Download Species Packing in Dusky Salamanders

SPECIES PACKING IN
DUSKY SALAMANDERS
PURPOSE

To examine habitat partitioning in three species of salamanders.
MATERIALS
Aquatic nets
Buckets, jars, or bags
Data sheets
Paper towels
INTRODUCTION
Members of the salamander genus Desmognathus (Phylum Chordata, Class Amphibia, Order
Urodela, Family Plethodontidae) are found most commonly in or near mountain streams, springs, or
seeps, but are usually absent from larger streams or rivers where predatory fish occur. Like other
members of the family Plethodontidae, dusky salamanders lack functional lungs. Gas exchange is
Copyright © Dr. Robert R. Glesener
primarily through the moist skin and mouth cavity. The lungless condition is thought to be an
adaptation to mountain streams. The lung created buoyancy and made them more likely to be
washed downstream from their territories; floating may also have made them more susceptible to
predation.
These salamanders reach their greatest abundance in the southern Appalachian region where they
probably evolved some 40 million years ago (Dunn 1926) or even earlier. In this region, members of
the genus occur together in combinations of 3, 4, or 5 species. They are usually thought of as streambank salamanders, but individually the species vary from being mostly aquatic
(D. quadramaculatus), through the “typical” stream bank habitat (D. monticola and/or D. fuscus), to
mostly terrestrial (D. ochrophaeus) and fully terrestrial (D. wrighti and D. aeneus). Only
D. quadramaculatus, D. monticola, and D. ochrophaeus occur in our study area.
All three of these species lay their eggs in or near water, and the female remains with them until
they hatch 2 or 3 months later. All three have aquatic larval stages with external gills. The duration
of the larval stage varies among these species from a few weeks to 2 years (Hairston 1984). After
metamorphosis, individuals of all three species remain close to the stream in which they hatched.
All three species also feed largely on arthropods (larvae and adults) and worms. Their body
mechanics being very similar, all three feed close to the ground. Like most amphibians, all three
species are also nocturnal. Thus, there is much overlap in their fundamental niches (Hairston 1964,
1973; Krzysik 1979).
In this field study, we will attempt to determine how these three similar species have partitioned
their common resource. There is one complicating factor: The larger salamanders may also feed on
the smaller ones. Therefore, predation may also be a factor determining the distribution (zonation) of
these salamanders about their stream habitat (Tilley 1968, Hairston 1984).
THE SPECIES
All Desmognathans have relatively short and stout bodies with hindlegs larger than forelegs
(they can jump several times their body length to escape capture). There is usually a pale diagonal
line from each eye to the angle of the jaw (Conant 1975).
Desmognathus quadramaculatus — the Black Bellied Salamander
D. quadramaculatus is a large (10-17 cm), robust salamander (Conant 1975). Their tails are very
stout at the base, but measure less than one half of the total body length, and they are knifed-edged
above. The belly is black in adults, while usually dark but flecked with yellow in young (put your
specimen in a bottle to see its underside). There is usually a conspicuous double row of light dots
along each side of the body.
This salamander, the heaviest and bulkiest of the lungless group, is daring enough to occasionally
pause in the open on a wet rock, even in sunshine, although they usually hide beneath rocks during
Copyright © Dr. Robert R. Glesener
the day. When disturbed, they plunge beneath a nearby stone or swim vigorously away (with or
against the current). Trying to catch these agile amphibians is like going fishing with your bare
hands.
Desmognathus monticola — the Seal Salamander
D. monticola is also a stout-bodied salamander, but adults are substantially smaller (8-13 cm)
than the Black-Bellied species (Conant 1975). Its tail is compressed and knife-edged above near the
tip and measures approximately ½ of the total body length. Most specimens are boldly patterned
above, but plain and quite pale below with a distinct lateral separation between dorsal (back) and
ventral (belly) pigmentation. The back has strong black or dark brown markings on a ground of buff,
gray, or light brown. The markings are extremely variable. Some specimens simply have scattered
dark or light spots or streaks, and in the south, adults may lose virtually all traces of pattern. The
belly is white in juveniles, becoming lightly and usually uniformly pigmented with gray or brown in
old adults. Sometimes there is a single row of light dots on the sides between the legs. Old adults
may be purplish brown, with dark markings few and obscure.
At night, poised at the entrance to a burrow or perched atop a wet rock and illuminated by the
observer’s flashlight, its appearance suggests a miniature seal, hence the common name.
Desmognathus ochrophaeus — the Mountain Dusky Salamander
D. ochrophaeus is medium-sized (7-10 cm) with a round tail (Conant 1975). The tail is about
half the total body length and as wide or even wider than its height at the base. This salamander is
extraordinarily variable in coloration and pattern. Most have a wavy or irregular dorsal (back) stripe,
and they may be marked with large areas that are remnants or light spots set in paired or zigzag
fashion down the backs of the juveniles. More terrestrial than most other dusky salamanders, they
sometimes wander far out into the woods during wet weather.
FIELD PROCEDURE
The focus of collecting will be on the stream bank, but will extend from the stream proper into
the surrounding forest. Students will work together in teams to complete this exercise. Each team
will be issued a plastic collecting bag; paper towels to be moistened, fluffed, and inserted into the
bag; a tape measure to determine the distance of a collection from the stream; and a data sheet to be
inserted inside the collecting bag upon completion of the exercise.
1. To insure that all areas get sampled, teams will be assigned to particular areas.

One group will “fish” the stream itself, another will comb the stream bank and nearby
“shore”, and the third group will search in the adjacent forest.
Copyright © Dr. Robert R. Glesener

Some overlap in search areas is desirable.

Rotate groups to account for variation in collecting ability.
2. Sample the assigned areas for the presence of salamanders.

Rocks, logs, etc., should be turned by hand (and returned to their original positions after
sampling).

You should expect that there will be many that “got away”. Keep track of how many.
3. Collecting technique

Use nets, if available, for collecting in the stream. Position the net downstream from a rock,
lifting the rock from that end.

Otherwise, specimens should be captured by hand and transferred to a bucket, jar, or bag for
identification.

Desmognathus species do not secrete any known odorous, slimy, or harmful chemicals
(that’s why they make good fish bait) and can be handled without concern to the collector.

Try not to handle them excessively; besides mechanical injury, your body heat and the
dryness of air may cause the salamander physiological stress.
4. Record field data

Measure the distance of the catch from the nearest running water (not pools or seeps) and
record on your data sheet being certain to identify units (inches, feet, meters). Critical
boundaries include: in or out of water, < or > 1 ft., < or > 5 ft., and < or > 20 ft.

Note the type of cover under which the animal was located and any unusual circumstances
associated with its behavior and/or capture.

Attempt to distinguish this salamander from others placed in the same bag on the basis of
coloration or pattern, snout/vent or snout/tail length, deformities, etc. Record your
description on the data sheet.
5. Do not release adult specimens

This is to avoid repeated capture of some specimens.

Salamanders will be released when the exercise is completed.
Copyright © Dr. Robert R. Glesener
6. Larvae can be released without recording.

Larvae have feather-like external gills in the neck region.

Since larvae are aquatic in all three species, it is not possible to partition the habitat in any
way we can determine in this exercise (it is also next to impossible to tell them apart).
ACKNOWLEDGEMENTS
The conceptual basis, design, and methodology of this laboratory exercise were adapted from the
works of N. G. Hairston, as cited below and as practiced with graduate students at both the
University of Michigan, Ann Arbor, and the University of North Carolina, Chapel Hill. His
permission and encouragement to develop this lab at the undergraduate level are greatly appreciated.
LITERATURE CITED AND OTHER REFERENCES
Conant, Roger. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North
America (Peterson Field Guide Series). Houghton Mifflin Company, Boston, MA. Brevard
College Call Number: 597.6 C743f
Dunn, E. R. 1926. Salamanders of the Family Plethodontidae. Smith College Anniversary Series,
Vol. 7, Northhampton, MA. Brevard College (Moore Science) Call Number: 597.9 D923s
Glesener, Robert R. Salamanders of Moore Cove and Transylvania County.
PowerPoint presentation available on Brevard College Public Folders Intranet.
Unpublished
Hairston, N. G. 1964. Studies on the organization of animal communities. Journal of Animal
Ecology 33(Supplement): 227-239.
———. 1973. Ecology, selection, and systematics. Breviora 414: 1-21.
———. 1980. Species packing in the salamander genus Desmognathus: what are the interspecific
interactions involved? American Naturalist 115:354-366.
———. 1984. Inferences and Experimental Results in Guild Structure, in D. R. Strong, D.
Simberloff, L. G. Abele, and A. B. Thistle (Eds.), Ecological Communities: Conceptual Issues
and the Evidence. Princeton University Press, Princeton, NJ. Brevard College (Moore Science)
Call Number: 574.5247 E19
———. 1987. Community Ecology and Salamander Guilds. Cambridge University Press,
Cambridge. (See Chapter 6) Brevard College (Moore Science) Call Number: 597.65 H153c
Krzysik, A. J. 1979. Resource allocation, coexistence, and the niche structure of a streambank
salamander community. Ecological Monographs 49(2): 173-194.
Copyright © Dr. Robert R. Glesener
Martof, B. S., W. M. Palmer, J. R. Bailey, and J. R. Harrison III. 1980. Amphibians and Reptiles of
the Carolinas and Virginia. University of North Carolina Press, Chapel Hill. Brevard College
Call Number: 598.10975 A526
Tilley, S. 1968. Size-fecundity relationships and their evolutionary implications in five
desmognathine salamanders. Evolution 22:806-816.
Copyright © Dr. Robert R. Glesener
Exercise — Species Packing in Salamanders
NAME
SECTION #
GROUP
DATE
TIME BEGIN ______
BAG #
TIME END
Specimen
Description of
Distance
Describe
Possible
Number
Salamander
(inches)
Location
Species
1
2
3
4
5
6
7
8
9
10
11
12
Main Foraging Zones:
 In stream (0 feet)

> 0 feet but <= 1 foot

> 1 foot but <= 5 feet

> 5 feet but <= 20 feet

> 20 feet
Copyright © Dr. Robert R. Glesener
Number of escapes (“ones that got away”) _____