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Hypsiglena torquata, Night snake

Page history last edited by PBworks 12 years, 2 months ago

Hypsiglena torquata, Night Snake


Kingdom Animalia

  Phylum Chordata

   Class Reptilia

      Order Squamata

  Suborder Serpentes

     Family Colubridae

      Genus Hypsiglena

 Species torquata




photographer unknown. http://www.hastingsreserve.org/herps/HerpPics/NightSnakeNeckMarking.gif


  There is a lot of debate about the divisions of subspecies of Night Snakes. Stebbins recognizes none of them, Bartlett recognizes six. Many herpetologists have recognized the need for clear divisions and refuse to accept any untill some more research into the matter is done. No research seems to be in progress and so casual Herpetologists can sometimes pick which subspecies they like the best or if they want to bother. As all of the literature disagrees and I am not an expert, I will make no guesses.



   Light brown or beige snake with darker brown markings. The three large dark blotches on the neck persist thruought all H. torquata subspecies, sometimes connecting behind the head. The pattern on the snake in the picture is very characteristic of this trait. Brown lines extend from behind the eyes. Pupils are vertical. Anal scale is divided. Night Snakes are small with adults ranging from one to two feet long. Most captured Night Snakes are juveniles from eight to sixteen inches long. 


  Glossy Snakes and juvenile Racers are similar to H. torquata in appearance but both have round pupils. Lyre Snakes can be differentiated by the V or lyre on their head.


Jones, Jason. http://www.californiaherps.com/snakes/images/htorquatajjones.jpg


Eating Habits

  Night Snakes mostly eat eggs and small lizards. They will also eat frogs, insects and other snakes. H. torquata are rear fanged lizards.They paralyze small lizards with venom secreted from their Duvernoy's Gland which sits above their small fangs in the back of their mouths. The enlarged teeth do not have any effective grooves for the venom to flow down so this poses no real threat to humans.



 The Night snake can be found in Western and Southern Idaho. Subspecies of H. torquata live in rocky arid areas around Western North America, from central Washington and  Oregon to Texas and Mexico.





 H. torquata stays mostly under dry substrate or in empty animal burrows during the day. This can include anything from fallen trees and dry leaves to under rocks or thick brush. Their prey is often lizards that live in the same habitat so they may not have to come out to feed at night. When they do come out it is usually at night and most sightings are on roads.


Nafis, Gary. http://www.californiaherps.com/snakes/pages/h.t.deserticola.html



  Females lay a clutch of 2 to 9 eggs between April and September in the same substrate they live in. They incubate for one and a half to two months and usually hatch in late summer. No mating displays are known.



  Night snakes seldom come out during the day so they are rarely seen even if a large population is present. If handled they probably won't bite though they may squirm or curl up.



  In their research paper Rodriguez et. al (1999) tried to gain information on the split in the phylogenetic tree between Hypsiglena torquata and their mostly Central American relatives. They wanted to do this using the feeding habits of the Night snake. This is not easy to do because it is generally nocturnal. To do this they analyzed the stomach contents of 178 preserved specimens from the California Academy of Sciences, San Francisco, and 219 specimens from the Museum of Vertebrate Zoology, University of California, Berkely. The researchers were meticulous in making sure that only wild specimens were included in the study and then only those which had never been kept in captivity. They also included in their research material recorded data about 39 prey items from previous literature where they could be sure it was not duplicated, and three unpublished observations as well as one witnessed field observation. Using this material they recorded what was eaten, to the species if possible, and the direction in which it was swallowed.


  All sizes of H. torquata eat lizards and squamate eggs. Small Night snakes may eat insects and larger ones may eat frogs, toads, and other snakes. Of the prey taken 52.2% were lizards. That is a significant amount of their diet. 77.1% of those lizards were diurnally active iguanians that take shelter in cracks and burrows, similar to where H. torquata stays, at night. This suggests easy hunting. Of the prey taken 22.8% were squamate eggs, which suggests that the snakes do come out of their burrows and are able to use chemosensory cues. The researchers hypothesized that if the Night snakes could use chemosensory cues to find eggs that they could also use them to find the inactive iguanians and utilize ambush tactics, which may also work during dawn and dusk hours. In arid climates it is often too cold for substantial activity even during summer nights and the researchers concluded that Hypsiglena torquata may have branched off of the tree from their Central American relatives when they developed the ability to hunt during warmer parts of the day.




Bartlett, R. and Alan Tennant. Snakes of North America, Western Region. Houston, Texas, Gulf Publishing Co. 2000.


Cossel, John Jr. Hypsiglena torquata (Night Snake) 1997. 1 Oct. 2008 <http://imnh.isu.edu/digitalatlas/bio/reptile/serp/hyto/hyto.htm>


Nafis, Gary. CaliforniaHerps.Com 2008. 1 Oct. 2008 <http://www.californiaherps.com/snakes/pages/h.t.deserticola.html>


Rodriguez, Javier, Daniel Mulcahy and Harry Greene. "Feeding Ecology of the Desert Nightsnake, Hypsiglena torquata (Colubridae)." Copeia. 1(1999):93-100


 Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.


 page created by Amber Williams

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