Desert night lizard

Desert night lizard
Conservation status
Least Concern  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Xantusiidae
Genus:	Xantusia
Species:	X. vigilis
Binomial name
Xantusia vigilis Baird, 1859

The desert night lizard (Xantusia vigilis) is a night lizard native to southern California east of the Sierras and San Gabriel Mountains into Baja California, southern Nevada, southwestern Utah and extreme western Arizona.

Description

The desert night lizard attains a snout-to-vent length (SVL) of 1.5 to 2.75 in (3.8 to 7.0 cm) with a tail roughly the same length. The lizard's coloring is usually grey, yellow-brownish, or olive. Despite their name, night lizards are active during the day. They are known to easily to change their color, from light olive (usually during the evening) to dark brown during the day. It is a good climber and usually eats termites, small insects, spiders and other arthropods.

The Desert Night Lizard is on the smaller side of reptile where the average adult female is 80 mm in total length and 1.3 g in weight. The average adult male Xantusia vigilis is 65mm in total length and 1.1 g in weight. Male Desert Night Lizards are distinguishable from female as they are lighter and shorter in length. Additionally, they sport a more stout and wide tail as well as enlarged femoral pores. Most Desert Night Lizard have 12 longitudinal rows of rectangular ventral scales with 30-50 granular dorsal scales around their mid region. Above each eye, they are found to have supraorbital scales (one around the nasal bone, two frontal ones, and two parietal scales). Typically, the color along their body runs from light gray to brown and can often be a single color throughout the body, but some species have been found to have variety in dark spots amongst their unicolor body. (1)(9)(5)

Habitat and Distribution

It is a secretive lizard of arid and semi-arid locales. During the day it may be found under fallen debris of desert plants and in rock crevices. It is usually associated with varieties of yucca such as the Joshua Tree, Spanish Dagger, and Spanish Bayonet.

Xantusia vigilis can be found along the Southwestern coast of the United States and northern regions of Mexico. Specifically, there is great prevalence of Xantusia vigilis in the Mohave and Sonoran Deserts, throughout southern California and Baja California. Smaller populations of Xantusia vigilis have been found in western Arizona, certain areas of Coast Ranges within Central California, Colorado, the Sierra Nevadas, and Utah. (1)

Xantusia vigilis received its more common name Yucca Night Lizard, because of its frequent prevalence around plants of the Yucca Genus (in example, the Joshua Tree). (1) Interesting, Xantusia vigilis is one of the few species of lizard or vertebrates that have this type of plant based habitat occupation (6). While this lizard is widespread across various regions in the United States and Mexico, it’s environmental setting seems standardized across its various regionalities (6). The Desert Night Lizard is most commonly found underneath fallen dead trees, fallen ecological debris (plant limbs, Spanish dagger, Quixote Plants), and amongst the spiny leaves of Joshua Trees. (6) The Desert Night Lizard is not fond of being in common sight and chooses this form of habitat as an added layer of protection and obscurity from predatory species. This lizard is not isolated to areas with Yucca plants, but their frequency or high prevalence is often associated with the presence of Yucca plants (6).

Behavior

Like all night lizards, the desert night lizard is viviparous, giving birth to live young and producing 1 to 3 young from August to December. Unusually for a lizard it forms family social groups with a father-mother pair and offspring, which may delay dispersing for years. The young are capable of feeding themselves but will huddle together with their relatives. They do not receive any direct care from their parents and older siblings and it is not yet known what the advantages of staying with their parents are. The baby lizards are well-camouflaged and are not much bigger than a toothpick.

Social Behavior

Groups of Xantusia vigilis with great levels of kin relatedness proved to be more stable than congregates of Xantusia vigilis that lacked close familial relation. It is believed that kin presence for this particular species of lizard encourages philopatry (or the tendency for an animal to remain in the region of their birth as it proves advantageous to remain in a group) and winter aggregation. It was found that reproductive success was heightened with female Xantusia vigilis when kin presence and kin relatedness within a living group was observed.

Winter groups (aggregates formed to survive through the cold winter) proved advantageous as it allowed for greater internal heat retention of individual lizards and thus for the collective group as a whole. Most winter groups are as large as 20 lizards (8). However, the winter groups do not last past the coldest months of winter, and typically dissolve by the time copulation occurs in June.

In terms of social behavior, Xantusia vigilis are a largely sedentary species of lizard that choose to remain obscure and hidden from plain sight. Xantusia vigilis follow the group stability hypothesis and are more stable within their families. (8)

Reproduction and Life Cycle

It has been reported that 2 offspring are the most to be expected to be produced by Xantusia vigilis during a given birth (5). There exists a preference based on specific oviduct and ovary used for ovulation; when only a single ovum is ovulated there is a pressure for the right ovary to overproduce a larger number of mature ova within the right ovary (3). Reproduction within Xantusia vigilis is dependent on a few factors largely centering climate preferences, diet, and nutrition.

Climatic changes heavily dictate the proceedings of gestation within Xantusia vigilis; during damp climates this species of lizard will either prepone or postpone ovulation for more dry conditions - for example, given a particular damp spring, ovulation is expected to occur in the middle of the following summer. Regardless of climate, breeding typically occurs during the season of Spring and Winter (5).

Similarly, diet carries a similar importance on determining the success of a given breeding season. Improper diet and malnutrition often leads to underdeveloped ova and lacking yolk deposition within female Desert Night Lizards. Dry climates are heavily associated with underdevelopment in reproductive organs and the general processes of reproduction within the Desert Night Lizard. Strangely, males during drier climates have shown to reach a greater level of testicular maturation in low resource settings.

Ovulation period for Xantusia vigilis lasts approximately 2 weeks at an optimal temperature range from 75 - 90℉. Gestation typically lasts 90 days. No day versus night preference exists for parturition itself, where the event of delivery itself lasts 10 minutes. Most desert night lizards live for as long as 8-10 years (8).

Subspecies

The yucca night lizard, Xantusia vigilis vigilis, is a subspecies.

References

1. Bezy, R. L. (1965). Xantusia vigilis Baird Desert Night Lizard. Evolution, 19(2), 268–268. https://doi.org/10.1111/j.1558-5646.1965.tb01719.x
2. Brattstrom, B. H. (1952). The Food of the Nightlizards, Genus Xantusia. Nature - American Society of Ichthyologists and Herpetologists, 139(3528), 168–172. https://doi.org/10.1038/1391014a0
3. Miller, R. M. (1954). Further Observations on Reproduction in the Lizard Xantusia vigilis. Coepia - American Society of Ichthyologists and Herpetologists (ASIH), 139(3528), 38–40. https://doi.org/10.1038/1391014a0
4. Cowles, R. B., & Burleson, G. L. (1946). The Sterilizing Effect of High Temperature on the Male Germ-Plasm of the Yucca Night Lizard, Xantusia vigilis. The American Naturalist, 79(1). https://doi.org/10.1086/281277
5. Perkins, M., S. C. Adolph, S. Granite, and W. Hein*. 1997. "Natural history notes: Xantusia vigilis (Desert Night Lizard) and Sceloporus magister (Desert Spiny Lizard). Predation and diet." Herpetological Review 28: 89.
6. Stebbins, R. C. (1948). New Distributional Records for Xantusia vigilis with Observations on Its Habitat. The University of Notre Dame - The American Midland Naturalist, 39(1), 96–101.
7. reptiles and amphibians of California. California Herps. (n.d.). Retrieved December 17, 2021, from http://www.californiaherps.com/lizards/pages/x.vigilis.html
8. Davis, A. R. (2009). Kin dynamics and adaptive benefits of social aggregation in the Desert Night Lizard, 0RW1S34RfeSDcfkexd09rT2Xantusia vigilis1RW1S34RfeSDcfkexd09rT2 (Order No. 3351041). Available from ProQuest Dissertations & Theses Global. (304855142).
9. Xantusia vigilis. The Reptile Database. (n.d.). Retrieved December 17, 2021, from https://reptile-database.reptarium.cz/species?genus=Xantusia&species=vigilis

Further reading

• Baird SF. 1859. Description of New Genera and Species of North American Lizards in the Museum of the Smithsonian Institution. Proc. Acad. Nat. Sci. Philadelphia 10: 253–256. (Xantusia vigilis, new species, p. 255).
• Behler JL, King FW. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743 pp. ISBN 0-394-50824-6. (Xantusia vigilis, pp. 551–552 + Plate 406).
• Boulenger GA. 1885. Catalogue of the Lizards in the British Museum (Natural History). Second Edition. Volume II. ... Xantusiidæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiii + 497 pp. + Plates I-XXIV. (Xantusia vigilis, pp. 327–328).
• Goin CJ, Goin OB, Zug GR. 1978. Introduction to Herpetology, Third Edition. San Francisco: W.H. Freeman and Company. xi + 378 pp. ISBN 0-7167-0020-4. (Xantusia vigilis, pp. 129, 132, 148, 286).
• Smith HM, Brodie ED Jr. 1982. Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. ISBN 0-307-13666-3. (Xantusia vigilis, pp. 84–85).
• Stebbins RC. A Field Guide to Western Reptiles and Amphibians, Third Edition. The Peterson Field Guide Series ®. Boston and New York: Houghton Mifflin Company. xiii + 533 pp. ISBN 978-0-395-98272-3. (Xantusia vigilis, pp. 307–309 + Plate 35 + Map 76).