1. Elephant

Elephants have the longest known gestation period of any land animal. The gestation period is about 22 months that allows the development of elephant's large brains and bodies.

2. Whale    

The gestation period of a whale is approximately 15-18 months. Whales have long pregnancies to allow their calves to develop enough to survive in the deep ocean environment.

3. Rhinoceros

The gestation period of Rhinoceros is about 15-16 months. Black rhinos have long gestation periods to give birth to well-developed calves that can quickly learn to avoid predators.

4. Camels

Camels have a gestation period of 12-14 months that helps the calf to develop adequately to survive the extreme conditions of its habitat.

5. Giraffe

The gestation period of Giraffe is of nearly 15 months. Newborns need to quickly learn to stand and move to avoid predators.