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Durham University

Department of Anthropology


Publication details for Professor Russell Hill

Hill, R.A., Barrett L., Gaynor D., Weingrill T., Dixon P., Payne H. & Henzi S.P. (2003). Day length, latitude and behavioural (in)flexibility in baboons (Papio cynocephalus ursinus). Behavioral Ecology and Sociobiology 53(5): 278-286.

Author(s) from Durham


Annual cycles in day length are an important
consideration in any analysis of seasonal behaviour
patterns, since they determine the period within which
obligate diurnal or nocturnal animals must conduct all of
their essential activities. As a consequence, seasonal
variation in day length may represent an ecological
constraint on behaviour, since short winter days restrict
the length of the time available for foraging in diurnal
species (with long summer days, and thus short nights, a
potential constraint for nocturnal species). This paper
examines monthly variation in activity patterns over a 4-
year study of chacma baboons (Papio cynocephalus
ursinus) at De Hoop Nature Reserve, South Africa. Time
spent feeding, moving, grooming and resting are all
significant positive functions of day length, even before
chance events such as disease epidemics and climatically
mediated home range shifts have been accounted for.
These results provide strong support for the idea that day
length acts as an ecological constraint by limiting the
number of daylight hours and thus restricting the active
period at certain times of year. Day length variation also
has important implications across populations. Interpopulation
variation in resting time, and non-foraging activity
in general, is a positive function of latitude, with long
summer days at temperate latitudes apparently producing
an excess of time that cannot profitably be devoted to
additional foraging or social activity. However, it is the
short winter days that are probably of greatest importance,
since diurnal animals must still fulfil their foraging
requirements despite the restricted number of daylight
hours and elevated thermoregulatory requirements at this
time of year. Ultimately this serves to restrict the
maximum ecologically tolerable group sizes of baboon
populations with increasing distance from the equator.
Seasonal variation in day length is thus an important
ecological constraint on animal behaviour that has
important implications both within and between populations,
and future studies at non-equatorial latitudes must
clearly be mindful of its importance.