Anthropogenic activities are negatively affecting the flora and fauna of Madagascar, including its Endangered flagship lemur species, the ring-tailed lemur Lemur catta. Population numbers at some sites are rapidly declining, yet much of the species' habitat is insufficiently surveyed. Because widespread population assessments are critical to guiding conservation management strategies, additional data are needed to monitor L. catta population trends and to identify the limits of their geographical range. Here we report survey results confirming the presence of this species at 65 of 83 sites in southern and south-western Madagascar, including three subpopulations that were previously considered likely to be locally extinct. We identified a minimum of 792 L. catta individuals (summing only maximum group sizes at each site) and as many as 1,221 individuals (using estimated population counts). These findings help refine the distribution of L. catta and reaffirm their presence in areas of their historical geographical range. Identifying species occupancy at sites such as these provides valuable data to support species conservation, but also highlights the need for additional surveys throughout the range of the species.

Monozygotic (MZ) twinning is generally considered to be rare in species other than human. We inspected sex ratios in European zoo-bred ring-tailed lemurs (Lemur catta), revealing a significant excess of same-sex twins. Of 94 pairs, 60 (64%) were either both males or both females (p = .004). Application of the Weinberg differential rule argues that 27% of all twins in this species are MZ pairs. In this protected species, where twinning is commonplace (~50% of newborns are twins), the probable existence of frequent MZ twinning has ramifications for breeding programs aimed to maximize genetic diversity, and suggests that twin studies in a species other than human could have potential as a medical research tool.

Substrate reaction forces (SRFs) were quantified for 502 forelimb and hindlimb contacts in two primate species, Eulemur fulvus and Lemur catta. Three individuals of each taxon were encouraged to traverse a force transducer. Reaction forces were evaluated for linear locomotion on runway and simulated arboreal substrates. Preferred gaits differed between substrates: galloping on the runway and walking on simulated arboreal substrates. Unlike vertical and fore–aft (FA) forces, mediolateral (ML) forces during linear locomotion were relatively independent of speed, which suggests balancing the centre of body mass in the coronal plane was not speed related. Since peak ML forces occasionally exceeded peak FA forces, ML forces were not of trivial importance during primate quadrupedal locomotion. Both lemurids regularly experienced lower ML peak forces during ‘arboreal’ than ‘terrestrial’ quadrupedalism, probably to minimize side-to-side fluctuations of their centre of mass over the simulated arboreal branch supports. Eulemur fulvus encountered greater ML peak forces in their forelimbs, while L. catta encountered greater hindlimb peak ML forces. Lemurids most frequently exerted medially directed peak side-to-side forces during arboreal quadrupedalism and laterally directed peak side-to-side forces during terrestrial quadrupedalism. The direction of hindlimb ML peak force, however, was less consistent than forelimb ML peak force regardless of substrate. The lemurs experienced oscillations in the direction of the forelimb and hindlimb ML force over the duration of support phase, suggesting that both pairs of limbs contributed to balance. More frequent changes in ML force direction of the hindlimb support the predominance of these limbs in keeping side-to-side balance. The results of our study suggest that ML forces warrant consideration in locomotion studies, especially when evaluating joint moments and bending regimes of long bones.

A recent survey of the high-mountain zone of the Madagascar Parc National (PN) d'Andringitra revealed the presence of an apparently isolated troop of the ring-tailed lemur Lemur catta. These animals display phenotypic and ecological characteristics that are unusual for the monotypic genus Lemur, thus raising the possibility that they are members of a different undescribed species. We present analyses of two mitochondrial genes to test the hypothesis that L. catta from Andringitra should be considered a distinct species. The results indicate that taxonomic revision is not warranted under the expectations of the phylogenetic, coalescent, or biological species concepts. Rather, the genetic patterns observed among the Andringitra and lowland mitochondrial haplotypes are consistent with those expected for a single species.