Developing a monitoring protocol for Siren and Amphiuma in the Southeastern United States

Kristina Sorensen <sup>1,2

1</sup> U.S. Geological Survey, Florida Integrated Science Center,
Gainesville, Florida, 32653
² Florida Cooperative Research Unit, Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida 32611-0485

Presented at the Joint Meeting of the American Elasmobranch Society, American Society of Ichthyologists and Herpetologists, Herpetologists' League, and Society for the Study of Amphibians and Reptiles, Kansas City, Missouri. July 3-8, 2002

ABSTRACT

       Siren and Amphiuma are two genera of aquatic salamanders in the Southeastern United States that have not been well studied.  A primarily muck-dwelling existence makes these salamanders difficult to detect with conventional sampling methodologies. Therefore, the status of their populations is unknown. To develop a monitoring protocol for Siren and Amphiuma, a mark-recapture study of S. lacertina and A. means was begun at Okefenokee National Wildlife Refuge (southern Georgia) and at Katharine Ordway Preserve (north-central Florida).  Monthly trapping began in August of 2001 and will continue until August 2002.  A new trap design modified from a commercial crayfish trap is being tested along with plastic minnow traps.  In the first nine months of the study, crayfish traps yielded 222 salamanders during 1260 trap nights. Only 10 individuals in minnow traps were captured in this same period. Evaluation of several marking techniques indicates that passive integrated transponder (PIT) tagging is the only permanent marking technique adequate for a long-term monitoring study.

INTRODUCTION

       Amphiuma means and Siren lacertina are large, fully aquatic salamanders that spend most of their time burrowed in mud and bottom debris.  They are difficult to sample and very few population studies have been conducted on either species (Gehlbach and Kennedy 1978, Raymond 1991, Machovina 1994). Very little is known about their life history, behavior, or population status.

       A yearlong mark-recapture study began in August of 2001.  The efficacy of a new trap design (Darby et al. 2001) was compared with minnow traps, a more traditional method of capture (Gehlbach and Kennedy 1978, Raymond 1991, Snodgrass et. al 1999).  Monthly trapping was conducted at two research sites - Katharine Ordway Preserve and Okefenokee National Wildlife Refuge.  Nine months of data have been collected to date, therefore all results presented are preliminary.

Study Sites

       The Katharine Ordway Preserve-Swisher Memorial Sanctuary is located in western Putnam County, Florida. It is a mosaic of sandhills, mesic hammocks, ruderal sites, bottomland forests, permanent lakes, and ephemeral wetlands.  Co-owned by The Nature Conservancy and the University of Florida Foundation, the 4,500 ha preserve serves as a research and teaching facility for the University of Florida.

       Okefenokee National Wildlife Refuge, in southeast Georgia, encompasses 158,000 ha of the 200,000 ha Okefenokee Swamp. Dominant habitat types include cypress swamps, dense shrub wetlands, pine flatwoods, canals, and wet prairies. The refuge also is an index site for the Amphibian Research and Monitoring Initiative (ARMI) on Department of Interior lands.

RESEARCH OBJECTIVES

1. To compare the efficacy of two trap designs (crayfish traps vs. minnow traps) in capturing Siren and Amphiuma
• Does baiting increase capture success?
• Does capture success vary monthly?
• Do animals exhibit a trap response? (trap shy or trap happy)
2. To develop a reliable method of marking Siren and Amphiuma for mark-recapture studies.
3. Collect population data using mark-recapture.
4. Develop a monitoring protocol incorporating the above information.

METHODS

Plastic minnow trap

       Commercial crayfish traps (Lee Fisher International, Inc.) are bell-shaped with three upturned funnels, each with openings of ca. 4.5cm in diameter, that are located at 45 degree angles near the bottom. Traps are built from 2.5cm plastic-coated chicken wire and are lined with 5mm plastic mesh (Vexar).

       Plastic minnow traps have 4cm diameter funnels on either end and have 5mm mesh size. They can be floated or placed on the substrate.

       Crayfish and minnow traps were paired in order to compare trap efficacy.  Crayfish traps were staked to the bottom using PVC pipe to which floating minnow traps were attached. Traps were set in the afternoon and checked the following day for a trapping period of no longer than 24 hours.

Modified crayfish trap with 5mm plastic lining.

       At Ordway Preserve, 40 traps (20 crayfish, 20 minnow) were set at Suggs Lake for four nights per month.  Trapping began in September of 2001 and will continue until August 2002.  Traps were placed in five groups of four. Half of the traps in each group were baited with sardines, the other half unbaited, in order to test for differences in capture success.  Ordway has a much higher overall capture success than Okefenokee NWR and was therefore chosen to test the efficiency of baiting.

       At Okefenokee NWR, five traps of each type were set at four sites, for a total of 40 traps. All traps were baited. Traps were set for three consecutive nights, once a month. Trapping began in August of 2001 and will continue for one year.

Ordway Preserve, Lake Suggs

RESULTS TO DATE

TRAP EFFICIENCY

       To date, nine sampling sessions have been conducted at Okefenokee NWR resulting in 56 captures, all Amphiuma means.  The overall capture success was 5.2% (56 captures/1080 trap nights). Capture success (Fig.1) for crayfish traps was 10.2% (55 captures/540 trap nights) vs. <1% for minnow traps (1 capture/540 trap nights). There have been 30 individuals marked, with 20 recaptures.

       At Ordway Preserve, there have been nine sampling periods to date, with 176 captures: 83 Amphiuma means (47%), 2 Pseudobranchus axanthus (1%), 68 Siren lacertina (39%), and 23 juvenile sirens, either S. lacertina or S. intermedia, classified as siren species (13%). Overall capture success was 12.2% (176 captures/1440 trap nights). Crayfish trap success was 23% (167 captures/720 trap nights) compared with 1% (9 captures/720 trap nights) for minnow traps. A total of 149 individuals have been caught with only 27 recaptures.

       There appears to be differences in overall monthly captures rates at both study locations (Fig. 2).  To date, Spring and Summer have yielded higher capture rates for A. means and S. lacertina.  In addition, at Ordway preserve, capture rates of S. lacertina and A. means differ by month.  S. lacertina are captured more frequently during winter months, whereas A. means are captured more frequently in Spring and Fall (Fig. 3).  Capture success is approximately equal between trap nights (Fig. 4).

       Baiting appears to have no effect on overall capture success at Lake Suggs. Forty-seven percent of all animals caught were from baited traps. However, A. means was caught 54% of the time in baited traps, whereas Siren sp. were only caught 22% of the time in baited traps, indicating that bait response may be different between species.

MARKING

       A variety of marking techniques were tested in order to find a reliable marking method for long-term population studies of Siren sp.and Amphiuma sp. Four captive adult salamanders (2 S. lacertina, 1 A. means, and 1 S. intermedia) were used in the experiments.  Cyano-acrylic (Superglue) did not produce a lasting mark on any animal, with legible marks persisting for only a few days. Tail notching/clipping was unsuccessful due to the high regenerative capabilities of these species, plus there is a high level of natural tail damage due to predation and/ or intra-specific aggression. Toe clipping is not a lasting option either due to quick regeneration time and a high occurrence of missing and/or extra toes.  Heat branding was used successfully in past studies of S. intermedia (Gehlbach and Kennedy 1978, Raymond 1991), with legible marks persisting for up to one year. However, in this study, brands became illegible by the second month and were completely gone after three months in all species tested.

       Passive Integrated Transponder (PIT) tags proved to be the only successful long-term method for marking these species. PIT tags were inserted dorsally in the fat reserves located above the tail.  All lab animals have retained tags for the duration of the study.. In the field, several individuals have been recaptured nearly eight months after first capture with tags still intact. In addition, individuals caught one day after first being marked, appear completely healed, with no visible signs of tagging.  Overall PIT tag retention rate in these species is still unknown, but because of a quick healing time, it is probably high.  It should be noted that juveniles and P. axanthus were not PIT tagged due to their small size. I am therefore unable to collect population data on this age group until a suitable marking technique is found.

DISCUSSION

       Crayfish traps have proved to be a more successful technique than minnow traps for trapping aquatic salamanders. At both Okefenokee NWR and Ordway Preserve, crayfish traps caught substantially more animals than minnow traps, most likely because of funnel placement within the water column.  These salamanders spend the majority of their time in muck and/or heavy vegetation, not open water.  Crayfish traps are trapping animals as they move along the bottom substrate.  This is consistent with other studies that have captured sirens by staking minnow traps to the bottom (Raymond 1991, Gehlbach pers. comm.). 

       Baiting appears to have no noticeable effect on overall trap success. There was little difference in the number of animals caught in baited vs. unbaited traps. However, more A. means were caught in baited traps than S. lacertina, indicating these species may respond differently to baiting. Capture success was approximately equal between trap nights at both study sites, suggesting that increasing the number of trap nights from one to four does not affect the number of daily captures.

       Capture rates differ between months and among species.  This may suggest that Siren and Amphiuma have different seasonal activity patterns. After a full year of trapping has been completed, more information will be available to address this question.

       Numerous marking methods were tested on Siren and Amphiuma including: cyano-acrylic, toe clipping, tail notching/clipping, heat branding, and PIT tags. Of these, PIT tags are the only reliable method for long-term studies of these species.  Results from this mark-recapture study will produce density estimates for both sites, as well as provide information on activity and movement patterns.

LITERATURE CITED

Darby, P.C., P.L. Valentine-Darby, H.F. Percival, and W.M. Kitchens. 2001. Collecting Florida applesnails (Pomacea paludosa) from wetland habitats using funnel traps. Wetlands 21(2): 308-311.

Gehlbach, F.R., and S.E. Kennedy.  1978. Population ecology of a highly productive aquatic salamander (Siren intermedia). The Southwestern Naturalist 23(3): 423-430.

Machovina, B.L. 1994.  Ecology and life history of the salamander Amphiuma means in Everglades National Park. M.S. thesis. University of Florida, Gainesville, FL, USA.

Raymond, L.R. 1991. Seasonal activity of Siren intermedia in northwestern Louisiana (Amphibia: Sirenidae).  The Southwestern Naturalist. 36:144.

Snodgrass, J.W., J.W. Ackerman, A.L. Bryan, Jr., and J. Burger.  1999. Influence of hydroperiod, isolation, and heterospecifics on the distribution of aquatic salamanders (Siren and Amphiuma) among depression wetlands. Copeia 1999:107-113.

ACKNOWLEDGEMENTS

This project is funded by the U.S. Department of Interior, Amphibian Research and Monitoring Initiative (ARMI).  I graciously thank Lora Smith, Franklin Percival and Ken Dodd for their support and advice, along with Ordway Preserve and Okefenokee NWR Refuge.  I would also like to thank the following people for their field assistance: Lora Smith, Maya Zacharow, Audrey Owens, Chris Gregory, Matt Chopp, Jennifer Staiger, Paul Loud, and Steve Johnson.