Deborah J. Curtis

Non-primate mammalian activity cycles are highly variable across and within taxonomic groups. In contrast, the order Primates has historically been recognized as displaying a diurnal-nocturnal dichotomy that mapped, for the most part, onto the taxonomic division between haplorhines and strepsirhines. However, it has become clear over the past two decades that activity cycles in primates are not quite so clear cut. Some primate species – like many large herbivorous mammals, mustelids, microtine rodents, and shrews – exhibit activity both at night and during the day. This activity pattern is often polyphasic or ultradian (several short activity bouts per 24-hour period), in contrast to the generally monophasic pattern (one long bout of activity per 24-hour period) observed in diurnal and nocturnal mammals. Alternatively, it can vary on a seasonal basis, with nocturnal activity exhibited during one season, and diurnal activity during the other season. The term now generally employed to describe the exploitation of both diurnal and nocturnal phases in primates is ‘cathemeral’. Cathemerality has been documented in one haplorhine, the owl monkey,Aotus azarai, in the Paraguayan and Argentinian Chaco and in several Malagasy strepsirhines, includingEulemurspp.,Hapalemursp. andLemur catta.In this paper, we review patterns of day-night activity in primates and other mammals and investigate the potential ecological and physiological bases underlying such 24-hour activity. Secondly, we will consider the role of cathemerality in primate evolution.

Data collected on the feeding behavior, food intake, and chemical analyses of plant foods were used to document seasonal variation in diet and nutrition in Eulemur mongoz in northwestern Madagascar. E. mongoz conforms to the general Eulemur dietary pattern, with a predominantly frugivorous diet supplemented mainly by leaves, flowers, and nectar. Phytochemical analysis revealed high water contents in all the main plant foods; mature fruit and flowers contained the most water‐soluble carbohydrates; immature leaves were richest in protein and essential amino acids; the limiting amino acids in all plant foods were methionine and cystine; ash (mineral) content was highest in petioles and mature leaves; crude lipid content was highest in seeds; and crude fiber content was indistinguishable between immature and mature fruit and leaves. High‐fiber foods were eaten during both seasons; the wet season diet was dominated by high‐energy foods (mature fruit, nectar, and seeds), while the dry season diet contained foods high in energy (mature fruit and flowers) and high in protein (immature leaves) and minerals (mature leaves and petioles). However, nutrient intake did not vary between seasons, implying that nutrient requirements are met throughout the year. These results suggest we draw more conservative conclusions when interpreting dietary variability in the absence of chemical analysis, and also draw into question the idea that nutritional stress is a factor in the timing of reproduction in lemurs and, by extension, is linked to the prevalence of female dominance and small group size in lemurs. Am J Phys Anthropol, 2003.

Endocrine profiles were investigated in wild and captive mongoose lemurs ( Eulemur mongoz ; Lemuridae) by analysing faecal progestagens and oestrogens. Oestrous cycle characterization was not possible, as most females appeared to conceive during the first oestrus of the breeding season. Conception was preceded by a pseudo-oestrus with no discernible luteal phase. Pseudo-oestrus and oestrus identification was possible by investigating the oestrogen : progestagen ratio. Pregnancy was reliably determined approximately 47 days after conception, when progestagen and oestrogen excretion increased above breeding season concentrations. Gestation was further characterized by high progestagen concentrations and a decline in oestrogen excretion 70–80 days after conception. Post partum, progestagens declined, but oestrogen excretion increased to exceed breeding season concentrations. In the wild group, a nulliparous daughter conceived while still a member of her natal group and aborted after 70–80 days of pregnancy at which time progestagens had declined but oestrogens remained high. Comparisons with other strepsirhine primates suggest that pseudo-oestrus followed by conception at first oestrus may be prevalent in lemurs. Gestational progesterone profiles vary between species, but a delayed increase in oestrogens during pregnancy could be common to all strepsirhines, although oestrogen levels during the final trimester of pregnancy differ between lemurs and lorises. Methodological investigations showed that prolonged storage of faeces in ethanol is viable and that the presence of undigested vegetable matter in the faecal pellets had no effect on the interpretation of hormone profiles.