Final answer:
The described individuals with large, sexually dimorphic body sizes, males with large cheek pouches, and solitary males are species that exhibit high degrees of sexual dimorphism, a result of male competition for matings.
Step-by-step explanation:
The creature described in the question is one that displays significant sexual dimorphism, meaning that males and females exhibit distinctly different characteristics, particularly in body size. These traits are a result of the need for males to compete for matings, leading to the evolution of larger body sizes and, in some cases, elaborate ornaments to attract females. In species like elephant seals, elk, lions, orangutans, and gorillas, dominant males are often significantly larger than females and may exhibit features such as large cheek pouches or elaborate manes. These males often lead solitary lives, only interacting with females for mating purposes, as is the case with orangutans. Females, on the other hand, are typically smaller and may select mates based on these exaggerated male traits.