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Jaw Muscles That Never Tire Make For Some Extreme Mating Strategies Among Lizards

author

Rachael Funnell

author

Rachael Funnell

Writer & Senior Digital Producer

Rachael is a writer and digital content producer at IFLScience with a Zoology degree from the University of Southampton, UK, and a nose for novelty animal stories.

Writer & Senior Digital Producer

If someone clamped onto your head for hours I suspect you'd look a little fed up too. Katie Goldin via iNatatural/CC 4.0

If someone clamped onto your head for hours I suspect you'd look a little fed up too. Katie Goldin via iNaturalist/CC BY 4.0

To the uninitiated, the southern alligator lizard (Elgaria multicarinata) might not look like much, but this feisty reptile is a lizard on the streets and a freak in the sheets, exhibiting a courtship behavior that sees the male grip the female's head in its jaws for hours at a time. While perhaps a bit aggressive, the male’s performance is surprising as it goes against long-held ideas about reptilian muscle strength, which wasn't thought to be capable of powering high-endurance behaviors.

Attention was first brought to this forceful approach when Katie Goldin came across a pair of lizards interlocked on the sidewalk in Los Angeles and, true to form, the male had its jaws tightly grasped around the female’s head. This behavior is known as “mate-holding,” and is seen in several species who will hold their mate in their mouth for hours and sometimes even days. Goldin photographed the locked lovers and sent the pictures to the Natural History Museum of Los Angeles who, since 2015, has made a call out for alligator lizard porn – much of which is published on the platform iNaturalist. The images revealed that around 7 percent of mating events are actually threesomes, mostly with two males biting a female though on some occasions males were seen biting another male locked onto a female. Whatever floats your boat.

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Alligator lizard threesomes come in all formations. Yuki Machida via iNaturalist/CC 4.0

To better understand how these amorous males were able to lock on for so long, research published in the journal Proceedings of the Royal Society B conducted experiments to investigate the jaw-adductor muscle of lizards (in simpler terms: the bits that make the mouth shut). They stimulated the muscles and measured the force of the bite, and also carried out fatigue tests.

Their findings revealed that when the lizards first close their mouths, they gradually develop a substantial and sustained force that continues after the peak bite force has weakened. The researchers believe this ability to slam the mouth closed and then keep it there constitutes a physiological specialization for these animals that benefits them by improving their chances of reproductive success.

The team also carried out a molecular analysis on the jaw muscles and found they contained tonic myosin fibers. These fibers are associated with gradual and sustained processes and are often present in opposition to fast-twitch muscle fibers which generate short, sharp movements. The researches explain that these tonic fibers likely explain the lizard’s capacity to clamp onto a mate for so long during copulation. The findings could have wider application in characterizing muscle properties that facilitate extreme performance during specialized behaviors, and could reveal novel mechanisms of muscle function, especially when looking at shared characteristics among species that have evolved convergently.

 

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[H/T: The New York Times]


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