Himalayan Blackberry and Rat

Himalayan blackberry (Rubus armeniacus) is an introduced variety of blackberry native to western Asia, from around Armenia and northern Iran. The plant was introduced to America from seeds imported from India, which resulted in the confusing common name.

The Himalayan blackberry was introduced to Hawai‘i as a backyard food crop. The large berries and fast growth rate make it an attractive ornamental plant. The Himalayan blackberry is more of a problem than the other introduced blackberries, because it can grow into a large impenetrable bush up to 12 feet (4 m) high and full of sharp thorns. It is difficult to remove, because it can regrow from roots. Many common herbicides are ineffective, and seeds remain viable for several years. Seeds are spread by birds and other animals, like the rat.

The Polynesian rat (Rattus exulans) was introduced to the Hawaiian Islands hundreds of years ago. More rats, and species of rats, have followed humans to the Hawaiian Islands in modern times. The black rat (Rattus rattus) and brown rat (Rattus norvegicus) are the most damaging species of rat today. When alien edible fruits grow in the forests, they feed a growing population of animals like pigs and rats which do even more damage.

Rats cause tremendous ecological damage to native plants and animals. They eat the seeds and flowers of native plants, as well as eggs of turtles and birds, and their young. They also spread diseases. Further ecological damage was caused when the mongoose was introduced to control the rats.