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Thursday, February 17, 2011

Lizards of Arizona, What We Can Learn

Lizards are a diverse, adaptable, usually quadrupedal reptile and in the scientific community fall into the order of Squamate. In recent years they have received much deserved attention. Breakthrough discoveries are being made about their natural history and even a seemingly miracle drug for diabetics has been derived from the Gila Monster’s saliva. Through the study of lizards there are insights into local ecological conditions and a multitude of methods of survival in some of the world’s most arid and seemingly inhospitable regions (Reilly McBraver Miles xi). Because of Arizona’s unique biogeographical history it has the most diverse lizard populations in the United States. This makes Arizona not only a fun and exciting place to take a closer look at lizards from an educational and conservational standpoint.

The study of reptiles and amphibians, herpetology, can become a life-long love affair. It often starts with a childhood captivation with these small creeping things. This fascination can become a catalytic force creating an inner drive to find out about the things unknown, leading to many discoveries in the sciences. In his forward of the book Lizards: Windows to the Evolution of Diversity, Harry W. Greene, makes this illustration about the authors, Eric Pianka and Laurie Vitt, “in some ways this is a book about two curious boys who grew up chasing lizards, learned to carefully ask questions of nature, traveled all over the world in search of answers” (Pianka Vitt xi). Others feel the same passion about lizards as well, “I know that I have become irreversibly obsessed, and wherever I go I will be looking for the tell-tail silhouette of a basking lizard”, reflects the Larry Jones the co-editor of the book Lizards of the American Southwest: A Photographic Field Guide Larry Jones. In support of his co-editor’s opinion of thought, Rob Lovich gratefully articulates, “lizards gave me my graduate degree, and in return a lifetime of admiration for their natural history, evolution, and all the unknown aspects of their biology” (Jones Lovich 16-17).

Undoubtedly most can agree that “lizards command our attention” many are brightly colored and just interesting to look at. That is probably why so many businesses use them as advertisements. From car insurance to soft drinks! “Perhaps more important, they are model organisms for ecological and evolutionary studies and, as such, can teach us volumes about the living world that surrounds us. Without lizards, our lives would be sadly impoverished” (Pianka Vitt 281). With how interesting and captivating lizards are one would think more people would know about and study them but as herpetologist Clifford H. Pope observed in 1956, “’few people live in the parts of the country where lizards abound, and vice versa.‘” Pope had noticed that in the eastern states lizards are less common and harder to find unlike the salamander what is frequently confused with lizards adding “greatly to the lack of clear thinking about lizards’” (Badger Netherton 15). A budding naturalist can find a great place to study these four-legged reptiles in the Southwest United States. Where even a lay observer can witness the great abundance and diversity of lizards (Jones Lovich 11). Because “lizards are among the most familiar and interesting creatures in the American Southwest” authors Lawrence L. C. Jones and Robert E. Lovich chose this region to “write another book devoted to the complete lizard fauna” of the region (Jones Lovich).

Arizona sports the highest number of lizard species, 53 of the 96, of the southwest region! (Jones Lovich 18). “Home to a richly varied terrain, Arizona is among the most biologically diverse states in the country” explains Brennon and Holycross in their book A Field Guide to Amphibians and Reptiles in Arizona. “A combination of diverse topography and location at the nexus of eight major biomes results in an extraordinary variety of… biotic communities.” With “this conglomeration of communities”, Arizona is able to house its extraordinary lizard populations (1-3).

The ability for lizards to survive in the extremes of the desert regions of Arizona is dumbfounding, “reptiles have thin skin with little insulation and most do not produce heat internally to fuel their metabolisms, adaptations to regulate body temperature (thermoregulation) are very important” (Arizona-Sonora Desert Museum 530). This ability is attributed to the great variety of traits given lizards through natural selection. In the areas close to Yuma Arizona found in the southwestern portion of the state, oceans of sand house an extraordinary product of natural selection, the Fringe-toed Lizard “is closely associated with windblown sand deposits in the Lower Colorado River subdivision of the Sonoran Desert” (Jones Lovich 274). It is a medium sand obligate lizard “with a flat body, a flattened tail, and a chisel-like snout” what makes their sand diving abilities greatly increased (Brennon Holycross 66). In Arizona, there are two species of this particular lizard fauna, the Yuman Fringe-toed Lizard and the Mohave Fringe-toed Lizard (Brennon Holycross 66). Both of which are “adept at diving into the sand head-first” and moving its body back and forth into the sand “to bury itself within a few centimeters of the surface” giving the lizard “better thermal cover” when things get a little too hot for its liking when the sandy above ground temperatures of which it is not uncommon to exceed 65°C (Jones Lovich 275). This behavior also works well against predators. (Arizona-Sonora Desert Museum 562). They get their name from the comb like fringes, which are scales that are enlarged that come off the long toes of their back legs. Pianka and Vitt explain, that the specialized back limbs “increase surface area exposed to substrate” giving it “the extra support necessary for lizards to achieve high running speeds on sand”(23, 29).

In a similar situation as of any Arizona desert dweller, the Desert Iguana has not only predators but also the extreme heat to deal with. The habitually herbivorous Desert Iguana takes advantage of its environment and “are most active in hot temperatures (above 35°C) and are considered the most heat-tolerant reptile in North America. Body temperatures have been recorded as high as 45°C,” what is far past the point when any other reptile in the region can tolerate without being cooked a live (Jones Lovich 132). What is an ability thought to have arisen as defense using the extreme heat as a barrier “perhaps as an anti-predator tactic” (Pianka Vitt 157). A possible answer to how they are so uniquely able to tolerate these ridiculously high temperatures may be in its suggested “adaptive advantage to fever” caused by microscopic parasites of which when present they are able to keep a temperature higher than when microbes are not present. Although the parasitic benefactor is not all good news, without maintaining the thermal extremes the “microbes prosper and” the “infected lizards suffer”(Pianka Vitt 157).

Survival often takes a more direct aggressive thoughtful approach, an ability to gage what tactics will generate the most desired result, not getting eaten! Regal Horned Lizards show a knack of survival, as they seem to discern when to run and when not to, the approach of slower moving snake i.e. a rattlesnake or the the very quick moving coachwhip snake. In the case of the latter, the horned lizard often “presents the largest part of its” very round flat “body to convince the snake that it’s too large to swallow” (Jones Lovich 197). Furthermore an ability to defend specifically against “canid predators such as Coyotes” suggests this knowledge of what defensive behavior works best against a specific predator (Jones Lovich 180). There is also evidence showing that the horned lizard primary food source, ants, “many of which are known to produce a variety of toxic or noxious chemicals for defense”, give them an added defensive advantage that manifests itself in a sort of pepper spray warding of would be attackers (Pianka Vitt 79).

But the lizard that takes the cake for its proactive defensive abilities is the lizard that is one of the only two venomous lizards in the world, the Gila Monster, with the scientific name of Heloderma, a term derived from the Greek words helos for ‘nail stud’ and derma for ‘skin’. This is an apt description of the studded skins of” the bumpy looking lizard of “which are embedded with bony, beadlike osteoderms” (Beck 1). Interestingly enough the species name of “suspectum was given the Gila Monster by E.D. Cope in 1869 because he suspected it was venomous, but it was nearly 50 years later before scientists agreed that, indeed this was true” (4). “Unlike other lizards that can rapidly skitter out of harm’s way, monstersaurs”, as Beck calls them in his Gila Monster account in Lizards of the American South West, “are not sprinters” and need “the threat of a painful, venomous bite” to help their ability in “defending themselves against potential predators such as Coyotes, foxes, hawks and cats.” To humans “a bite from a Gila Monster or Beaded Lizard causes excruciating pain, swelling, and, in more severe bites, a rapid drop in blood pressure, profuse sweating, and vomiting. Gila Monsters pose little threat to human health and safety, however… there has not been a human death reported from a Gila Monster bite since 1930” and this is primarily because “bites to people are rare and almost always result from careless handling” (Jones Lovich 497).

It seems to be all about peptides so far with Gila Monster research and its medical field applications what “have brought the shy, venomous lizards into pharmacology journals and headlines in medicine” (Beck 52). Studies show that “Gilatide”, derived from the saliva of the lumpy looking lizard, dramatically improves memory retention in rats” what “might boost memory receptors in the brains of humans suffering from Alzheimer’s disease” (Badger 118). But “the best-known lizard peptide, exendin-4 (exenatide) is a leading candidate for treating adult-onset (Type II) diabetes, which accounts for most of the 17 million cases of diabetes in the United States. Prospects for this drug is so bright that Eli Lilly & Company recently closed a $325 million deal with Amylin Pharmaceuticals for rights to develop and market this compound” (Beck 52).

A favorite period of time for many lizard watchers is breeding season, when the males are, most often, the ones who put on their Sunday best to attempt at getting a female, or in many cases a territory with a harem of females in which case they need to use their bright vivid colors and physical displays to ward off the other lizard antagonists. Featuring a seemingly complicated method of mate selection ”the Common Side-blotched Lizard,” has a set of three male color patterns found within the species all of which have different strategies to get a mate. There “fixed” color forms “according to the color of their throat: blue, yellow, or orange. The orange-throated males are the most aggressive and maintain large territories with females inside them; but yellow-throated males, who do not defend territories, sneak into the territories of the orange-throated males at opportune times and copulate with the resident’s females. Blue-throated males also do not defend territories, but instead mate-guard their females after copulation. This mate guarding is effective against yellow-throated males, but not against the super-aggressive orange-throated males” A makeshift “game of rock-paper-scissors” (Jones Lovich 37).

There are concerns with how long we can keep lizards around in their full biodiversity. “Many lizards, along with other retile species, are declining or have declined historically for myriad reasons”, Jones and Lovich convey, “in general, most population declines are due to habitat loss and habitat conversions resulting from the invasion of non-native species.” They go on to say how thankfully no southwestern lizards have gone extinct “yet.”

A lizard who is having a hard time in Arizona is the Flat-tailed Horned Lizard what has “behavior patterns” what make them “particularly susceptible to mortality on roads” since they tend to stay motionless as a vehicle approaches “therefore, roads and new road construction are recognized as threats influencing the long-term persistence of this species” (Painter Ingraldi 1). Thankfully there is some progress being made when “in 1997 flat-tailed horned lizards gained protective status on public lands under a conservation agreement signed by several state and federal agencies” (Painter Ingraldi 3).

I have lived in Arizona and loved lizards my whole life and thought there was pretty much no more I could learn about my home state and the lizard I often saw in it. As I attempt to convey their stories I find there is much we can learn and much we can do for lizards, that we are not the only things that have a desire to live have a life. That we need to look where we tread and observe how beautiful and interesting life can be and is. For me I have chosen the degree path of wildlife restoration and ecology of which I can attribute to my childhood playing outside with captivation to these scaled and tailed educational ambassadors we call lizards!

Works Cited

Arizona-Sonora Desert Museum. A Natural History of the Sonoran Desert. Arizona Sonora Desert Museum Press. 2000. Print.

Badger, David. Lizards: A Natural History of Some Uncommon Creatures—Extraordinary Chameleons, Iguanas, Geckos, & More. Voyageur Press, Inc. 2002. Print.

Beck, Daniel D. Biology of Gila Monsters and Beaded Lizards. University of California Press. 2005. Print.

Brennon, Thomas C. and Andrew T. Holycross. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game and Fish Department. 2006. Print.

Jones, Lawrence L. C. and Robert E. Lovich. Lizards of the American Southwest: A photographic Field Guide. Tucson: Rio Nuevo Publishers, 2009. Print.

Painter, Mikele L. and Michael F. Ingraldi. Use of Simulated Highway Underpass Crossing Structures by Flat-tailed Horned Lizard. Arizona Game and Fish Department, 2007. Print.

Pianka Eric R., and Laurie J. Vitt. Lizards: Windows to the Evolution of Diversity. University of California Press, 2003. Print.

Reilly, Stephen M., Lance B. McBrayer and Donald B. Miles, Eds. Lizard Ecology. Cambridge University Press, 2007. Print.

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