Common side-spotted iguana
| Common side-spotted iguana | ||||||||||||
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Common sidelock iguana, female |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Uta stansburiana | ||||||||||||
| Baird & Girard , 1852 |
The common sideline iguana ( Uta stansburiana ) is a representative of the iguanas belonging to the Phrynosomatidae and reaches a body length of maximally 17 centimeters. It lives in the mostly sandy-rocky arid regions of North America. The common name side spot iguana refers to the noticeable dark spot on the animal's flanks just behind the legs.
features
The side spotted iguana is relatively small with a maximum body length of 17 centimeters. It is gray-brown in color and has darker spots on both sides behind the neck and front legs. The throat is speckled and, especially in the males, can have a large proportion of blue pigment spots, but there are no colored spots on the stomach. This noticeable coloration only appears in adulthood. There is a noticeably dark spot on the flanks of the animals directly behind the legs. The back scales are small and folds of skin are formed below the throat . The iguana resembles the western fence iguana ( Sceloporus occidentalis ) in its appearance , but it is somewhat larger and darker.
As a sexual dimorphism , the base of the tail is clearly swollen in the male and there are clearly enlarged scales behind the anus . The coloring is more clearly spotted blue and yellow on the back. In the male there are several different color morphs, which differ mainly in the blue, yellow or orange throat coloration. Studies have shown that the different color variants are associated with different behavior before mating (see below). The females lack this colorful spot, instead it is patterned in brown and black.
distribution
The side spotted iguana is one of the most common lizards of dry areas in the western United States . Its distribution area extends from the state of Washington via southern California to western Texas and Mexico , in the west to Colorado . The animals can also be found on a number of offshore islands on the Pacific coast .
habitat
The sideline iguana lives almost exclusively in arid areas, i.e. in desert and semi-desert areas with sparse vegetation. It can also be found in dry river beds, rocky canyons and in the area of larger roads and, less often, in dry forest stands. Its distribution extends up to a height of a maximum of about 3000 meters. It can usually be found frequently within its habitats.
The individual territory size and the animals' scope of action is very small. For the animals in Colorado it could be proven that the individual animals do not move more than a few hundred meters away from their hatching nests in the course of their life, whereby the males cover the longer distances. The area of activity for the males is on average 440 to 610 square meters, for the females 190 to 225 square meters. The breeding cave is usually very centrally located in the females' activity area. Between 10 and 285 animals can live per hectare, according to studies in Washington, Oregon, Nevada and California.
Way of life
The side spotted iguana is diurnal, although it is mainly active in the morning or in the late afternoon. He spends the hottest hours of the day hidden under stones or in his burrow in the sandy soil. He stays in hiding on rainy or even more cloudy days. In the northern range it is active from March to November, and spends the winter buried in hibernation . In the southern area he is active all year round.
Sideline iguanas feed on insects , scorpions and spiders , and in very rare cases cannibalism has been observed in young animals. He himself is hunted by larger lizards, snakes , owls and birds of prey .
During its activity times, it mainly hides in hiding places such as plants or larger stones on the ground, but can also regularly be seen sunbathing on flat stones and sunlit rocks. In contrast to most lizard species, these animals are also active at low temperatures in winter, as they are very quickly warmed up in the sun due to their small body size.
Mating behavior
The mating behavior of the side-spotted iguanas is mainly determined by the males, who behave very differently according to their appearance. For example, within the individual populations among the males there are specimens with blue, yellow and orange throats, each of which has a different mating behavior. In 2004, Barry Sinervo and Jean Clobert published their observations on these males and their mating strategies and were able to observe a number of interesting mating strategies:
- The orange males are very aggressive and mate with as many females as possible, threatening other males and urging them to release their females.
- the yellow males usually hide and mate with females if they find them alone in unobserved moments. They use the inattentiveness of the other males.
- the blue males defend their females against other males and are therefore very fixated on individual females.
Different conflict situations result from these different behaviors. Orange males regularly attack the blue males and are usually superior to them, which is why they steal the female from them. The yellow males are less aggressive and are usually chased away by the attentive blue males, but can benefit from the inattentiveness of the orange males and mate with the females of these males. Because of this constellation, there is a balance like in the game of scissors, rock, paper , since each of the three strategies is stronger than the first, but weaker than the second of the other strategies. Hence, the three types coexist and the genes for coloring and behavior are kept in balance within the population.
Another observation made by the researchers was that blue males usually settle in the vicinity of other blue males, which, however, are only very rarely siblings. In this case, the neighbors pay attention to the associated females and also cooperate in the defense against the orange-colored animals and accordingly have a significant advantage over them. Orange-colored males also prefer to settle in the vicinity of blue males without further blue neighbors, since this is where the chance of reproductive success is greatest, whereas it is unfavorable for them to have orange-colored neighbors as well.
The researchers presented these strategies as a very interesting case of developing a range of behaviors that, along with coloration, are only caused by one gene. The cooperation as well as the behavior towards the females and the other color morphs is coupled with the gene for the blue color morph, and it is the same with the genes of the other color variants.
Oviposition and development
Depending on the region, the female creates several clutches in the animals' underground structures in March and August. In the northern range there are up to three clutches with one to five eggs each and in the southern range there are two to seven clutches with one to eight eggs. The female is able to keep sperm in the body and only achieve fertilization a few weeks later. The first hatchlings hatch from around mid-July, although the breeding season in the north lasts a little longer than in the south. The animals reach sexual maturity at one to two years.
The mortality of the young animals is very high, less than 10% survive the first year of life. As a result, the death rate and the number of new young animals largely equalize and the population is relatively stable.
Systematics
The sidelong iguana was first described in 1862 by the zoologists Baird and Gerard in the Proceedings of the Academy of Natural Sciences as a type species and at the same time the first species of the genus Uta . The genus Uta was named after the state of Utah in which the animals were discovered, and the species name U. stansburiana is a tribute to the zoologist Howard S. Stansbury .
Overall, depending on the author, a distinction is made between several subspecies of the spotted iguana, the distribution areas of which sometimes overlap very strongly. In addition to the nominate form , the northern spotted iguana Uta stansburiana stansburiana , there are six other subspecies. According to an analysis published in 1997 on the basis of mitochondrial DNA, the animals of the islands of Angel de la Guarda, Mejia and Raza are said to be their own species. However, this view has not yet prevailed. The following subspecies are currently recognized:
- Western spotted iguana - Uta stansburiana elegans Yarrow , 1882
- Uta stansburiana martinensis Van Denburgh , 1905
- Nevada sideline iguana - Uta stansburiana nevadensis Ruthven , 1913
- Northern spotted iguana - Uta stansburiana stansburiana Baird & Girard , 1852
- Eastern sideline iguana - Uta stansburiana stejnegeri Schmidt , 1921
- Uta stansburiana taylori Smith , 1935
- Plateau sideline iguana - Uta stansburiana uniformis Pack & Tanner , 1970
Inventory numbers and exposure
The side-spotted iguana is very common in most of its range and cannot be assessed as endangered. It is naturally rarer in the northern, cooler states, but there is no human hazard here either. The only state in which the sideline iguana is classified as critically endangered is Oklahoma , as there are very few areas in which the habitat conditions for the animals are given. There is no special protection or trade restrictions within the framework of the Washington Convention on Endangered Species .
In addition to rivers, lakes or mountain ranges, roads form the limits of their distribution, and crossing them often has fatal consequences for the animals, especially on busy main roads.
Terrarium keeping
The side spotted iguana is a popular terrarium animal because it is generally considered to be an easy-to-keep species. It is very adaptable and is not very sensitive to irregular conditions.
The animals are kept in pairs in medium-sized terrariums , which should be at least 60 × 40 × 40 centimeters (W × D × H). A sand display serves as the substrate and climbing opportunities in the form of larger stones should be given. Correct temperature control is important. Accordingly, the daytime temperature should rise to 30 ° C and cool down to around 23 ° C at night. In a place in the sun below a spotlight, temperatures of up to 40 ° C can also be reached. A morning humidity in the range of 75% should also be maintained, as well as sufficient lighting with a UV component. The diet is based on insects and spiders.
Advice from specialists and further training through suitable literature before purchasing these animals is essential despite the information presented here.
literature
- John L. Behler, Frederic Wayne King: The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, New York 1979, ISBN 0-394-50824-6 .
- Robert C. Stebbins : A Field Guide to Western Reptiles and Amphibians. Field Marks of all Species in Western North America (= Peterson Field Guide Series. Vol. 16). Houghton Mifflin Company, Boston 1966 (2nd edition revised. Ibid 1985, ISBN 0-395-19421-0 ).
- Barry Sinervo, Jean Clobert: Morphs, Dispersal Behavior, Genetic Similarity, and the Evolution of Cooperation. In: Science . Vol. 300, No. 5627, 2003, pp. 1949–1951, doi: 10.1126 / science.1083109 .
Web links
- Sideline iguanas at NatureServe (English)
- Uta stansburiana in Death Valley (English)
- Cooperation between unrelated male lizards adds a new wrinkle to evolutionary theory (English)
- Uta stansburiana in The Reptile Database
- Uta stansburiana inthe IUCN 2013 Red List of Threatened Species . Posted by: Hammerson, GA, Frost, DR & Santos-Barrera, G., 2007. Retrieved January 30, 2014.
