The elephant fetus is unique for its 22-month gestation period,
the longest pregnancy of all mammals.
Female elephants go into heat once every four months for about two to three days. The females don't regularly mingle with males, so they let out a call when they're ready to mate. While she's fertile, the male and female will mate about five times a day, but the male won't penetrate the female. Rather, it will spray a quarter of a liter of semen at the female's vagina, an amount more than 100 times that produced by a healthy human man. Among other hurdles, the male sperm must swim 6.5 feet to meet the elephant egg. Human sperm, in contrast, swims 3 inches.
In the fetus, the elephant develops a unique mammalian feature called nephrostomes, or funnel-like ducts in the kidneys. These ducts can be found in freshwater fish and frogs, leading scientists to believe that elephants may have evolved from aquatic beginnings, when they used their trunks as snorkels. Elephants can swim more than 15 miles without stopping by using their trunks to breathe.
The fertilized elephant egg weighs under a thousandth of a gram. In contrast, the adult elephant weighs close to five tons. Three months before birth (at 19 months), the elephant fetus is fully developed at about 140 pounds. But its mother's uterus becomes increasingly cramped as the fetus gains about a pound a day before birth. In its late stages, the elephant fetus is covered in bristly hair to eventually protect it from sun and mosquito bites, and its wrinkles serve to keep the animal cool.
At birth, the elephant can't see, nor control its trunk. Yet it can stand erect in order to reach its mother for nourishment. As an adult, its brain grows to weigh almost 10 pounds, about the size of a football. The brain has the same capacity for memory as humans, helping it remember locations of food and water for as long as 20 years.
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