NEWTON's Question of the Week

Question of the Week

Name:  Jayden
Status: student
Grade: 9-12
Location: Outside U.S.
Country: Australia
Date: Spring 2012

Why do pigs have curly tails?

Answers from Our Expert Staff

Good question, very good question. There seems to be no advantage in having a curly tail as such.

Wild hogs have straight tails and use them for signaling things such as aggression and retreat. I think it most probable that curly tails are an unintended consequence of the domestication of hogs.

In other words, during the domestication and breeding of domestic hogs, the curly tail gene was somehow selected for, (perhaps it was linked with another gene we selected for),so as humans bred hogs for meat, large litters and so on we got curly tails in the bargain. Since the domestic hog does not need to signal with its tail and there seems to be no problem with curly tails, the gene was not selected against and just stayed on as it were.

Short of some genomic information of which I am unaware, that’s my best guess. Similar stories exist for other species humans have domesticated and selectively bred.

Robert “Mr. A." Avakian
Instructor
Arts and Sciences
Oklahoma State Univ. Inst. of Technology

Hi Jayden,

Pigs are herd animals. For pigs to maintain the hierarchy of leadership, scolding of a juvenile pig consists of biting the tail. In domestication as a food animal, that leads to open sores, infection and possibly death of the pig... therefore no money for the farmer.

The curly tail was selected by years of breeding to prevent tails being bitten and therefore, less sores.

Wild pigs have straight tails. http://www.sandiegozoo.org/animalbytes/t-wild_swine.html

Hope this helps!

Peter E. Hughes, Ph.D.
Milford, NH

Jayden

I can’t think of any evolutionary advantage for pigs to have curly tails. That is, an advantage that would contribute to the survival of the pig. But there is no obvious disadvantage to it either so we must conclude that it must just be some genetic remnant remaining that carried over from generation to generation of pig.

Sincere regards,
Mike Stewart

First, not all pigs have curly tails. That said, I have seen speculation on various evolutionary benefits of curly tails, but I haven't seen any proper data-driven explanation. Perhaps one of the speculations is true, or, perhaps there may not be a definitive, deterministic "reason".

Hope this helps,
Burr

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