Despite extensive research on agriculture and climate in equatorial Africa, few studies integrate hydroclimate change with land use, crop vulnerability, pest and pathogen pressures, and the increasing dependence on pesticides in smallholder systems. Therefore, this study evaluated how changing hydroclimate conditions may influence pesticide use in smallholder landscapes surrounding a forested national park in western Uganda. Recent and projected trends in temperature, precipitation, and soil-water availability were used to assess future crop suitability and pest and pathogen impacts on major crops, while interviews with local stakeholders provided insight into the extent and risks of current pesticide use. Results showed that warming and wetting trends over the past several decades are expected to continue until at least mid-century. The current warming and wetting trends may strengthen and weaken, respectively, in the future. Despite the changing climate, temperatures and soil-water availability of the region as a whole should remain suitable for the current suite of crops grown there. Unfortunately, the combined effects of changing hydroclimate variables are likely to increase pest and pathogen pressure on crops. Interviews indicated that pesticide use is widespread and increasing, driven by pest outbreaks, labor constraints, and market pressures, with misuse, low adoption of protective equipment, limited extension support, and health and environmental impacts. Therefore, pesticide use is expected to increase further in upcoming decades, posing growing risks to farmer health, wetlands, and wildlife. Sustainable pest-management strategies, exemplified by integrated pest management, together with improved extension services, will be essential to reduce chemical exposure while maintaining yields.

Primate exposure to anthropogenic pollutants: A role for comparative aging research Daniella E. Chusyd of Indiana University discusses how variation in rates of aging across species can help us understand the consequences of our chemical exposome. Aging research seeks to understand why health, physical function, and cognitive abilities change over time. While aging is often thought of simply as ‘getting older,’ biologically it reflects a gradual accumulation of damage and dysregulation across multiple systems. In 2013, researchers proposed the ‘hallmarks of aging’ framework, which identified core biological processes that contribute to age-related decline. (1) These include genomic instability (i.e., DNA damage), telomere (i.e., protective caps on chromosomes) shortening, epigenetic alterations (i.e., changes to how genes are regulated), impaired protein maintenance, deregulated nutrient sensing, disrupted energy production in mitochondria, accumulation of senescent cells, stem cell exhaustion, and altered communication between cells. More recent updates have incorporated impaired cellular recycling (i.e., autophagy), chronic inflammation, and imbalances in the microbiome as additional contributors. (2)

Michael Wasserman of Indiana University discusses interactions among the chemical exposome, microbes, and hormones in wild primates. The use of omics methodology to look at a range of biological molecules from genes to proteins in organisms facing rapidly changing environments globally, especially to explore causal relationships between exposomes and biological outcomes within real-world complex social-ecological systems, offers the potential to address environmental and public health concerns. (1,2)

Background Elephants provide valuable insight into how early-life adverse events (ELAEs) associate with animal health and welfare because they can live to advanced ages, display extensive cognitive and memory capabilities, and rely heavily on social bonds. Although it is known that African savanna elephants that experienced ELAEs, such as being orphaned due to human activities, have altered behavioral outcomes, little is known regarding the physiological consequences associated with those stressors. Methods We compared fecal glucocorticoid (fGCM) and thyroid (fT3) metabolites as well as body condition scores (BCS) in rescued and rehabilitated orphaned (early-dry season: n = 20; late-dry season: n = 21 elephants) African savanna elephants in Kafue National Park, Zambia to age- and sex-matched wild non-orphaned controls groups (early-dry season: n = 57; late-dry season: n = 22 elephants) during the early- (May/June) and late- (September/October) dry seasons, respectively. Age and sex were known for orphans. For non-orphan controls, age was estimated based on dung diameter, and sex was determined based on external genitalia. Hormone concentrations were compared between groups by age class to account for developmental and nutritional transitions experienced in early life. Given that environmental stressors (e.g., availability of food and water sources) change over the course of the dry season, early- and late-dry seasons were separated in the analyses. Results fGCM concentrations were higher in orphans at younger ages than non-orphaned controls of any age. This may be due to the younger orphans being temporally closer to the traumatic event and thus not having had sufficient time to establish meaningful social bonds that could buffer the negative outcomes associated with ELAEs. Alternatively, orphans could have acclimated to living under human care, resulting in fGCM concentrations that were not different from wild controls at older ages. Orphans also had significantly higher mean fT3 concentrations than non-orphans, suggesting increased caloric intake during rehabilitation. There was no difference in BCS between orphan and non-orphan elephants at any age or time period, possibly reflecting the limitations associated with BCS assessments in younger elephants. Conclusions Together, these results provide insight into possible physiological responses underlying ELAEs and/or living under human care, including alterations in fGCM and fT3 concentrations, particularly in younger orphans. While these hormonal changes suggest a physiological response to trauma, the support of social bonds and acclimation to human care may mitigate long-term stress effects, highlighting the critical role of social integration in elephant rehabilitation and conservation efforts.

Primate exposure to anthropogenic pollutants: An overlooked conservation concern Michael Wasserman of Indiana University discusses research on wild primate exposure to endocrine disruptors, such as pesticides, flame retardants, and phytoestrogens. What are the current threats primates face globally? Tropical forests are home to the majority of terrestrial biodiversity, regulate climate, and purify air and water. (1) Despite their importance, deforestation continues to threaten these ecosystems, with both their loss and fragmentation leading to declines in primate populations that depend on them for habitat, food, and other resources. (2) As a result of tropical forest loss and fragmentation, along with hunting, infectious diseases (e.g., emerging pathogens and reverse zoonoses), and climate change, more than sixty percent of primate species are vulnerable to extinction. (3) Chemical pollution from increasing agricultural expansion, urbanization, and industrialization is also a threat to primates, but one that has been largely overlooked. (4)

Elephant populations across much of Africa face severe rates of decline due to poaching and habitat loss. The recent decision by the International Union for the Conservation of Nature (IUCN) to separately list African forest ( Loxodonta cyclotis ) and savanna ( L. africana ) elephants on the IUCN Red List both highlights the different threats of extinction faced by these two species and emphasizes the need for genetic data to classify taxonomically undefined populations across the continent. This includes western Uganda – a region that harbors the largest known modern hybrid zone between the two species. We combined a new high-throughput amplicon sequencing (HTAS) approach with fecal DNA-based Capture Mark Recapture (CMR) analysis to infer the population sizes and species compositions of elephants living in two forests. We demonstrate that Kibale National Park hosts a relatively large elephant population (573 individuals, 95% CI: 410 to 916; 0.72 elephants/km2) composed primarily of hybrids (81.5%) and savanna elephants (17.7%), while Bwindi Impenetrable National Park hosts a smaller population (96 individuals, 95% CI: 64 to 145; 0.29 elephants/km2) composed of forest elephants (86.8%) and hybrids (13.2%). We then sequenced maternally inherited (mtDNA) and paternally inherited (AMELY) genetic markers and found that the two parks’ populations exhibit different patterns of sex-linked genetic variation. The contrasting patterns of species identity and genetic variation between these parks demonstrate different histories of hybridization and highlight the importance of site-specific monitoring where elephants are taxonomically undefined. ### Competing Interest Statement The authors have declared no competing interest.

Primates exhibit diverse diets and related dietary adaptations which are expected to play a role in the exposure and toxicity of persistent organic pollutants. In the habitat of four primate species in Kibale National Park, Uganda, we quantified brominated flame retardants and organochlorine pesticides (OCPs) in air samples (n = 9), dietary plant samples (n = 32), and fecal samples from adult males and juveniles (n = 53). We also measured the fecal hormone metabolites cortisol and estradiol in juveniles (n = 38). In dietary plant samples, Σ32 brominated flame retardants (BFRs) ranged from 12–22 ng/g and Σ21OCPs ranged from 61–334 ng/g across primate species. In primate fecal samples, median Σ32BFRs ranged from 6–158 ng/g and Σ21OCPs s ranged from 39–261 ng/g. In juveniles, higher Σ32BFRs were associated with decreased cortisol in baboons and chimpanzees as well as total polybrominated diphenyl ethers and dechlorane plus in baboons and chimpanzees, respectively. In red-tailed monkeys, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate and Σ21OCPs were positively associated with cortisol. No significant associations between targeted pollutants and hormones were found in red colobus nor between estradiol and any chemical for any species. Our results indicate that despite their phylogenetic relatedness, the exposure, movement, and potential endocrine activity of pollutants varies across primate species. We suggest future studies exploring the mechanisms underlying phytochemical detoxification may help further elucidate connections between dietary niche and pollutant sensitivity in primates and at a broad taxonomic scale.

Parallel laser photogrammetry (PLP), which consists of attaching two or three parallel laser beams at a known inter-beam distance to a camera, can be used to collect morphological measurements of organisms noninvasively. The lasers project onto the photo being taken, and because the inter-beam distance is known, they act as a scale for image analysis programs like ImageJ. Traditionally, this method has been used to measure larger morphological traits (e.g., limb length, crown-rump length) to serve as proxies for overall body size, whereas applications to smaller anatomical features remain limited. To that end, we used PLP to measure the testes of 18 free-living mantled howler monkeys (Alouatta palliata) at La Selva Biological Station, Costa Rica. We tested whether this method could reliably measure this relatively small and globular morphology, and whether it could detect differences among individuals. We tested reliability in three ways: within-photo (coefficient of variation [CV] = 4.7%), between-photo (CV = 5.5%), and interobserver (intraclass correlation = 0.92). We found an average volume of 36.2 cm3 and a range of 16.4-54.4 cm3, indicating variation in testes size between individuals. Furthermore, these sizes are consistent with a previous study that collected measurements by hand, suggesting that PLP is a useful method for making noninvasive measurements of testes.

Variation in tropical forest management directly affects biodiversity and provisioning of ecosystem services on a global scale, thus it is necessary to compare forests under different conservation approaches such as protected areas, payments for ecosystem services programs (PES), and ecotourism, as well as forests lacking any formal conservation plan. To examine the effectiveness of specific conservation approaches, we examined differences in forest structure and tree recruitment, including canopy cover; canopy height; seedling, sapling, and adult tree density; and average and total diameter at breast height (DBH) across 78 plots in 18 forests across Costa Rica representing protected areas, private forests utilizing PES and/or ecotourism, and private forests not utilizing these economic incentives. The effectiveness of conservation approaches in providing suitable primate habitat was assessed by conducting broad primate census surveys across a subset of eight forests to determine species richness and group encounter rate of three primate species: mantled howler monkey (Alouatta palliata), Central American spider monkey (Ateles geoffroyi), and the white-faced capuchin monkey (Cebus imitator). Only canopy height was significantly different across the three approaches, with protected areas conserving the tallest and likely oldest forests. Canopy height was also significantly associated with the group encounter rate for both mantled howler and spider monkeys, but not for capuchins. Total group encounter rate for all three monkey species combined was higher in incentivized forests than in protected areas, with capuchin and howler monkey group encounter rates driving the trend. Group encounter rate for spider monkeys was higher in protected areas than in incentivized forests. Incentivized conservation (PES and ecotourism) and protected areas are paragons of land management practices that can lead to variation in forest structure across a landscape, which not only protect primate communities, but support the dietary ecologies of sympatric primate species.

While anthropogenic pollutants are known to be a threat to primates, our understanding of exposure to pollutants in situ and their sub-lethal effects is still limited. We used non-invasive biomonitoring to examine associations between faecal concentrations of 97 chemical pollutants and faecal hormone metabolites of cortisol and oestradiol in four primate species inhabiting Kibale National Park, Uganda (chimpanzees-Pan troglodytes, olive baboons-Papio anubis, red colobus-Piliocolobus tephrosceles and red-tailed monkeys-Cercopithecus ascanius). Across all species (n = 71 samples), results demonstrated positive associations of organochlorine pesticides (OCPs) (β = 0.143, p = 0.020) and organophosphate esters (β = 0.112, p = 0.003) with cortisol in adult females. Additionally, we observed positive associations of OCPs (β = 0.192, p = 0.013) and brominated flame retardants (β = 0.176, p = 0.004) with cortisol in juveniles. Results suggest that cumulative pesticides and flame retardants are disruptive to endocrine function in these populations, which could have implications for development, metabolism and reproduction. Our study further demonstrates that faeces can be an important, non-invasive matrix for examining pollutant-hormone associations in wild primates and other critical wildlife populations.

Abstract Wild elephant populations provide a natural experiment to study biological effects of early adverse events, such as being orphaned due to poaching. We compared fecal glucocorticoid metabolite (fGCM) and thyroid hormone (T3) concentrations, and body condition between rescued orphaned elephants and similarly age-matched, control wild elephants. In 2021, single fecal samples were collected during the early (n=20 orphans; n=58 controls) and late (n=20 orphans; n=22 controls) dry seasons. Age was known (+/- 3 months) for orphans and estimated by dung diameter (+/- 1 year) for controls. Sex was assigned based on morphology and unknown for some controls. Body condition scores (BCS: 1 to 9) were assigned at time of sample collection. Linear Mixed Models accounting for repeated measures were performed adjusted for age and season. There was no difference in fGCM between orphans (mean 101.48, SD 59.62ng/g) and controls (mean 93.86, SD 49.97ng/g) (p=0.213). Orphans (mean 271.75, SD 123.16ng/g) had higher T3 concentrations compared to controls (mean 98.65, SD 71.89ng/g) (p< 0.001). There was no difference in BCS between groups (p=0.629). In orphans, fGCM was associated with age (beta=-0.499, p=0.011). In controls, T3 was correlated with fGCM (beta=0.287, p=0.011) and season was associated with fGCM (p=0.008) and BCS (p=0.044). Either because of living under human care or because of alterations in T3 secretion, seasonal factors do not seem to impact orphans’ health status to the same extent as in control elephants. The support of an adopted herd may attenuate the physiological stress associated with experiencing trauma in our study population.

Hormone laboratories located “on-site” where field studies are being conducted have a number of advantages. On-site laboratories allow hormone analyses to proceed in near-real-time, minimize logistics of sample permits/shipping, contribute to in-country capacity-building, and (our focus here) facilitate cross-site collaboration through shared methods and a shared laboratory. Here we provide proof-of-concept that an on-site hormone laboratory (the Taboga Field Laboratory, located in the Taboga Forest Reserve, Costa Rica) can successfully run endocrine analyses in a remote location. Using fecal samples from wild white-faced capuchins (Cebus imitator) from three Costa Rican forests, we validate the extraction and analysis of four steroid hormones (glucocorticoids, testosterone, estradiol, progesterone) across six assays (DetectX® and ISWE, all from Arbor Assays). Additionally, as the first collaboration across three long-term, wild capuchin field sites (Lomas Barbudal, Santa Rosa, Taboga) involving local Costa Rican collaborators, this laboratory can serve as a future hub for collaborative exchange.