Deborah J. Curtis

Cathemerality in the mongoose lemur, Eulemur mongoz

Results of a 10 month study of the mongoose lemur (Eulemur mongoz) at Anjamena are presented. The activity pattern is documented in detail for both wet and dry seasons based on observations conducted over the entire 24 h period. E. Mongoz was found to be cathemeral throughout the year but exhibited shifts towards more diurnal activity in the wet season and more nocturnal activity in the dry season. The cathemeral activity pattern in the mongoose lemur appears to be coordinated with sunrise, sunset, and day length and modulated by an inhibitory effect of low nocturnal light intensity in the forest during the wet season, resulting in mainly diurnal activity. Temperature and rainfall may also influence the activity pattern. Few advantages to food‐related behavior appear to derive from this activity pattern, although resource accessibility may be enhanced by nocturnal behavior in the dry season, leading to reduction in interspecific competition. Cathemerality may also represent a behavioral thermoregulatory mechanism allowing the mongoose lemur to conserve energy by being active during the cool nights of the dry season. In addition, nocturnal behavior in the dry season probably allows avoidance of predation by raptors at the time of year when least protection is afforded by vegetation. Am. J. Primatol. 47:279–298, 1999.

Group size, home range use, and seasonal variation in the ecology of Eulemur mongoz

We collected data during a 10-month study carried out on the mongoose lemur, Eulemur mongoz, at Anjamena in northwestern Madagascar, which provide baseline information on seasonal variation in the ecology, home range use and some aspects of the behavior of two neighboring groups. We monitored group size of nine groups in the study area and assessed them for seasonal variation. We present additional information collected during short-term surveys in other areas before and during the study for comparison. The study groups were small family units, and changes in group size were limited to births and emigrations of sexually mature progeny. In spite of clear seasonal changes in climate and vegetation, there is no variation in grouping patterns, so it is not possible to correlate variation in group size with seasonal variation of ecological variables. Comparison with ecological data from other field studies on lemurids reveals differences in food resource distribution in western forests versus other types of Malagasy forest. This distribution of food resources may predict home range size in mixed frugivorous–folivorous lemurs. Small home ranges, mainly in the West, could be correlated with a uniform distribution of food resources. Finally, we suggest that the dry season in the West may not present frugivorous–folivorous lemurs with major problems in finding an adequate food supply. This is supported by the lack of seasonal differences in ranging behavior of mongoose lemurs.

Non-invasive monitoring of reproductive status in wild mongoose lemurs (Eulemur mongoz)

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.

Positional Behaviour in Captive Aye-Ayes (Daubentonia madagascariensis)

The aye-aye shows numerous special features in its postcranial skeleton, partly in association with its unusual feeding habits and partly in association with locomotor specialisation connected with the possession of claws. This study examined the positional behaviour of 3 captive adult aye-ayes in order to throw light on these morphological specialisations. Locomotion was dominated by quadrupedal walking and climbing. Given the relatively large body size of aye-ayes, an unexpectedly high frequency of head-first descent was observed. This may provide an explanation for two characteristics of aye-ayes: robusticity of the shoulder girdle and high compressive and bending strengths of the humerus. Agile leaping was also observed, contrasting with previous reports that this species is characterised by slow, cautious movement. Specific morphological features that are shared with slow-moving lorisids may be attributable to a combination of frequent head-first descent and postural suspension.

Field and Laboratory Methods in Primatology: Tips from the bush: an A-Z of suggestions for successful fieldwork

SIMON K . BEARDER 1 , K . A . I . NEKARIS 1 , DEBORAH J . CURTIS 2 , J . LAWRENCE DEW 3 , JUL IA N. LLOYD 1 AND JOANNA M. SETCHELL 2 1Nocturnal Primate Research Group, Department of Anthropology, School of Social Sciences and Law, Oxford-Brookes University, Oxford, UK 2Centre for Research in Evolutionary Anthropology School of Life and Sport Sciences, University of Surrey Roehampton, London, UK 3Department of Anthropology, University of California, Davis, California, USA