Activity budget and seasonal activity shifts in sympatric lemurs: Increased lean season effort in a cathemeral frugivore contrasts with energy conservation in a diurnal folivore.

One of the most fundamental aspects of a species' behavioral strategy is its activity budget; for primates this generally involves the allocation of available time among resting, feeding, traveling, and social behavior. Comparisons between species, populations, or individuals can reveal divergences in adaptive strategies and current stressors, and reflect responses to such diverse pressures as predation, thermoregulation, nutrition, and social needs. Further, variation across seasons is an important part of behavioral strategies to survive food scarcity; this can involve increasing or decreasing effort. We documented activity over the 24-h cycle for the cathemeral, frugivorous Eulemur fulvus and the diurnal, folivorous Propithecus diadema across 13-18 months at Tsinjoarivo, Madagascar. Their activity budgets were dominated by resting (E. fulvus: 74.1%; P. diadema: 85.2%), followed by feeding (15.8%, 12.4%), traveling (9.31%, 1.74%) and social activities (0.76%, 0.70%), respectively. The lower feeding and higher resting in P. diadema likely reflect slower gastrointestinal transit and higher reliance on microbial fermentation to extract energy from fibrous food. The two species showed opposite lean season strategies. E. fulvus increased activity, with more feeding but less travel time, consistent with a shift to less-profitable fruits, and some leaves and flowers, while increasing feeding effort to compensate ("energy maximizing"). P. diadema showed less variation across months, but the lean season still evoked reduced effort across the board (feeding, travel, and social behavior), consistent with a "time minimizing" strategy prioritizing energy conservation and microbe-assisted digestion. Understanding these divergent shifts is key to understanding natural behavior and the extent of behavioral flexibility under stressful conditions. Finally, the complex patterns of fruit availability (intra- and interannually) and the species' behavioral responses across months underscore the need to move beyond simplistic "lean/abundant season" and "fruit/leaf" dichotomies in understanding underlying energetic strategies, and species' vulnerability to habitat change.

Lateralization in seven lemur species when presented with a novel cognitive task.

OBJECTIVES: Asymmetrical behavior patterns are observed in many animal species, but the potential adaptive significance of lateralization and the evolutionary forces driving it remain unclear. Most laterality studies have focused on a single species, which makes interspecies comparisons difficult. The aim of this study was to examine differences in the strength and direction of lateralization in multiple lemur species when engaged in a standardized, novel cognitive task. MATERIALS AND METHODS: We assessed laterality in seven lemur species at the Duke Lemur Center when using a novel puzzle-box. We recorded which hand opened the apparatus door and which hand picked up the food reward. We also recorded whether the mouth was used for either action instead of the hands. We then calculated handedness indices (HI), z-scores, and mouth-use rates. RESULTS: Overall, 62% of individuals were more lateralized than chance. However, within-genera, there were relatively equal numbers of individuals with a left- or right-hand bias, which resulted in ambipreference at the genus level. The hand a lemur used on its first success in the task predicted its overall HI value, and the strength of lateralization increased as the number of successes increased. Varecia had significantly higher mouth-use rates than all other genera. DISCUSSION: We found evidence of an individual learning trajectory in which the hand used on a lemur's first success was canalized as the preferred (and lateralized) hand, in support of the "cognitive simplicity" hypothesis. Individual variability in hand preference was high, which is consistent with previous research. Between-genera differences in mouth use appear to reflect species-specific feeding postures and differences in manual dexterity.

Life in a fragment: Evolution of foraging strategies of translocated collared brown lemurs, Eulemur collaris, over an 18-year period.

While the drivers of primate persistence in forest fragments have been often considered at the population level, the strategies to persist in these habitats have been little investigated at the individual or group level. Considering the rapid variation of fragment characteristics over time, longitudinal data on primates living in fragmented habitats are necessary to understand the key elements for their persistence. Since translocated animals have to cope with unfamiliar areas and face unknown fluctuations in food abundance, they offer the opportunity to study the factors contributing to successful migration between fragments. Here, we illustrated the evolution of the foraging strategies of translocated collared brown lemurs (Eulemur collaris) over an 18-year period in the Mandena Conservation Zone, south-east Madagascar. Our aim was to explore the ability of these frugivorous lemurs to adjust to recently colonized fragmented forests. Although the lemurs remained mainly frugivorous throughout the study period, over the years we identified a reduction in the consumption of leaves and exotic/pioneer plant species. These adjustments were expected in frugivorous primates living in a degraded area, but we hypothesize that they may also reflect the initial need to cope with an unfamiliar environment after the translocation. Since fragmentation is often associated with the loss of large trees and native vegetation, we suggest that the availability of exotic and/or pioneer plant species can provide an easy-to-access, nonseasonal food resource and be a key factor for persistence during the initial stage of the recolonization.

Determining Mhc-DRB profiles in wild populations of three congeneric true lemur species by noninvasive methods.

The major histocompatibility complex (MHC) is a highly polymorphic and polygenic genomic region that plays a crucial role in immune-related diseases. Given the need for comparative studies on the variability of immunologically important genes among wild populations and species, we investigated the allelic variation of MHC class II DRB among three congeneric true lemur species: the red-fronted lemur (Eulemur rufifrons), red-bellied lemur (Eulemur rubriventer), and black lemur (Eulemur macaco). We noninvasively collected hair and faecal samples from these species across different regions in Madagascar. We assessed DRB exon 2 polymorphism with a newly developed primer set, amplifying nearly all non-synonymous codons of the antigen-binding sites. We defined 26 DRB alleles from 45 individuals (17 alleles from E. rufifrons (N = 18); 5 from E. rubriventer (N = 7); and 4 from E. macaco (N = 20). All detected alleles are novel and show high levels of nucleotide (26.8%) and non-synonymous codon polymorphism (39.4%). In these lemur species, we found neither evidence of a duplication of DRB genes nor a sharing of alleles among sympatric groups or allopatric populations of the same species. The non-sharing of alleles may be the result of a geographical separation over a long time span and/or different pathogen selection pressures. We found dN/dS rates > 1 in the functionally important antigen recognition sites, providing evidence for balancing selection. Especially for small and isolated populations, quantifying and monitoring DRB variation are recommended to establish successful conservation plans that mitigate the possible loss of immunogenetic diversity in lemurs.

Local habitat, not phylogenetic relatedness, predicts gut microbiota better within folivorous than frugivorous lemur lineages.

Both host phylogenetic placement and feeding strategy influence the structure of the gut microbiome (GMB); however, parsing their relative contributions presents a challenge. To meet this challenge, we compared GMB structure in two genera of lemurs characterized by different dietary specializations, the frugivorous brown lemurs ( Eulemur spp.) and the folivorous sifakas ( Propithecus spp.). These genera sympatrically occupy similar habitats (dry forests and rainforests) and diverged over similar evolutionary timescales. We collected fresh faeces from 12 species (six per host genus), at seven sites across Madagascar, and sequenced the 16S rRNA gene to determine GMB membership, diversity and variability. The lemurs' GMBs clustered predominantly by host genus; nevertheless, within genera, host relatedness did not predict GMB distance between species. The GMBs of brown lemurs had greater evenness and diversity, but were more homogeneous across species, whereas the GMBs of sifakas were differentiated between habitats. Thus, over relatively shallow timescales, environmental factors can override the influence of host phylogenetic placement on GMB phylogenetic composition. Moreover, feeding strategy can underlie the relative strength of host-microbiome coadaptation, with Madagascar's folivores perhaps requiring locally adapted GMBs to facilitate their highly specialized diets.

BIOMEDICAL EVALUATION OF A BROWN LEMUR (EULEMUR FULVUS SPP.) POPULATION FROM MBOUZI ISLET, MAYOTTE ISLAND.

The brown lemur population (Eulemur fulvus spp.) in Mbouzi islet is not native, and was introduced in 1997. Since then, the population has grown. In 2012 the National Council for Protection of Nature of Mayotte requested to remove this population of lemurs from Mbouzi, as they were suspected to be a threat to the protected endemic flora of the islet. The Association Francophone des Vétérinaires de Parcs Zoologiques (French-speaking Zoo Veterinarians Association, AFVPZ) was asked to conduct a biomedical evaluation of the population. Fifty-two animals were captured, anesthetized, and weighed. They all underwent a general physical examination. Feces were sampled for bacterial and parasitological screening. Hair was sampled for genetic studies and blood was sampled for hematology, biochemistry, viral serology, and haemoparasitology. Results showed that three individuals had a positive feces culture for Salmonella enterica and six had Lemuricola or Callistoura parasite infestations. Blood analyses for hematology and biochemistry showed 46 animals with elevated transferrin, 42 with low ferritin levels, 19 with hyperglycemia, and 10 with neutrophilia. Finally, 10 were positive for Toxoplasma serology, one was positive for α herpesvirus, five for pox virus, five for simian virus 40, and two for flavivirus. This publication reports the first complete biomedical evaluation of lemurs on Mayotte Island.

Anatomy, histology, and ultrasonography of the normal adrenal gland in brown lemur: Eulemur fulvus.

BACKGROUND: The medical care currently to brown lemurs (Eulemur fulvus) is limited by a lack of knowledge of their anatomy. The aim of this study was to describe the anatomy and histology and obtain ultrasonographic measurements of normal adrenal glands in these animals. METHODS: The adrenal glands of four lemurs cadavers were used for the anatomical and histological studies, and those of 15 anesthetized lemurs were examined by ultrasonography. RESULTS: Anatomically, the adrenal glands of brown lemurs are comparable to those of other species. The histological findings showed that the cortex is organized into three distinct layers, whereas most domestic mammals have an additional zone. The surface area of the adrenal glands increased with body weight, and the area of the right adrenal was slightly larger than the left. CONCLUSIONS: We suggest using ultrasonography to aid the etiological diagnosis of behavioral abnormalities that might be due to dysfunctions of the adrenal gland.

Stuck in fragments: Population genetics of the Endangered collared brown lemur Eulemur collaris in the Malagasy littoral forest.

OBJECTIVES: The Endangered collared brown lemur (Eulemur collaris) is the largest primate living in the littoral forest of southeastern Madagascar, a top priority habitat for biodiversity conservation on the island. Because this lemur is a key seed-disperser, an evaluation of the structure and connectivity of the populations surviving in the forest fragments is urgently needed to guide conservation plans. MATERIALS AND METHODS: Genetic variability at autosomal microsatellites and mitochondrial DNA was investigated in a total of 49 collared brown lemurs sampled by non-invasive methods in three littoral forest fragments and in the nearby lowland humid forest. RESULTS: The overall genetic diversity of E. collaris in the southeastern coastal region of Madagascar was lower than in other populations, as well as in other lemur species. The population appears highly structured, with less variable and more inbred groups inhabiting the littoral forest fragments compared to the inland area. Major barriers to gene flow were identified isolating littoral forest fragments from each other and from the inland lowland humid forest. DISCUSSION: Medium to long-term drift and scarce gene flow is the scenario that best explains the current genetic distribution. Habitat discontinuities such as rivers and grassland between forest fragments played a major role in structuring the population. A common history of size contraction is pointed out by several genetic estimators, indicating a possible ecological crisis triggered around 1,300 years ago. The adoption of strategies aimed at facilitating gene flow and population growth appears crucial to delay further loss of genetic diversity.

The role of acoustic signals for species recognition in redfronted lemurs (Eulemur rufifrons).

BACKGROUND: Signals are essential for communication and play a fundamental role in the evolution and diversification of species. Olfactory, visual and acoustic species-specific signals have been shown to function for species recognition in non-human primates, but the relative contributions of selection for species recognition driven by sexual selection, natural selection, or genetic drift for the diversification of these signals remain largely unexplored. This study investigates the importance of acoustic signals for species recognition in redfronted lemurs (Eulemur rufifrons). We conducted playback experiments in both major populations of this species separated by several hundred kilometers: Kirindy Forest in the west and Ranomafana National Park in the east of Madagascar. The playback stimuli were composed of species-specific loud calls of E. rufifrons, three closely related species (E. albifrons, E. fulvus and E. rufus) and one genetically more distant species (E. rubriventer) that occurs in sympatry with eastern redfronted lemurs. We tested the ability of redfronted lemurs to discriminate conspecific from heterospecific loud calls by measuring the time spent looking towards the speaker after presentation of each loud call. We also tested the difference between female and male responses because loud calls may play a role in mate choice and the avoidance of heterospecific mating. RESULTS: Redfronted lemurs in Kirindy Forest did not discriminate their own loud calls from those of E. albifrons, E. fulvus and E. rufus, but they discriminated loud calls of E. rubriventer from their own. The Ranomafana population was tested only with three playback stimuli (E. rufifrons, E. albifrons, E. rubriventer) and did not discriminate between their own loud calls and those of E. albifrons and E. rubriventer. The response of females and males to playbacks did not differ in both populations. However, subjects in Ranomafana National Park responded more strongly to playback stimuli from E. rubriventer than subjects in Kirindy Forest. CONCLUSIONS: We conclude that in both populations individuals were not able to discriminate between loud calls of closely related species living in allopatry and that responses to more distantly related congeners are likely to be modulated by experience. Subjects in Ranomafana paid more attention to loud calls of syntopic E. rubriventer in comparison to the Kirindy subjects, suggesting that experience is important in facilitating discrimination. Because acoustic and genetic distances among eulemurs are correlated, diversification in their acoustic signals might be the result of genetic drift.

GASTROINTESTINAL PARASITES OF CAPTIVE AND FREE-LIVING LEMURS AND DOMESTIC CARNIVORES IN EASTERN MADAGASCAR.

Fecal samples from captive and free-living lemurs at Ivoloina Zoological Park (IZP) and domestic carnivores from six villages surrounding IZP were evaluated between July and August 2012. Free-living lemurs from Betampona Natural Reserve (BNR), a relatively pristine rainforest fragment 40 km away, were also evaluated in November 2013. All 33 dogs sampled (100%) and 16 of 22 cats sampled (72.7%) were parasitized, predominantly with nematodes (strongyles, ascarids, and spirurids) as well as cestodes and protozoans. Similar types of parasites were identified in the lemur populations. Identification of spirurid nematodes and protozoans in the lemur fecal samples were of concern due to previously documented morbidity and mortality in lemurs from these parasitic agents. Twelve of 13 free-living (93%) and 31 of 49 captive (63%) lemurs sampled at IZP had a higher parasite prevalence than lemurs at BNR, with 13 of 24 (54%) being parasitized. The lemurs in BNR are likely at risk of increased exposure to these parasites and, therefore, increased morbidity and mortality, as humans and their domestic animals are encroaching on this natural area.

Evolutionary history inferred from the de novo assembly of a nonmodel organism, the blue-eyed black lemur.

Lemurs, the living primates most distantly related to humans, demonstrate incredible diversity in behaviour, life history patterns and adaptive traits. Although many lemur species are endangered within their native Madagascar, there is no high-quality genome assembly from this taxon, limiting population and conservation genetic studies. One critically endangered lemur is the blue-eyed black lemur Eulemur flavifrons. This species is fixed for blue irises, a convergent trait that evolved at least four times in primates and was subject to positive selection in humans, where 5' regulatory variation of OCA2 explains most of the brown/blue eye colour differences. We built a de novo genome assembly for E. flavifrons, providing the most complete lemur genome to date, and a high confidence consensus sequence for close sister species E. macaco, the (brown-eyed) black lemur. From diversity and divergence patterns across the genomes, we estimated a recent split time of the two species (160 Kya) and temporal fluctuations in effective population sizes that accord with known environmental changes. By looking for regions of unusually low diversity, we identified potential signals of directional selection in E. flavifrons at MITF, a melanocyte development gene that regulates OCA2 and has previously been associated with variation in human iris colour, as well as at several other genes involved in melanin biosynthesis in mammals. Our study thus illustrates how whole-genome sequencing of a few individuals can illuminate the demographic and selection history of nonmodel species.

Transitive inference in two lemur species (Eulemur macaco and Eulemur fulvus).

When confronted with tasks involving reasoning instead of simple learning through trial and error, lemurs appeared to be less competent than simians. Our study aims to investigate lemurs' capability for transitive inference, a form of deductive reasoning in which the subject deduces logical conclusions from preliminary information. Transitive inference may have an adaptative function, especially in species living in large, complex social groups and is proposed to play a major role in rank estimation and establishment of dominance hierarchies. We proposed to test the capacities of reasoning using transitive inference in two species of lemurs, the brown lemur (Eulemur fulvus) and the black lemur (Eulemur macaco), both living in multimale-multifemale societies. For that purpose, we designed an original setup providing, for the first time in this kind of cognitive task, pictures of conspecifics' faces as stimuli. Subjects were trained to differentiate six photographs of unknown conspecifics named randomly from A to F to establish the order A > B > C > D > E > F and select consistently the highest-ranking photograph in five adjacent pairs AB, BC, CD, DE, and EF. Then lemurs were presented with the same adjacent pairs and three new and non-adjacent pairs BD, BE, CE. The results showed that all subjects correctly selected the highest-ranking photograph in every non-adjacent pair, reflecting lemurs' capacity for transitive inference. Our results are discussed in the context of the still debated current theories about the mechanisms underlying this specific capacity.

Clinal variation in a brown lemur (Eulemur spp.) hybrid zone: combining morphological, genetic and climatic data to examine stability.

Studies of hybrid zones can inform our understanding of reproductive isolation and speciation. Two species of brown lemur (Eulemur rufifrons and E. cinereiceps) form an apparently stable hybrid zone in the Andringitra region of southeastern Madagascar. The aim of this study was to identify factors that contribute to this stability. We sampled animals at 11 sites along a 90-km transect through the hybrid zone and examined variation in 26 microsatellites, the D-loop region of mitochondrial DNA, six pelage and nine morphological traits; we also included samples collected in more distant allopatric sites. Clines in these traits were noncoincident, and there was no increase in either inbreeding coefficients or linkage disequilibrium at the centre of the zone. These results could suggest that the hybrid zone is maintained by weak selection against hybrids, conforming to either the tension zone or geographical selection-gradient model. However, a closer examination of clines in pelage and microsatellites indicates that these clines are not sigmoid or stepped in shape but instead plateau at their centre. Sites within the hybrid zone also occur in a distinct habitat, characterized by greater seasonality in precipitation and lower seasonality in temperature. Together, these findings suggest that the hybrid zone may follow the bounded superiority model, with exogenous selection favouring hybrids within the transitional zone. These findings are noteworthy, as examples supporting the bounded superiority model are rare and may indicate a process of ecologically driven speciation without geographical isolation.

Spontaneous neoplasms in captive red-bellied lemurs (Eulemur rubriventer).

Red-bellied lemurs (Eulemur rubriventer: genus Eulemur, family Lemuridae, Suborder Strepsirrhini) are non-human primates endemic to the forests of Madagascar and listed as 'vulnerable' on the IUCN Red List of Threatened Species. Currently, descriptions of neoplasia in this species are extremely scarce, with only one case of hepatocellular adenoma reported. Prosimian submissions received by the Anatomic Pathology Service at North Carolina State University from January 2010 to January 2021 were retrieved. A total of 200 cases of Strepsirrhini prosimians were identified, representing 57 (28.5%) individuals from the genus Eulemur of which seven (12.3%) cases were red-bellied lemurs. Neoplasia was identified in two of the seven (28.57%) cases. The first case was a 25-year-old, intact female with hepatocellular carcinoma and the second a 33-year-old, intact female with a cervical mass consistent with osteoblastic osteosarcoma arising from the left clavicular bone. Hepatocellular neoplasms are commonly reported in prosimians, with carcinomas more frequent than adenomas. In contrast, osteosarcoma has been rarely described in lemuriformes, with four cases reported. To our knowledge, this is the first report of osteosarcoma and hepatocellular carcinoma in a red-bellied lemur.

A Pervasive History of Gene Flow in Madagascar's True Lemurs (Genus Eulemur).

In recent years, it has become widely accepted that interspecific gene flow is common across the Tree of Life. Questions remain about how species boundaries can be maintained in the face of high levels of gene flow and how phylogeneticists should account for reticulation in their analyses. The true lemurs of Madagascar (genus Eulemur, 12 species) provide a unique opportunity to explore these questions, as they form a recent radiation with at least five active hybrid zones. Here, we present new analyses of a mitochondrial dataset with hundreds of individuals in the genus Eulemur, as well as a nuclear dataset containing hundreds of genetic loci for a small number of individuals. Traditional coalescent-based phylogenetic analyses of both datasets reveal that not all recognized species are monophyletic. Using network-based approaches, we also find that a species tree containing between one and three ancient reticulations is supported by strong evidence. Together, these results suggest that hybridization has been a prominent feature of the genus Eulemur in both the past and present. We also recommend that greater taxonomic attention should be paid to this group so that geographic boundaries and conservation priorities can be better established.

Taenia martis in a white-headed lemur (Eulemur albifrons) from a zoological park in North Rhine-Westphalia, Germany.

We present the case of Taenia martis metacestode infection in a white-headed lemur (Eulemur albifrons) from a zoological park. A post-mortem examination was conducted on the unexpectedly perished animal and focal granulomatous pneumonia with metacestodic tissue was discovered. Identification of T. martis was conducted through amplification and sequencing of a 12S rRNA gene fragment. We discuss the possible sources of infection and underline the importance of this infection in public health and conservation.

Sexual Dimorphism in Crowned Lemur Scent-Marking.

Primates are traditionally considered to have a poor sense of smell. However, olfaction is important for non-human primates as demonstrated by conspicuous scent-marking behaviours in lemurs. We studied two pairs (n = 4) of crowned lemurs (Eulemur coronatus) housed at Colchester and Twycross zoos (UK) by combining behavioural observations and chemical analyses of scent-marks and glandular swabs. We recorded observations of olfactory behaviours for 201 h using instantaneous scan sampling. We investigated the volatile compounds of ano-genital odour secretions (n = 16) using solid-phase microextraction and gas chromatography-mass spectrometry. Males scent-marked most frequently, displaying ano-genital marking for allomarking, head marking for countermarking and wrist marking in specific areas of the enclosure. Females displayed ano-genital marking, predominantly on feeding devices. We detected a total of 38 volatile components in all male ano-genital scent-marks and 26 in all female samples of ano-genital odour secretions, including a series of esters, aldehydes, ketones, alcohols, terpenes, volatile fatty acids and hydrocarbons that have been identified in odour profiles of other primates. In conclusion, we found sexual dimorphism in crowned lemur scent-marking. Male head and wrist marking behaviours might play defensive territorial functions, while ano-genital marking would be related to socio-sexual communication as chemical mate-guarding. Female ano-genital marking might be involved in resource defense.

The Tongue in Three Species of Lemurs: Flower and Nectar Feeding Adaptations.

The mobility of the primate tongue allows for the manipulation of food, but, in addition, houses both general sensory afferents and special sensory end organs. Taste buds can be found across the tongue, but the ones found within the fungiform papillae on the anterior two thirds of the tongue are the first gustatory structures to come into contact with food, and are critical in making food ingestion decisions. Comparative studies of both the macro and micro anatomy in primates are sparse and incomplete, yet there is evidence that gustatory adaptation exists in several primate taxa. One is the distally feathered tongues observed in non-destructive nectar feeders, such as Eulemur rubriventer. We compare both the macro and micro anatomy of three lemurid species who died of natural causes in captivity. We included the following two non-destructive nectar feeders: Varecia variegata and Eulemur macaco, and the following destructive flower feeder: Lemur catta. Strepsirrhines and tarsiers are unique among primates, because they possess a sublingua, which is an anatomical structure that is located below the tongue. We include a microanatomical description of both the tongue and sublingua, which were accomplished using hematoxylin-eosin and Masson trichrome stains, and scanning electron microscopy. We found differences in the size, shape, and distribution of fungiform papillae, and differences in the morphology of conical papillae surrounding the circumvallate ones in all three species. Most notably, large distinct papillae were present at the tip of the tongue in nectar-feeding species. In addition, histological images of the ventro-apical portion of the tongue displayed that it houses an encapsulated structure, but only in Lemur catta case such structure presents cartilage inside. The presence of an encapsulated structure, coupled with the shared morphological traits associated with the sublingua and the tongue tip in Varecia variegata and Eulemur macaco, point to possible feeding adaptations that facilitate non-destructive flower feeding in these two lemurids.

Should I stay or should I go? Individual movement decisions during group departures in red-fronted lemurs.

Collective movements are essential for maintaining group cohesion. However, group members can have different optimal departure times, depending on individual, social and contextual factors whose relative importance remains poorly known. We, therefore, studied collective departures in four groups of red-fronted lemurs (Eulemur rufifrons) in Kirindy Forest, Madagascar, to investigate the influence of an individual's age, sex, their affiliative relationships and their proximity to other group members at the time of departure on their individual departure decision. We recorded behavioural and spatial data on individual departures during 167 group movements and conducted group scans (181-279 per group) to assess affiliative relationships. All factors influenced individual departures. Both affiliation and proximity determined a mimetic joining process in which dyads with stronger affiliative bonds departed in closer succession, and individuals followed the initiator and predecessors more quickly when they were in closer proximity at departure. While the influence of affiliation is common, the effect of inter-individual distance has rarely been considered in groups with heterogeneous social relationships. Although local rules influenced joining, the overall movement pattern was mainly determined by individual traits: juveniles took protected central positions, while females made up the van and males brought up the rear. Individual needs, expressed in the departure order, to an extent overruled the effect of affiliation. These results highlight the importance of considering individual, social and contextual factors collectively in the study of collective movements.

Evidence for the possible occurrence of Grave's disease in a blue-eyed black lemur (Eulemur flavifrons).

The blue-eyed black lemur (Eulemur flavifrons) is classified by the International Union for Conservation of Nature (IUCN) as critically endangered. A 23-year-old male housed at Mulhouse Zoo presented with lethargy, polyphagia, alopecia, and chronic weight loss. Clinical examination suggested an endocrine pathology such as hyperthyroidism. Secondary examinations included cervical ultrasound, thyroid biopsy, and scintigraphy. The latter revealed elevated thyroid activity. Blood analysis was performed to measure the level of anti-receptor thyroid-stimulating hormone antibodies, which allowed us to test the autoimmune hypothesis. The high level of antibodies together with levels of thyroid-stimulating hormone and the scintigraphy images led to the diagnosis of Grave's disease. Carbimazole treatment followed by thyroidectomy resulted in a quick weight gain and general improvement in health status. The following breeding season, the treated individual sired an offspring. To the authors' knowledge, this is the first report of likely Grave's disease in a non-human primate.