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Scincus scincusSandfish Skink

By Kailey Smith

Geographic Range

Habitat

Sandfish skinks spend most of their lives burrowed beneath desert sand, only emerging to eat, excrete waste, and reproduce. They typically remain 1 to 3 cm below the surface of the sand during most of their lives. Environments in which sandfish skinks are commonly found are particularly arid and experience high daytime temperatures with extreme temperature variance. These habitats are also very barren, and often lack vegetation or proximal water sources. (Hetherington, 1989; Stadler, et al., 2016; Vihar, et al., 2015)

Physical Description

Sandfish skinks share many traits with other members of the Scincidae family. These traits include a flattened, wide body with four limbs for locomotion. They also have flat bellies with specialized structures which allow them to breathe while submerged in the sand. Compared to wedge-snouted skinks (Sphenops sepsoides) and ocellated skins (Chalcides ocellatus), sandfish skins have morphological differences including increased hind limb length, and greater body mass.

There are several niches of desert skinks that share many features with sandfish skinks such as a sub-quadrangular subsection, and limbs with webbed digits and toes. Sandfish skinks also have very specialized lung structures, which allow them to burrow in their sandy environments without getting particles of sand in their lungs. Their uniquely-shaped bodies allow them to perform a specialized burrowing technique that allows them to “swim” in the sand, and burrow to thermoregulate in their hot environments. (Attum, et al., 2007; Baumgartner, et al., 2008; Knight, 2016; Stadler, et al., 2016)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    16.6 g
    0.59 oz
  • Average length
    8.9 cm
    3.50 in

Development

There is little known about the development of sandfish skinks; however, it is believed that they share many developmental traits with other members of the Scincidae family. Sandfish skinks are believed to be viviparous, meaning that embryos develop in the body of the mothers. In most squamate reptiles, embryos develop within the oviduct of females, where embryos are able to receive nutrition from their mothers. Once embryos are fully developed, female gives birth live young (Blackburn and Flemming, 2010). From birth, sandfish skinks grow to present a triangular-shaped snout, small ear openings, and limbs with webbed digits. They also develop a wide, flattened body shape, which allows them to burrow beneath the sand. While their average length is about 9 cm, it is unknown if they have determinate growth. (Baumgartner, et al., 2008; Sharpe, et al., 2013)

Reproduction

The mating system of sandfish skinks is unknown. Compared to similar members of the Scincidae family, it can be implied that sandfish skinks are monogamous. They mate over a period of 2 to 3 months (May to July) after a period of precipitation in their habitat. After they have been able to accumulate weight in preparation for the mating season, males and females reproduce and internal fertilization occurs. Fertilized eggs develop into an embryo, which females carry until they are fully developed. (Al-Johany, et al., 1997)

Sandfish skinks reproduce after precipitation has occurred, as it leads to a high amount of prey availability and ecological stability. While there is little direct evidence to support the mating behaviors of sandfish skinks, it is suggested that they take part in sexual reproduction. This is due to scarring found on their bodies during their reproductive period. In closely related skinks it has been observed that they accumulate body weight during their reproductive period in order to store more energy for the reproductive process. After birth, offspring are hypothesized to be very similar to their parents in color and body structure. (Al-Johany, et al., 1997)

  • Breeding interval
    Sandfish skinks breed once a year.
  • Breeding season
    May to June
  • Average gestation period
    3 months

There is little evidence to provide insight into parental investment in sandfish skinks. It is suggested that they are viviparous, but there is little known about the parental relationships of these lizards after females give birth. (Al-Johany, et al., 1997; Blackburn and Flemming, 2010)

  • Parental Investment
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

The exact lifespan of sandfish skinks is relatively under-investigated. However, in captivity they have been reported to live anywhere from 5 years and 3 months to 10 years. Based on data from several captive sandfish skinks, their average expected lifespan in captivity is 10 years. (Ellis, et al., 2011)

  • Average lifespan
    Status: captivity
    10 years
  • Average lifespan
    Status: captivity
    8 to 9 years

Behavior

One of the most studied and interesting behaviors of sandfish skinks is their ability to maneuver through sand as if it were swimming. They able to "swim" through sand by using their trowel-shaped mouths and flat bodies. They burrow themselves below the sand in order to hide from predators or ambush prey, as well as to avoid overheating. These fossorial tendencies are unique to the species.

There has been extensive research into the mechanisms behind the ability of sandfish skinks to preform their unique sand-swimming behavior. One of their most interesting adaptations is the unique sand-filtering system that allows sandfish skinks to inhale and exhale within the sand without aspirating sand particles into their lungs. They also have unique morphological characteristics, such as skin that is resilient to abrasion, which allows them to live in unfavorable desert environments. Another unique behavior of sandfish skinks is known as "stilting". This behavior consists of sandfish skinks using their limbs to position themselves away from the hot surface of the sand in order to manipulate air flow beneath their bodies. (Attum, et al., 2007; Knight, 2016; Sharpe, et al., 2013; Stadler, et al., 2016; Vihar, et al., 2015)

Home Range

Little is known about the home range of sandfish skinks.

Communication and Perception

Sandfish skinks are sand specialists and spend most of their time underneath the sand. Because of this, much of their behavior and communication is elusive to researchers. When found in the wild, they are not found in communities or colonies, but rather are found individually. Very little is understood about their communication and perception behaviors with other individuals of their species.

One investigated aspect of sandfish skink perception is their use of vibrations within the sand to hunt prey. When burrowed beneath the sand, sandfish skinks can locate insects as far as 15 cm from the surface of the sand using unique structures within their ear bones. It is also suggested that these organisms rely very little, if at all, on scent to detect prey. (Attum, et al., 2007; Hetherington, 1989; Stadler, et al., 2016)

Food Habits

Sandfish skinks are insectivores. They rely on vibrations from the surface of the sand to detect prey. Generally, they are known to eat crickets and mealworms. From a study of their responses to mealworms and crickets, it was found that sandfish skinks have a more intense reaction to crickets. They are not considered dietary specialists. However, due to the harsh environments they live in, there is little prey diversity.

There is currently no evidence to suggest that sandfish skinks feed on vegetation, or any food sources other than insects. Thus they are considered to be carnivores. (Hetherington, 1989)

  • Animal Foods
  • insects

Predation

While sandfish skinks do not have clearly identified predators, they do have many morphological and behavioral adaptations which suggest that they protect themselves from predators. Firstly, they spend most of their lives beneath sand, leaving very little of their bodies visible to predators above the sand. When disturbed in a laboratory setting, sandfish skinks also demonstrate fleeing and burrowing behaviors beneath sand. It is not known if there are additional protective behaviors or characteristics which allow sandfish skinks to protect themselves from predators. (Attum, et al., 2007; Stadler, et al., 2016)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Sandfish skinks do not have clearly investigated interactions with other organisms in their environment. Because of their unique ability to live within arid, desert environments, there is little interaction between sandfish skinks and other desert dwelling organisms. They display defensive behaviors, suggesting that they have predators, but the identities of these predators have not yet been investigated.

Sandfish skinks feed on surface-dwelling insects, controlling insect populations in their environment. The general environmental impact of sandfish skinks has not been extensively investigated, but their role as a predator and their unique morphological adaptations suggest that they interact with other species in their environment. (Ellis, et al., 2011; Stadler, et al., 2016)

Economic Importance for Humans: Positive

There is no clear research into the economic impacts of sandfish skinks. However, they have been studied extensively in order to understand their complex body plans and the way in which they are able to survive in desert. They have provided significant information regarding the specialization of sand skink species to their environments. Their lung structures have also given significant insight into the morphology of other sand specialist organisms. (Attum, et al., 2007; Baumgartner, et al., 2008; Knight, 2016; Stadler, et al., 2016)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

There are no known adverse effects of sandfish skinks on humans.

Conservation Status

Because they are elusive and live in deserts, the conservation status of sandfish skinks is unknown. They have not been evaluated on the IUCN Red List, and have no special status on the U.S. Federal List or CITES.

Contributors

Kailey Smith (author), Colorado State University, Kate Gloeckner (editor), Colorado State University, Galen Burrell (editor), Special Projects.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

insectivore

An animal that eats mainly insects or spiders.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

soil aeration

digs and breaks up soil so air and water can get in

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

References

Al-Johany, A., M. Al-Sadoon, S. Al-Farraj. 1997. Reproductive biology of the skink Scincus mitranus (Anderson, 1871) in the central region of Saudi Arabia. Journal of Arid Environments, Volume 36: 319-326. Accessed February 28, 2019 at https://www-sciencedirect-com.ezproxy2.library.colostate.edu/science/article/pii/S0140196396902414.

Attum, O., P. Eason, G. Cobbs. 2007. Morphology, niche segregation, and escape tactics in a sand dune lizard community. Journal of Arid Environments, Volume 68: 564-573. Accessed March 01, 2019 at https://doi.org/10.1016/j.jaridenv.2006.07.010.

Baumgartner, W., S. Rands, F. Fidler, A. Weth, M. Habbecke, P. Jakob, C. Butenweg, W. Böhme. 2008. nvestigating the Locomotion of the Sandfish in Desert Sand Using NMR-Imaging. PLoS ONE, Volume 3(10): 1-10. Accessed March 07, 2019 at https://ezproxy2.library.colostate.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&AuthType=cookie,ip,url,cpid&custid=s4640792&db=aph&AN=55701006&site=ehost-live.

Blackburn, D., A. Flemming. 2010. Reproductive Specializations in a Viviparous African Skink and its Implications for Evolution and Conservation. Herpetological Conservation and Biology, Volume 5(2): 263-270.

Ellis, E., J. Groves, M. Overly. 2011. Scincus scincus (North African Sand Skink) Longevity. Herpetological Review, Volume 42(2): 234.

Hetherington, T. 1989. Use of Vibratory Cues for Detection of Insect Prey by the Sandswimming Lizard Scincus Scincus. Animal Behaviour, Volume 37: 290-297. Accessed March 07, 2019 at https://doi.org/10.1016/0003-3472(89)90118-8.

Knight, K. 2016. Dynamic Filter Keeps Sandfish Lungs Sand-Free. Journal of Experimental Biology, Volume 219(22): 3493-3494. Accessed March 07, 2019 at 10.1242/jeb.151969.

Sharpe, S., Y. Ding, D. Goldman. 2013. Environmental interaction influences muscle activation strategy during sand-swimming in the sandfish lizard Scincus scincus. The Journal of Experimental Biology, Volume 216: 260-274. Accessed March 03, 2019 at 10.1242/jeb.070482.

Stadler, A., B. Vihar, M. Günther, M. Huemer, M. Riedl, S. Shamiyeh, B. Mayrhofer, W. Böhme, W. Baumgartner. 2016. Adaptation to life in aeolian sand: how the sandfish lizard, Scincus scincus, prevents sand particles from entering its lungs. Journal of Experimental Biology, Volume 219(22): 3597-3604. Accessed March 14, 2019 at https://ezproxy2.library.colostate.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&AuthType=cookie,ip,url,cpid&custid=s4640792&db=aph&AN=119591053&site=ehost-live.

Vihar, B., C. Wolf, W. Bohme, F. Fiedler, W. Baumgartner. 2015. Respiratory physiology of the sandfish (Squamata: Scincidae: Scincus scincus) with special reference to subharenal breathing. Salamandra, Volume 51(4): 326-334.

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