When Do You Hyphenate a Compound Modifier?

Is it a golden mantled ground squirrel or a golden-mantled ground squirrel?

“Golden” is an adjective; “mantled” is a participle (verb form acting as an adjective).

When an adjective and participle precede a noun, they are hyphenated:

• The golden-mantled ground squirrel approached cautiously.

When they follow a noun, they’re not:

• The ground squirrel on the log was golden mantled.