Showing off your weapons in the animal kingdom

June 20, 2006

In a paper from the July issue of The American Naturalist, Kristopher Lappin (Northern Arizona University), Yoni Brandt (University of Toronto), Jerry Husak (Oklahoma State University), Joe Macedonia (Arizona State University), and Darrell Kemp (James Cook University), demonstrate that a threat display can provide accurate information about the performance of a weapon.

Working at the Wichita Mountains National Wildlife Refuge in Oklahoma, the researchers showed that when an adult male lizard gapes his jaws at a rival male during an intense territorial interaction, information is made available to his opponent about how hard he can bite - indeed, the lizard's jaw muscles become clearly visible. Further, some lizards have evolved bright patches that reflect ultraviolet light, which lizards can see, to delineate the jaw muscles.

Lappin and colleagues point out that the information about bite force provided by the display does not correspond to body or head size because males of similar size can vary substantially in how hard they can bite. The display thus provides unique and honest information about weapon quality, as well as a mechanism for making the decision to fight or to back down. Adult male collared lizards (the species examined in this study) are larger than the females, have hypertrophied jaw muscles, and are highly territorial toward other males. All of this relates to males having evolved the ability to bite with great force, which means that they can seriously wound rivals in fights.

"When you've seen what these lizards can do to each other with their jaws, inflicting deep lacerations and even breaking bones, it makes sense that avoiding fights would be advantageous, even if you are likely to win," Lappin says.

When two competing males engage in a gaping display, each shows off its weapon while simultaneously affording an opportunity to evaluate its rival's weapon. In animals from insects to humans, such displays likely play an important role in assessing the risks associated with fighting, as well as in reinforcing the experiences of past fights with specific individuals.

"You see the same with humans," Lappin explains. "Think back to the rivalries of adolescence. Fights took place in order to establish dominance relationships in the neighborhood, but the fights themselves were rare. Most of it was posturing and showing off, displays per se, that served to advertise physical prowess as well as to reinforce the consequences of previous confrontations."
A. Kristopher Lappin, Yoni Brandt, Jerry F. Husak, Joseph M. Macedonia, and Darrell J. Kemp, "Gaping displays reveal and amplify a mechanically based index of weapon performance." The American Naturalist 167:7.

University of Chicago Press Journals

Related Lizards Articles from Brightsurf:

Not just lizards - alligators can regrow their tails too
A team of researchers from Arizona State University and the Louisiana Department of Wildlife and Fisheries have uncovered that young alligators have the ability to regrow their tails up to three-quarters of a foot, or 18% of their total body length.

Cockroaches and lizards inspire new robot developed by Ben-Gurion University researcher
'The AmphiSTAR uses a sprawling mechanism inspired by cockroaches, and it is designed to run on water at high speeds like the basilisk lizard,' says Ben-Gurion University Prof.

Giant lizards learnt to fly over millions of years
Most detailed every study into how animals evolve to better suit their environments shows that pterosaurs become more efficient at flying over millions of years before going extinct with the dinosaurs.

Study highlights lack of evidence for plasticity-led evolution in lizards
Scientists have challenged a popular theory behind the evolution of similar traits in island lizards, in a study published recently in eLife.

Biodiversity may limit invasions: Lessons from lizards on Panama Canal islands
Introduced species can become invasive, damaging ecosystems and disrupting economies through explosive population growth.

Double take: New study analyzes global, multiple-tailed lizards
Curtin research into abnormal regeneration events in lizards has led to the first published scientific review on the prevalence of lizards that have re-generated not just one, but two, or even up to six, tails.

Lizards develop new 'love language'
Free from the risk of predators and intent to attract potential mates, male lizards relocated to experimental islets in Greece produce a novel chemical calling card, according to new research from biologists in Arts & Sciences at Washington University in St.

Hot time in the city: Urban lizards evolve heat tolerance
Faced with a gritty landscape of metal fences, concrete walls and asphalt pavement, city lizards in Puerto Rico rapidly and repeatedly evolved better tolerance for heat than their forest counterparts, according to new research from Washington University in St.

Detection dogs and DNA on the trail of endangered lizards
Detection dogs trained to sniff out the scat of an endangered lizard in California's San Joaquin Valley, combined with genetic species identification, could represent a new noninvasive sampling technique for lizard conservation worldwide.

Realistic robots get under Galápagos lizards' skin
Male lava lizards are sensitive to the timing of their opponents' responses during contest displays, with quicker responses being perceived as more aggressive, a study in Behavioural Ecology and Sociobiology suggests.

Read More: Lizards News and Lizards Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to