Can you trademark a curl?

Cone wrapper for Dairy Queen softserve

A few days ago I made the mistake of taking my daughter to the mall to go to Safeway. She had wanted to get a hot chocolate, but as we walked by the Dairy Queen shop she changed her mind and decided that an ice cream cone was now the desired treat.

Now, the contents of a Dairy Queen cone can not really be defined as "ice cream", (it is described as "softserve" and has a much lower percentage of milk fat) but for my daughter anything cold and white in a cone must be ice cream.

Does my daughter even notice the "Curl on Top"? Does anyone else? Can you trademark the curl on top? Does it offer any protection? Would any other company selling softserve put a curl on the top of their cones? Could Dairy Queen do anything to prevent it?

It makes me wonder why a firm would pin their brand to something so ephemeral and reproducible.