There's no single answer to how big a herd is because it depends on the animal!
Here's a breakdown:
General sense: A herd is generally considered a group of animals of the same species that live and travel together.
Specific herds: The size of a herd can vary greatly:
Elephants: Herd sizes can range from a few individuals to hundreds, depending on the environment and resources.
Buffalo: Herds can number in the thousands, especially in areas with abundant grazing land.
Deer: Herds are usually smaller, with a few dozen individuals being common.
Cattle: A herd can be as small as a few cows or as large as a few hundred, depending on the ranch or farm.
So, to know the size of a herd, you need to specify what kind of animal you're talking about!