Reproductive Cycle of the Orcas
There is a huge amount of information about orca reproduction even though it has been very difficult for scientists to research this species in its natural habitat. While some aspects of reproduction are still unknown, a lot of data has been collected from the individuals held in captivity.
Killer whales are a polygamous species, and they may have multiple partners in a single season.
Males reach sexual maturity at around 13 years of age or 5.2-6.4 meters in length, depending on the ecotype, while females reach it between six and ten years or when they are 4.6 to 5.4 meters long. However, females mate until they are 14 or 15 years old.
In nature, social factors influence the reproduction of male orcas, as they cannot mate until they achieve size and strength enough to compete with other individuals of their species.
Females can become ready for mating several times a year, so there is no regular pattern in the reproductive aspect of killer whales. In captivity it has been observed that some males may court the females ready for mating up to ten days and may even mate with already pregnant females.
The gestation period is very long, and it lasts for 15-18 months and births occur in any part of the year, but most often occur in the winter season in their respective regions. Studies say that 50% of females do not reproduce once they are close to turning 40 years old, and those living in the North Pacific do not usually reproduce after age 46.
Mothers give birth to a single offspring, and birth intervals vary according to geographic location; the range is from three to ten years. Curiously, a few years ago a female had a new offspring just 19 months after the death of the previous brood. We can conclude from this that there are no cycles or fixed periods in the life of a killer whale, and several results depend only on the circumstances.
In most births, the tail goes outside first, but there are also cases registered where the head is the first body part that has been exposed. The young are fed for about an 18 months, and all the nutrients from the mother’s milk give them the large amount of fat needed in their body to support changes in sea temperatures.
As most mammal mothers, females tend to protect their young against other predators and remain beside them until they are capable of protecting themselves. During this period, they learn to hunt and defend. Males do not have any parental contact with the young.
According to a water park located in the United States, newborns have a length of 2.6 meters long and weigh up to 160 kilograms. Their dorsal fin and tail are flexible during this period of immaturity, but as they grow both will strengthen to acquire a rigid texture. Younger orcas maintain a yellow tone in the skin that turns white as they grow, but as we can sometimes see, yellow tones fail to disappear from some adults.
It is unknown exactly the life expectancy of orcas, but it is estimated to be about 35 years according to the study of their teeth. Some of those who remain in captivity have surprisingly reach 50.
Mortality is very high within the first six months of life, but the causes of such deaths are unknown. Once they reach their large size have no enemies, becoming marine apex predators.
