Western Fence Lizards declare their territories and fight their battles by doing pushups. Their basic territorial pushup is a bobbing motion executed with the front legs at a particular frequency between two levels of leg-extension, both greater than the sprawled position of a lizard not actively engaged in territorial dispute.
The scientist, Stephen Adolph, studies Western Fence Lizards and told me that they come out of the egg already hyper-sensitive perceptually to the frequency and pattern of the pushup and that their neuromuscular system is, even at the early age, hyper-ready to do the pushup, the hatchlings doing juvenile versions of the pushup the way a human infant kicks their legs in anticipation of walking, the species' distinctive staccato bobbing the pervasive rhythm of the lizards' lives.
As they grow to become adults, the lizards increasingly use the pushup from the best perches in their territories to broadcast their claim to their small domains. These basic territorial pushups are executed mostly with the forelimbs and pale in comparison to what the scientists call the "Full Show" which occurs mostly during mating season when the males are the randiest and the most aggressive.
In the Full Show, two males will be pushing the boundaries of their territories seeking and hoping to attract mates. One will find himself in a territory that another thinks is rightfully his and the only recourse becomes an old-fashioned pushup showdown. These standoffs proceed from the, by comparison, genteel forelimb movements of the basic pushup to pushups that also engage the hindlimbs. As the enmity of the two combatants grows, they flatten their bodies to display the vibrant blue patches on their bellies (always otherwise hidden from view of predator and conspecific alike), and extend their throats to show the blue there too.
At a point the lizards cease the downward bob of their pushup, instead holding themselves rigidly at the pushup's apex. Now the true competition begins. The lizards strain to keep themselves in this hyper-erect position, legs straight out below them in almost a mammal-like way, throat and belly blue patches brazenly displayed. Like a blinking contest, the winner is the one who can hold out longest, the loser the one that calls uncle. This feat of endurance (only a minute or so long as it is) is truly hard for the lizards to do. It is therefore what is termed an honest signal, a signal that is actually tied to the health and fitness of the signaler, the winner not a cheat but now a proven superior to the loser.
When a lizard loses this fight, they not only drop down from their rigid, erect stance to their natural posture but go beyond it, actually flattening themselves into the ground, in essence going negative on the pushup. Their machismo, so to speak, is so entirely wrapped up in a few millimeters of height from the ground that a lizard loser must not just submit, but prostrate themselves.
During the spring, my yard feels like a pushup war zone or more aptly like a Hollywood Western in which trigger-happy gunslingers are likewise always hyper-ready to enter standoffs for pride and territory, moseying around town just an errant stink-eye or a disputed poker hand away from a bracing showdown. Like their Hollywood cowboy counterparts, the lizards (who are, incidentally, living within a few miles of Hollywood itself) even appear to have formed little bands of bandits and sheriffs: the Log Pile Posse, the Front Stair Pair, the Fallen Tree Bunch, and, the most notorious, the Gap Crack Gang. I am never certain which group is on which side of the law.
My little pushupping automaton, "Nary A Yellow-Bellied Blue Belly," enters the ongoing border disputes between these various bands like Yul Brynner's robotic gunslinger in the 1973 movie "West World." As with the members of those dueling bands, its perception is keenly attuned to the bobbing pattern of the Western Fence Lizard's distinctive pushup. In fact, its perceptual system is aware of nothing else. It would not know a lizard that wasn't doing pushups if it came up and smacked it in the lens but it would know a Western Fence Lizard's pushup even if it were Yul Brynner doing one himself. And as soon as the robot sees the pushup, it responds in kind with its own pushup, immediately instigating a pushup skirmish that the lizards dutifully engage in but can't win. Biological organisms that have such limited energetic resources and so much else they need to accomplish will always lose to a robot whose every part is solely bent on winning the duel.