Jordi Galbany1,2, Thadée Muhire3, Veronica Vecellio3, Antoine Mudakikwa4, Aisha Nyiramana5, Michael R Cranfield6, Tara S Stoinski3, Shannon C McFarlin1. 1. Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, District of Columbia. 2. Department of Social Psychology and Quantitative Psychology, University of Barcelona, Barcelona, Spain. 3. Dian Fossey Gorilla Fund International, Atlanta, Georgia. 4. Department of Tourism and Conservation, Rwanda Development Board, Kigali, Rwanda. 5. Department of Biology, University of Rwanda, Butare, Rwanda. 6. Mountain Gorilla Veterinary Project, University of California at Davis, Davis, California.
Abstract
OBJECTIVES: Ecological factors, but also tooth-to-tooth contact over time, have a dramatic effect on tooth wear in primates. The aim of this study is to test whether incisor tooth wear changes predictably with age and can thus be used as an age estimation method in a wild population of mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda. MATERIALS AND METHODS: In mountain gorillas of confidently known chronological age (N = 24), we measured the crown height of all permanent maxillary and mandibular incisors (I1 , I1 , I2 , I2 ) as a proxy for incisal macrowear. Linear and quadratic regressions for each incisor were used to test whether age can be predicted by crown height. Using these models, we then predicted age at death of two individual mountain gorillas of probable identifications, based on their incisor crown height. RESULTS: Age decreased significantly with incisor height for all teeth, but the upper first incisors (I1 ) provided the best results, with the lowest Akaike's Information Criterion corrected for small sample size (AICc) and lowest Standard Error of the Estimate (SEE). When the best age equations for each sex were applied to gorillas with probable identifications, the predicted ages differed 1.58 and 3.33 years from the probable ages of these individuals. CONCLUSIONS: Our findings corroborate that incisor crown height, a proxy for incisal wear, varies predictably with age. This relationship can be used to estimate age at death of unknown gorillas in the skeletal collection, and in some cases, to corroborate the identity of individual gorillas recovered from the forest postmortem at an advanced state of decomposition. Such identifications help fill gaps in the demographic database and support research that requires individual-level data.
OBJECTIVES: Ecological factors, but also tooth-to-tooth contact over time, have a dramatic effect on tooth wear in primates. The aim of this study is to test whether incisor tooth wear changes predictably with age and can thus be used as an age estimation method in a wild population of mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda. MATERIALS AND METHODS: In mountain gorillas of confidently known chronological age (N = 24), we measured the crown height of all permanent maxillary and mandibular incisors (I1 , I1 , I2 , I2 ) as a proxy for incisal macrowear. Linear and quadratic regressions for each incisor were used to test whether age can be predicted by crown height. Using these models, we then predicted age at death of two individual mountain gorillas of probable identifications, based on their incisor crown height. RESULTS: Age decreased significantly with incisor height for all teeth, but the upper first incisors (I1 ) provided the best results, with the lowest Akaike's Information Criterion corrected for small sample size (AICc) and lowest Standard Error of the Estimate (SEE). When the best age equations for each sex were applied to gorillas with probable identifications, the predicted ages differed 1.58 and 3.33 years from the probable ages of these individuals. CONCLUSIONS: Our findings corroborate that incisor crown height, a proxy for incisal wear, varies predictably with age. This relationship can be used to estimate age at death of unknown gorillas in the skeletal collection, and in some cases, to corroborate the identity of individual gorillas recovered from the forest postmortem at an advanced state of decomposition. Such identifications help fill gaps in the demographic database and support research that requires individual-level data.
Authors: Christopher B Ruff; Juho-Antti Junno; Winnie Eckardt; Kirsten Gilardi; Antoine Mudakikwa; Shannon C McFarlin Journal: Philos Trans R Soc Lond B Biol Sci Date: 2020-09-21 Impact factor: 6.237
Authors: Kate McGrath; Amandine B Eriksen; Daniel García-Martínez; Jordi Galbany; Aida Gómez-Robles; Jason S Massey; Lawrence M Fatica; Halszka Glowacka; Keely Arbenz-Smith; Richard Muvunyi; Tara S Stoinski; Michael R Cranfield; Kirsten Gilardi; Chantal Shalukoma; Emmanuel de Merode; Emmanuel Gilissen; Matthew W Tocheri; Shannon C McFarlin; Yann Heuzé Journal: Proc Biol Sci Date: 2022-02-23 Impact factor: 5.530