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Note: The species in the list below include only those species reported in scientific journal articles that were encountered in stream transects. These species should not be considered the only amphibians that could be encountered in stream transects. For more detailed species lists, consult Crother et al. (2000), Petranka (1998), Conant and Collins (1998), and Stebbins (1998). Crother et al. (2000) is published by the Society for the Study of Amphibians and Reptiles and contains the most up-to-date taxonomic classifications used in our list below. Asterisks indicate terrestrial breeding salamanders that have also been found using stream transects.
Eastern United States:
Ambystoma barbouri, Streamside Salamander; Desmognathus aeneus, Seepage Salamander; Desmognathus fuscus, Northern Dusky Salamander; Desmognathus imitator, Imitator Salamander; Desmognathus monticola, Seal Salamander; Desmognathus ochrophaeus, Allegheny Mountain Dusky Salamander; Desmognathus quadramaculatus, Black-bellied Salamander; Desmognathus wrighti, Pigmy Salamander; Plethodon cinereus, Red-backed Salamander* ; Plethodon cylindraceus, White-spotted Slimy Salamander*; Plethodon glutinosus, Northern Slimy Salamander* ; Plethodon jordani, Jordan's Salamander*; Plethodon richmondi, Southern Ravine Salamander*; Hemidactylium scutatum, Four-toed Salamander; Gyrinophilus p. duryi, Kentucky Spring Salamander; Gyrinophilus p. porphyriticus, Northern Spring Salamander; Pseudotriton m. montanus, Eastern Mud Salamander; Pseudotriton r. ruber, Northern Red Salamander; Eurycea bislineata, Northern Two-lined Salamander; Eurycea cirrigera, Southern Two-lined Salamander; Eurycea l. longicauda, Long-tailed Salamander; Eurycea wilderae, Blue Ridge Two-lined Salamander
Western United States:
Dicamptodon ensatus, California Giant Salamander; Dicamptodon tenebrosus, Coastal Giant Salamander; Rhyacotriton kezeri, Columbia Torrent Salamander; Rhyacotriton olympicus, Northern Olympic Salamander; Rhyacotriton variegatus, Southern Torrent Salamander; Taricha g. granulosa, Rough-skinned Newt; Taricha rivularis, Red-bellied Newt; Plethodon dunni, Dunn's Salamander*; Plethodon vandykei, Van Dyke's Salamander*; Plethodon vehiculum, Western Red-backed Salamander*; Ensatina e. eschscholtzii, Monterey Ensatina*; Aneides ferreus, Clouded Salamander*; Aneides flavipunctatus, Black Salamander*; Batrachoseps attenuatus, California Slender Salamander*; Ascaphus truei, Tailed Frog
The transect technique is a common sampling method for amphibians in terrestrial or aquatic habitats (Jaeger 1994). When used to survey stream amphibians, transects are typically linear areas set up either parallel or perpendicular to the stream, including stream channel, bank or both (Table 1). Various sizes and configurations of transects have been used, and sometimes multiple survey methods are employed along the same transects (Table 1). Transects can provide species presence/absence data, counts of species and life stages, relative abundance, and density (number of individuals/area surveyed). If the number of cover objects turned over is tallied (e.g., using clicker counters), salamander catch per unit effort can also be calculated. Also, if transects are time-constrained (e.g., set at 30 minutes), or the start and end times of the survey are recorded, the number of salamanders per observer-hour effort can be recorded. Capture-recapture or removal estimation techniques can also be used in conjunction with transect surveys (see "Approaches to analyzing your data" below).
A visual encounter survey technique is typically employed within the transect, in which the observer looks for amphibians on the surface and usually also under rocks, logs, and other debris. Cover objects turned over to look for amphibians can be tallied with clicker counters. All cover objects are returned to their original positions to avoid disturbing the habitat. Fine mesh dip nets are the primary tool used to capture the salamanders, but larvae and adults can also be captured with zip-lock bags or by hand. If using a net or zip-lock bag, place the net or bag firmly against the bottom substrate downstream of the cover object. Lift the cover object in front of the net. Sometimes salamanders immediately swim away, but often larvae stay in the area where the rock had been. If you do not see movement, wait for the sediment to settle and look carefully in the area. To capture larval salamanders, position the net or zip-lock bag in front of the salamander's head and gently touch the tail; often they will move forward into the net. Sometimes larvae are swimming around in the open and you can direct them into the net or zip-lock bag. For adults, you can use the same tactic, or you may have to go after them using your hand or dip net if they try to escape. On land, have your net ready to catch amphibians from under overturned rocks. Once you have turned over the rock or log, you might see movement right away, in which case you need to catch it quickly. If a salamander escapes, write down as much information about identification and age (e.g., species, life stage, estimation of total length) as can be positively determined.. If you cannot ascertain the exact species, but know the genus, record the genus and leave the species as unknown (e.g., Desmognathus unknown).
Things that could bias your counts
Observers differ in their abilities to identify salamanders, and this can be particularly true for larval forms. To diminish this problem, observers should be trained prior to going into the field and species identification keys should be taken into the field for those who are not completely familiar with how to identify larval and adult salamanders. However, it should be noted that at times even the experts have difficulty discriminating among larval salamanders. Geographic locality and local species occurrence should be factored into species identification.
Rising temperatures and rainfall are known to initiate breeding activities in many amphibians (Stebbins and Cohen 1995). Heavy rains early in the breeding season result in the congregation of large breeding groups of many salamander species (Petranka 1998). Surveys conducted under ideal weather conditions for peak salamander activity will provide highest and most consistent salamander counts and estimates. Unfortunately, ideal and standardized weather conditions for conducting transects are not presented in the literature.
Time of year:
Streamside salamander species differ in their courtship and breeding seasons, length of larval periods, and time spent within the stream versus surrounding terrestrial areas. According to Pauley (pers. comm.), June and October in West Virginia are the best months to survey for streamside salamanders, as these are the months when the greatest numbers of species are present at streams (see "Leaf Litter Bag" section). Bury and Corn (1991) suggest the optimum time of year for stream surveys to be June and July in California and the Oregon Coast Range, and June through August may be ideal for the Cascade Range of Oregon and Washington. Ashton and Ashton (1978) found that Eurycea bislineata tend to congregate in "winter retreats." They found temperatures in these retreats (areas where warm groundwater springs enter the stream) to be 1 to 4°C warmer than the surrounding stream. The last salamanders entered these winter refugia when stream temperatures reached 7°C. Their study suggests that Eurycea bislineata would probably be unevenly distributed in streams during the winter months. Optimal times of year to survey for streamside salamanders will vary depending on target species and geographical location. Consult scientific literature relevant to the species you want to sample in determining ideal times of year to conduct transect surveys (Petranka 1998).
Time of day:
Streamside salamanders are more active at night, when they come to the surface to forage for invertebrates, defend territories, and seek mates (Petranka 1998). In a study in Giles County, Virginia, Keen (1982) found that Desmognathus monticola and Desmognathus fuscus in field enclosures showed the highest levels of activity in the evening between 20:00 and 0:00, a lull in activity between 0:00 and 02:00, and a resurgence of activity between 03:00 and 06:00. In North Carolina, Hairston (1986) determined that night searches captured 1.65, 1.81, and 3.75 times more D. ochrophaeus, D. monticola, and D. quadramaculatus, respectively, than during the day.
Observer bias could be a possible factor when sampling stream transects. The ability to see or spot salamanders (search image) could vary among observers, particularly in the case of very small larval salamanders (e.g., young larval Eurycea). The largest bias comes from the ability of observers to catch salamanders. Some people are better at capturing salamanders than others, so capture results will often depend on the individuals involved in the study. If a person is not very good at catching salamanders, there will be more escapes, leading to higher inaccuracy in population estimates and assessing species presence. The physical strength of observers can vary (e.g., some observers may be better able to turn over larger, heavier rocks than others), which can lead to bias in search method and species detection along transects. Training, including observer covariates in analyses, double-observer techniques and the use of some mark-recapture techniques can all be used to reduce this bias.
With capture-recapture, salamanders are captured and marked individually or batch-marked (in which a unique mark is used during each survey). Marking techniques for stream salamanders include tail notching, toe clipping, tagging with visible implant fluorescent elastomer (VIE) (Northwest Marine Laboratories), or photographing individuals (if they have unique patterns or spots) in such a way that the observer can identify previously caught individuals. Invasive marking techniques are not necessarily recommended because of the potential harm it can cause salamanders. All salamanders are recorded (species, life stage), measured (snout-vent length, total length, etc.) and released. Once individuals are assumed to have mixed evenly back into the population, another capture-recapture survey in the transect is made. Capture-recapture can be conducted just once (in which a Lincoln-Peterson estimator can be used), or multiple times, in which case open (we recommend the software program MARK from Patuxent Wildlife Research Center's Software Archive) or closed (we recommend the software program CAPTURE from Patuxent Wildlife Research Center's Software Archive) population models can be used to estimate the population size for each species and age class within the stream (White et al. 1978; Rexstad and Burnham 1991).
Removal methods are less time-consuming than capture-recapture. With removal, an initial pass along the transect is conducted and all salamanders encountered are captured, recorded, and retained in buckets or in individual zip-lock bags. Any escaped individuals should also be documented. The salamanders should be kept in the shade; salamanders can be kept in buckets or resealable bags with adequate water (for larvae) or a small amount of water and an air pocket (for adults). A second pass after a certain period of time is then conducted following the same procedure. Three passes is recommended, but more can be conducted. Once all the passes are completed, salamanders are returned to the transect. To avoid disturbing the stream habitat excessively and to avoid problems with new salamanders moving into the count area during the night, it is probably best to limit removal passes to three passes within a day. Mitchell (2000) suggests that it may be best to limit daytime studies to once per spring or fall season since cover objects may be unattractive to salamanders for several days or weeks following a disturbance.
Ideally, for the removal estimation method to work, the population counts should decrease with each pass (i.e., the population in the transect decreases or is depleted over time). Removal data can be analyzed using Program CAPTURE (removal or Zippen models) to estimate detection rates and population sizes of specific species and age classes sampled within the transect.
Hyde and Simons (2001) found extremely high spatial and temporal variation in capture rates of Plethodontid salamanders using terrestrial 50 m long transects (some located within 50 m of streams), though the spatial variation was always greater than temporal variation. They found that natural cover transects had the lowest spatial and temporal variation for all species (except Desmognathus wrighti) of the three diurnal methods they used (natural cover objects along transects, artificial cover boards, and leaf litter searches). Night transects had the lowest variation of any method, but Hyde and Simons (2001) make the point that these coefficients of variation were not directly comparable to the others because the night transects were conducted in conditions ideal for surficial salamander activity.
Cook et al. (in prep.) found coefficients of variation of counts within streams using 50 x 1 m stream bank transects ranging from 0.8 for D. monticola adults, 0.9 for E. bislineata adults to 1.4 for D. fuscus adults. For 15 x 2 m transects spanning the stream bank and channel, coefficients of variation in counts within streams were as follows: 0.5 and 0.7 for E. bislineata larvae and adults, respectively, 0.6 for D. monticola adults, 0.7 for D. fuscus adults, and 0.9 for G. porphyriticus larvae (Cook et al., in prep.).
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