Does diet and elevation reliably predict mandibular shape in gorilla populations?

Gorillas live across a vast range of altitudes spanning from sea level to about 4,000m. This range places individual populations in very different ecological zones. The extreme differences in elevation and access to fruit resources between western lowland and mountain gorillas is often cited as the reason for variation in behavioural ecology and skeletal morphology. The mandible’s primary function is eating. Therefore, it provides an honest signal of dietary variation. The effects of diet on mandibular morphology have been well studied, but it is unknown whether gorillas as a whole have altered one or two aspects of the mandible in response to changes in diet or if each species can independently adopt population-specific morphology. Additionally, it is unknown what effects elevation has on skeletal morphology independent of dietary differences.