You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Plymouth

Context:
Some of the greatest imports to Plymouth from the Americas and Europe during the latter half of the 19th century included maize, wheat, barley, sugar cane, guano, sodium nitrate and phosphate Aside from the dockyard in the town of Devonport, industries in Plymouth such as the gasworks, the railways and tramways and a number of small chemical works had begun to develop in the 19th century, continuing into the 20th century.

Question:
What animal byproduct was imported to Plymouth in the 19th century?

guano