Walrus breeding season
There are issues regarding the reproduction of the walrus that researchers are stumped by. For example it is believed that the males are sexual mature around 8 years of age. Why then do they choose not to mate until they are about 15 years of age? The females are mature between 5 and 6 years of age, yet they generally won’t do so until they are about 10 years of age. You will find groups of males around the females trying to get their attention.
They make a variety of noises which have a dual propose. First, they are to convey to the other males that they wish to mate with a certain female. Second, these noises are a way to get the attention of the female they are interested in mating with. This all takes place on the land. It is known that the actual mating takes place in the water rather than on the ice.
Mating season is long, from about December through March. The walruses will consume much less food during this period of time. The males can become very aggressive with each other for the right to mate. They can also become aggressive towards the female that they are mating with. There is evidence that the various types of scars and cuts around the necks and backs of walruses are due to this type of interaction.
Not all of the females are ready to mate in a given season. Those that are have gone into what is called estrus. This is due to the additional hormones that are in their bodies. These females separate from those that are already pregnant or that are not in estrus to form their own herd. One male may mate with about 20 females.
It is hard to know at first if the female has conceived or not. This is due to the embryo living in the body for up to four months before it will attach itself to the placenta. Then it can take up to 16 months for the young to be born. This means that the offspring are born in optimal time when there is a higher chance that they can survive the conditions of their natural habitat.
The offspring can weigh from 100 to 170 pounds at birth. They instinctively know how to swim. They are born on land or ice and then make their way to the water with their mother soon afterwards. They will consume only milk from the body for their mother for the first year. What is fascinating about this bond is that the offspring will stay with their mother’s for two years or more if the mother doesn’t have a new calf.
When the offspring are about six months of age they start to feed on food items in the water as well as continue to consume the milk from their mother. It is unknown how often the young nurse or how much of the milk they consume at a time. Females that are caring for young often move from their natural herd to one that consists of other mothers and offspring. They tend to help care for the young of others, even going as far as to nurse the orphans when possible.
Generally the female will have a new offspring every two years but she allows the older offspring to remain with her as well. The use of the sense of smell is very evident between mothers and their offspring. The males will go their own way once the mating season is over. They will return to their all male herds. The level of aggression there is much less than when it is time for mating.