![]() Males and females typically reach sexual maturity at approximately 10 years of age 18. Ganges river dolphin females give birth to a single offspring, usually weaning them within a few months. Females are generally longer than males due to a longer rostrum 1, 18. At birth, calves are about 70 cm long, but adults can reach about 2.60m and weigh up to 90 kg as adults. Gestation is thought to be 8 to 9 months 4, 18. Not much is known about the mating and reproduction of Ganges river dolphins except that they breed year-round and most births are thought to occur between October-March 17. Ganges River Dolphin Illustration by Uko Gorter Reproduction and growth Externally, the eye appears to be barely larger than a pinhole and therefore restricting light from reaching the retina, there is no lens, and the optic nerve is very narrow, leading scientists to conclude that their eyes are incapable of forming clear images, but that they may still serve as light receptors 4, 16. This species is functionally blind, and therefore relies heavily on echolocation to navigate and hunt 4, 16. The pectoral flippers on the side of the body are large and paddle shaped. They have long, sharp teeth which are visible even when the mouth is closed. They have an elongated snout that can bend slightly upward it can reach up to 20% of total body length in females. The dolphins have a steep forehead, and flexible necks with unfused vertebrae which permit them to turn their heads from side to side. The dorsal fin is very small, and is a low fleshy lump on the back, usually just a few centimetres in height. Ganges river dolphins are usually a grey or light brown colour, but may also have a pinkish tone to the belly 1. ![]() River cetaceans, including the Ganges river dolphin, are considered to be indicators of river health 15. As long-lived top predators, Ganges river dolphins are vulnerable to negative health effects from living in waterways contaminated with heavy metals, industrial pollution and agricultural run-off 13, 14. Ganges river dolphins, as with many other cetacean species, frequently become entangled in fishing nets and then drown. They also affect river habitats by reducing water availability and habitat quality, and blocking passage for migratory fish 11, 12. Dams and barrages fragment the dolphins habitat, reducing population connectivity and isolating animals in river sections. The major threats to the Ganges river dolphin include water-related infrastructure such as dams, barrages, diversions, and embankments which cause flow regulation and habitat fragmentation, mortality from entanglement in fishing nets, hunting of dolphins for oil and meat, pollution from domestic, industrial and agricultural sources, and disturbance from human activities including boat traffic, dredging and underwater noise 7, 9, 10.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |