The house mouse (Mus musculus) and various species of field mice are prolific small mammals known for their rapid life cycles. Baby mice are often referred to by a few different terms depending on the context and their specific developmental stage. Understanding the nomenclature requires examining both the formal biological term and the colloquial names used in the pet and feeder animal trade industries.
Naming Conventions for Baby Mice
The most accurate and widely accepted biological term for a young mouse is a pup. This designation is shared across many small mammalian species, reflecting the classification of their young as altricial, meaning they are born underdeveloped and entirely dependent on parental care. The term pup is the standard name used in scientific literature and laboratory settings to describe mouse offspring until they are weaned.
However, the term pinky is the most common name for a newborn mouse in general conversation and commercial contexts. This descriptive nickname relates directly to the infant mouse’s physical appearance at birth. The designation of kitten is sometimes used, but it is far less frequent than pup or pinky, and is more often associated with the young of other small mammals. Pinky is the term most frequently encountered when discussing mice used as feeders for reptiles or other carnivorous pets.
Defining the Early Developmental Stages
The name pinky is used because newborn mice are born in an extremely underdeveloped, or altricial, state. At birth, the mouse is completely hairless, revealing the pink or reddish skin underneath, and the eyes and ear canals are sealed shut. The skin is thin enough to appear translucent, often allowing the milk spot in the stomach to be visible.
This pinky stage typically lasts for about one week to ten days, during which the young are completely reliant on the mother for warmth and nutrition. Around day four, the ear flaps begin to develop, and a faint covering of fuzzy hair starts to appear around day five or six. Once the fur starts to grow in, usually by the end of the second week, the young mice are sometimes referred to as “fuzzies” before they reach their juvenile stage.
Comparing Terminology for Related Rodents
The use of “pup” as a general term is not unique to mice, applying to the young of many other rodents and small mammals. Baby rats are also accurately called pups, and they similarly go through an early, hairless stage often referred to as a pinky, especially in the pet trade. Young hamsters are also consistently referred to as pups.
In contrast, the young of species like squirrels and rabbits are commonly called kits or kittens. While “pup” is a broad classification for the young of many small rodents, “pinky” is the specific, descriptive term for the earliest, hairless stage of a newborn mouse or rat due to its distinct coloration and appearance.