Asking Salamanders Questions
Like most animals, if we wish to know something about salamanders, we cannot simply ask them questions and expect answers. Instead we ask questions in such a way that they can’t help but give us some information.
I have been impressed by the numbers of salamanders I have encountered on campus. So far I have identified the following species:
Redback SalamanderPlethodon cinereus
Slimy SalamanderPlethodon glutinosus
Mountain Dusky SalamanderDesmognathus ochrophaeus
Spotted SalamanderAmbystoma maculatum
Two-lined SalamanderEurycea bislineata
Red-spotted NewtNotophthalmus viridescens
Spring SalamanderGyrinophilus porphyriticus
Jefferson SalamanderAmbystoma jeffersonianum
Long-tailed SalamanderEurycea longicauda
Other species that are possible on campus include
Northern Dusky SalamanderDesmognathus fuscus
Northern Red SalamanderPseudotriton rubber
There are records of about 8 other species of salamanders that have been found in Lackawanna or Wyoming Counties (McCoy 1982). However, not all of the habitats characteristic of these species (Shaffer 1991; Pfingsten and Downs 1989) are found on KeystoneCollege property, so we cannot expect to find all of these nearby.
In this lab we will attempt to ask and answer one or more questions about the habitat choices of these and other species. These might include (but are not limited to) the following:
- Do the different species of salamanders choose different habitats, or are they found in the same niches (as well as we can determine them)?
- Can we determine anything about the age structure of the organisms which we find? For example, do we have both juveniles and adults present?
- Do different age classes of salamanders select different habitats? If so, in reference to which environmental variables?
When we find a salamander, we will identify it as a group so that we can all identify each species. We will search an area of woodland and stream habitat. We will describe the locality where each individual was found. What was it under (rock, log, leaves)? What kind of substrate was it on (dirt, rock, gravel, etc.)? How wet or dry was the substrate (dry, wet, moist, standing water)? We will measure the distance at which we found the animal from the stream.
In addition, you will measure the length of the animal to the nearest millimeter from its snout to its vent (Figure 1). This is the standard length taken for species that frequently lose their tail (as you will probably witness!) Once you have finished with a salamander, put it back and put back the rock, leaves, or log that covered it. If you destroy the microhabitat, you destroy the animal’s home.
Figure 1. Snout-length measurement for salamanders.
Is there more than one age class present? It is unlikely that the factors that determine the distribution of adults apply equally to juveniles, too. So, we will construct a length-frequency distribution. To do this, subtract the measurement of the smallest animals from the largest to find the range. Subdivide the range into 1 cm groups and tally the number of animals in each class.
If our data look like those in Table 1, we would conclude that there are two age classes of species A present. This sort of pattern is expected from animals which breed only once per year. If we get this pattern, we would analyze the ‘large’ and ‘small’ groups separately.
Table 1. Length-frequency distribution of salamanders of Species A.
Size Class (cm)Frequency
0.5 – 1.41
1.5 – 2.410
2.5 – 3.42
3.5 – 4.46
4.5 – 5.414
5.5 – 6.416
6.5 – 7.42
Can you think of any other questions we might ask? If so, let us know before we go out in the field so we might plan the best way to collect the data necessary.
Questions to be considered in your analysis:
- Within each species found for which you feel we collected a large enough sample size, do you feel there is more than one age class present? Construct length-frequency histograms to provide evidence of this. By doing a little research into the life history of these species, how can you explain the presence or absence of more than one age class?
- Did you find any species to seemingly prefer one habitat, cover, wetness, or substrate category? How might you explain these preferences?
- By checking with range maps and habitat requirements, what other species of salamanders might we expect to find on campus?
- Are there any differences in preferences of these factors between age classes?
- Almost all of the salamanders caught were under rocks. Do you think this represents a true preference for rocks, or as an alternative explanation, do they choose anything that they can crawl under, and rocks were the most common thing that fits that description?
Resources and Literature Cited
Conant, Roger & Joseph Collins. 1998. Reptiles and Amphibians: Eastern/Central North America. Houghton-Mifflin Co., Boston. 616 pp. ISBN 0-395-90452-8.
Hulse, Arthur et al. 2001. Amphibians and Reptiles of Pennsylvania and the Northeast. Comstock Publishing. 419 pp. ISBN: 0801437687
McCoy, C. J. 1982. Amphibians and Reptiles in Pennsylvania. CarnegieMuseum of Natural History. Special Publication #6, CarnegieMuseum. Pittsburgh. 91 pp. ISBN 091123912X
Serrao, John. 2000. The Reptiles and Amphibians of the Poconos and Northeastern Pennsylvania. Llewellyn & McKane, Inc. Wilkes-Barre.
Shiffer, Larry. 1991. Pennsylvania Amphibians & Reptiles. PA Fish Commission. Harrisburg, PA. 166 pp.
Tyning, Thomas. 1990. A Guide to Amphibians and Reptiles. Little, Brown and Co. Boston. 400 pp. ISBN 0-316-81713-9.