Face to face with the woolly spider monkey. Review of faces in the forest: The Endangered Muriqui Monkeys of Brazil,by Karen B. Strier. New York,Oxford University Press,Inc., 1992, 138 pp, $49.50

During an intertroop encounter, an infanticide was observed in a population of ringtailed lemurs (Lemur catta) at Berenty Reserve, Madagascar. The killer was a male that had not been previously observed to mate with any females in the infant's troop. This observation, combined with other observations of infanticidal behavior by males at Berenty Reserve and the Duke University Primate Center, is consistent with the hypothesis that infanticide is a reproductive tactic for some male ringtailed lemurs. © 1994 Wiley-Liss, Inc.     

Lemur catta in small forest fragments: Which variables best predict population viability?

Habitat fragmentation is an increasingly serious issue affecting primates in most regions where they are found today. Populations of Lemur catta (ring-tailed lemur) in Madagascar's south-central region are increasingly restricted to small, isolated forest fragments, surrounded by grasslands or small-scale agriculture. Our aim was to evaluate the potential for population viability of L. catta in nine forest fragments of varying sizes (2–46 ha, population range: 6–210 animals) in south-central Madagascar, using a set of comparative, quantitative ecological measures. We used Poisson regression models with a log link function to examine the effects of fragment size, within-fragment food availability, and abundance of matrix resources (food and water sources) on L. catta population sizes and juvenile recruitment. We found a strong association between overall population size and (a) fragment size and (b) abundance of key food resources Melia azedarach and Ficus spp. (per 100 m along transect lines). Juvenile recruitment was also associated with fragment size and abundance of the two above-mentioned food resources. When the largest population, an outlier, was removed from the analysis, again, the model containing fragment size and abundance of M. azedarach and Ficus spp. was the best fitting, but the model that best predicted juvenile recruitment contained only fragment size. While our results are useful for predicting population presence and possible persistence in these fragments, both the potential for male dispersal and the extent of human disturbance within most fragments play crucial roles regarding the likelihood of long-term L. catta survival. While seven of the nine fragments were reasonably protected from human disturbance, only three offered the strong potential for male dispersal, thus the long-term viability of many of these populations is highly uncertain.     

Correlates between locomotor anatomy and behavior in two sympatric of Lemur.

Sympatric populations of Lemur catta and Lemur fulvus show major differences in their occupation of canopy forest levels. Lemur catta is usually found in the lowest levels of the forest, and uses the ground for travel over 65% of the time. Lemur fulvus uses the upper levels of the canopy forest and is observed on the ground in less than 2% of all observations. Comparison of hindlimb musculoskeletal anatomy show statistically significant differences in the lengths of the long bones and the height of the talus. Differences also occur in ranges of tibio-talar and mid-talar joint mobility. The details of insertion of the biceps femoris muscle are distinct in the two species as is the relative mass of muscle associated with flexion of the pedal digits, and flexion of th tibio-talar joint. The metric and morphological differences in the hindlimb anatomy of Lemur catta and Lemur fulvus are consistent with differences in habitat and substrate utilization.     

Optimal group size and seasonal stress in ring-tailed lemurs (Lemur catta)

Adaptive explanations for social grouping assume that thereare fitness consequences associated with group size, and individualsmaintain membership in groups of favorable size to maximizefitness. Here I examine fecal cortisol concentrations as a hormonalmeasure of stress to assess the relative well-being of Lemurcatta in groups of different size and in seasons of normal andlow tamarind fruit availability. I test the hypotheses thatthere is an optimal group size at which cortisol is lowest andthat optimal group size changes in food-scarce conditions. Icollected 799 fecal samples from 87 individuals in seven free-rangingL. catta groups at Berenty Reserve, Madagascar, over a 1-yearperiod (August 1999–July 2000) and determined fecal cortisolconcentrations using a radioimmunoassay. Expressing these asresiduals from monthly population means to control for temporalfluctuations in cortisol concentration, I calculated mean fecalcortisol levels for each animal in seasons of normal and lowtamarind fruit abundance and over the entire year. Overall,females exhibited lowest mean cortisol levels in groups of intermediatesize, suggesting that there are benefits to maintaining membershipin these groups. Females in groups that were atypically largeor small for their habitat type had higher mean cortisol levelsthan typical groups. Cortisol levels increased in food-scarceconditions for larger groups, suggesting that intergroup competitiveadvantages do not outweigh intragroup feeding competition atthis time. Group size may be optimized for long-term averageconditions, and short-term stresses may intermittently alterthe costs associated with group size.     

Beyond odor discrimination: demonstrating individual recognition by scent in Lemur catta

The current study demonstrates, for the first time, the occurrence of olfactory individual recognition in a nonhuman primate species. The empirical demonstration of recognition systems requires 1) a set of cues produced by the sender (expression component), 2) the perception of these cues by the receiver (perception component), and 3) a functional response by the receiver (action component). On the basis of this framework, we analyzed by gas chromatography 35 brachial secretions collected from 10 males of Lemur catta. Moreover, we performed habituation/discrimination tests to demonstrate the perception component, and we designed a specific bioassay, based on territorial competition, to highlight a functional response to individual odors. We demonstrated that recognition of conspecific odors goes beyond the perception of cues other than individuality (familiarity, kin, season, age, and rank) and that the receiver actually forms a mental representation of a specific individual by its scent.