About

Tierra Smiley Evans is an Assistant Professor of Emerging Zoonoses at UC Berkeley with a joint appointment in the department of Integrative Biology. She uses computational methods and natural field systems to study pathogen spillover at the interface of humans, wildlife, and the environment. Her research investigates how anthropogenic forest change influences the ecology and evolution of zoonotic viruses, focusing on the relationship between global forest change, biodiversity loss, and disease emergence. The Smiley Lab studies patterns of disease spillover at newly created forest edges and their impact on human and wildlife health. Her educational background includes a PhD in Infectious Disease Epidemiology from the University of California, Davis, a DVM (Doctor of Veterinary Medicine) from Tufts University, and a BS in Combined Sciences from Santa Clara University. Her work emphasizes scientific capacity strengthening in low- and middle-income countries and contributes to understanding zoonotic disease emergence, wildlife health, conservation, and transmission dynamics of pathogen spillover.

Research topics

• Ecology
• Biology
• Political Science
• Business
• Zoology
• Environmental planning
• Environmental health
• Virology
• Medicine
• Economics
• Geography
• Environmental resource management

Selected publications

• Craniofacial Fluctuating Asymmetry in Cross River Gorillas ( <scp> <i>Gorilla gorilla diehli</i> </scp> )

  American Journal of Biological Anthropology · 2026-04-01

  article

  OBJECTIVES: Craniofacial fluctuating asymmetry (FA) in gorillas has been linked to environmental and/or genetic stress. Prolonged population declines increase levels of inbreeding, leading to developmental instability, which can manifest as FA. Among gorillas studied to date, craniofacial FA levels are highest in mountain gorillas (G. beringei beringei) and lowest in western lowland gorillas (G. gorilla gorilla), reflecting known levels of genetic diversity and inbreeding in these subspecies. This study assessed craniofacial FA in Cross River gorillas (G. gorilla diehli), a little-known subspecies with high levels of inbreeding due to a recent genetic bottleneck. MATERIALS AND METHODS: Thirty fixed landmarks of the craniofacial skeleton were used to assess FA in 30 Cross River gorillas using Procrustes ANOVA. Principal component analysis assessed variation in both symmetric and asymmetric components. Differences in FA magnitudes between Cross River gorillas and published data for other Gorilla subspecies were assessed using permutation tests. RESULTS: Craniofacial FA accounts for 9.9% of shape variation in Cross River gorillas, whereas directional asymmetry accounts for 0.5%. Allometry accounts for 14.1% of shape variation in the symmetric component and 3.8% in the asymmetric component. Craniofacial FA magnitudes are higher in Cross River gorillas than in western lowland gorillas and lower than in mountain gorillas. DISCUSSION: High FA in Cross River gorillas aligns with known levels of inbreeding, supporting the link between genetic stress and craniofacial FA in gorillas. Persistent inbreeding and the loss of genetic diversity may decrease population fitness, further increasing the risk of extinction.

  PublisherOA PDFDOI

• Frequency of arboreality is correlated with longer hand skeletons in <i>Gorilla</i> : Analysis of a new skeletal sample of Bwindi mountain gorillas

  Journal of Anatomy · 2026-04-19

  articleOpen access

  Understanding how ecological variation shapes skeletal morphology is important for linking observed locomotor behavior to anatomical correlates in extant hominoids, and for the subsequent interpretation of locomotor behavior in extinct taxa. In this study, we investigate ecomorphological variation in the metacarpals and phalanges across all five manual rays within Gorilla, focusing particularly on differences between western lowland gorilla (Gorilla gorilla gorilla) and the Rwandan (Volcanoes National Park) and Ugandan (Bwindi Impenetrable National Park) populations of mountain gorilla (Gorilla beringei beringei). This work incorporates the first substantial set of skeletal measurements from the Bwindi mountain gorilla population, derived from individuals recovered by the Mountain Gorilla Skeletal Project between 2018 and 2025. By comparing these data with samples from low and high-elevation Grauer's gorillas (Gorilla beringei graueri), we assess how variation in arboreality correlates with digit element lengths, demonstrating that the Bwindi mountain gorillas exhibit intermediate metacarpal and phalangeal lengths between the more arboreal western lowland gorillas and the more terrestrial Virunga mountain gorillas. These findings indicate a correlation between longer digital rays in more arboreal populations, even within the same species, which may enhance grasping and stability on arboreal substrates. We show a population-specific relationship between ecology and hand morphology in Gorilla and emphasize the value of documenting localized skeletal responses to environmental and behavioral variation to better interpret patterns in the hominoid fossil record.

  PublisherDOI

• Non-invasive genomic sampling uncovers novel connectivities and origins of confiscated gorillas

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-02-05

  articleOpen access

  Abstract Background Gorillas are a group of African great apes with two species and four subspecies that are currently critically endangered or endangered. Previous studies that analysed the genetics of wild gorillas from non-invasive samples, such as faeces or hair, analysed short mitochondrial or nuclear markers, which may not reflect the wider nuclear genome. Recent technical advances in target capture hybridisation, enrich the endogenous DNA content of non-invasive samples, allowing contiguous genomic regions to be sequenced. Results Here, we generated georeferenced genetic data from faecal and hair samples of 280 wild gorillas, sampled from three of the four gorilla subspecies, across large parts of their present-day distributions. With this expanded representation of gorilla genetic diversity in the wild, we detected three population clusters in western lowland gorillas, with the Sangha River and its affluents acting as significant barriers to gene flow. We reconstructed patterns of past population connectivity between western lowland gorillas in the north-eastern distribution range and Cross River gorillas, which may have been facilitated by a migration corridor also used by the Central and Nigeria-Cameroon chimpanzee subspecies. Finally, we predicted the geographic origins of wild-born gorillas, achieving a mean prediction error of 65 km, with a population-level resolution for mountain gorillas and some populations of western lowland gorillas. Conclusion Our work characterises fine-scale population structure in western lowland gorillas, which will be informative for future conservation strategies. This proof of concept in predicting geographic locations of wild gorillas, will be useful for future applications to geolocalise trafficked or rescued gorillas.

  PublisherDOI

• Limestone karst ecology and anthropogenic activities associated with cave-dwelling bats of Southern Shan State, Myanmar

  Global Ecology and Conservation · 2026-01-15

  articleOpen accessSenior authorCorresponding

  Limestone cave systems constitute an important ecological niche supporting numerous bat species in Southeast Asia, with Myanmar, having a particular high number of understudied caves. Investigating the natural and anthropogenic ecological drivers that influence higher densities and species diversity of bats co-roosting in these natural caverns is therefore vital for identifying regions of heightened conservation need. We examine characteristics of limestone caves and alternative sites of bat congregation / roosting associated with cave-dwelling bat abundance at 41 sites in Pinlaung Township, Southern Shan State, Myanmar. The characteristics evaluated included cave surface area and complexity, microclimate conditions, seasonality, and a modified biotic vulnerability (BV) index. Larger caves and caves with warmer temperatures were significantly more likely to support higher total numbers of bats. Further distance from the road was also associated with higher bat abundance; as the distance increased, human disturbance decreased, resulting in larger bat populations. The majority (63.2%) of caves were classified as moderately vulnerable (BV class B), 18.4% highly vulnerable (BV class A), and 18.4% vulnerable (BV class C), indicating that environmental protections are essential to ensuring the long-term sustainability of cave-dwelling bat habitat within limestone karsts. Most cave sites evaluated faced multiple threats to bat populations, including bat hunting, guano harvesting, and cave development, which are known threats to cave-dwelling bats in other parts of Southeast Asia. This study identifies Southern Shan State, Myanmar as a critical habitat for limestone karst cave-dwelling bat species habitat that is in urgent need of conservation.

  PublisherDOI

• Environmental and demographic risk factors for respiratory illness in endangered wild mountain gorillas (Gorilla beringei beringei) in Rwanda

  Frontiers in Conservation Science · 2026-02-23

  articleOpen access

  Morbidity and mortality from infectious diseases are an important health consideration for free ranging great apes, and respiratory illness (RI) is of particular concern in mountain gorillas ( Gorilla beringei beringei ), accounting for 25% all of mortalities. In addition to ongoing efforts to determine the etiology of RI in mountain gorillas, an improved understanding of environmental and demographic risk factors for the development of RI is critical for informing a disease prevention strategy for this species. To evaluate potential risk factors for RI, data were compiled from medical and life history records on free-ranging human-habituated mountain gorillas in Rwanda over a 7-year period from December 2005-December 2012. Associations between demographic, environmental and management risk factors and the presence of signs of clinical RI were evaluated using a multivariable mixed-effects logistic regression model. Clinical records from 21 habituated gorilla family groups, including 346 individuals, were included in analyses. Seventy-one percent of groups (n=15/21 gorilla groups) and 55% of individuals (n=192/346 gorillas) experienced at least one RI event. Rainy season (odds ratio [OR]=2.30, 95% CI = 1.74-3.03, P-value&amp;lt;0.001) and group size (OR = 1.15, 95% CI = 1.11-1.18, P-value&amp;lt;0.001) were associated with increased odds of RI in mountain gorillas, and there was a significant trend of increasing odds of RI with increasing group size for groups larger than 16 individuals and a more than 3-fold increase in odds of RI for groups larger than 38 individuals compared to groups of ten or less.

  PublisherOA PDFDOI

• Detection of Wencheng shrew virus and cardiovirus from small mammals in Myanmar

  Scientific Reports · 2026-02-18

  articleOpen access

  Myanmar is one of the most biodiverse countries from a species perspective in Southeast Asia, yet there is minimal published data on zoonotic viruses in small mammals. From July 2017 to August 2018, wildlife sampling was conducted at human-animal interfaces at sites in the Yangon Region and Kayin State. To investigate virus diversity of commensal rodents and shrew, rectal swabs were collected from mice (Mus sp., N = 3), rats (Rattus norvegicus, N = 80; Rattus rattus, N = 6), and Southeast Asian shrews (Crocidura fuliginosa, N = 8). RNA was extracted from rectal swabs, made into cDNA, and subjected to metagenomic next-generation sequencing followed by phylogenetic analysis for virus identification and taxonomic placement. The study provides the first detection of Wencheng shrew virus (WESV) in Myanmar and the first report in C. fuliginosa. A novel member of the genus Cardiovirus was also detected in R. norvegicus and clustered with Cardiovirus theileri sequences previously identified in wild rats from China. Further characterization of viruses circulating in small mammals will help inform public health officials of potential zoonotic risks in a region with virus surveillance gaps and ongoing land use change which may be increasing the risk of zoonotic disease emergence.

  PublisherOA PDFDOI

• The potential threat of Strongyloides spp. to mountain gorillas and public health in Bwindi Impenetrable National Park, Uganda

  Parasitology Research · 2026-02-18

  articleOpen access

  Soil-transmitted nematodes Strongyloides spp. parasitize a range of vertebrates, including endangered great apes and humans. Since 2018, the Mountain Gorilla Veterinary Project has observed an increase in gastrointestinal parasitic infections, including suspected strongyloidiasis in mountain gorillas in Bwindi Impenetrable National Park (BINP), Uganda. To investigate the prevalence of Strongyloides and potential cross-host transmission, we conducted noninvasive fecal sampling of mountain gorillas, olive baboons, domestic dogs and pigs. Samples were examined by coproscopy and real-time PCR followed by sequencing of the HVR-IV 18S rRNA and cox1 genes. Strongyloides prevalence was higher in mountain gorillas ranging near the park edge compared to forest interiors inside the park and among infant and juvenile mountain gorillas compared to other age groups. Strongyloides fuelleborni, a known zoonotic species, was identified in both baboons and mountain gorillas, suggesting sharing this particular parasite between the two primate species with potential implications for humans surrounding the park. In domestic animals, S. ransomi was detected in pigs, a zoonotic lineage S. stercoralis haplotype was detected in one dog, and another haplotype closely related to S. ransomi and S. venezuelensis was identified in another dog. The presence of zoonotic S. fuelleborni and S. stercoralis in Bwindi ecosystem poses a threat to mountain gorilla as well as human public health. Our study underscores the need for continued monitoring and community sensitization about the risk of cross-species transmission of these parasites.

  PublisherDOI

• Assessment of exposure to zoonoses and perceptions of zoonotic transmission surrounding the Bwindi impenetrable forest, Uganda

  PLoS neglected tropical diseases · 2025-11-17

  articleOpen accessSenior authorCorresponding

  INTRODUCTION: Emerging infectious diseases with regional spread and potential to escalate to a global pandemic have increased in the last century. Western Uganda has experienced many emerging infectious disease outbreaks over the last five decades, some with worldwide implications. Outbreaks have originated from wild animal reservoir hosts including Marburg and Sudan virus. The goal of this study was to better understand communities contacts with wild and domestic animals and their knowledge of potential disease risks associated with these interactions around Bwindi Impenetrable National Park (BINP), a known foci for spillover events. METHODS: Focus groups (n = 24 groups) with 153 participants were convened and interview guide (See S1 Text) was used to conduct discussions in rural and urban settings surrounding BINP in Southwestern Uganda. Mixed methods were used for data analysis. For qualitative data, thematic analysis was used to identify and organize patterns of meaning related to the study objectives. Inductive coding and deductive analysis using a codebook was used to explore key themes associated with community understanding of zoonotic infections and participation in high-risk activities. For the quantitative analysis, a count data set was generated using the themes, sub-themes, and codes from the codebook. Multivariable logistic regression was used to assess the association of demographic, geographic and occupational factors with zoonotic understanding. RESULTS: Few participants believed animals could transmit diseases to humans (or vice versa), with rural, younger residents as well as those working in healthcare showing higher awareness. Interviews corroborated this finding noting that even when recognized as potentially unsafe, meat from diseased animals was rarely reported and often consumed or resold. CONCLUSIONS: Misconceptions about zoonotic disease transmission are prevalent in Southwestern Uganda despite high-risk for spillover. Policy makers and government entities should prioritize culturally appropriate community education, contextually relevant mitigation of potential spillover events, and comprehensive research into drivers of high-risk activities.

  PublisherDOI

• NEOPLASIA AND PROLIFERATIVE LESIONS IN FREE-RANGING MOUNTAIN AND GRAUER'S GORILLAS (GORILLA BERINGEI)

  Journal of Zoo and Wildlife Medicine · 2025-06-05

  articleCorresponding

  There are no published data on the occurrence of neoplasia in wild great apes of any species. The aim of this study was to utilize postmortem and histopathology reports collected from wild human-habituated mountain gorillas (Gorilla beringei beringei) and Grauer's gorillas (Gorilla beringei graueri) to determine both the incidence and types of spontaneous neoplasms and proliferative lesions that occur in these species. Pathology records of 194 mountain gorillas and 12 Grauer's gorillas necropsied from 1985 to 2020 were examined for all cases of neoplasia or hyperplastic/proliferative disease. Slides and/or scanned images were reviewed to confirm morphologic diagnoses. Data were collected on comorbidities that may have contributed to neoplastic/proliferative transformation. A total of nine malignant neoplasms were identified: large cell anaplastic B-cell lymphoma, gastric adenocarcinoma (two cases), gastric carcinoid, oral mucocutaneous malignant melanoma, gastric carcinoma in situ (two cases), squamous cell carcinoma of the lip, and renal adenocarcinoma. Benign lesions included pheochromocytoma, adrenocortical adenoma (two cases), parathyroid adenoma, mandibular fibroma with gingival hyperplasia, and uterine hemangioma. Proliferative gastritis was commonly identified secondary to gastrointestinal parasitism (n = 35); chronic inflammation from nematodiasis may have led to neoplastic transformation of hyperplastic mucosal epithelium. Other hyperplastic lesions included nodular hyperplasia of the adrenal cortex (n = 9), adrenal medulla (n = 7) and thyroid glands (n = 3), pulmonary reactive lymphoid hyperplasia in infants and juveniles (n = 16), as well as nodular splenic siderofibrosis (n = 5) that may be associated with parasite migration. These findings demonstrate that free-ranging mountain and Grauer's gorillas in a natural environment develop neoplasia and proliferative disease.

  PublisherDOI

• Confirmation of Skywalker Hoolock Gibbon (Hoolock tianxing) in Myanmar Extends Known Geographic Range of an Endangered Primate

  International Journal of Primatology · 2024-02-14 · 4 citations

  articleOpen accessSenior author

  Abstract Characterizing genetically distinct populations of primates is important for protecting biodiversity and effectively allocating conservation resources. Skywalker gibbons ( Hoolock tianxing ) were first described in 2017, with the only confirmed population consisting of 150 individuals in Mt. Gaoligong, Yunnan Province, China. Based on river geography, the distribution of the skywalker gibbon has been hypothesized to extend into Myanmar between the N’Mai Kha and Ayeyarwaddy Rivers to the west, and the Salween River (named the Thanlwin River in Myanmar and Nujiang River in China) to the east. We conducted acoustic point-count sampling surveys, collected noninvasive samples for molecular mitochondrial cytochrome b gene identification, and took photographs for morphological identification at six sites in Kachin State and three sites in Shan State to determine the presence of skywalker gibbons in predicted suitable forest areas in Myanmar. We also conducted 50 semistructured interviews with members of communities surrounding gibbon range forests to understand potential threats. In Kachin State, we audio-recorded 23 gibbon groups with group densities ranging between 0.57 and 3.6 group/km 2 . In Shan State, we audio-recorded 21 gibbon groups with group densities ranging between 0.134 and 1.0 group/km 2 . Based on genetic data obtained from skin and saliva samples, the gibbons were identified as skywalker gibbons (99.54–100% identity). Although these findings increase the species’ known population size and confirmed distribution, skywalker gibbons in Myanmar are threatened by local habitat loss, degradation, and fragmentation. Most of the skywalker gibbon population in Myanmar exists outside protected areas. Therefore, the IUCN Red List status of the skywalker gibbon should remain as Endangered.

  PublisherOA PDFDOI

Recent grants

• Epidemiology of zoonotic viruses in forest communities in a key biodiversity area of rural Myanmar

  NIH · $763k · 2016–2022

Frequent coauthors

• Christine K. Johnson

  University of California, Davis

  51 shared

• Hlaing Myat Thu

  Ministry of Health

  36 shared

• Ye Tun Win

  Livestock Breeding and Veterinary Department

  34 shared

• Wai Zin Thein

  Livestock Breeding and Veterinary Department

  33 shared

• Kirsten Gilardi

  24 shared

• Jonna A. K. Mazet

  University of California, Davis

  22 shared

• Min Thein Maw

  Livestock Breeding and Veterinary Department

  22 shared

• Aung Than Toe

  Center for Disease Dynamics, Economics & Policy

  21 shared