Colophon
The animal on the cover of Docker: Up and Running is a blue whale (Balaenoptera musculus). Blue whales can grow up to 100 feet in length, and 200 tons in weight, making them the largest animals on Earth, and the largest animals to ever exist. At birth, a blue whale calf is as large as an adult hippopotamus, and can gain up to 200 pounds a day. When fully grown, blue whales are long and thin, with a small dorsal fin, two flippers at their side, and a horizontal tail, also known as a “fluke.” Blue whales are named for their bluish-grey coloring.
Blue whales are migratory and can be found in every ocean. They generally feed in colder polar regions, and then head to warmer tropical waters to give birth. Blue whales usually travel alone or in pairs, and communicate through a series of complex vocalizations. As a member of the balaenopteridae or rorqual family, blue whales feed by straining their prey through bony plates in their mouth known as baleen. Their diet consists almost entirely of krill, a small crustacean similar to shrimp. They can eat up to 7,900 pounds of krill a day, and require 1.5 million kilocalories of energy every day. Because of their speed and size, blue whales have practically no natural predators.
Blue whales were once widespread, with a population estimated in the hundreds of thousands. While they were initially too large and fast for whalers to capture, the invention of the harpoon gun in the late 1800s enabled whalers to successfully hunt blue whales. Decades of whaling followed, causing a significant population decline. An international ban on the hunting of blue whales was enacted in 1966, allowing their numbers to recover, although they remain endangered.
Many of the animals on O’Reilly covers are endangered; all of them are important to the world. To learn more about how you can help, go to http://animals.oreilly.com.
The cover image is from British Quadrupeds. The cover fonts are URW Typewriter and Guardian Sans. The text font is Adobe Minion Pro; the heading font is Adobe Myriad Condensed; and the code font is Dalton Maag’s Ubuntu Mono.