Gesner does not question the ancient belief that a hedgehog will carry fruit back to its nest using the sharp quills on its back. He notes, however, that the spines are mainly a defense and protect the hedgehog from its mortal enemies, the wolf, the fox, and the snake. Historiae Animalium (Studies on Animals) is considered to be the first modern zoological work. This first attempt to describe many of the animals accurately is illustrated with hand-colored woodcuts drawn from personal observations by Gesner and his colleagues. Conrad Gesner (March 26, 1516 - December 13, 1565) was a Swiss naturalist and bibliographer. To his contemporaries he was best known as a botanist, but in 1551 he was the first to describe brown adipose tissue; and in 1565 the first to document the pencil. He died of the plague, at the age of 49, the year after his ennoblement.