By Erin Lane
Part III: Visual Virtuosos
It is finally that time of year—the days are getting longer, the weather is milder, and your herps are just starting to wake up from brumation. Spring is in the air, and reptiles and amphibians are responding accordingly. This is perhaps the most exciting time for reptile and amphibian keepers as it is when many of our pets begin to show the most interesting and diverse behaviors. For some species, breeding season is well underway. Over the past couple of months we have discussed how herps use auditory and chemical communication to find and attract mates. This month we will be wrapping up our talks with perhaps the most evident form of reptile behavior—visual communication.
Visual communication is perhaps one of the most interesting forms as it takes advantage of our own primary sensory system. What makes it particularly enjoyable to watch is that it is an extremely diverse mode, which can range from push ups and head bobs to flashes of intense color. Previously we discussed how many frogs and toads use auditory communication to attract mates, and that others take advantage of chemical cues to sniff out a good mate. When it comes to visual communication, lizards reign supreme.
The unique eyes of a young male Jackson’s Chameleon!
The right kind of attention
The way to get attention for most lizards is to be visible to conspecifics (animals of the same species). Unlike anurans (frogs and toads), very few lizards vocalize, and most that do typically reserve it for when they are threatened. And, while some lizards also use chemical signals to communicate, these appear to be secondary to visual signals. For a lizard, it’s all about the show!
Almost every reptile enthusiast can conjure a picture of a lizard doing pushups on a rock, or a bearded dragon head bobbing. Lizard visual displays are often eye catching and rhythmic in nature. One problem that lizards run into is one that most small animals have to worry about—when you make yourself visible, you run the risk of predation. There is often a fine line between being visible enough to attract attention from conspecifics without drawing attention from predators. In many cases, caution is thrown to the wind in favor of attracting a mate.
An agama in the wild displaying brilliant colors intending to attract a mate!
Peacocks are a perfect example of this phenomenon. While these birds have been bred in captivity for centuries, their true wild form is not much different from those you might see at a park. With their overly long tail feathers, bright colors, and larger than life display, they stand out in almost any environment. In addition, those beautiful tails also make quick movement and flying more cumbersome. While peafowl may be good enough at escaping a human, they are a much easier target for their wild predators. However, it is exactly these traits that make males so attractive to females. A number of studies have shown that females (peahens) are more likely to breed with makes whose trains have certain qualities, such as those that are longer or have more eye spots1. Sometimes safety is sacrificed in order to gain access to reproductive partners, and in many cases it pays off. After all, the success of an animal is not measured in its longevity, health, or looks, except how these relate to the number of offspring they produce, that in turn live long enough to reproduce themselves.
Capitalizing on calisthenics
Reptiles are no exception to the rule. Attracting a mate is of upmost importance, but you still have to be careful about not attracting predators. One way around this dilemma is to produce signals that are only visible to conspecifics. For lizards, this usually means signals that are highly visible to other animals on the same horizontal plane, but less visible to aerial predators a primary concern for most small lizards). The push up is a great example of this.
Many lizards, such as sceloporus species (e.g. fence lizards and spiny lizards), common out here in Southern California, can be seen doing pushup displays on any high point in the terrain (usually a rock or boulder). The movement is easily seen by us human onlookers, and is also visible to other nearby lizards that are likely keeping an eye on their neighbors. However, if seen from above, this is not a display that creates a lot of visual commotion. While movement of any kind is a risk, the type of movement can make all the difference. A display that is highly visible to conspecifics, but not particularly visible to predators is a great form of communication.
But back to the point—how do visual signals, such as a push up, relate to breeding behavior? Like the peacock, it’s all about getting attention. Many signals can communicate the same thing to both sexes, but with very different outcomes. For example, a male bearded dragon that performs a lot of head bobs may be communicating his dominance, ownership of a territory, his energy reserves, or a combination of all three. To other males, this may be sign that they should stay away. After all, if the displaying male is confident enough to display himself prominently, he has likely had to fight for that position, and may be a formidable opponent. He must also have lots of energy reserves to continually display, meaning that he may also have lots of energy for fighting as well.
Lateral Compression in a Fence Lizard
While a push up might signal health and dominance to an onlooker, this may have a very different effect on females. To a female, these traits communicate that a particular male has good genes to pass on to his offspring. And remember—at its most basic level, life is about reproduction. Signals that show off a male’s ability to survive, thrive, and produce hardy offspring may have the dual purpose of reinforcing a male’s status while also attracting females.
Color me pretty
While displays of physical ability are common forms of communication among lizards, it is perhaps overshadowed by the incredible array of color exhibited by these squamates.
Unlike most mammals, many lizards see in wide range of colors. As humans, we have three different color receptors in our eyes that through combination (and your brain’s interpretation) give us the standard rainbow colors, and all those in between. Most other mammals see the world with comparably limited color. Your dog and cat, for example, can see blue, but lack the receptors to see red and green. Some animals see in shades of black, white, and gray. While it is impossible to make a blanket statement about reptile color vision, we can say that some species possess a highly evolved visual system that allows them to see color the same way, and in some cases even better than, the way we humans do.
From the black beard of a bearded dragon to the myriad colors exhibited by chameleons, color display is perhaps visual communication at its most interesting. Like physical displays, color is usually an excellent communicator of health and good genetics. More or more vibrant color has been linked to a number of other fitness indicators across different species, including an animal’s size2, fighting ability3, the amount of courtship a male performs4, body condition5, and even parasite load6, 7. All of these qualities can contribute to a healthy individual that is bothnot worth fighting, and probably worth mating with. Color is a way to communicate fitness without putting much physical effort into it.
Male Beardie with dark beard
Color is also used to enhance other displays, making them more visible to conspecifics. Think of a male bearded dragon head bobbing on his perch. The dark black beard makes that head and the motion more visible, further emphasizing the overall display. A fence lizard’s defensive and aggressive displays also utilize color and position. When the body is laterally compressed (sides pressed flat), it emphasizes the blue ventral (tummy) color that gives them the colloquial name of “blue belly” lizard. Flashing some color when you need to may help dissuade an aggressor.
Although many males exploit color for communication, they are not the only ones. Females of many species also use color to communicate. One example is the color changes that some female lizards undergo when gravid. What is the first sign that a female chameleon is gravid? Her color changes—and it is not limited to chameleons. Many female lizards change color to indicate that they are no longer receptive to a male’s advances. This saves the male wastedtime courting a female he cannot impregnate, and the female is saved the hassle of prolonged male harassment.
Animals have a number of ways that they communicate with one another. For some, auditory communication is preferred, for others, chemical cues are of upmost importance. For many lizards, visual communication is perhaps the most widely used. From pushups to head bobs, flashy agamas to gravid chameleons, visual signals are some of the most interesting. They can often communicate incredibly important information to conspecifics, sometimes with no immediate effort at all. So next time your anole flashes his dewlap, your bearded dragon head bobs, or your chameleon changes color, give ‘em a nod back.
1) Loyau et al. (2005)
2) Vásquez & Pfennig (2007)
3) McElroy et al. (2007)
4) Sorenson & Derrickson (1994)
5) Elder & Friedl (2010)
6) Mougeot et al. (2009)
7) Václav et al. (2007)