Costs of injury for scent signalling in a strepsirrhine primate

Honesty is crucial in animal communication when signallers are conveying information about their condition. Condition dependence implies a cost to signal production; yet, evidence of such cost is scarce. We examined the effects of naturally occurring injury on the quality and salience of olfactory signals in ring-tailed lemurs (Lemur catta). Over a decade, we collected genital secretions from 23 (13 male, 10 female) adults across 34 unique injuries, owing primarily to intra-group fights. Using gas chromatography-mass spectrometry, we tested for differences in the chemical composition of secretions across pre-injury, injury and recovery, in animals that did and did not receive antibiotics. Lemur genital secretions were significantly dampened and altered during injury, with patterns of change varying by sex, season and antibiotics. Using behavioural bioassays (excluding odorants from antibiotic-treated animals), we showed that male 'recipients' discriminated injury status based on scent alone, directing more competitive counter marking towards odorants from injured vs. uninjured male 'signallers.' That injured animals could not maintain their normal signatures provides rare evidence of the energetic cost to signal production. That conspecifics detected olfactory-encoded 'weakness' suggests added behavioural costs: By influencing the likelihood of intra- or inter-sexual conflict, condition-dependent signals could have important implications for socio-reproductive behaviour.

Coevolution of Cyanogenic Bamboos and Bamboo Lemurs on Madagascar

Feeding strategies of specialist herbivores often originate from the coevolutionary arms race of plant defenses and counter-adaptations of herbivores. The interaction between bamboo lemurs and cyanogenic bamboos on Madagascar represents a unique system to study diffuse coevolutionary processes between mammalian herbivores and plant defenses. Bamboo lemurs have different degrees of dietary specialization while bamboos show different levels of chemical defense. In this study, we found variation in cyanogenic potential (HCNp) and nutritive characteristics among five sympatric bamboo species in the Ranomafana area, southeastern Madagascar. The HCNp ranged from 209±72 μmol cyanide*g-1 dwt in Cathariostachys madagascariensis to no cyanide in Bambusa madagascariensis. Among three sympatric bamboo lemur species, the greater bamboo lemur (Prolemur simus) has the narrowest food range as it almost exclusively feeds on the highly cyanogenic C. madagascariensis. Our data suggest that high HCNp is the derived state in bamboos. The ancestral state of lemurs is most likely "generalist" while the ancestral state of bamboo lemurs was determined as equivocal. Nevertheless, as recent bamboo lemurs comprise several "facultative specialists" and only one "obligate specialist" adaptive radiation due to increased flexibility is likely. We propose that escaping a strict food plant specialization enabled facultative specialist bamboo lemurs to inhabit diverse geographical areas.

The Nutritional Geometry of Resource Scarcity: Effects of Lean Seasons and Habitat Disturbance on Nutrient Intakes and Balancing in Wild Sifakas

Animals experience spatial and temporal variation in food and nutrient supply, which may cause deviations from optimal nutrient intakes in both absolute amounts (meeting nutrient requirements) and proportions (nutrient balancing). Recent research has used the geometric framework for nutrition to obtain an improved understanding of how animals respond to these nutritional constraints, among them free-ranging primates including spider monkeys and gorillas. We used this framework to examine macronutrient intakes and nutrient balancing in sifakas (Propithecus diadema) at Tsinjoarivo, Madagascar, in order to quantify how these vary across seasons and across habitats with varying degrees of anthropogenic disturbance. Groups in intact habitat experience lean season decreases in frugivory, amounts of food ingested, and nutrient intakes, yet preserve remarkably constant proportions of dietary macronutrients, with the proportional contribution of protein to the diet being highly consistent. Sifakas in disturbed habitat resemble intact forest groups in the relative contribution of dietary macronutrients, but experience less seasonality: all groups' diets converge in the lean season, but disturbed forest groups largely fail to experience abundant season improvements in food intake or nutritional outcomes. These results suggest that: (1) lemurs experience seasonality by maintaining nutrient balance at the expense of calories ingested, which contrasts with earlier studies of spider monkeys and gorillas, (2) abundant season foods should be the target of habitat management, even though mortality might be concentrated in the lean season, and (3) primates' within-group competitive landscapes, which contribute to variation in social organization, may vary in complex ways across habitats and seasons.

Variation in fecal testosterone levels, inter-male aggression, dominance rank and age during mating and post-mating periods in wild adult male ring-tailed lemurs (Lemur catta)

In primate species exhibiting seasonal reproduction, patterns of testosterone excretion in adult males are variable: in some species, peaks correlate with female receptivity periods and heightened male-male aggression over access to estrous females, in others, neither heightened aggression nor marked elevations in testosterone have been noted. In this study, we examined mean fecal testosterone ( f T) levels and intermale aggression in wild adult male ring-tailed lemurs residing in three groups at Beza Mahafaly Reserve, Madagascar. Results obtained from mating and post-mating season 2003 were compared to test Wingfield et al. [1990. Am Nat 136:829-846] "challenge hypothesis", which predicts a strong positive relationship between male testosterone levels and male-male competition for access to receptive females during breeding season. f T levels and rates of intermale aggression were significantly higher during mating season compared to the post-mating period. Mean f T levels and aggression rates were also higher in the first half of the mating season compared with the second half. Number of males in a group affected rates of intermale agonism, but not mean f T levels. The highest-ranking males in two of the groups exhibited higher mean f T levels than did lower-ranking males, and young males exhibited lower f T levels compared to prime-aged and old males. In the post-mating period, mean male f T levels did not differ between groups, nor were there rank or age effects. Thus, although male testosterone levels rose in relation to mating and heightened male-male aggression, f T levels fell to baseline breeding levels shortly after the early mating period, and to baseline non-breeding levels immediately after mating season had ended, offsetting the high cost of maintaining both high testosterone and high levels of male-male aggression in the early breeding period.

Distribution of caveolin isoforms in the lemur retina

The distribution of caveolin isoforms was previously evaluated in the retinas of different species, but has not yet been described in the primate retina. In this study, the distribution of caveolins was assessed via immunochemistry using isoform-specific antibodies in the retina of the black-and-white ruffed lemur. Here, we report the presence of a variety of caveolin isoforms in many layers of the lemur retina. As normal human retinas were not available for research and the retinas of primates are fairly similar to those of humans, the lemur retina can be utilized as a model for caveolin distribution in normal humans.

Enzyme-linked immunosorbent assay to quantitate serum ferritin in black and white ruffed lemurs (Varecia variegata variegata)

Lemurs in captivity progressively accumulate iron deposits in a variety of organs (hemosiderosis) including duodenum, liver, and spleen throughout their lives. When excessive, the toxic effects of intracellular iron on parenchymal cells, particularly the liver, can result in clinical disease and death. The pathogenesis of excessive iron storage in these species has been attributed to dietary factors related to diets commonly fed in captivity. Tissue iron stores can be directly estimated by tissue biopsy and histologic examination, or quantitated by chemical analysis of biopsy tissue, However, expense and risk associated with anesthesia and surgery prevent routine use of tissue biopsy to assess iron status. A noninvasive means of assessing total body iron stores is needed to monitor iron stores in lemurs to determine whether dietary modification is preventing excessive iron deposition, and to monitor potential therapies such as phlebotomy or chelation. Serum ferritin concentration correlates with tissue iron stores in humans, horses, calves, dogs, cats, and pigs. Serum ferritin is considered the best serum analyte to predict total body iron stores in these species and is more reliable than serum iron or total iron binding capacity, both of which may be affected by disorders unrelated to iron adequacy or excess including hypoproteinemia, chronic infection, hemolytic anemia, hypothyroidism, renal disease, and drug administration. We have developed an enzyme-linked immunosorbent assay to measure serum ferritin in lemurs. The assay uses polyclonal rabbit anti-human ferritin antibodies in a sandwich arrangement. Ferritin isolated from liver and spleen of a black and white ruffed lemur (Varecia variegata variegata) was used as a standard. Ferritin standards were linear from 0 to 50 microg/L. Recovery of purified ferritin from lemur serum varied from 95% to 110%. The within-assay variability was 4.5%, and the assay-to-assay variability for three different samples ranged from 10% to 17%. The assay also measures serum ferritin in several other lemur species.

High faecal glucocorticoid levels predict mortality in ring-tailed lemurs (Lemur catta)

Glucocorticoid levels are commonly used as measures of stress in wild animal populations, but their relevance to individual fitness in a wild population has not been demonstrated. In this study I followed 93 ring-tailed lemurs (Lemur catta) at Berenty Reserve in Madagascar, collecting 1089 faecal samples from individually recognized animals, and recording their survival over a 2 year period. I evaluated faecal glucocorticoid levels as predictors of individual survival to the end of the study. Animals with high glucocorticoid levels had a significantly higher mortality rate. This result suggests that glucocorticoid measures can be useful predictors of individual survival probabilities in wild populations. The 'stress landscape' indicated by glucocorticoid patterns may approximate the fitness landscape to which animals adapt.

Olfactory signals and the MHC: a review and a case study in Lemur catta

The major histocompatibility complex (MHC) is the most polymorphic genetic system known in vertebrates. Decades of research demonstrate that it plays a critical role in immune response and disease resistance. It has also been suggested that MHC genes influence social behavior and reproductive phenomena. Studies in laboratory mice and rats report that kin recognition and mate choice are influenced by olfactory cues determined at least in part by an individual's MHC genes. This issue has stimulated intense but controversial research. However, work in this field has only been carried out in rodents and humans. Thus far, no study has directly investigated the relationship between olfactory cues and MHC genotype in nonhuman primates. Furthermore, other genetic loci, including those linked to the MHC, have not been ruled out as the primary influence on odor profiles. To explore the relationship between individual odor profiles and MHC alleles, we are studying ring-tailed lemurs (Lemur catta). These animals are an ideal model species because they are extremely scent-oriented and their behaviors suggest that olfactory signals form an important part of their intra- and intergroup communication systems. Individual odor profiles from tail and scent gland samples were generated for six males using gas chromatography mass spectrometry (GC-MS). MHC genotypes were identified using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). The GC-MS analyses demonstrated a difference between profiles obtained from tail and scent gland samples. Although our sample size is relatively small and statistical significance could not be obtained, our analyses suggest a relationship between MHC and concentrations of volatile compounds. While these results are preliminary, they support the need for further studies of the MHC and olfactory signals in lemurs and other primates.

FIBER DIGESTIBILITY BY BLACK LEMURS (EULEMUR MACACO MACACO)

Black lemurs, Eulemur macaco, are classified as generalist feeders, consuming a proportion of fruits and leaves that varies with seasonal availability. It is hypothesized that black lemurs are capable of using neutral detergent fiber (NDF) as a source of energy through fiber fermentation in the cecum and large intestine. In captivity, they are typically fed a diet of commercially available primate biscuits and readily available produce, both of which are limited in NDE Digestibility trials were conducted on 14 black lemurs; 12 were housed in groups (four, three, three, and two) and 2 were individually housed. The lemurs were fed four manufactured feeds differing in fiber form and content. A commercially available primate biscuit, containing approximately 27% NDF, served as the control diet. The second diet contained the same primate biscuits, which were ground and then incorporated into a fiber-based gel matrix. The third and fourth diets were formulated using soybean hulls or ground corncobs as the fiber source, resulting in 53% and 47% NDF, respectively. Produce was added to the diet at 36% (dry matter basis). Dry matter digestibility differed significantly among all diets. Neutral detergent fiber digestibility was highest for the ground biscuit in gel and lowest for the two high-fiber gel diets, with biscuit digestibility values falling between the two extremes. The high-fiber gel diets were successful in increasing the NDF concentrations of the primate diets; however, black lemurs were capable of only limited fiber digestion.

Anogenital gland secretions ofLemur catta andPropithecus verreauxi coquereli: A preliminary chemical examination

Although prosimians are greatly olfaction-oriented, little is known about the specifics of how they use scent to communicate. In this preliminary study we attempted to delineate intra- and interspecific differences among the anogenital gland secretions of two lemur species (Lemur catta and Propithecus verreauxi coquereli) using gas chromatography-mass spectrometry (GC-MS). The results indicate that the two species are discernible through scent. Furthermore, we were able to identify reproductive status using this technique. The anogenital secretions of the different sexes in L. catta, though perhaps not P. v. coquereli, are chemically distinguishable. Given this information, it appears that at least some lemur species can use scent marks to determine species, sex, and reproductive status.

Androgen levels and female social dominance in Lemur catta

Morphological and behavioural traits which improve agonistic power are subject to intrasexual selection and, at the proximate level, are influenced by circulating androgens. Because intrasexual selection in mammals is more intense among males, they typically dominate females. Female social dominance is therefore unexpected and, indeed, rare. Ring-tailed lemurs (Lemur catta) are sexually monomorphic primates in which all adult females dominate all males. The goal of our study was to test the prediction that female dominance in this species is associated with high androgen levels. Using two captive groups, we collected data on agonistic behaviour and non-invasively assessed their androgen concentrations in faeces and saliva by enzyme immunoassay. We found that adult female L. catta do not have higher androgen levels than males. However, during the mating season there was a twofold increase in both the androgen levels and conflict rates among females. This seasonal increase in their androgen levels was probably not due to a general increase in ovarian hormone production because those females showing the strongest signs of follicular development tended to have low androgen concentrations. At the individual level neither the individual aggression rates nor the proportion of same-sexed individuals dominated were correlated with their androgen levels. We conclude that female dominance in ring-tailed lemurs is neither based on physical superiority nor on high androgen levels and that it is equally important to study male subordination and prenatal brain priming effects for a complete understanding of this phenomenon.

Urinary estrogens during pregnancy of the ruffed lemur (Lemur variegatus)

Pregnancy in the ruffed lemur (Lemur variegatus) was monitored by analyses of urinary estrogens. Urine samples were collected weekly throughout pregnancy (gestation: 100 +/- 1.6 days) from ten females analyzed for total immunoreactive estrogen (Et) and indexed by creatinine (Cr). Maternal urinary total estrogen excretion remained low until the last half of gestation at which time excretion increased steadily, reaching values 1000 times greater than those observed at estrus. Chromatographic separation after enzyme hydrolysis of lemur urine indicates that estrone is the major estrogenic component of pregnancy in the ruffed lemur, with the remaining components consisting of equal amounts of estradiol-17 alpha and -17 beta.

Acetylcholinesterase enzyme localization in the amygdala: a comparative histochemical and ultrastructural study

The distribution of acetylcholinesterase enzyme was studied in the amygdala of some rodents, subprimates and several primates. The cytoarchitecture of the amygdala has presented various problems to anatomists, including the question as to how many nuclear groups and subgroups should be identified. Among the mammals examined, the arrangement of the amygdaloid nuclei is remarkably uniform and no clear phylogenetic trend can be recognised. Although there are minor differences, there seems to be a general similarity between most mammals examined in so far as the distribution of cholinesterase is concerned. The staining is less intense in the brains of the monkeys examined. The sole exception to the rule, that cholinesterase distribution is slightly different from nucleus to nucleus in different animals, is the magnocellular part of the basal nucleus. This amygdaloid nucleus stains quite strongly in all animals examined. From these findings, and those of others studying the distribution of choline acetyltransferase, it was concluded that the basal amygdaloid nucleus is cholinergic and possible cholinoceptive. The ultrastructural investigations appear to confirm this point. This is particularly applicable to the magnocellular part of the basal amygdaloid nucleus.

Comparative feeding and nutrition in captive, non-human primates

1. Food intake studies were carried out on three groups of captive primates (anthropoid apes (Pongidae), lemurs (Lemuridae) and marmosets (Callitrichidae). 2. Determination and analysis of the nutrient intakes were carried out by calculations based on food tables. The results from all groups were compared. 3. Marmosets were found to have higher intakes of energy and many other nutrients than the apes and lemurs. 4. The results suggest that there is a tendency towards over use of dietary supplements and foods of higher nutrient density for captive primates.

Codominant autosomal inheritance of polymorphic red cell acid phosphates of lemurs and some properties of the enzymes

Red cell acid phosphatase phenotypes of 207 captive animals of the genera Lemur, Hapalemur, and Prophithecus were determined by starch gel electrophoresis and phosphatase-specific staining. In Lemur fulvus, three phenotypes, designated A, B, and AB, were observed. In each of the species L. catta, L. macaco, L. mongoz, and L. variegatus, a single phenotype was observed, In Hapalemur griseus, three phenotypes were found: A,B, and AB. In Propithecus verreauxi, a single phenotype was found. Examination of breeding records in conjunction with the results of the electrophoretic analyses supports the conclusion that the erythrocytic acid phosphatases in this group of nonhuman primates are the products of at least two codominant autosomal alleles. There is a wide range of specific activities of the acid phosphatases as determined by colorimetric assays. The values range from 60.6 micronmoles of p-nitrophenol released per gram of hemoglobin per 30 min in Lemur catta to 429.1 micronmoles in Propithecus verreauxi. The enzymes of L. fulvus and P. vereauxi were purified approximately 400-fold, and Michaelis-Menten constants were determined on the purified preparations. For L. fulvus phenotype A, Km = 0.8 mM; for L. fulvus phenotype B, Km = 0.8 mM; and for P. verreauxi, Km = 0.6 mM; the substrate in each case was p-nitrophenylphosphate.