aquarium on Budapester Straße or through the Lion Gate on Hardenbergplatz. The original Elephant Gate, built in 1899, was destroyed in World War II. It was faithfully reconstructed to original plans in 1984. The zoo has always maintained an extensive and diverse collection. At the outbreak of World War II there were 4000 birds and mammals of 1400 species, while the aquarium held 8300 reptiles, amphibians and invertebrates of 750 species. In 2001, the combined collection numbered 14188 animals of 1517 species, similar to present. The number of larger animals displayed has gradually thinned as enclosures become increasingly designed to recreate natural habitat. The zoo maintains studbooks for black and Indian rhinoceroses and gaurs. The populations of rare deer and pigs are part of several captive breeding projects. Berlin Zoo supports conservationists in other countries (for instance, in Madagascar) and as a partner of the , a species protection foundation. The zoo houses four types of great ape: orangutans, gorillas, chimpanzees, and bonobos. The carnivore house displays all big cats and many rare small predators, such as ring-tailed mongooses and narrow-striped mongooses from Madagascar. In the basement, visitors are invited to a view into the world of nocturnal animals. The bird house presents a walk-through aviary and offers a broad variety of forms, including several regularly breeding species of hornbills and many parrots. Numerous big aviaries show waders, herons and many other species. The Berlin Zoo is one of the few zoos to exhibit tuatara (in the aquarium) and Luzon tarictic hornbills. Aquarium The aquarium was built in 1913 as part of the Zoologischer Garten complex. In addition to fish and other aquatic life, it is home to most of the zoo's reptiles, amphibians and invertebrates. Animals Polar bear Knut was born in captivity at the zoo on 5 December 2006. He and his twin brother or sister were directly rejected by their mother on the day of birth. He was subsequently raised by zookeeper Thomas Dörflein and became the center of a mass media phenomenon that spanned the globe, quickly spawning numerous toys, media specials, DVDs, and books. Because of this, the cub was largely responsible for a significant increase in revenue, estimated at five million euros, at the Berlin Zoo in 2007. Zoo attendance figures for the year increased by an estimated 30%, making it the most profitable year in its 165-year history. Knut died on 19 March