Juvenile salamander dispersal and terrestrial microhabitat

1
Juvenile salamander dispersal and terrestrial
microhabitat cuesKristen Malone, Michael S.
Osbourn and Raymond D. Semlitsch University of
Missouri-Columbia - Biological Sciences

Introduction The effects of deforestation and
fragmentation are profound on amphibian
populations (Stuart et al 2004). In order to
balance land use practices with amphibian
conservation, biologists and land managers must
understand the habitat requirements of amphibians
at all life stages. Ambystomatid
salamanders have an aquatic larval stage followed
by metamorphosis and a terrestrial adult stage
(Johnson 2000). They disperse from their natal
ponds at night when it is raining. We have very
limited knowledge about the mechanisms recently
metamorphosed Ambystomatid salamanders use to
select a favorable habitat when dispersing from
their natal pond. It is possible that olfactory
cues are one mechanism that can lead a salamander
to a moist, cool environment. Finding the source
of these cues will help us to understand the
effects human-altered habitat has on juvenile
dispersal. In this study, we attempt to uncover
these cues by conducting substrate choice tests.
We compare the substrate preferences of two
Ambystomatid species, the spotted salamander, who
is strongly associated with woodland habitat, and
the small-mouthed salamander, who can be found in
a variety of habitats including woodlands,
prairies, and farmlands (Johnson 2000).

• Research Questions
• Do juvenile ambystomatid salamanders use an
  olfactory cue to select a favorable terrestrial
  habitat for shelter and movement?
• Experiment 1 Is there a preference for litter
  type?
• Because the spotted
  salamander is forest-
• associated, will it have
  a greater preference
• for forest litter than
  the small-mouthed
• salamander?
• Experiment 2 If a preference for forest litter
  exists, is the
• source of the cue in
  freshly fallen leaves as
• well as old, decomposing
  leaf litter?

• Conclusion
• Spotted salamanders respond to an olfactory cue
  from the microhabitat indicating the more
  favorable habitat for a woodland species.
• Small-mouthed salamanders do not dmonstrate a
  strong response to an olfactory cue in either
  litter type.
• Both species respond to a cue in decomposing
  leaves.
• The source of the cue is not the leaves, but
  likely some byproduct of their decomposition
  found only in forest litter such as a fungus.

Bill Peterman
Spotted salamander (Ambystoma maculatum)
Bill Peterman

• Conservation Implications
• If olfactory cues remain in the habitat for a
  period of time after a forest has been cleared,
  the cues can mislead a juvenile to disperse into
  an unfavorable habitat.
• Microhabitat cues have the potential to be
  maladaptive in situations of human forest
  alteration and become an ecological trap.

• Methods
• Spotted salamander n26, small-mouthed
  salamander n41
• Substrates were mulched to eliminate structural
  differences and then placed on one half of a test
  chamber.
• A salamander was placed in a release platform in
  the center of the chamber.
• The salamander was released, and its location on
  the substrates was recorded every three minutes
  for one hour.
• If the salamander chose one substrate more than
  50 of the time, then that was its preference. We
  used a G-test to determine whether substrate
  preference was different from random.

Small-mouthed salamander (Ambystoma texanum)
Results In Experiment 1, we found that juvenile
spotted salamanders prefer forest litter to
grassland litter. Juvenile small-mouthed
salamanders do not have a preference either
litter type. In Experiment 2, we found that both
species of juveniles have a preference for
decomposing leaf litter.
Question for further study Does burning effect
the olfactory cue salamanders get from
decomposing leaf litter? If burned litter no
longer has the cue, it would not misguide
juveniles into unfavorable habitat.

Acknowledgements Thanks to Julia Earl, Shannon
Pittman, and Jenni Geib. Funding NSF REU grant
Indicates that percentage is significant
Literature Cited Johnson, Tom R. The Amphibians
and Reptiles of Missouri. 2000. Missouri
Department of Conservation. Jefferson City,
MO. Stuart, Simon N. 2004. Status and Trends of
Amphibian Declines and Extinctions Worldwide.
Science. Vol. 306 1783-1786.


Michael S. Osbourn
Michael S. Osbourne
Figure 1 Test chambers were arranged to face
different cardinal directions.
Figure 2 A spotted salamander choosing the
forest litter substrate.