Final answer:
The world's largest ruminant by weight, whose females are called 'cows', is the giraffe. Giraffes are hoofed animals or ungulates that are capable of rumination, allowing them to digest plant material through fermentation in their specialized stomachs.
Step-by-step explanation:
The African mammal referred to in the question, whose females are called 'cows' and which is the world's largest ruminant by weight, is the giraffe. Among the options provided, elephants, hippos, and blue whales are not ruminants. Ruminants are a classification of mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, through a process called rumination. Although blue whales are the largest mammals, they are not ruminants, as they feed primarily on krill, not plants.
The giraffe is a large hoofed animal, known scientifically as an ungulate, which includes other animals such as deer, sheep, goats, and elephants. Ungulates use their hooves to sustain their whole body weight and the giraffe's unique adaptations allow them to browse on leaves high up in trees.
Giraffes, being the tallest land animals, have a highly specialized physiology and anatomy adapted for reaching foliage at high elevations. They are distinguished not only by their long necks but also by their spotted coat patterns and the fact that they are ruminants capable of digesting fibrous plant material thanks to their multi-compartment stomachs.