Huturu

The Huturu is a species of methane breathing aquatic animal found on Balaho, the Unggoy's homeworld. They are a very popular meat eaten by Grunts and is used in Huturu racing, a sport involving Grunts riding Huturus through obstacle courses while trying to stay on making almost certain death. These animals are huge, some larger then blue whales from Earth, reaching up to 100 meters on rare occasions. They can be domesticated and are of little use to the Covenant though.
Even though nicknamed Covenant whales, they do not breathe air.There main predators are the Gretiu.The Huturu use a form of Symbiosis with the Pweda, in which the Pweda hitches a ride on the Huturu protecting the small animal from smaller predators, and feeds on the Huturu's parasites that live on it.