Snake Imitators Persist

A harmless snake in the Carolina Sandhills has been mimicking a poisonous species for decades, and has become a better imitator since the latter went extinct.

By | June 12, 2014

WIKIMEDIA, GLENN BARTOLOTTI Scarlet kingsnakes (Lampropeltis elapsoides), nonpoisonous snakes that are common throughout the American Southeast, mimic a species that’s been extinct for more than 50 years, according to a study published this week (June 11) in Biology Letters. Christopher Akcali and David Pfennig of the University of North Carolina, Chapel Hill, study how mimicry evolves in animals and were surprised to find that scarlet kingsnakes’ mimicry of the poisonous coral snake became better since the poisonous snake disappeared from the Carolina Sandhills region during the 1960s.

Mimicking a nonexistent snake should not confer any advantage, so Akcali and Pfennig expected that in the intervening years, which represent about 15 to 20 snake generations, the copycat pattern should have deteriorated instead of becoming more pronounced.

When coral snakes were common, their predators avoided even poor imitators, but when coral snakes became rare, it was less of a risk for predators to approach poor mimics, leaving only the best mimics behind to breed.

“This selection continues to act, even after the coral snakes have gone completely extinct,” Pfennig told Live Science, “presumably because there have not been enough generations of predators to cause a reversal in the avoidance of things that look like coral snakes, and because the fitness consequences to the predators of avoiding coral snakes—and, therefore, also their precise mimics—has been historically strong."

Eventually, the mimicry will break down, Akcali and Pfennig said. At some point, perhaps during a drought when prey are in short supply, predators will act as if there are no coral snakes and begin to attack scarlet kingsnakes.

But Tom Sherratt, an evolutionary biologist at Carleton University in Ottawa, Canada, doubts that scarlet kingsnakes’ mimicry will cease. “Many of the predators—especially avian ones—are mobile and may visit locations where the model is present, which might explain why selection for mimicry still lingers,” he told Nature News.

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Avatar of: Paul R Walsh

Paul R Walsh

Posts: 5

June 13, 2014

I think there's something missing from this article.  

Notably, the article mentions one predator: the Scarlet hawk.  There must be others.  What are the major predators of the poisonous snake and its mimic?    If the predator is a mammal (or any other creature who spends years nurturing and teaching its progeny to hunt) then there will be a long lag time before the benefit of mimicry no longer benefits the prey.   The taught lessons by the parental predator will persist across generations even in the absence of the selective pressure which kills any predator which eats the poisonous prey.  

To interpret this persistent mimicry, we must identify all of the major the predators.

The Nature News article provides some insight:
"The result makes sense, Akcali says. “If you are a predator, and you’re in an area like Florida, where coral snakes are everywhere, then you should avoid anything that looks like a coral snake,” he says. “If you are in North Carolina where coral snakes are really, really rare, predators can benefit from attacking [mimics] sometimes.”

While interesting, that answer isn’t sufficiently encompassing.  It ignores the role of multigenerational teaching by the predator.    

I'm surprised at the persistence of the mimicry and the reported improvement of mimicry after the local extinction of the poisonous coral snake.  The logical conclusions seem to be either:

1.  The coral snake is not yet extinct in North Carolina, despite the accepted consensus. or

2.  The multigenerational memory of predators exceeds previous assumptions.  

This second possible conclusion is exciting (IMHO). Given that the poisonous coral snake is locally extinct, the lack of predation implies that predators have conveyed lessons to their progeny with impressive accuracy.    

The article reports improved mimicry by the Scarlet kingsnake of the Coral snake.  The observed improvement of mimicry among the non-poisonous prey snakes implies a continued selective pressure.    And that continued selective pressure implies that the multigenerational communication must have been exquisitely clear, even though the conveyed information was false.  That's interesting and worthy of investigation.  Can selective pressure be maintained merely because a predator species has communicated false information to its progeny over many generations?   How long can this false logic be perpetuated among the predative species in the absence of any ‘real’ selective pressure (such as the presence of the poisonous coral snake)?

Long persistence of taught information among predators implies a ‘culture’ among the predatory species.  It constitutes a trait perpetuated by behavior, not by genetics. 

This seems to be a fine opportunity to investigate the multigenerational communication among predatory species in the absence of selective pressure to reinforce the lessons.  
 

 

Avatar of: GuruOfChem

GuruOfChem

Posts: 1

June 13, 2014

For the love of all that is holy, can you please correctly describe coral snakes as VENOMOUS? It's hard enough to get non-scientists to understand the difference, but it's not too much to expect that you as a science publication get it right.

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