising risk of predation are all be important promoting cathemerality, although previous studies have produced inconsistent results. This paper adopts different approach first asking whether an obligate species, chacma baboon (Papio hamadryas ursinus), exhibits seasonal variation flexibility annual cycles day length. While short lengths constraint on baboons at De Hoop Nature Reserve, South Africa, long summer days permit thermoregulatory response, diet selection patterns habitat choice. Given that adapt relaxation time constraints, question thus arises why primates do not adopt cathemeral when constrained? For baboons, costs appear prohibit exploitation it likely constraints true most primates. It follows Madagascar's predatory environment must some way select for lifestyle. The importance fossa (Cryptoprocta ferox) evolution discussed.