Why do Moose have Bells?

We've all been seeing many moose around this spring, and I like it.

Do you notice the piece of skin and hair---the dewlap--- hanging under her chin? I'm calling this one a "her" because she had a calf in the weeds, which was why we quickly left her alone. There's not a great way for me to otherwise distinguish the hims and hers in this season of the year before antlers emerge. The gender of the one in the video? I do not know.

At any rate, the dewlaps, or bells, or moostaches, are a mystery. Both males and females have them, but male bells tend to be larger. Some of them are fat and 20 inches long, some are just tufts of hair.
The moose experts aren't in agreement as to the purpose of the dewlap. Some say it helps with heat regulation. The long strands that sometimes hang down can also freeze and break off in the winter. Ouch.

Apparently they reach their biggest magnitudes on the chins of 3-5 year old bull moose.

Many biologists speculate that dewlaps (bells) play a part in the mating rituals, perhaps for dispensing scents (from bull urine and saliva, if that could ever be appealing). Perhaps size and shape are attractiveness indicators.

I'm thinking that the bells have to get caught up in the brush sometimes, and that can't be comfortable. And that is all I know.