What is a permanent identification mark placed on the ear using needles and ink called?

The correct answer is tattoo because it refers to a permanent identification mark that is applied to the skin, typically through needles and ink. In the context of animal husbandry, a tattoo is often used to ensure that livestock can be identified reliably over time. This practice is common for livestock such as cattle and pigs, where identification is crucial for tracking breeding, health statuses, and ownership.

Tags can be temporary or removable and are usually made of plastic or metal, while branding typically involves using heat to imprint a unique identifying symbol on the skin. Piercing generally refers to creating a hole in the skin to insert jewelry, rather than marking the skin for identification purposes. Therefore, tattoo is the most appropriate term for a permanent mark made with ink on the ear.