Paul McCartney of the Beatles included a dog whistle into one of his songs "A Day in the Life". The ultrasonic whistle could only be heard by dogs and was meant for his Shetland Sheepdog. Paul McCartney and his Shetland Sheepdog At first glance, a Shetland Sheepdog resembles a Colie. However, they are much smaller, and this makes them great pets for those living in Apartments. They are remarkably healthy, and make very loyal companions. Observations show that they are very good around children too. They are noted for their Intelligence. Ranking 6th out of 132 breeds according to Stanley Coren, they are one of the most intelligent dogs around.