1Department of Biology, University of Victoria, Victoria, B.C, Canada
V8W 3N5, e-mail: teddavis@uvvm.uvic.ca; 2Department of Forest Sciences,
University of British Columbia, Vancouver, B.C., Canada V6T 1Z4, e-mail:
kovaska@jdmicro.com
Since July 1997, we have examined the effectiveness of fluorescent-elastomer tagging and toe-clipping for individual recognition of Plethodon vehiculum and Hyla regilla on Vancouver Island, British Columbia. Here we present the preliminary results for the first year of the ongoing study.
In the laboratory, we marked 20 P. vehiculum and 12 H. regilla each with toe-clipping (3 toes/animal excised) and sub-cutaneously injected elastomer-tags (3 tags/animal); the same number of unmarked animals served as controls. No mortality was associated with either marking method during the first 11 (P. vehiculum) and 10 months (H. regilla) of the study. During the same period, 10.5% of P. vehiculum and 22.2% of H. regilla lost one of their three elastomer-tags. Tag loss occurred within 1-11 months after application, but most likely resulted from improper initial application (i.e., material protruded from or was too close to the injection wound). Loss of toe-clip marks due to regeneration was also relatively high: 10% for P. vehiculum and 8.3% for H. regilla.
In the field, we alternately marked P. vehiculum caught under 12 artificial cover objects with toe-clipping and with elastomer-tagging (3 marks/salamander). For elastomer injection, we used the following positions on the ventral surface on each side of the salamander’s body: (1) anterior to hind leg, (2) posterior to hind leg, and (3) behind foreleg just below the dorsal stripe.
To date we have marked 115 P. vehiculum each with elastomers and toe-clipping. A total of 42 elastomer-tagged and 35 toe-clipped salamanders have been recaptured 1-5 times. Of the recaptured salamanders, 9.5% have lost one of their three elastomer-tags. The number of recaptures, residency time, and daily weight change, calculated as percentage of original weight, all were similar for the elastomer-tagged and toe-clipped group. Movement patterns between the two groups, however, were statistically different: 15 elastomer-tagged salamanders (35.7%) used more than one cover object, whereas only four toe-clipped salamanders (11.4%) did so. Reflecting the pattern of cover use, both the mean distance moved between captures and the maximum distance between two farthest locations for individual salamanders were greater in the elastomer-tagged group than in the toe-clipped group (2.1 m and 2.7 m versus 0.6 m and 0.6 m, respectively). Our initial interpretation is that toe-clipping discourages longer movements by P. vehiculum. However, the possibility cannot be ruled out that greater movements of the elastomer-tagged salamanders resulted from increased stress during the marking process, as reflected by a longer handling time (ca 2 min 20 s versus 40 s for toe-clipping). Over the next year, we plan to examine the persistence of the differences and to compare movement patterns of marked salamanders with those of unmarked salamanders identified photographically.
Our preliminary results suggest that elastomer-tagging is suitable for
marking small amphibians. However, care should be taken both to avoid tag
loss and to document its occurrence. The effects of any marking method
on movements should not be assumed to be insignificant without study.
In July 1997, we initiated a study to compare the effectiveness of two marking methods, toe-clipping and fluorescent-elastomer tagging, on Plethodon vehiculum and Hyla regilla on Vancouver Island, British Columbia. In the laboratory, we are investigating mark retention and the effects of marking on survival and weight change of both species. In the field, we are comparing tag retention, movement patterns, and residency time between P. vehiculum marked with the two methods.
Here we present the preliminary results of the study from July 1997
to June 1998. The laboratory component of the study will continue until
at least the fall; the field component is expected to continue until summer
1999.
Plethodon vehiculum. - We collected 60 P. vehiculum (36-60 mm in SVL) from southern Vancouver Island, British Columbia. On 10 July 1997, we randomly divided the salamanders into three treatments, each including 20 individuals: (1) toe-clipped, (2) elastomer-tagged, and (3) control (unmarked) treatments. From each salamander in the toe-clipped treatment, we excised a unique combination of three toes, removing no more than one toe per foot. We marked each salamander in the elastomer-tagged treatment with fluorescent substance (obtained from Northwest Marine Technology, Inc.) injected sub-cutaneously at three different locations of the salamander’s body. The positions used on the ventral surface of both sides of the body were: (1) anterior to hind leg, (2) posterior to hind leg by the anterior end of the vent, and (3) posterior to hind leg by the posterior end of the vent. We marked salamanders on 10 July 1997, and checked all marks for visibility each month thereafter.
Hyla regilla. - We collected 30 H. regilla (16-34 mm in SVL) from southern Vancouver Island. On 8 September 1997, we divided similar-sized frogs into ten groups of three and randomly designated each frog in a group for toe-clipping or fluorescent-marking, or as an unmarked control. On 7 November 1997, we increased the sample size by two in each treatment to account for mortality.
We excised three toes from each frog in the toe-clipping treatment with
no more than one toe per foot being taken; we never removed the thumb.
For each frog in the elastomer-tagged treatment, we injected a tag sub-cutaneously
at three locations on the ventral surface of the body: (1) anterior end
of thigh, (2) posterior end of thigh, and (3) mid-calf. We checked all
marks for visibility once per month.
There has been no mortality of P. vehiculum during the 11 months
of the study. Six small (16-21 mm in SVL) H. regilla have died,
three from the fluorescent-marked treatment and three from the control
group. The mortality was not associated with marking.
During the 11-month period since marking, two of the P. vehiculum injected with elastomers each have lost one their three tags (Table 1). One salamander lost a tag during the month following marking. The lost tag of the other salamander was seen slightly protruding from the injection site during monthly checks until it was lost in June 1998, 11 months after application. One of the tags of an additional salamander was by chance injected relatively deep under the skin and was not detected during two of the 11 monthly checks.
Marks of two toe-clipped P. vehiculum could not be decoded during the June 1998 check due to regeneration. Also due to regeneration, marks of an additional three salamanders were misread during 1-3 previous checks. Substantial regeneration of clipped toes was first noted in November 1997, four months after marking.
By 1998, two H. regilla marked with elastomers had lost one of their three tags (Table 1). One frog lost a tag within the first month of application, whereas the lost tag of the other frog, which protruded slightly from the injection site, was lost by June 1998, ca nine months after application. One of the three tags of an additional frog was injected relatively deep under the skin and could not be seen on two monthly checks.
In June 1998, the toe-clip mark of one frog could not be decoded due to regeneration. The toe-clip mark of an additional two frogs could not be decoded during one and three previous monthly checks, respectively. Substantial regeneration of toes, complete with toe-pads, was first noted in April, seven months after clipping.
Table 1. Survival and tag retention of P. vehiculum (12 July 1997 - 16 June 1998) and H. regilla (8 September 1997 - 16 June 1998).
Species and treatment n # dead # with lost marks # with marks that were
misread at least once
| Species and Treatment | n | # dead | # with lost marks | # with marks that were misread at least once |
| P. vehiculum:
Flourescent-marked |
19* | 0 | 2 | 1 |
| Toe-clipped | 20 | 0 | 2 | 3 |
| Control | 20 | 0 | NA | NA |
| H. regilla:
Flourescent-marked |
12 | 3 | 2 | 1 |
| Toe-clipped | 12 | 0 | 1 | 2 |
| Control | 12 | 3 | NA | NA |
From 28 September 1997 to 26 May 1998, we caught salamanders under 12 artificial cover objects in Goldstream Park, southern Vancouver Island, British Columbia. The cover objects, established in 1992, were arranged within an area of ca 12 x 19 m. Each cover object consisted of a 6’ long baseboard of untreated Douglas Fir, covered with two top boards (Heyer et al. 1994). The salamanders used spaces both between the top boards and under the baseboard.
Salamanders caught under the cover objects were alternately assigned to either the toe-clipped or elastomer-tagged treatment. Salamanders that had misshapen toes or other distinguishing marks were assigned to a third, reference group.
We excised three toes from each salamander in the toe-clipping treatment and sub-cutaneously injected three tags in each salamander in the elastomer-tagging treatment. For elastomer injection, we used the following positions on the ventral surface on each side of the body: (1) anterior to hind leg, (2) posterior to hind leg, and (3) behind the foreleg just below the dorsal stripe. After marking, each salamander was released at its original capture location. The fluorescent dyes were mixed in the laboratory and placed in syringes that were then frozen. During the field session, when not in use, we kept the syringes in a cooler to prevent premature hardening of the substance.
To date we have marked 115 P. vehiculum with elastomers (SVL = 28.0-57.2 mm) and 115 with toe-clipping (SVL = 22.2-54.8 mm). There were 22 salamanders in the self-selected reference group (SVL = 30.0-54.2 mm).
Forty-two (36.5%) elastomer-tagged salamanders and 35 (30.4%) toe-clipped salamanders were recaptured 1-5 times; there were five (22.7%) recaptured salamanders in the reference group. The frequency distribution of the number of captures per salamander was similar for the two treatments (X2 = 1.24, df = 3, P > 0.75, salamanders caught 4-6 times combined).
Four elastomer-tagged salamanders (9.5% of recaptures) had either lost one of their three tags or the tags were inserted too deeply to be visible. However, these salamanders could be matched with a previous capture based on their body size and dorsal colouration. In addition, the elastomer tag of one salamander had migrated from its original lateral location on the body posterior to the forefoot to the middle of the chest. We noted no lost marks in the toe-clipped group from September to May.
For those salamanders caught at least twice, we measured residency time as the number of days between the first and last capture, the maximum residency time being 241 days. The mean residency time was similar for salamanders in the two treatments: 121 days (SD = 83 days, n = 42) for the elastomer-tagged salamanders and 124 days (SD = 91 days, n = 35) for the toe-clipped salamanders (t = -0.178, df = 75, P = 0.859).
For recaptured salamanders, we calculated the daily weight change as a percentage of the original weight at first capture. Most salamanders gained weight between the first and last capture (81% of elastomer-tagged and 77% of toe-clipped salamanders). The daily weight change was similar in the two treatments (t = 1.524, df = 75, P = 0.132). The results were also similar if only salamanders that were caught at least 100 days apart were included in the comparison.
We conclude that the effects of marking, if any, on capture frequency,
residency time, and weight change were similar for the elastomer-tagged
and toe-clipped P. vehiculum.
Individual, recaptured salamanders were found under 1-3 different cover objects. Fifteen (35.7%) elastomer-tagged salamanders used more than one cover object, whereas only four (11.4%) toe-clipped salamanders did so. The difference between the two treatment groups is statistically significant (X2 = 6.07, df = 1, P < 0.025, salamanders using 2 and 3 covers combined; Fig. 1). Reflecting the pattern of cover object use, the mean distance moved between captures by individual salamanders was greater in the elastomer-tagged group (2.1 m) than in the toe-clipped group (0.6 m; t = 2.416, df = 75, P = 0.018). Similarly, the mean distance between two farthest captures of individuals was greater in the elastomer-tagged group (2.7 m, greatest distance = 11.9 m) than in the toe-clipped group (0.6 m; greatest distance = 7.6 m; t = 2.734, df = 75, P = 0.008; Fig. 2).
The residency time and the number of captures per individual were similar for recaptured salamanders in both elastomer-tagged and toe-clipped treatments, and the differences in movements persisted if only salamanders with two captures were included in the analysis. The five recaptured salamanders in the reference group, all of which were distinguished by toe or leg deformities, were always found under the same artificial cover object.
Our initial interpretation is that toe-clipping discourages longer movements by P. vehiculum. However, the possibility cannot be ruled out that greater movements of the elastomer-tagged salamanders result from increased stress during the marking process, as reflected by a longer handling time, rather than from normal movements. Movements of the reference group were similar to those of the toe-clipped group. However, only five reference salamanders were recaptured, and all five were distinguished by deformities in toes or feet that could have affected movements in a similar way to those of toe-clipped animals. To distinguish between the two possibilities, we plan to examine the persistence of the differences over time and to compare movements of unmarked salamanders, identified through photographic methods, with those of marked salamanders.
Figure 1. Number of cover objects used by individual, recaptured Plethodon vehiculum in Goldstream Park, Vancouver Island, British Columbia, from 28 September 1997 to 26 May 1998.
Figure 2. Average and maximum movement distances by individual Plethodon vehiculum in Goldstream Park, Vancouver Island, British Columbia, from 28 September 1997 to 26 May 1998. Bars - means; vertical lines - 1SD.
As expected, toe-clipping was faster than elastomer-tagging. Toe-clipping
(3 toes per salamander) took an average of 38 s (SD = 11 s; range: 19-75
s, n = 114) to complete, whereas elastomer-tagging (3 marks per salamander
using 1-2 colours) took an average of 138 s (SD = 32 s; range: 75-210 s,
n = 114). The additional time required for elastomer-tagging resulted mostly
from positioning of the salamander and greater restraint required for this
method.
Clarke, R. D. 1972. The effect of toe clipping on survival
in Fowler's toad (Bufo woodhousei fowleri). Copeia 1972:182-185.
Golay, N., and H. Durrer. 1994. Inflammation due to toe-clipping
in natterjack toads (Bufo calamita). Amphibia-Reptilia 15:81-83.
Heyer, W.R., Donnelly, M.A., McDiarmid, R.W., Hayek, L-A. C., and M.S.
Foster. 1994. Measuring and Monitoring Biological Diversity. Standard Methods
for Amphibians. Smithsonian Institution Press, Washington.
Nishikawa, K. C., and P. M. Service. 1988. A fluorescent
marking technique for individual recognition of terrestrial salamanders.
J. Herpetol. 22:351-353.
Elastomer Marking
of Amphibians
U.S. Department of the Interior
U.S. Geological Survey
Patuxent Wildlife Research Center
Laurel, MD, USA 20708-4038
<http://www.pwrc.usgs.gov/marking>
Contact: Sam Dreoge
<sam_droege@usgs.gov>
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