The Visible Implant Fluorescent Elastomer (VIE) marking technique was recently developed by the Northwest Marine Technology, Inc. (http://www.nmt-inc.com) as a marking technique for fishes (Bonneau et al. 1995, Frederick 1997). Researchers at the USGS Patuxent Wildlife Research Center and elsewhere (http://www.mp1-pwrc.usgs.gov/marking/vie.html) have begun to use this method to mark amphibians. VIE marking has successfully been used to mark Pacific Giant salamanders (Dicamptodon tenebrosus) (Karl Mallory, mallory@zoology.ubc.ca), red-backed salamanders (Plethodon cinereus) (see web site above and recent work in Shenandoah National Park), larval northwestern salamanders (Ambystoma gracile) and tadpoles of Rana esculenta and Rana lessonae (Brad Anholt, banholt@uvic.ca).

This marking technique represents a less invasive and more lasting technique than toe-clipping. Toe-clipping is not only disadvantageous to amphibians which need their digits to burrow or grasp onto females, but is also disadvantageous to researchers if amphibian toes regenerate. The "contrasting texture of VIE, the small volume of material required, its tendency to occupy available space rather than displace and irritate surrounding tissue, combine to make VIE very useful in small specimens" (Northwest Marine Technology, Inc. website), such as amphibians.  Other advantages of the VIE tags are their high retention rate, minimal impact on survival, growth and behavior, low cost, high visibility, and relatively easy application. Some limitations may be that the VIE tags are difficult to detect beneath pigmented tissue.  We will have to test the usefulness of the VIE marking on several species and life stages at Big Bend National Park.

The VIE tagging method involves injecting a fluorescent elastomer material just underneath the skin.  Two elastomer materials, a color elastomer and a curing agent, are mixed at a 10:1 ratio and placed into 0.3 cc syringes.  Elastomer is injected as a liquid that soon cures into a pliable, biocompatible solid.  The syringes are kept in a freezer to slow hardening, which occurs within 24 hours at room temperature.

Four VIE colors are available (red, orange, yellow, and green).  The colors facilitate visibility under normal lighting conditions but are even more visible when viewed under ultraviolet light or with other fluorescence enhancing techniques.

VIE marking can provide unique individual marks.  If only one mark per amphibian is used, the number of potential unique marks is the product of the numbers of colors used and the locations.  If two marks are used on an individual, in combination with several different locations, a large number of unique codes can be devised.

The following formula relates to determining the number of unique codes that can be devised utilizing two marks per individual:

Number of Unique Codes = ({[C + 1]^L} - 1).

C = no. of colors used, L = no. of body locations.

At Big Bend National Park, we will test the technique on juveniles and adults of various species to see how visible and retentive the marks are and use this technique to estimate population sizes.

References

PRIMENet Amphibian Monitoring Program Homepage

Patuxent Homepage