The impact of dental impairment on ring-tailed lemur food processing performance

What Can the Gut Microbiota of Animals Teach Us about the Relationship between Nutrition and Burden of Lifestyle Diseases?

The gut microbiota performs several crucial roles in a holobiont with its host, including immune regulation, nutrient absorption, synthesis, and defense against external pathogens, significantly influencing host physiology. Disruption of the gut microbiota has been linked to various chronic conditions, including cardiovascular, kidney, liver, respiratory, and intestinal diseases. Studying how animals adapt their gut microbiota across their life course at different life stages and under the dynamics of extreme environmental conditions can provide valuable insights from the natural world into how the microbiota modulates host biology, with a view to translating these into treatments or preventative measures for human diseases. By modulating the gut microbiota, opportunities to address many complications associated with chronic diseases appear. Such a biomimetic approach holds promise for exploring new strategies in healthcare and disease management.

Characteristics of gut microbiota in captive Asian elephants (Elephas maximus) from infant to elderly

Gut microbiota play an important role in the health and disease of Asian elephants, however, its characteristics at each stage of life have not been thoroughly investigated in maintaining and regulating health of elephants. This study, therefore, aimed to characterize the profiles of the gut microbiota of captive Asian elephants from infants to the elderly. Gut microbiota were identified by 16S rRNA sequencing from the feces of captive Asian elephants with varying age groups, including infant calves, suckling calves, weaned calves, subadult and adult elephants, and geriatric elephants. The diversity of the gut microbiota was lowest in infants, stable during adulthood, and slightly decreased in the geriatric period. The gut microbiota of the infant elephants was dominated by milk-fermenting taxa including genus Bifidobacterium of family Bifidobacteriaceae together with genus Akkermansia. The fiber-fermenting taxa such as Lachnospiraceae_NK3A20_group were found to be increased in suckling elephants in differential abundance analysis by Analysis of Compositions of Microbiomes with Bias Correction (ANCOM-BC). The gut microbiota profiles after weaning until the adult period has been uniform as indicated by no significant differences in beta diversity between groups. However, the composition of the gut microbiota was found to change again in geriatric elephants. Understanding of the composition of the gut microbiota of captive Asian elephants at various life stages could be beneficial for promoting good health throughout their lifespan, as well as ensuring the welfare of captive elephants.

Primates and disability: Behavioral flexibility and implications for resilience to environmental change

Congenital malformations, conditions, injuries, and illness can lead to long-term physical impairment and disability in nonhuman primates. How individual primates change their behaviors flexibly to compensate for their disabilities can inform our understanding of their resilience and ability to adjust to environmental change. Here, we synthesize the literature on nonhuman primates and disability, addressing the questions: how does disability influence behavior in primates? What insights can we take from the literature to better understand and predict the capacity of primates to modify their behaviors in the face of human-induced environmental change? We conducted a systematic review of the literature on spontaneous physical impairment and disability in captive, free-ranging, and wild primates. We surveyed 2807 articles on Web of Science and Scopus and identified 114 studies that fit our predetermined inclusion criteria. Behavioral plasticity, maternal and conspecific care, and the potential for innovation of novel behaviors allow many primates with disabilities to compensate when faced with challenges that are outside the scope of usual circumstances. We also found that 60% of the publications connected primate physical impairment and disability to human activities, suggesting an entangled relationship among humans, the environment, and primate disability. Disability and physical impairments provide an opportunity to examine how primates modify their behavior when presented with challenging conditions, and their potential resilience to a changing environment.

Diademed sifakas (Propithecus diadema) in intact and degraded forest habitat at Tsinjoarivo, Madagascar, show high reproductive success and no evidence that dental senescence or rainfall affects reproductive output

Sifakas (genus Propithecus) diverge from other lemurs in their strategy to contend with Madagascar’s highly seasonal climate and maximize reproductive success: they have long lifetimes (presumably to wait out unfavorable times) and extreme dental precocity (to allow weanlings to effectively process tough foods and thereby relieve energetic stress on mothers). However, as sifakas age, dental senescence can contribute to reproductive failure, especially when coupled with unfavorable weather conditions (as shown by King et al., 2005 for P. edwardsi at Ranomafana). To extend the effective life of the teeth, compensatory blades maintain functionality for the female sifaka, but wear may eventually have consequences on infant survival in certain climatic scenarios. We investigate the impacts of climate, age, and dental senescence on the reproduction of another sifaka, Propithecus diadema, in fragmented and intact habitats of Tsinjoarivo, Madagascar. We documented birth and infant survival between 2002 and 2017 across twelve groups, including 73 births, and we used 77 dental casts representing 54 adults to estimate age when exact age was not known. We report that sifakas in Tsinjoarivo do not conform to the expectations that link advanced age with dental and reproductive senescence. Propithecus diadema at Tsinjoarivo show slower tooth wear, higher reproductive output and higher infant survival compared to congeners. Likelihood of birth and infant mortality do not correlate with intrinsic (mother’s age, tooth wear) or extrinsic (rainfall or habitat type) stressors. However, the small number of years without births or with infant deaths limits statistical power. At the local level, this study suggests that the long-term viability of Propithecus diadema at Tsinjoarivo is promising and reproductive output is high, even in disturbed fragments where nutrient intakes are reduced. Further research is needed to contextualize and understand these differences among sites and regions within Madagascar and avoid over-generalizing from single study sites.

Effects of diet and age-sex class on the fecal particle size of wild Japanese macaques (Macaca fuscata yakui)

Fecal particle size provides important information on the feeding and digestion of herbivores. Understanding the effects of the potential proximate determinants on fecal particle size helps us interpret this widely used measurement. In folivores, previous studies found that diet composition, dietary toughness, and age-sex-related factors, such as body size and tooth wear, influenced fecal particle size. However, the role of these factors remains unknown in frugivorous and omnivorous primates. This study aims to clarify how age-sex class and diet influence fecal particle size in omnivorous Japanese macaques in Yakushima. We expected that their variable diet and differences among age-sex classes would cause variations in fecal particle size. We simultaneously documented Japanese macaques' diet, dietary toughness, and fecal particle size in the lowland area of Yakushima in the period from March 2018 to April 2019. Unexpectedly, fecal particle size showed limited differences across months and no difference among age-sex classes. Dietary toughness showed no effects on fecal particle size, while the consumption of fruits showed only a marginally significant negative effect. Our data indicate that the results of chewing were not affected by dietary toughness in our study subjects, while age-sex classes showed no difference in food comminution. This lack of variation might derive from a diet with low dietary toughness. We also found that the physical structure of preferred foods played an important role in fecal particle size variations. These results suggest that food comminution is less variable in frugivorous and omnivorous primates compared to highly specialized species (e.g., geladas). Factors other than what we examined in this study, such as food physical structure and chewing behavior, should also be taken into consideration.

Host age, social group, and habitat type influence the gut microbiota of wild ring-tailed lemurs (Lemur catta)

The gut microbiota contributes to host health by maintaining homeostasis, increasing digestive efficiency, and facilitating the development of the immune system. The composition of the gut microbiota can change dramatically within and between individuals of a species as a result of diet, age, or habitat. Therefore, understanding the factors determining gut microbiota diversity and composition can contribute to our knowledge of host ecology as well as to conservation efforts. Here we use high-throughput sequencing to describe variation in the gut microbiota of the endangered ring-tailed lemur (Lemur catta) at the Bezà Mahafaly Special Reserve (BMSR) in southwestern Madagascar. Specifically, we measured the diversity and composition of the gut microbiota in relation to social group, age, sex, tooth wear and loss, and habitat disturbance. While we found no significant variation in the diversity of the ring-tailed lemur gut microbiota in response to any variable tested, the taxonomic composition of the gut microbiota was influenced by social group, age, and habitat disturbance. However, effect sizes were small and appear to be driven by the presence or absence of relatively low abundance taxa. These results suggest that habitat disturbance may not impact the lemur gut microbiota as strongly as it impacts the gut microbiota of other primate species, highlighting the importance of distinct host ecological and physiological factors on host-gut microbe relationships. Am. J. Primatol. 78:883-892, 2016. © 2016 Wiley Periodicals, Inc.

Age-related changes in molar topography and shearing crest length in a wild population of mountain Gorillas from Volcanoes National Park, Rwanda

OBJECTIVES

Great ape teeth must remain functional over long lifespans. The molars of the most folivorous apes, the mountain gorillas, must maintain shearing function for 40+ years while the animals consume large quantities of mechanically challenging foods. While other folivorous primates experience dental senescence, which compromises their occlusal surfaces and affects their reproductive success as they age, it is unknown whether dental senescence also occurs in mountain gorillas. In this article, we quantified and evaluated how mountain gorilla molars change throughout their long lifespans.

MATERIALS AND METHODS

We collected high-resolution replicas of M(1)s (n = 15), M(2)s (n = 13), and M(3)s (n = 11) from a cross-sectional sample of wild mountain gorilla skeletons from the Virunga Volcanoes, ranging in age from 4 to 43 years. We employed dental topographic analyses to track how aspects of occlusal slope, angularity, relief index, and orientation patch count rotated change with age. In addition, we measured the relative length of shearing crests in two- and three-dimensions.

RESULTS

Occlusal topography was found to decrease, while 2D relative shearing crest length increased, and 3D relative crest lengths were maintained with age.

DISCUSSION

Our findings indicate that shearing function is maintained throughout the long lifetimes of mountain gorillas. Unlike the dental senescence experienced by other folivorous primates, mountain gorillas do not appear to possess senesced molars despite their long lifetimes, mechanically challenging diets, and decreases in occlusal topography with age.

Sources of tooth wear variation early in life among known-aged wild ring-tailed lemurs (Lemur catta) at the Bezà Mahafaly Special Reserve, Madagascar

Ring-tailed lemurs (Lemur catta) at the Bezà Mahafaly Special Reserve (BMSR), Madagascar display a high frequency of individuals with notable and sometimes extreme tooth wear. Adult lemurs display a range of tooth wear even among individuals of the same age, but we do not know at what age this variation first appears. This study's goal was to determine whether wear variation occurs in younger wild lemurs. Based on the decade-long study of ring-tailed lemur feeding and dental ecology at BMSR, we hypothesized that younger, natal lemurs (under 5 years of age), would display variation in their degree of tooth wear that would correspond to microhabitat differences, given differences in food availability in different troops' home ranges. We also hypothesized that wear would differ between sexes at this young age, given differences in feeding between males and females in this population. Hypotheses were tested using dental topographic analyses using dental impressions collected from known-aged lemurs across 10 years at BMSR. Results illustrate significant differences in wear-related tooth topography (i.e., relief and slope, presented here as "occlusal lift") for microhabitat, sex and troop affiliation among lemurs under 5 years of age in this population. Although, all lemurs in this population consume mechanically challenging tamarind fruit, those in more disturbed habitats eat additional introduced foods, some of which are also mechanically challenging. Thus, dietary variation is the likely cause of variation in tooth wear. The wear variation we show at a young age suggests caution when assigning age based on tooth wear in living and fossil primates. These wear-related tooth shape changes early in life, which reflects sex, habitat variation and levels of anthropogenic disturbance, may potentially impact reproductive fitness later in life.

A comparison of antemortem tooth loss in human hunter-gatherers and non-human catarrhines: implications for the identification of behavioral evolution in the human fossil record

Middle and Late Pleistocene fossil hominin specimens with severe antemortem tooth loss are often regarded as evidence for the precocious evolution of human-like behaviors, such as conspecific care or cooking, in ancient hominin species. The goal of this project was to ask whether the theoretical association between antemortem tooth loss and uniquely human behaviors is supported empirically in a large skeletal sample of human hunter-gatherers, chimpanzees, orangutans, and baboons. Binomial regression modeling in a Bayesian framework allows for the investigation of the effects of tooth class, genus, age, and sex on the likelihood of tooth loss. The results strongly suggest that modern humans experience more antemortem tooth loss than non-human primates and identify age in years as an important predictor. Once age is accounted for, the difference between the humans and the closest non-human genus (chimpanzees) is less pronounced; humans are still more likely on average to experience antemortem tooth loss though 95% uncertainty envelopes around the average prediction for each genus show some overlap. These analyses support theoretical links between antemortem tooth loss and modern human characteristics; humans' significantly longer life history and a positive correlation between age and antemortem tooth loss explain, in part, the reason why humans are more likely to experience tooth loss than non-human primates, but the results do not exclude behavioral differences as a contributing factor.