Halszka Glowacka

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Journals/Publications

• McGrath, K., Eriksen, A. B., García-Martínez, D., Galbany, J., Gómez-Robles, A., Massey, J. S., Fatica, L. M., Glowacka, H., Arbenz-Smith, K., Muvunyi, R., Stoinski, T. S., Cranfield, M. R., Gilardi, K., Shalukoma, C., de Merode, E., Glissen, E., Tocheri, M. W., McFarlin, S. C., & Heuzé, Y. (2022). Facial fluctuating asymmetry tracks genetic diversity among Gorilla subspecies. Proceedings of the Royal Society B: Biological Sciences, 289, 20212564. doi:https://doi.org/10.1098/rspb.2021.2564
• Glowacka, H., & Schwartz, G. T. (2021). A Biomechanical Perspective on Molar Emergence and Primate Life History. Science Advances, 7(41), eabj0335. doi:10.1126/sciadv.abj0335
• Edmonds, H., & Glowacka, H. (2020). The ontogeny of maximum bite force in humans. Journal of Anatomy, 237, 529– 542. doi:https://doi.org/10.1111/joa.13218
• Arbenz‐Smith, K., Bromage, T. G., Chan, K. C., Cranfield, M. R., Glowacka, H., Kralick, A. E., Loring Burgess, M., McFarlin, S. C., McGrath, K., Mudakikwa, A., Ruff, C. B., & Stoinski, T. S. (2017). A radiographic study of permanent molar development in wild Virunga mountain gorillas of known chronological age from R wanda. American Journal of Physical Anthropology, 163(1), 129-147. doi:10.1002/ajpa.23192
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  While dental development is important to life history investigations, data from wild known-aged great apes are scarce. We report on the first radiographic examination of dental development in wild Virunga mountain gorillas, using known-age skeletal samples recovered in Rwanda.In 43 individuals (0.0-14.94 years), we collected radiographs of mandibular molars, and where possible, cone beam CT scans. Molar crown and root calcification status was assessed using two established staging systems, and age prediction equations generated using polynomial regression. Results were compared to available data from known-age captive and wild chimpanzees.Mountain gorillas generally fell within reported captive chimpanzee distributions or exceeded them, exhibiting older ages at equivalent radiographic stages of development. Differences reflect delayed initiation and/or an extended duration of second molar crown development, and extended first and second molar root development, in mountain gorillas compared to captive chimpanzees. However, differences in the duration of molar root development were less evident compared to wild chimpanzees.Despite sample limitations, our findings extend the known range of variation in radiographic estimates of molar formation timing in great apes, and provide a new age prediction technique based on wild specimens. However, mountain gorillas do not appear accelerated in radiographic assessment of molar formation compared to chimpanzees, as they are for other life history traits. Future studies should aim to resolve the influence of species differences, wild versus captive environments, and/or sampling phenomena on patterns observed here, and more generally, how they relate to variation in tooth size, eruption timing, and developmental life history.
• Glowacka, H., McFarlin, S. C., Vogel, E. R., Stoinski, T. S., Ndagijimana, F., Tuyisingize, D., Mudakikwa, A., & Schwartz, G. T. (2017). Toughness of the Virunga mountain gorilla (Gorilla beringei beringei) diet across an altitudinal gradient. American Journal of Primatology, 79(Issue 8). doi:10.1002/ajp.22661
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  The robust masticatory system of mountain gorillas is thought to have evolved for the comminution of tough vegetation, yet, compared to other primates, the toughness of the mountain gorilla diet is unremarkable. This may be a result of low plant toughness in the mountain gorilla environment or of mountain gorillas feeding selectively on low-toughness foods. The goal of this paper is to determine how the toughness of the mountain gorilla diet varies across their habitat, which spans a large altitudinal range, and whether there is a relationship between toughness and food selection by mountain gorillas. We collected data on the following variables to determine whether, and if so how, they change with altitude: leaf toughness of two plant species consumed by mountain gorillas, at every 100 m increase in altitude (2,600–3,700 m); toughness of consumed foods comprising over 85% of the gorilla diet across five vegetation zones; and toughness of unconsumed/infrequently consumed plant parts of those foods. Although leaf toughness increased with altitude, the toughness of the gorilla diet remained similar. There was a negative relationship between toughness and consumption frequency, and toughness was a better predictor of consumption frequency than plant frequency, biomass, and density. Consumed plant parts were less tough than unconsumed/infrequently consumed parts and toughness of the latter increased with altitude. Although it is unclear whether gorillas select food based on toughness or use toughness as a sensory cue to impart other plant properties (e.g., macronutrients, chemicals), our results that gorillas maintain a consistent low-toughness dietary profile across altitude, despite toughness increasing with altitude, suggest that the robust gorilla masticatory apparatus evolved for repetitive mastication of foods that are not high in toughness.
• Bromage, T. G., Catlett, K. K., Cranfield, M. R., Glowacka, H., McFarlin, S. C., Mudakikwa, A., Schwartz, G. T., & Stoinski, T. S. (2016). Age‐related changes in molar topography and shearing crest length in a wild population of mountain Gorillas from Volcanoes National Park, Rwanda. American Journal of Physical Anthropology, 160(1), 3-15. doi:10.1002/ajpa.22943
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  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 M1s (n = 15), M2s (n = 13), and M3s (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.
• Coiner-Collier, S., Scott, R. S., Chalk-Wilayto, J., Cheyne, S. M., Constantino, P., Dominy, N. J., Elgart, A. A., Glowacka, H., Loyola, L. C., Ossi-Lupo, K., Raguet-Schofield, M., Talebi, M. G., Sala, E. A., Sieradzy, P., Taylor, A. B., Vinyard, C. J., Wright, B. W., Yamashita, N., Lucas, P. W., & Vogel, E. R. (2016). Primate dietary ecology in the context of food mechanical properties. Journal of Human Evolution, 98(Issue). doi:10.1016/j.jhevol.2016.07.005
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  Substantial variation exists in the mechanical properties of foods consumed by primate species. This variation is known to influence food selection and ingestion among non-human primates, yet no large-scale comparative study has examined the relationships between food mechanical properties and feeding strategies. Here, we present comparative data on the Young's modulus and fracture toughness of natural foods in the diets of 31 primate species. We use these data to examine the relationships between food mechanical properties and dietary quality, body mass, and feeding time. We also examine the relationship between food mechanical properties and categorical concepts of diet that are often used to infer food mechanical properties. We found that traditional dietary categories, such as folivory and frugivory, did not faithfully track food mechanical properties. Additionally, our estimate of dietary quality was not significantly correlated with either toughness or Young's modulus. We found a complex relationship among food mechanical properties, body mass, and feeding time, with a potential interaction between median toughness and body mass. The relationship between mean toughness and feeding time is straightforward: feeding time increases as toughness increases. However, when considering median toughness, the relationship with feeding time may depend upon body mass, such that smaller primates increase their feeding time in response to an increase in median dietary toughness, whereas larger primates may feed for shorter periods of time as toughness increases. Our results emphasize the need for additional studies quantifying the mechanical and chemical properties of primate diets so that they may be meaningfully compared to research on feeding behavior and jaw morphology.
• Bromage, T. G., Cranfield, M. R., Galbany, J., Glowacka, H., Imanizabayo, O., McFarlin, S. C., Mudakikwa, A., Romero, A., Stoinski, T. S., & Vecellio, V. (2015). Tooth wear and feeding ecology in mountain gorillas from Volcanoes National Park, Rwanda. American Journal of Physical Anthropology, 159(3), 457-465. doi:10.1002/ajpa.22897
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  Objectives Ecological factors have a dramatic effect on tooth wear in primates, although it remains unclear how individual age contributes to functional crown morphology. The aim of this study is to determine how age and individual diet are related to tooth wear in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda. Material and Methods We calculated the percent of dentine exposure (PDE) for all permanent molars (M1-M3) of known-age mountain gorillas (N = 23), to test whether PDE varied with age using regression analysis. For each molar position, we also performed stepwise multiple linear regression to test the effects of age and percentage of time spent feeding on different food categories on PDE, for individuals subject to long-term observational studies by the Dian Fossey Gorilla Fund International's Karisoke Research Center. Results PDE increased significantly with age for both sexes in all molars. Moreover, a significant effect of gritty plant root consumption on PDE was found among individuals. Our results support prior reports indicating reduced tooth wear in mountain gorillas compared to western gorillas, and compared to other known-aged samples of primate taxa from forest and savanna habitats. Discussion Our findings corroborate that mountain gorillas present very low molar wear, and support the hypothesis that age and the consumption of particular food types, namely roots, are significant determinants of tooth wear variation in mountain gorillas. Future research should characterize the mineral composition of the soil in the Virunga habitat, to test the hypothesis that the physical and abrasive properties of gritty foods such as roots influence intra- and interspecific patterns of tooth wear. Am J Phys Anthropol 159:457-465, 2016.
• Clauss, M., Fashing, P. J., Fritz, J., Glowacka, H., Nguyen, N., Seyoum, C., & Venkataraman, V. V. (2014). Effects of dietary fracture toughness and dental wear on chewing efficiency in geladas (Theropithecus gelada): Chewing Efficiency in Geladas. American Journal of Physical Anthropology, 155(1), 17-32. doi:10.1002/ajpa.22571
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  Chewing efficiency has been associated with fitness in mammals, yet little is known about the behavioral, ecological, and morphological factors that influence chewing efficiency in wild animals. Although research has established that dental wear and food material properties independently affect chewing efficiency, few studies have addressed the interaction among these factors. We examined chewing efficiency, measured as mean fecal particle size, as a function of seasonal shifts in diet (and corresponding changes in food fracture toughness) in a single breeding population of a grazing primate, the gelada monkey, at Guassa, Ethiopia. We also measured dental topographic traits (slope, angularity, and relief index) and relative two- and three-dimensional shearing crest lengths in a cross-sectional wear series of gelada molars. Chewing efficiency decreased during the dry season, a pattern corresponding to the consumption of foods with higher fracture toughness. Older individuals experienced the most pronounced decreases in chewing efficiency between seasons, implicating dental wear as a causal factor. This pattern is consistent with our finding that dental topographic metrics and three-dimensional relative shearing crest lengths were lowest at the last stage of wear. Integrating these lines of behavioral, ecological, and morphological evidence provides some of the first empirical support for the hypothesis that food fracture toughness and dental wear together contribute to chewing efficiency. Geladas have the highest chewing efficiencies measured thus far in primates, and may be analogous to equids in their emphasis on dental design as a means of particle size reduction in the absence of highly specialized digestive physiology.

Presentations

• McFarlin, S. C., Baiges-Sotos, L., Galbani, J., Glowacka, H., Junno, J., Muhire, T., Ruff, C. B., Bromage, T. G., Cranfiled, M. R., Eckardt, W., Gilardi, K., Stoinski, T. S., & Mudakikwa, A. (2019, March). Skeletal aging in Virunga mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda. 88th Annual Meeting of the American Association of Physical Anthropology. Cleveland, OH: American Association of Physical Anthropology.

Poster Presentations

• Romero, A. N., Spies, A. J., Eriksen, A., McGrath, K., Massey, J. S., & Glowacka, H. (2025, Spring).

  Ontogeny of fluctuating facial asymmetry in African great apes

  . 94th Annual Meeting of the American Association of Biological Anthropologists. Baltimore, MD: American Association of Biological Anthropologists.
• Glowacka, H., Ritzman, T. B., & Massey, J. S. (2024). Skull ontogenetic trajectory variation and phylogeny in primates
  . Annual Meeting of the American Association for Anatomy.
• Jeyasingh, D., Kisiel, S., & Glowacka, H. (2024). Impact of an orthopaedic surgeon instructor during a cadaveric anatomy course on first-year medical student interest in surgery. Arizona Medical Association Annual Conference. Phoenix, AZ: Arizona Medical Association.
• Kisiel, S., Jeyasingh, D., & Glowacka, H. (2024). First year medical students’ views on orthopedic surgery as a specialty across racial strata. Arizona Medical Association Annual Conference. Phoenix, AZ: Arizona Medical Association.
• Kisiel, S., Jeyasingh, D., & Glowacka, H. (2024). First year medical students’ views on orthopedic surgery as a specialty across racial strata. Medical Student Orthopedic Society Annual Research Symposium. Virtual: Medical Student Orthopedic Society.
• Glowacka, H., Massey, J. S., & Ritzman, T. B. (2023). An evaluation of the use of developmental simulations for taxonomic assessment. 92 nd Annual Meeting of the American Association of Biological Anthropologists.
• Spies, A. J., Glowacka, H., Eriksen, A., Massey, J. S., Arlegi, M., Heuzé, Y., Tocheri, M. W., & McGrath, K. (2023). Facial asymmetry, inbreeding, and stress in Cross River gorillas (Gorilla gorilla diehli). 92 st Annual Meeting of the American Association of Biological Anthropologists.
• Glowacka, H., & Schwartz, G. T. (2019, March). The evolution of gape and bite force potential in primates. 88th Annual Meeting of the American Association of Physical Anthropology. Cleveland, OH: American Association of Physical Anthropology.