Tagging Reptiles and Amphibians

In the past, the most widely used method of identifying amphibians and reptiles has been toe clipping. Although the potential detrimental effects have been well documented, the removal of one to eight digits is used extensively because it is inexpensive and quick. Toe clipping can reduce survival (Clarke 1972; McCarthy & Parris 2004), and cause infection at the wound site (Golay and Durrer 1994). Furthermore, toe clipping is unreliable because digits may regenerate (Donnelly et al. 1994), and larvae and the adults of certain species lack limbs. In an article in Nature, May (2004) questioned whether this practice is ethical.

Our Visible Implant Elastomer Tags (VIE), Visible Implant Alpha Tags (VI Alpha), and Coded Wire Tags (CWT), offer alternatives for identifying reptiles and amphibians. All three tag types are injected beneath the skin with little effect on the host animals. VIE and VI Alpha tags can usually be seen in ambient light and tag detection is greatly enhanced by fluorescing the tags with NMT’s VI Light.

Visible Implant Elastomer Tags

Reptiles and amphibians can be tagged with Visible Implant Elastomer. This lizard is shown with a yellow tag in the front leg, and an orange tag in the hind leg.

Reptiles and amphibians can be tagged with Visible Implant Elastomer. This anole lizard is shown with a yellow tag in the front leg, and an orange tag in the hind leg. Photo courtesy of J. Losos.

Visible Implant Elastomer (VIE) is probably the most widely used alternative to toe clipping for identifying reptiles and amphibians, and many publications about its use are available. Please contact NMT (biology@nmt.us) if you would like help finding relevant references or would like help determining if VIE is suitable for your project and species.

Many researchers do not anesthetize amphibians, while others prefer the ease of handling that anesthetic provides. Others have developed techniques in which the animal is placed in a plastic bag with some water and they tag through the bag.

Correct injection provides high retention and readability. Because the material is fluorescent, it can be seen under pigmented skin and at night with the help of the VI Light. Anholt et al. (1998) state that the consistency and biocompatibility of the VIE tags allows for the tagging of small animals, including larvae, that could not be tagged using other methods. In a novel approach to monitoring the development of salamander egg masses, Regester & Woosley (2005) used VIE to identify and track the egg masses.

Visible Implant Elastomer tags are an excellent choice for batch identification, and they also offer a surprising number of individual codes if colors and body locations are combined. Jung et al. (2000) used three colors and four body locations to create 255 individual codes in his study of salamanders. Successful tagging sites include between the toes in frogs, on the upper hind leg of frogs, and at the base of the limbs and tail on the ventral side of salamanders. Lizards have been tagged in the upper legs and in the tail.

Some amphibians lack septa between the skin and underlying tissue. VIE tags injected into these animals can therefore migrate from the original tagging location, making it impossible to use those tagging locations to create individual codes. This is relatively common with tags placed in the upper legs and body in frogs. In such cases, we recommend considering Visible Implant Alpha tags or using body locations where the tags will remain in their original location (such as the feet in frogs).

With reptiles, VIE retention tends to be high, but it’s visibility depends on the pigmentation and thickness of the scales. It has proven to be an effective tagging method in smaller reptilians, including lizards (Penny et al. 2001, Kondo & Downes, 2004; Losos et al. 2004; Daniel et al. 2006; Waudby & Petit 2011;), snakes (Hutchens et al 2008), and turtles. Hatchling turtles have been tagged in two ways. Davy et al. (2010, see volume 41(4)) injected the tags into the limbs, while Anderson et al (2015) adapted a binary coding scheme on the plastron to create individual tag numbers.

Links to videos from our customers (YouTube):


Visible Implant Alpha (VI Alpha) Tags

VI Alpha Tags can be injected under clear and lightly pigmented tissue, as in this frog leg.

VI Alpha Tags can be injected under clear and lightly pigmented tissue, as in this frog leg.

VI Alpha Tags are not as widely used as VIE, but there are also many publications available that describe their use. In thick skinned, or heavily pigmented species, the numbers may not be visible, so it is important to consider the species to be tagged and the location of the tag. For example, Clemas et al. (2009, pdf) found that the pigmentation of Litoria raniformis obscured the tags, but VI Alpha were reliable for tagging large Litoria ewingii. On the other hand, Heard et al.  (2008) was able to tag juvenile Litoria raniformis with VI Alpha tags and found they remained readable. As with VIE tags, using the VI Light dramatically improves the detection and readability of VI Alpha tags, sometimes even through highly pigmented skin.

Measey et al. (2001, pdf) found there to be no negative effects of VI Alpha tags in a legless amphibian (Gegeneophis ramaswamii ), and further stated that when individual identification is necessary that these tags are the “most promising” of the investigated tags. Buchan et al. (2005) tested VI Alpha in a number of species, and concluded that VI Alpha “appears to be an effective and low cost method for individually marking and identifying amphibians”.  Kaiser et al. (2009) evaluated and used VI Alpha Tags to track individual Dendropsophus microcephalus.

Osbourne et al (2011, pdf) discuss the use of VI Alpha tags in juvenile ambystomid salamanders and provide extensive detail about their application and readability.

VI Alpha Tags have been used to identify individual hatchling turtles by gluing them to the carapace (Rosenburg & Swift, 2010, pdf).

Coded Wire Tags

Species that have been successfully tagged with Coded Wire Tags include Lampropholis guichenoti, Rana aurora, Malaclemys terrapin, Spea multiplicata, and Chelonia mydas.

If the experiment requires reading the tag code, the animal is killed to retrieve the tag. However, if the presence or absence of a tag will provide the necessary information, the tag can be externally detected without harming the animal. It is also possible to use the location of the tag in the animal for a limited number of individual or batch codes without killing the animal. In a novel approach to evaluating the prey choices of snakes, Downes (2000) identified individual skinks with Coded Wire Tags using several body sites, then used a fluoroscope to identify the skinks while in the digestive system of snakes. Martin (2011) demonstrated that sequential Coded Wire Tags (pdf) can be used to identify individual tadpoles.


The list of publications about tagging reptiles and amphibians with our products is quite long. You will be able to find many publications with a quick online search. Including the terms for the tag you are considering – “coded wire tag”, “visible implant elastomer”, “vi alpha” along with your species or family, or general term (such as “frog” or “snake” or “lizard”) should generate a number of links to start with. Please contact NMT Biology (biology@nmt.us) if you can’t find relevant publications, or would like to talk over the tag suitability for your project.


Anholt, B. R., Negovetic, S., & C. Som. 1998. Methods for anaesthetizing and marking larval anurans. Herpetological Review 29(3):153-154.

Buchan, A., L. Sun & R. S. Wagner. 2005. Using alpha numeric fluorescent tags for individual identification of amphibians. Herpetological Review. 36 (1):43-44.

Daniel, J. A., K. A. Baker & K. E. Bonine. 2006. Retention rates of surface and implantable marking methods in the Mediterranean House Gecko (Hemidactylus turcicus), with notes on capture methods and rates of skin shedding. Herptological Review 37(3):319-321

Donnelly, M. A., C. Gutoad, J. E. Juterbock, & R. A. Alford. 1992. Techniques for marking amphibians. In W. R. Heyer, M.A. Donnely, R. W. McDiarmid, L.-A. D. Hayek, and M. S. Foster (eds.). Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians, pp. 275-276. Smithsonian Institution Press, Washington, D.C.

Kaiser, K., et al. 2009. “Use of visual implant alpha (VIAlpha) fluorescent tags in a small hylid frog with a new technique for application.” Herpetological Review (40): 421-422.

Kondo, J. & S. J. Downes. 2004. Using visible implant elastomer to individually mark geckos. Herpetofauna 34:19–22.