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Gender Dimorphism in Northern Leopard Frogs

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Title: Gender Dimorphism in Northern Leopard Frogs


1
Gender Dimorphism in Northern Leopard Frogs Erin
Gould (Exercise Science), Ashley Urra (Biology),
Tom Williams (Exercise Science) St. Ambrose
University
Diagrams showing the Eleven Standard
Morphological Measurements 2.1 Snot-vent 2.2
Head length 2.3 Head width 2.4 Eye-nostril 2.5
Eardrum 2.6 Thigh 2.7 Shank 2.8 Foot 2.9
Forearm 2.10 Hand 2.11 Thumb
Purpose and Hypothesis It is difficult to know
the gender of immature Northern Leopard frogs
from external measurements. Our purpose is to
develop a method by which field workers can
reliably determine gender. Null There is no
correlation between external measurements and
gender of Northern Leopard frogs. Alternate We
predict that male Northern Leopard frogs will
have larger measurements overall than females.
Discriminant Function Graph of Significant
Variables
MaleMean0.6Std. Dev. 0.967N20
FemaleMean-0.54Std. Dev. 1.029N22
Background Northern Leopard frogs can be very
easily recognized by their slim bodies, their
leopard-like spots outlined with pale yellow and
white, and the background coloring which varies
from green to gray to brown (Graham, 2007).
Northern Leopard frogs live in many aquatic
habitats, such as marshes, swamps, lakes, and
streams. Leopard frogs spend a great amount of
time out of water and searching for food in
meadows (Sutton, 2003). Gender roles adapted by
males and females in different species strongly
influence the evolution of sex-specific sizes,
forms, and structures (Fairbairn, 2007).

Conclusion Overall, no standard system of
measurement for determining the gender of an
immature Northern Leopard frog by its
morphological features can be derived from this
experiment. Although there were significant
variables, none of them can be considered
reliable because of the variation in size of
frogs. The only inference that can be made is
that males are generally larger than females
because the means of each measurement were larger
in males than females. Males are clearly larger
than females with respect to overall size and a
number of other structural variables. Despite
there being a significant difference with respect
to six morphological variables, no single
variable can be used to identify frogs to
gender.
Works Cited and Acknowledgements Fairbairn, D.
(2007). Why do males and females frequently
differ in body size and structure? University of
California. Retrieved from http//newsroom.ucr.e
du/cgi- bin/display.cgi?id1682. Graham, D.
(1997). Northern leopard frog. Northern State
University. Retrieved from http//www.northern.e
du/natsource/AMPHIB1/Nort he1.htm. Sutton, B.
(2003). Northern leopard frogs. Marshall
University. Retrieved from http//www.marshall.
edu/herp/Toads_Frogs/Leopa rd_Frog.htm. We would
like to acknowledge Dr. Paul Koch and Dr. Rich
Legg for their help and support during this
project.
  • Methods
  • We captured immature Northern Leopard Frogs using
    a net at Nahant Marsh.
  • We filled a jar with 25 diluted alcohol solution
    to sacrifice the frogs. Ten frogs were placed at
    a time for one hour.
  • Eleven standard morphological measurements were
    taken using a caliper.
  • The reproductive systems of the frogs were
    exposed with a scalpel and scissors by opening
    the lateral side of the frog.
  • Gender was determined by identification of testes
    or oviducts.
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