The tiger, the largest cat species in the world, begins life completely dependent on its mother. A pregnant tigress has a gestation period of about 103 days (roughly three and a half months). She retreats to a secluded den to give birth to a litter, which typically ranges from two to three cubs, though up to seven have been recorded.
Initial Measurements at Birth
Newborn tiger cubs are altricial. They are born blind, with sealed eyes, relying entirely on smell and touch to locate their mother. The average weight at birth ranges from 780 grams to 1.6 kilograms (approximately 1.75 to 3.5 pounds).
The tigress is intensely protective, remaining with her young for the first few days and only leaving briefly to hunt and drink. She stimulates the cubs’ circulation and digestion by constant licking. Their survival is entirely dependent on her milk, which is rich in fats and proteins.
Rapid Growth and Developmental Milestones
The first three months of a tiger cub’s life are characterized by rapid growth, driven by the mother’s nutritious milk. The cubs’ eyes begin to open between six and twelve days after birth, though vision remains blurry for another week or two. Hearing develops around this time, with ears becoming fully functional approximately nine to eleven days after birth.
Around the third or fourth week, the cubs start to explore their immediate den area and become increasingly mobile. This increased activity is fueled by rapid weight gain, as the mother’s milk supports growth. By eight to ten weeks of age, the cubs begin the transition from an all-milk diet to solid food.
The mother introduces solid food by bringing small prey back to the den, marking the beginning of the weaning process. This shift in diet provides the protein and fat needed for muscle and bone development. By three months old, the cubs are typically large enough and mobile enough to leave the den and follow their mother to a kill site, where they start to consume meat regularly. At this stage, they can be compared in size to a medium-sized dog.
Size Variation Among Tiger Subspecies
The initial size of a tiger cub is not uniform across the species; it directly correlates with the expected adult size of its subspecies. The largest adult subspecies, such as the Siberian or Amur tiger, produce the largest cubs at birth. Conversely, subspecies from warmer, equatorial regions, like the Sumatran tiger, are the smallest at maturity and have the smallest average birth weights.
This predictable size difference between populations is an example of Bergmann’s Rule, an ecogeographic principle observed in many warm-blooded animals. The rule suggests that individuals of a species living in colder climates tend to be larger than those in warmer climates. Larger animals possess a smaller surface area-to-volume ratio, which is an adaptation that helps them retain body heat more efficiently in cold environments.
For tigers, the Siberian tiger, living in the frigid Russian Far East, can reach over 600 pounds as an adult, while the Sumatran tiger, inhabiting a tropical climate, may weigh less than half of that. This adult size difference begins with the birth weight, meaning that a three-month-old Siberian cub will be significantly larger than a three-month-old Sumatran cub, even though their developmental timeline is similar.