Reading 2 for questions 168-174
Narwhal, robust-bodied, toothed whale, occuring only in deep waters of the high arctic, almost always close to floating ice. It is closely related to the beluga whale. Narwhals are mottled black and white, with more dark mottling on the back than on the belly. Females grow to 4.2 m(14ft) in length, and males to 4.7m(15ft). Narwhals have only two teeth, both in the upper jaw. The left tooth of the adult male continues to grow, spiraling forward from the head, until the tusk is up to 3m(up to 10ft) long. Including this tusk, the overall body length of an older male may be nearly 8m(nearly 26ft).
Narwhals often occur in small pods of 2 to about 12 animals, which are parts of larger herds. They migrate seasonally as the ice edge moves, and they can be found in remarkably thick ice. Fish, squid, and shrimp make up their diet. The members of a herd may segregate themselves according to age and sex, especially during migration. In such cases, subadult male or adult male groups can be easily distinguished by the size of their tusk.
The social systems of narwhals is not known, although researches believe that males may display or fight one another for access to females. Males have been observed to use their tusks for sparring with other males at or above the surface of the water, and males may occasionally be seen with their tusks partially broken off or with tusks embedded in their bodies. Actual spearing of one male by another, however, is probably less common. A mature female may give birth once every three years. Gestation lasts about 15months, and a single calf is born in the summer.
Narwhals are hunted by Inuits and some northen Europeans for their skin, meat, blubber, and especially for their tusks. The tusk is used as an ornament, both whole and carved, and is sometimes ground into a powder for reputed medicinal purposes. Although the existence of the species does not appear to be threatened, local overhunting of individual narwhals and their food supply may be limitting populations.
168. The word their in paragraph 3 refers to …