What do rats look like at four months old? - briefly
At four months a rat is fully grown, with a body length of roughly 20–25 cm, weight around 250–300 g, and a dense coat that may be white, brown, black or mixed. The ears are proportionally large, and the tail is long, hairless, and about the same length as the body.
What do rats look like at four months old? - in detail
At approximately four months, a rat has reached near‑full adult development. Body length, measured from nose to the base of the tail, typically ranges from 18 to 22 cm (7–8.5 in). The tail adds an additional 15–20 cm (6–8 in) and is proportionally slender, covered with sparse, fine hair and a slightly darker dorsal surface.
Weight varies with strain and sex. In common laboratory strains such as Sprague‑Dawley or Wistar, males average 300–350 g (10.5–12.3 oz) while females are slightly lighter, around 250–300 g (8.8–10.5 oz). Body condition is generally robust, with a clearly defined torso and well‑developed hindquarters.
Fur is dense and short, exhibiting the coloration pattern established at weaning. Typical coat colors include albino (white with pink eyes), black, brown, or agouti, often with a dorsal stripe or ventral lighter patch. Hair density is uniform across the back, while the underbelly may appear softer and lighter.
Facial features are mature: eyes are fully pigmented, with a clear corneal surface and a dark pupil. Ears are erect, measuring roughly 2 cm (0.8 in) in height, and are covered by thin, translucent skin. Whiskers (vibrissae) are long, stiff, and arranged in several rows around the snout, providing tactile feedback.
Dental anatomy is fully functional. The incisors are continuously growing, sharp, and orange‑tinged due to enamel pigmentation. Molar and premolar crowns are fully erupted, allowing efficient gnawing and chewing.
Sexual dimorphism becomes evident. Males display larger overall size, a broader head, and a more pronounced anogenital distance. The testes descend into the scrotum, which is visible externally. Females have a narrower pelvis and a visible vaginal opening, but lack the pronounced abdominal bulge seen in pregnant individuals.
Skeletal maturation is complete; long bones have fused epiphyses, and the vertebral column shows full curvature. Musculature is well‑defined, especially in the forelimbs and hindlimbs, supporting agile climbing and rapid sprints.
Overall, a four‑month‑old rat presents as a compact, fully furred mammal with adult proportions, distinct coloration, functional dentition, and clear sexual characteristics.