Steep Hierarchies without Skew? Modeling How Ecology and Decision-Making Shape Despotism of Relationships.

AbstractAnimals can form dominance relationships that vary from highly unequal, or despotic, to egalitarian, and this variation likely impacts the fitness of individuals. How and why these differences in relationships and fitness exist among groups, populations, and species has been the subject of much debate. Here, we investigated the influence of two major factors: (1) spatial resource distribution and (2) the presence or absence of winner-loser effects. To determine the effects of these factors, we built an agent-based model that represented 10 agents directly competing over food resources on a simple landscape. By varying the food distribution and using either asymmetry of strength or experience, we contrasted four scenarios from which we recorded attack decisions, fight outcomes, and individual energy intake to calculate dominance hierarchy steepness and energetic skew. Surprisingly, resource distribution and winner-loser effects did not have the predicted effects on hierarchy steepness. However, skew in energy intake arose when resources were distributed heterogeneously, despite hierarchy steepness frequently being higher in the homogeneous resource scenarios. Thus, this study confirms some decades-old predictions about feeding competition but also casts doubt on the ability to infer energetic consequences from observations of agonistic interactions.

Consumption of underground storage organs is associated with improved energetic status in a graminivorous primate.

Early hominin species likely had access to open, grassy habitats where periodic reliance on underground storage organs (USOs) is hypothesized to have played a crucial dietary role. As the only living graminivorous primate today, geladas (Theropithecus gelada) provide a unique perspective for understanding the energetic consequences of seasonal consumption of USOs. Geladas rely heavily on above-ground grasses throughout the year, but when grass is seasonally less available, they feed more on USOs. To assess whether USOs fit the definition of fallback foods (i.e., foods that are difficult to access, less preferred, or both), we examined how foraging effort (measured via time spent feeding and moving) and energetic status (measured via urinary C-peptide) fluctuated during seasonal dietary changes in a population of wild geladas in the Simien Mountains National Park, Ethiopia. If, indeed, USOs are fallback foods, we predicted an increase in foraging effort and a decline in energetic status during the dry season, when geladas rely more heavily on USOs. We collected behavioral and physiological data from 13 adult gelada males across a 13-month period. As expected, we found that male geladas spent more time moving during drier months. However, counter to the hypothesis that USOs are fallback foods in geladas, urinary C-peptide concentrations were significantly higher during the dry season. We suggest that USOs may represent an energy-rich food item for geladas, but it remains unclear why USOs are not consumed year-round. Future work is needed to better understand seasonal variation in the availability, nutrient content, and digestibility of USOs. However, results indicate that exploiting USOs seasonally could have been a valuable dietary strategy for the evolutionary success of early hominins.

Female-biased birth sex ratio in a female dispersal primate suggests local resource competition.

Group living may entail local resource competition (LRC) which can be reduced if the birth sex ratio (BSR) is biased towards members of the dispersing sex who leave the group and no longer compete locally with kin. In primates, the predicted relationship between dispersal and BSR is generally supported although data for female dispersal species are rare and primarily available from captivity. Here, we present BSR data for Phayre's leaf monkeys (Trachypithecus phayrei crepusculus) at the Phu Khieo Wildlife Sanctuary, Thailand (N = 104). In this population, nearly all natal females dispersed, while natal males stayed or formed new groups nearby. The slower reproductive rate in larger groups suggests that food can be a limiting resource. In accordance with LRC, significantly more females than males were born (BSR 0.404 males/all births) thus reducing future competition with kin. This bias was similar in 2-year-olds (no sex-differential mortality). It became stronger in adults, supporting our impression of particularly fierce competition among males. To better evaluate the importance of BSR, more studies should report sex ratios throughout the life span, and more data for female dispersal primates need to be collected, ideally for multiple groups of different sizes and for several years.

Laccase-Treated Polystyrene Surfaces with Caffeic Acid, Dopamine, and L-3,4-Dihydroxyphenylalanine Substrates Facilitate the Proliferation of Melanocytes and Embryonal Carcinoma Cells NTERA-2.

This study presents the effects of treating polystyrene (PS) cell culture plastic with oxidoreductase enzyme laccase and the catechol substrates caffeic acid (CA), L-DOPA, and dopamine on the culturing of normal human epidermal melanocytes (NHEMs) and human embryonal carcinoma cells (NTERA-2). The laccase-substrate treatment improved PS hydrophilicity and roughness, increasing NHEM and NTERA-2 adherence, proliferation, and NHEM melanogenesis to a level comparable with conventional plasma treatment. Cell adherence dynamics and proliferation were evaluated. The NHEM endpoint function was quantified by measuring melanin content. PS surfaces treated with laccase and its substrates demonstrated the forming of polymer-like structures. The surface texture roughness gradient and the peak curvature were higher on PS treated with a combination of laccase and substrates than laccase alone. The number of adherent NHEM and NTERA-2 was significantly higher than on the untreated surface. The proliferation of NHEM and NTERA-2 correspondingly increased on treated surfaces. NHEM melanin content was enhanced 6-10-fold on treated surfaces. In summary, laccase- and laccase-substrate-modified PS possess improved PS surface chemistry/hydrophilicity and altered roughness compared to untreated and plasma-treated surfaces, facilitating cellular adherence, subsequent proliferation, and exertion of the melanotic phenotype. The presented technology is easy to apply and creates a promising custom-made, substrate-based, cell-type-specific platform for both 2D and 3D cell culture.

Influence of aging of PEEK attachment inserts on the pull-off force of implant-retained overdentures - A laboratory study.

OBJECTIVES: The aim of the current study is to investigate the influence of mechanical stress as well as cleaning agents on the performance of various polyether ether ketone (PEEK) inserts for implant-retained overdentures (IOD). MATERIALS AND METHODS: Three different standard PEEK inserts were subjected to rapid artificial aging through storage in chemical denture cleaning agents (acetic acid, sodium hypochlorite, or sparkling denture cleaner) as well as demineralized water. The pre-aged PEEK inserts were then placed in unilateral IOD and subjected to 200,000 chewing loads (5 kg ~ 50 N), with 5000 thermal cycles (5/55°C), and 1100 removal/insertion cycles (vertical movement 2 mm). RESULTS: For all the PEEK inserts, the retention forces decreased significantly with an increasing number of mechanical load cycles and after exposure to all the cleaning agents. PEEK inserts aged by exposure to chemical cleaning agents showed a significantly higher decline in retention force than the inserts stored in water. Confocal laser scanning microscopy indicated that the decline in retention force might be caused by wear on the internal insert surface in contact with the patrix. CONCLUSIONS: Within the limitations of this study, it can be concluded that the application of chemical cleaning agents accelerates the decline in the retention forces of PEEK retentive inserts in IODs.

The influence of different storage media on Vickers hardness and surface roughness of CAD/CAM resin composites.

INTRODUCTION: This study examined Vickers hardness as well as surface characteristics of different computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites prior to and after storage in various media. MATERIALS AND METHODS: CAD/CAM resin composite blocks (Grandio Blocs (GB), Lava Ultimate (LU), Brilliant Crios (BC), Cerasmart (GC), Shofu Block HC (SB), Tetric CAD (TC), Luxacam Composite (LC); incl. different translucency variants) were prepared, polished and surface free energy was determined. The specimens were divided into four groups: dry conditions for 24 h (25 °C), demineralized water (37 °C), Pepsi Cola (37 °C) and 75% ethanol (37 °C). After seven and 28 days of storage, Vickers hardness was determined. Surface roughness was measured after the entire storage period. RESULTS AND DISCUSSION: Vickers hardness was in the range of about 150 HV for GB, around 115 HV for LU, and 80-100 HV for BC, GC, SB, TC and LC. Only minor differences (total: 50.2 (6.4)-56.2 (3.2) mN/m) in surface free energy could be detected. No relationship was observed between surface free energy and filler content. However, a correlation between filler content and Vickers hardness was evident. Artificial aging caused a decrease of Vickers hardness (up to -40 HV or 35%) depending on storage media, duration and material. The changes in surface texture after immersion in different media were below a value of ΔSa = 0.015 µm. CONCLUSION: Artificial aging of CAD/CAM resin composites leads to a significant decrease of Vickers hardness for most materials, while only small changes in surface roughness were identified.

Influence of dental prophylaxis procedures on the tooth veneer interface in resin-based composite and polymer-infiltrated ceramic veneer restorations: an in vitro study.

OBJECTIVES: The aim of this study was to investigate the influence of dental prophylaxis cleaning procedures and artificial aging on veneers in human teeth. The external marginal and internal tooth veneer as well as the restoration surfaces were examined. MATERIAL AND METHODS: Thirty-two extracted premolars were restored with resin-based composite (RBC) and polymer-infiltrated ceramic network (PICN) veneers. Artificial aging by alternating thermocycling and subsequent prophylaxis procedure (glycine-based powder air polishing or ultrasonic scaling) was conducted for five consecutive cycles. The external marginal interface was examined by height profile measurements and the internal interface was investigated using micro X-ray computed tomography. In addition, the surface texture of the veneer surface was analyzed using confocal laser scanning microscopy. RESULTS: The application of both prophylaxis procedures resulted in a deepening of the marginal interface (10 µm ± 8 µm) for materials. Furthermore, the internal interface of PICN restorations showed marginal gaps after both treatments and artificial aging (16 µm ± 3 µm). In contrast to the RBC specimens, a significant increase in surface roughness was identified for PICN veneers after ultrasonic scaling. CONCLUSIONS: The marginal and internal interface regions in veneers fabricated from PICN and RBC were affected by prophylaxis procedures. Furthermore, it may result in increased veneer surface roughness, especially in PICN and after ultrasonic scaling, which might affect bioadhesion and longevity. CLINICAL RELEVANCE: After dental prophylaxis procedures, examination of the marginal and the internal interface as well as the veneer surface provides a precise insight into damage mechanisms and offers an assessment of longevity.

The effect of data provenance on estimates of gestation length in African and Asian colobines.

OBJECTIVES: It seems to be commonly accepted that gestation length within the subfamily Colobinae lasts several weeks longer in the African tribe (Colobini) than in the Asian tribe (Presbytini) even though closely related taxa of similar body mass should have similar life histories. Suspecting problems with data provenance to cause the difference, we revisited the published records expecting similar gestation lengths in both tribes if based on vetted, accurate data. MATERIALS AND METHODS: We compiled published gestation length data for Colobini and Presbytini, labeling them as "unspecified" (n = 16) if the primary reference could not be located, methods were not described, and/or conceptions, the beginning of gestation, were determined based on sporadic observations of mating. If conceptions were determined based on changing hormone levels or patterns of daily mating records, we labeled the data as "accurate" (n = 12). We analyzed the ln transformed data in a phylogenetic framework in relation to adult female body mass. RESULTS: In the unspecified dataset, gestation length in the two tribes overlapped extensively and did not differ significantly. However, in the accurate dataset, gestation length was significantly shorter in Colobini (not longer, as previously assumed). DISCUSSION: Data provenance had a strong impact on the comparison, reversing the relationship in gestation length in the two sister tribes. It remains to be determined why gestation lengths differ, whether, relative to the other primates, Colobini have a shortened gestation or Presbytini a lengthened gestation, and whether similar differences exist in other closely related taxa. Addressing these questions will require additional, broader, comparative analyses.

Behavioral and physiological responses to instability in group membership in wild male woolly monkeys (Lagothrix lagotricha poeppigii).

In group-living species, integrating into a new social group after dispersal is an important life history milestone associated with physical and social challenges. Generally, this process seems to be accompanied by heightened glucocorticoid (GC) concentrations; however, most studies of physiological responses to group transfer have been conducted on species with despotic social relationships, where integrating individuals are often targets of frequent aggression. Here we present data on fecal glucocorticoid (fGC) concentrations during periods of unstable group membership for male woolly monkeys (Lagothrix lagotricha poeppigii), a species with extremely low rates of male-male aggression and generally tolerant male-male associations. We collected data on males in four study groups at the Tiputini Biodiversity Station, Ecuador, and observed three attempted transfer events, involving a total of four adult males, in one study group. We observed only three instances of overt aggression (chases) between males across the entire study period, though male display behaviors were more frequent. We tested whether rates of displays were higher during periods of unstable group membership using a generalized linear mixed model (LMM). We also examined whether male status, group stability, and the occurrence of intergroup encounters affected fGC concentrations using LMMs. Contrary to our predictions, rates of display behaviors were not higher during periods of unstable group membership. However, both transient/integrating males and those who were already group members showed elevated fGC concentrations during these unstable periods. Our results suggest that even in species with tolerant male-male relationships, the integration of unfamiliar individuals can provoke an increase in GCs.

Exploratory analysis reveals arthropod consumption in 10 lemur species using DNA metabarcoding.

Arthropods (insects, spiders, etc.) can fulfill major nutritional requirements for primates, particularly in terms of proteins, fats, vitamins, and minerals. Yet, for many primate species we know very little about the frequency and importance of arthropod consumption. Traditional methods for arthropod prey identification, such as behavioral observations and fecal dissections, offer limited taxonomic resolution and, as a result, underestimate true diversity. Metabarcoding arthropod DNA from primate fecal samples provides a promising but underused alternative. Here, we inventoried arthropod prey diversity in wild lemurs by sequencing two regions of the CO1 gene. Samples were collected opportunistically from 10 species of lemurs inhabiting three national parks in southern Madagascar using a combination of focal animal follows and live trapping. In total, we detected arthropod DNA in 98 of the 170 fecal samples analyzed. Although all lemur species included in these analyses showed evidence of arthropod consumption, those within the family Cheirogaleidae appeared to consume the highest frequency and diversity of arthropods. To our knowledge, this study presents the first evidence of arthropod consumption in Phaner pallescens, Avahi peyrierasi, and Propithecus verreauxi, and identifies 32 families of arthropods as probable food items that have not been published as lemur dietary items to date. Our study emphasizes the importance of arthropods as a nutritional source and the role DNA metabarcoding can play in elucidating an animal's diet.

Alkalinity and Its Consequences for the Performance of Steel-Reinforced Geopolymer Materials.

This paper investigates the development of the alkalinity and its impact on carbon steel reinforcement embedded in alkali-activated fly ashes (AAFA) and alkali-activated fly ashes with ten percentage mass (wt%) of blast furnace slag (AAFAS)-based materials (geopolymer-GP). The pH analysis of eluates indicates a remarkable decrease of alkalinity in AAFA and AAFAS in the first hours of the geopolymerization process. Phenolphthalein solution and pore solution tests on concretes also show a sharp decrease of alkalinity with increased Ca content in the binder due to carbonation. Micro X-ray computer tomography (µXCT) and electrochemical techniques indicate that the changed pH in the GP systems was accompanied by a decrease in the corrosion rates of steel reinforcement when compared to ordinary Portland cement (OPC) systems. In contrast to calcite and vaterite, which were detected in OPC and AAFAS after a carbonation process, only sodium carbonate natron was determined at lower levels in AAFA by X-ray diffraction (XRD).

The function of geophagy in Nepal gray langurs: Sodium acquisition rather than detoxification or prevention of acidosis.

OBJECTIVES: Geophagy has several hypothesized functions, among them (1) detoxification of plant secondary compounds, for example, tannins, (2) buffering stomach pH to alleviate acidosis caused by high sugar intake, and (3) supplementing the diet with mineral nutrients. We tested these hypotheses in Nepal gray langurs (Semnopithecus schistaceus), a foregut fermenter for which fruits and leaves dominate the diet at different times of the year. MATERIALS AND METHODS: We collected data on feeding time per food item for 21 unprovisioned adult langurs at Ramnagar, Nepal, for 1 year using instantaneous sampling (773 observation hours). We combined these data with relative sugar and tannin content of food items to estimate diet content. We collected rainfall data to distinguish the wet season (May-September) from the dry season (October-April). We collected soil samples from consumption and control sites to test for pH and sodium, potassium, magnesium, and calcium concentrations. RESULTS: Langurs consumed soil from two sources: termite structures (in almost all months) and river banks and beds (mainly in the dry season). Soil feeding was not positively correlated with dietary tannin or sugar content (GLMM). Soil pH was not high enough to buffer stomach contents. Only sodium was significantly higher in consumed soil. DISCUSSION: The most likely function of geophagy was the acquisition of sodium. This conclusion is consistent with reports for other animals. Buffering stomach pH, an often-suggested function for animals with ruminant-like digestion, was not supported. Detoxification, often proposed for animals with a diet high in secondary compounds, was also not supported.

Characteristics of alpha males in Nepal gray langurs.

In species with strong male-male competition, access to females in multimale-multifemale groups is usually regulated via a dominance hierarchy. The highest ranking (alpha) male often has priority of access and sires most offspring. The alpha male can change in three basic ways: (i) a recent immigrant or a resident challenges and becomes the new alpha; (ii) formation of a new group; (iii) succession-becoming alpha after higher ranking males have left. When, in a given primate population, the alpha male changes in different ways, two questions arise: (a) which is the most successful tactic and (b) do male attributes, such as age, aggressiveness or propensity to commit infanticide, affect the outcome? We examined these questions in the seasonally breeding Nepal gray langurs (Semnopithecus schistaceus) at Ramnagar, where new alpha males were either recent immigrants or residents. Success was measured as alpha tenure, residency duration, and the number of offspring sired (paternity exclusion based on DNA analysis, 28 infants). We documented 12 alpha-male tenures across two multimale-multifemale groups between 1991 and 1997. The predominant mode of change was the immigrant tactic. Age had no effect perhaps because alpha males were among the youngest adult males in their group. As expected, infanticidal males performed similarly to non-infanticidal ones. Alpha tenure was highly variable and longer for immigrant alphas and hyper-aggressive ones. However, none of the tactics or attributes examined resulted in significantly longer residencies or more offspring, likely because of the timing of immigrations and stochastic effects (i.e., the number of conceptions occurring per alpha tenure). The influence of female mate choice on male reproductive success requires further investigation. Furthermore, it remains to be examined why resident alpha males-with their presumed better knowledge of their opponents -performed so poorly. Am. J. Primatol. 79:e22437, 2017. © 2015 Wiley Periodicals, Inc.

The importance of protein in leaf selection of folivorous primates.

Protein limitation has been considered a key factor in hypotheses on the evolution of life history and animal communities, suggesting that animals should prioritize protein in their food choice. This contrasts with the limited support that food selection studies have provided for such a priority in nonhuman primates, particularly for folivores. Here, we suggest that this discrepancy can be resolved if folivores only need to select for high protein leaves when average protein concentration in the habitat is low. To test the prediction, we applied meta-analyses to analyze published and unpublished results of food selection for protein and fiber concentrations from 24 studies (some with multiple species) of folivorous primates. To counter potential methodological flaws, we differentiated between methods analyzing total nitrogen and soluble protein concentrations. We used a meta-analysis to test for the effect of protein on food selection by primates and found a significant effect of soluble protein concentrations, but a non-significant effect for total nitrogen. Furthermore, selection for soluble protein was reinforced in forests where protein was less available. Selection for low fiber content was significant but unrelated to the fiber concentrations in representative leaf samples of a given forest. There was no relationship (either negative or positive) between the concentration of protein and fiber in the food or in representative samples of leaves. Overall our study suggests that protein selection is influenced by the protein availability in the environment, explaining the sometimes contradictory results in previous studies on protein selection. Am. J. Primatol. 79:e22550, 2017. © 2016 Wiley Periodicals, Inc.

Transparency, usability, and reproducibility: Guiding principles for improving comparative databases using primates as examples.

Recent decades have seen rapid development of new analytical methods to investigate patterns of interspecific variation. Yet these cutting-edge statistical analyses often rely on data of questionable origin, varying accuracy, and weak comparability, which seem to have reduced the reproducibility of studies. It is time to improve the transparency of comparative data while also making these improved data more widely available. We, the authors, met to discuss how transparency, usability, and reproducibility of comparative data can best be achieved. We propose four guiding principles: 1) data identification with explicit operational definitions and complete descriptions of methods; 2) inclusion of metadata that capture key characteristics of the data, such as sample size, geographic coordinates, and nutrient availability (for example, captive versus wild animals); 3) documentation of the original reference for each datum; and 4) facilitation of effective interactions with the data via user friendly and transparent interfaces. We urge reviewers, editors, publishers, database developers and users, funding agencies, researchers publishing their primary data, and those performing comparative analyses to embrace these standards to increase the transparency, usability, and reproducibility of comparative studies.

Dominance relationships in male Nepal gray langurs (Semnopithecus schistaceus).

OBJECTIVES: Reproductive skew is proposed to link to despotism in dominance hierarchies. While studies illustrating male skew are plentiful, demonstrating the link to despotism is rare. Likewise, it is often unknown which factors (e.g., resource holding potential, age, physical condition) affect a male's dominance rank. Here we investigated correlates of male rank and hierarchy characteristics in Nepal gray langurs (Semnopithecus schistaceus), a population with high male reproductive skew, and compared the results to other multi-male groups of nonhuman primates. METHODS: We collected dyadic displacement interactions from two groups (mean 3.0 and 4.1 adult males) for five years each. We assessed dominance ranks for demographically stable phases (n = 11, n = 28) and analyzed the effects of age and physical condition through linear mixed models (LMM). We analyzed hierarchy characteristics via the program MatMan. We used data from 27 primate groups (cercopithecines, colobines, hominoids) as a comparative sample. RESULTS: The highest ranks were attained by adults in one group (LMM, P < 0.091) and by young adults in the other group (LMM, P < 0.001). With some exceptions, rank was highest for males with higher physical condition scores (LMM, P < 0.05). Hierarchies had high directional consistency (mean > 0.93) and linearity (mean >0.81) and were relatively steep (mean >0.66) when compared with other species. DISCUSSION: Dominance rank followed a pattern predicted by resource holding potential, but other individual attributes and group composition also seemed important. As predicted, hierarchy characteristics indicated a despotic system in line with the strong reproductive skew. Across primates, however, the degree of despotism did not appear to match the degree of reproductive skew. Am J Phys Anthropol 160:208-219, 2016. © 2016 Wiley Periodicals, Inc.

The c-FLIPL cleavage product p43FLIP promotes activation of extracellular signal-regulated kinase (ERK), nuclear factor κB (NF-κB), and caspase-8 and T cell survival.

Caspase-8 is now appreciated to govern both apoptosis following death receptor ligation and cell survival and growth via inhibition of the Ripoptosome. Cells must therefore carefully regulate the high level of caspase-8 activity during apoptosis versus the modest levels observed during cell growth. The caspase-8 paralogue c-FLIP is a good candidate for a molecular rheostat of caspase-8 activity. c-FLIP can inhibit death receptor-mediated apoptosis by competing with caspase-8 for recruitment to FADD. However, full-length c-FLIPL can also heterodimerize with caspase-8 independent of death receptor ligation and activate caspase-8 via an activation loop in the C terminus of c-FLIPL. This triggers cleavage of c-FLIPL at Asp-376 by caspase-8 to produce p43FLIP. The continued function of p43FLIP has, however, not been determined. We demonstrate that acute deletion of endogenous c-FLIP in murine effector T cells results in loss of caspase-8 activity and cell death. The lethality and caspase-8 activity can both be rescued by the transgenic expression of p43FLIP. Furthermore, p43FLIP associates with Raf1, TRAF2, and RIPK1, which augments ERK and NF-κB activation, IL-2 production, and T cell proliferation. Thus, not only is c-FLIP the initiator of caspase-8 activity during T cell activation, it is also an initial caspase-8 substrate, with cleaved p43FLIP serving to both stabilize caspase-8 activity and promote activation of pathways involved with T cell growth.

The meaning of weaning in wild Phayre's leaf monkeys: last nipple contact, survival, and independence.

In primates and other mammals, weaning is an equivocal concept, as is reflected in the numerous ways it is measured: a) first intake of solid food, b) conflict over access to the nipple, c) ability to survive without mother, d) maternal resumption of cycling, or e) the cessation of nipple contact. The lack of a consistent definition means that weaning age, although it falls between gestation (fetal growth) and age at first reproduction (most energy diverted from growth), is currently not a reliable life history variable capturing offspring independence. Using data for wild Phayre's leaf monkeys (Trachypithecus phayrei crepusculus) at Phu Khieo Wildlife Sanctuary, Thailand (51 offspring, four groups), we asked whether the end of nipple contact indicates offspring independence as measured by survival to 3 years. To establish a baseline for the onset of independence, we assessed the youngest age at which individuals were orphaned (15-17 months) but then survived to 3 years. Next we determined that offspring age at last nipple contact (19.0 months) was comparable to two other independently calculated measures: offspring age at mother's first postpartum ovulation (11.5 months), and age at mother's re-conception (15.6 months). Using these separate "starting points," we arrived at similar ages for nipple contact cessation (18.4 and 19.2 months, respectively). Overall, in wild (but not in provisioned) Asian colobines, age at last nipple contact was allometrically related to adult female body mass, supporting its designation as a life history variable. Future comparisons need to show if this holds for other taxa.

Timing of conceptions in Phayre's leaf monkeys: Energy and phytochemical intake.

OBJECTIVES: Raising offspring imposes energetic costs, especially for female mammals. Consequently, seasons favoring high energy intake and sustained positive energy balance often result in a conception peak. Factors that may weaken this coordinated effect include premature offspring loss and adolescent subfertility. Furthermore, seasonal ingestion of phytochemicals may facilitate conception peaks. We examined these factors and potential benefits of a conception peak (infant survival and interbirth interval) in Phayre's leaf monkeys (Trachypithecus phayrei crepusculus). MATERIALS AND METHODS: Data were collected at Phu Khieo Wildlife Sanctuary, Thailand (78 conceptions). We estimated periods of high energy intake based on fruit and young leaf feeding and via monthly energy intake rates. Phytochemical intake was based on fecal progestin. We examined seasonality (circular statistics and cox proportional hazard models) and compared consequences of timing (infant survival and interbirth intervals, t-test, and Fisher exact test). RESULTS: Conceptions occurred in all months but peaked from May to August. This peak coincided with high fecal progestin rather than presumed positive energy balance. Primipara conceived significantly later than multipara. Neither infant survival nor interbirth intervals were related to the timing of conception. DISCUSSION: Periods of high energy intake may not exist and would not explain the conception peak in this population. However, the presumed high intake of phytochemicals was tightly linked to the conception peak. Timing conceptions to the peak season did not provide benefits, suggesting that the clustering of conceptions may be a mere by-product of phytochemical intake. To confirm this conclusion, seasonal changes in phytochemical intake and hormone levels need to be studied more directly.

Costs and benefits of allomaternal care to mothers and others in wild Phayre's leaf monkeys.

OBJECTIVES: Allomaternal care (AMC) is suggested to be energetically beneficial to mothers and costly to allomothers. However, among primates, AMC is a heterogeneous phenomenon and its implications are less clear especially in female dispersal species. Here, we investigated infant care in a female dispersal species, Phayre's leaf monkeys (Trachypithecus phayrei crepusculus), to evaluate whether mothers were constrained by infant care and benefitted energetically from AMC, whether AMC was energetically costly for allomothers and how maternal experience was associated with AMC. MATERIALS AND METHODS: Data were collected via instantaneous focal animal sampling between 2004 and 2005 for juvenile and adult females (N = 18) from two groups at the Phu Khieo Wildlife Sanctuary, Thailand (440 h). We used generalized linear mixed models to determine how infant care during the first month after birth affected the time mothers and allomothers spent feeding, socializing, resting, and locomoting and how AMC varied. RESULTS: In the first month, infants spent 26% of their time with an allomother. We found no differences in mothers' overall activity before versus after birth, although mothers fed significantly more and rested less when without their infant. Allomothers fed and rested less when with an infant. AMC varied between 0.0% and 20.5%, with immature females being most active. DISCUSSION: Mothers appear to benefit energetically from AMC such that their overall activity after birth remained unchanged. Costs and benefits for allomothers seem to be variable. Some very active immature females may be benefitting from learning-to-mother. The overall low cost of AMC may facilitate a reciprocal social network among unrelated females.