Cisco router port lights blinking - nothing on other end though

I've got some cisco routers booted up. They have some cables plugged into some of their ports. On the other end of the cables, are other devices. On those devices, the ports the cables are plugged into are shutdown.

Therefore, there should be no traffic flow to/from the routers. However, the port LEDs are blinking as if there is data flow.

Is it possible for link lights to blink inconsistently/randomly even if it was isolated and off the network? It still has cables plugged in and ports are up, but there's nothing on the other end.

Thanks!