[question] API methods when edit page is open

[beechnut]

When I leave the edit page of project 3 open, I see in the server logs, every few seconds:

[17/Dec/2014 14:31:53] "POST /api/v1/projects/3/activity HTTP/1.1" 204 0

When I close the edit page, I see

[17/Dec/2014 14:31:59] "DELETE /api/v1/projects/3/activity HTTP/1.1" 204 0

Saves happen manually, so what are these POST requests monitoring?