What do newborn rats look like? - briefly
Newborn rats are hairless, pink, and weigh roughly 5–7 g; their eyes and ears are sealed, and only a few whiskers are present. They rely entirely on the dam for warmth and nourishment.
What do newborn rats look like? - in detail
Newborn rodents are extremely small, usually weighing between 5 g and 7 g and measuring 2 cm to 3 cm from nose to base of the tail. Their bodies are covered with a thin, sparse layer of fine hair that appears almost translucent; the hair becomes denser after the first week. The skin is pinkish‑white and delicate, often showing visible blood vessels.
At birth the eyes are closed and the pupils are non‑functional. Vision develops over the subsequent 10‑14 days. Ear pinnae are flattened against the head and lack cartilage, giving a smooth contour. The external auditory canals are present but not yet open. Whiskers (vibrissae) are absent; they emerge during the second week.
Limbs are proportionally short, with forepaws and hind paws equipped with undeveloped claws that are barely visible. The tail is short, naked, and flexible, measuring roughly half the body length. The spinal column is flexible, allowing the pups to curl tightly when undisturbed.
Physical parameters differ slightly among laboratory strains and wild species:
- Weight: 4.5 g – 8 g (average 5.8 g)
- Body length: 18 mm – 25 mm (head‑to‑rump)
- Tail length: 10 mm – 15 mm
- Hair density: ~10 hairs mm⁻¹ at birth, increasing to >30 hairs mm⁻¹ by day 7
- Eye opening: day 10 – 14
- Ear unfolding: day 5 – 7
These characteristics define the external appearance of neonatal rats during the first days of life.