Snout–vent length (SVL) is a

morphometric Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...

measurement taken in

herpetology Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians (gymnophiona)) and rept ...

from the tip of the

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is c ...

to the most posterior opening of the cloacal slit (vent)."direct line distance from tip of snout to posterior margin of vent" It is the most common measurement taken in herpetology, being used for all

amphibian Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbor ...

lepidosaurs The Lepidosauria (, from Greek meaning ''scaled lizards'') is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizards, and amphisbaenians. Squamata contains over 9,000 species, ...

, and

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period (Cenomanian stage) and are the closest livin ...

ns (for turtles,

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the under ...

length (CL) and plastral length (PL) are used instead). The SVL differs depending on whether the animal is struggling or relaxed (if alive), or various other factors if it is a preserved specimen. For fossils, an osteological correlate such as precaudal length must be used. When combined with weight and body condition, SVL can help deduce age and sex.

Advantages

Because tails are often missing or absent, especially in juveniles, SVL is seen as more invariant than total length. Even in the case of crocodiles, tail tips may be missing.

Methods

The measurements may be taken with dial calipers or digital calipers. Various devices are used to position the animal while the measurement is being taken, such as a snake tube, "Mander Masher", or a "Salamander Stick".

Advantages

Methods

References

Further reading