In those mammals which are seasonal breeder, the females are receptive only once in a year ; the cycle is termed as:
**Core Concept**
The seasonal breeding pattern in mammals is characterized by a specific reproductive cycle that is influenced by environmental factors, such as daylight hours and temperature. This type of cycle is often seen in temperate climates where food availability and breeding opportunities are linked to the season.
**Why the Correct Answer is Right**
The correct answer refers to the **estrous cycle**, which is a reproductive cycle that occurs in some mammals, including seasonal breeders. In these animals, the estrous cycle is regulated by the hypothalamic-pituitary-gonadal axis and is influenced by the length of daylight hours, temperature, and other environmental factors. The estrous cycle is characterized by a short breeding season, during which the female is receptive to mating only once a year.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it refers to the **menstrual cycle**, which is a type of reproductive cycle that occurs in humans and some other primates. The menstrual cycle is not typically seen in seasonal breeders.
**Option B:** This option is incorrect because it refers to the **diestrus** phase of the estrous cycle, which is a period of quiescence or dormancy during which the reproductive system is not active.
**Option C:** This option is incorrect because it refers to the **anestrus** phase of the estrous cycle, which is a period of reproductive quiescence that can occur in both seasonal and non-seasonal breeders.
**Clinical Pearl / High-Yield Fact**
In seasonal breeders, the length of daylight hours is a critical factor in regulating the estrous cycle, with longer daylight hours typically triggering the breeding season.
**Correct Answer: C. Anestrus**