straggler
A person or animal who lags behind the main group.
A straggler is someone who falls behind the main group, moving more slowly than everyone else. When a class walks to the library, the stragglers are the kids dawdling at the back, tying their shoes or chatting while the rest of the group moves ahead. On a long hike, stragglers might lag behind because they're tired, distracted, or just naturally slower walkers.
The word usually suggests someone who's separated from where they should be. A few straggling geese might arrive days after the main flock has already migrated south. At the end of a birthday party, the stragglers are the last guests still hanging around after most people have left.
Being a straggler isn't always bad. Sometimes people straggle because they're enjoying the scenery or talking with a friend. But it can cause problems when the group needs to stay together for safety or arrive somewhere on time. That's why hiking guides often remind everyone to keep pace so no one straggles too far behind.