Which of the following animal shows oestrus cycle?

The correct answer is Option (4) → Dog

Option (4) Dog — Correct. The reproductive cycle in female primates (monkeys, apes and humans) is the menstrual cycle. Non-primate mammals such as cows, sheep, rats, deer, dogs and tigers show the oestrus cycle instead.

Note: This question is from Chapter 1, Reproduction in Organisms, of the pre-rationalised NCERT book. This chapter is not in the present NCERT book (2026-27). The extract below is from the pre-rationalised edition.

NCERT Extract (Pre-rationalised edition, Chapter 1, Reproduction in Organisms):
Sexual Reproduction – “… The females of placental mammals exhibit cyclical changes in the activities of ovaries and accessory ducts as well as hormones during the reproductive phase. In non-primate mammals like cows, sheep, rats, deers, dogs, tiger, etc., such cyclical changes during reproduction are called oestrus cycle where as in primates (monkeys, apes, and humans) it is called menstrual cycle.”