Cave canem mosaic: the story behind Pompeii's 'beware of dog' art

Part 1

What the cave canem mosaic actually shows

The mosaic fills the floor of a narrow entrance hall, worked in black and white tesserae in a checker pattern with a dark stripe border. It shows a dog on a leash, chained to a fixed point on the floor. One writer describes the animal as a snarling black dog wearing a spiked collar and chain, while other accounts simply call it a growling dog. Directly under the dog's paws runs the inscription CAVE CANEM.

Cave canem is Latin, and it means beware of the dog. It reads much like a modern beware of dog sign. If you have ever put up a warning for your own dog, you are following a habit that goes back this far.

Part 2

Where it was found and why it matters

The mosaic decorates the entrance of the House of the Tragic Poet, a home in Regio VI of Pompeii. The house dates to the second century BCE. Archaeologists led by Antonio Bonucci discovered it in November 1824.

The house and its mosaics survived because volcanic ash from the eruption of Mount Vesuvius in 79 AD buried and preserved them. That ash effectively froze the house in time, safeguarding its treasures.

The dog mosaic sat in the vestibule, the narrow entrance hall that led from the street into the more private rooms of the house. Placed there, it worked like today's warning signs, telling visitors to enter at their own risk and guarding the family's more private quarters beyond.

Part 3

Was it a warning or a joke

Dogs in ancient Rome often served as a household's security system. Romans kept dogs to guard homes, businesses, and livestock, and the ideal guard dog was large with a deep bark. The poet Virgil wrote that with a dog on guard you need not fear a midnight thief or a wolf near your stalls. The Roman writer Columella noted that black dogs terrify thieves by day and are harder for trespassers to spot at night. If you have a dark-coated dog yourself, you already know that low-light watchfulness.

Several other houses in Pompeii displayed similar mosaics of chained dogs near their front doors. Many of these guard dogs died alongside their owners when Vesuvius erupted. In one house, archaeologists found the imprint of a dog still contorted in a struggle to escape its collar.

Part 4

Other cave canem mosaics found in the Roman world

Given how common guard dogs were, it is likely that cave canem warnings were widespread across the Roman world. The phrase also turns up in Roman literature. Petronius's satirical novel the Satyricon describes a painted dog on a chain on a wall, with the words BEWARE THE DOG written above it. A few decades before Vesuvius erupted, the apostle Paul used the phrase beware of dogs in a letter to followers in Philippi, later part of the New Testament.

The Tragic Poet dog is remembered as a snarling or growling black animal on a chain. That coloring fits Roman guard dog preference, since black dogs were valued for frightening thieves and staying hidden after dark. Romans of the period also kept other types, from the large mastiff-like Molossian to small white dogs that were early forms of the modern Maltese.

Part 5

How the mosaic is displayed and preserved today

Photographs taken at the entrance of the House of the Tragic Poet, inside the Pompeii Archaeological Park, show a cave canem mosaic still in place there. At the same time, a cave canem mosaic from Pompeii is held in the mosaic collection of the National Archaeological Museum in Naples. Many of the house's other mosaics and frescoes, including panels showing scenes from the Iliad and a theatre scene, were moved to that same Naples museum.

It might be the oldest known example of a beware of dog sign. If your dog already patrols your doorway, this mosaic shows that instinct on display has a very long history.