Two endangered tigers, sisters Hana and Hani, have arrived at the Greater Vancouver Zoo's large cat program.

The twin Siberian tigers, also known as Amur tigers after the river in northeastern Russia, were born on May 22 last year and now weigh about 180 pounds and 130 pounds - considerably more than the average 15-month-old!

Typically, Siberian tigers are solitary animals unless related, said Jody Henderson, general manager of the zoo.

Siberian tigers are listed as endangered, and the zoo hopes these sisters will be part of its Species Survival Plan program, which works to manage specific animals that are threatened or in danger of extinction.

Tigers face few threats from other animals, but are in high demand as trophies and in traditional Chinese medicines.

The tigers arrived as part of the first exchange with their sister zoo, the Seoul Grand Park Zoo in South Korea. The partnership was formed in 2010.

This is one of several new arrivals at the zoo in recent months, including a new young giraffe and a number of births to animals already living at the zoo.