Explanation:

• Statement 1 is correct: The elephant herd is led by the oldest and largest female cow known as the matriarch
• Statement 2 is correct: Females (called “cows”) can usually breed when they are 10-15 years old. After a pregnancy (called the “gestation period”) of 22 months, they give birth to a single baby (called a “calf”) which weighs about 220 lb (100 kg). Elephant calves are cared for by their mothers, and also by other females in the herd (called “aunties”).
• Statement 3 is incorrect: Calves stay with their mothers until they are about 5 years old, at which time males often leave the herd, but females remain.
• Statement 4 is incorrect: Karnataka has the highest number of elephants (6,049), followed by Assam (5,719) and Kerala (3,054).

Hence option 1st is correct.