Snout-vent length

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Snout–vent length (SVL) is the length of an amphibian's body from the tip of its nose to opening in its rear end, called the vent. So, in a frog, it is the length of the frog's body but not the frog's legs. Amphibian scientists use it to study all kinds of amphibians,[1] lepidosaurs, and crocodilians. For turtles, they use carapace length (CL) and plastral length (PL) are instead.

The SVL can change depending on whether the animal is alive, dead, moving, or still. It can change if scientists have used chemicals to preserve its dead body.[2] Scientists also try to determine snout-vent length in fossils using an osteological correlate such as precaudal length. A scientist can look at the animal's SVL, weight, and body and tell if it is male or female or even how old it is.[3]

Advantages[change | change source]

Scientists use snout-vent length instead of the animal's whole body length because it does not change much. Whole body length can change much more: Animals like crocodiles can lose the ends of their tails. In some animals, young ones do not have tails or do not have large tails.[4]

Methods[change | change source]

The scientist or other person can measure snout-vent length with dial calipers or digital calipers.

The scientist can use other tools to hold the animal still. For example, snake tubes, "Mander Mashers,"[5] or a "Salamander Stick."[6]

References[change | change source]

  1. "direct line distance from tip of snout to posterior margin of vent" Watters, Jessa L.; Cummings, Sean T.; Flanagan, Rachel L.; Siler, Cameron D. (2016). "Review of morphometric measurements used in anuran species descriptions and recommendations for a standardized approach". Zootaxa. 4072 (4): 477. doi:10.11646/zootaxa.4072.4.6. ISSN 1175-5334.
  2. Vitt, Laurie J.; Zug, George R. (2012). Herpetology: An Introductory Biology of Amphibians and Reptiles. Academic Press. p. 34. ISBN 978-0127826202.
  3. Kupfer, A. (2007). "Sexual size dimorphism in amphibians: an overview". In Fairbairn, D. J.; Blanckenhorn, W. U.; Székely, T. (eds.). Sex, Size, and Gender Roles: Evolutionary Studies of Sexual Size Dimorphis. New York: Oxford University Press. pp. 50–59.
  4. Bolton, Melvin (1989). "7. Capture, Transport, Marking and Measuring of Young Crocodiles". The management of crocodiles in captivity. FAO.
  5. Wise, S. E.; Buchanan, S. W. (1992). "An efficient method for measuring salamanders". Herpetological Review. 23: 56–57.
  6. Walston, L. J.; Mullin, S. J. (2005). "Evaluation of a new method for measuring salamanders". Herpetological Review. 36: 290–292.

Further reading[change | change source]