Effects of shade and predation on survival and growth of larval gray treefrogs Hyla veriscolor in Mi

1
Effects of shade and predation on survival and
growth of larval gray treefrogs (Hyla veriscolor)
in Missouri Allison Barlows, Daniel Hocking and
Raymond Semlitsch Department of Biological
Sciences, University of Missouri- Columbia

• Introduction
• One of this planets most pertinent ecological
  issues is the loss of natural habitat due to
  human encroachment
• Worldwide biodiversity has been most seriously
  endangered by the degradation of habitats (Groom
  et al., 2006).
• Clear-cutting forests in Missouri for
  development and agriculture changes the
  landscape, affecting many species
• We examined some implications of timber harvest
  on larval grey treefrog development and survival
  
• Shade and predator levels are two factors that
  differ in clearcuts and forest expected to
  significantly impact treefrog larvae

Results Days to Metamorphosis There was very
little difference between treatments. Sur
vival Shade treatments Percent survival was 5
greater in low shade than high. Predator
treatments Ponds that had zero predators have
20 greater survival than ponds that had high
larval dragonfly density. Mass at
metamorphosis Shade treatments Metamorphs in low
shade ponds weighed an average of about 0.02 g
more than the high shade individuals. Predator
treatments The average mass of the zero and high
treatments were similar and smaller than masses
in the low and medium treatments.
Conclusions Shade treatments The higher average
growth rate in lower shade treatments may have
been due to a higher level of solar radiation
causing increased periphyton growth, which the
tadpoles utilize as food. Predator Treatments As
expected, fewer individuals survived in the high
density predator treatments and tadpoles
metamorphosed at a smaller size to avoid
predation (Skelly et al. 1990). As a result of
greater survival in the zero predator treatment,
less food was available per individual causing
smaller size at metamorphosis.
Future Studies Carry-over effects A cage study
using our emerged metamorphs has already
commenced which aims to determine how these
larval environments effect adult treefrogs. It
has been previously demonstrated that juvenile
size has effects on future fitness, such as adult
survival, body size at first reproduction, age of
first reproduction, and fecundity (Semlitsch et
al. 1988 )
Fig. 8 Dragonfly larvae were the predators in
this experiment
Fig 1 Cattle Tanks kept at the Botany Research
Facility were checked daily for metamorphs
Acknowledgments Life Sciences Undergraduate
Research Opportunity Program Nation Science
Foundation L. Barlows, D. Carson, S. Gaynor, A.
Hogan, B. Scheffers, J. Shipman, and E. Wengert

• Methods
• 24 cattle tanks as have been used in previous
  studies (Wilbur et al., 1987) were stocked with
  100 tadpoles in mid-May 2006.
• Each tank was randomly assigned one of 8
  treatments, allowing for 3 replicates of each
  treatment.
• 2 shade treatments were created with greenhouse
  cloth tank covers that simulated high or low
  levels of shade.
• 4 predator treatments consisted of different
  densities of dragonfly larva (family
  Libellulidae), which catch anuran tadpoles using
  a protrusible labium (Skelly et al. 1990).
• Frogs were removed from the tanks once they
  metamorphosed and were
• weighed.

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Larval American Toads to an Odonate Predator.
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