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.

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.

Social structure and seasonal variation in the behaviour of Eulemur mongoz.

Data presented here were collected during a 10-month study carried out on the mongoose lemur, Eulemur mongoz, at Anjamena in northwestern Madagascar. Baseline information is provided on behaviour and assessed for seasonal variation. Given the highly seasonal nature of the environment, remarkably little behavioural variation was observed. This may be directly linked to the cathemeral activity pattern, where differential movement into either the diurnal or the nocturnal 'niche' could reduce the effect of selective seasonal pressures, thus reducing behavioural and ecological adaptation to seasonal variation. The behavioural mechanisms of reinforcement of the pair bond through close proximity, mutual anogenital marking, paternal participation in the care of offspring and territoriality are all in accord with the general characteristics of monogamy in primates. The feature of mate monopolization by males, proposed as typical of monogamous social systems, seems to be more attributable to females in E. mongoz, as only they exhibit high levels of intrasexual aggression. Female dominance, characteristic of most species of lemur, may thus include more than just female feeding priority in E. mongoz.