Factors other than feeding habits - including age at sexual maturity and average rainfall in their home habitat - have greatly influenced skull shape in carnivores, according to a new study. This finding contrasts with the idea that dominant shapes among the skulls of carnivores are mostly attributed to shared diets. To date, experts have believed that the evolution of carnivore skull shape is largely influenced by these animals' feeding activities, which vary greatly one species to the next. The idea has been that different skull shapes feature unique biomechanical attributes, like stiffness, that allow for specialized feeding. To determine if other, non-feeding variables have played a part in the evolution of skull shape among carnivoran species, however, Z. Jack Tseng and John J. Flynn created sophisticated digital and physical models of carnivore skulls, across all living carnivoran families, and tested, through various analyses, how skull shape and size correlated with habitat, diet, life expectancy, movement, and other non-feeding variables. Four of the nine non-feeding variables they studied were significantly correlated with cranial shape, they report, particularly trophic (or food web) levels and age at sexual maturity. Additionally, the authors note, skulls of species that tend to live in regions with higher average precipitation showed more elongated and narrow skull features. Skulls of carnivores with narrower diets and exhibiting earlier sexual maturity were more likely to have very stiff lower elements, say the authors, whereas skulls of carnivores that may also eat plants and which live in areas with lower average precipitation were associated with higher stiffness. The authors believe their general biomechanical findings could pertain to other vertebrate families as well.