Patuxent Wildlife Research Center  

Using the Visible Implant Fluorescent Elastomer to mark

In March 1998 we started several experiments to investigate the bias and variability of monitoring techniques for terrestrial salamander populations. The objective of one of these experiments was to estimate the population size of red-backed salamanders (Plethodon cinereus) using mark/ recapture. A total of six study plots located on the Patuxent Wildlife Research Center (PWRC) in Laurel, MD were used for this research study. Each plot consisted of 50 wood cover boards in a 10 X 5 grid  and numerous natural cover objects.
Captured salamanders were measured (snout-vent-length, mm) and marked individually. We marked salamanders by injecting a bio-compatible fluorescent elastomer pigment in 1 to 4 body positions. A portable ultra-violet-light was used to check for successful first time marked individuals and for recaptures. A total of 459 P. cinereus (> 25 mm SVL) were marked between 9 March and 22 April 1998 and 135 of these salamanders were recaptured.
 

In numerous research studies, mark-recapture procedures are essential to aquire demographic data and behavior. Thus viable, adequate and harmless marking methods are necessary to minimize risks to the animal. For our study we needed a means to individually identify red-backed salamander without affecting their recapture probabilities. Reports on negative aspects of toe-clipping amphibians, ( e.g., Clark (1972) for Bufo woodhousei fowleri), and the small size of red-backed salamanders  (6.4-12.7 cm), the Visible Implant Fluorescent Elastomer (VIE) tagging system was chosen as marking method for this capture-recapture experiment.  This system was developed by Northwest Marine Technology Inc.  and provides the possibility of individual marks using several fluorescent colors and tag locations.
 

If possible we tried to inject elastomer into the legs. This is advantageous since little color is necessary to mark the salamander. Furthermore, in some cases  green and yellow spots were often not clearly visible in the body if they were injected too deep but were always visible on the legs. Using three colors in combination with four body positions allowed 255 unique marks per plot. Prior to using this technique in the field, these locations were tested on 15 adult Plethodon cinereus during February and March. During testing, we have had no fatality and tags remained visible under UV light.
To handle salamanders we used a clip board. On the top of this clip board is another board about 1/3 as large with an  longish opening (Figure 2.). Salamanders were placed in a small zip lock plastic bag with a small amount of water to avoid dessication and for easier handling.  Afterwards, the second board was lifted and a part of the plastic bag with the salamander was inserted  through the opening and was pulled to the edge. It is easier to inject salamanders once they are snuggly wedged between the edge of the bag and the padded board since they are unable to move.
Figure 2. Clipboard and elastomer

Elastomer pigment was injected through the plastic bag under skin in 1 to 4 suitable tag locations . Before and after injection, the 0.3 cc syringes  was cleaned with an antiseptic wipe to reduce the likelihood of infections. Before we injected the elastomer pigment, we made sure that the pigment did not harden.  If the color hardened, injecting  is very difficult and certainly more harmful for salamanders. We advise using new elastomer material since this material can be injected most easily when new and seems to retain its fluorescence better. Furthermore we recommend placing as little elastomer material into syringes as is possible to avoid waste since in some cases elastomer hardened very fast and only a little bit goes a long way. With practice, the marking procedure, for four tags per salamanders, tooks between 1/2-2 minutes. But the entire procedure, from capture to release of salamanders (approximately 20-40 per plot), took 2-5 hours, depending on number of salamanders per plot and collaborators present. In most cases 3 persons checked one plot during a marking session.

After marking a UV light was employed to check if the marks were visible. In some cases we had to repeat the marking procedure. For checking tags, we used a blanket to dim the surroundings since it has to be almost completely dark to see the tags. Salamanders were placed in a petri-dish and examined with a UV light. Because we didn't have a portable lamp, the UV light was plugged in to a car lighter, thus it was necessary to transport salamanders from the plot to the car. During transporting and marking, salamanders were placed in a insulated box with damp paper towels and a little bit ice to prevent overheating. Each salamander was kept in a separate plastic bag with the cover board or natural cover object number written on the bags. During collecting, natural cover objets were marked with flags to relocate the correct objects.