Gender Dimorphism in Northern Leopard Frogs Erin Gould (Exercise Science), Ashley Urra (Biology), Tom Williams (Exercise Science) St. Ambrose University 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. 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 Discriminant Function Graph of Significant Variables MaleMean=0.6Std. Dev. =0.967N=20 FemaleMean=-0.54Std. Dev. =1.029N=22 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.edu/cgi- bin/display.cgi?id=1682. Graham, D. (1997). Northern leopard frog. Northern State University. Retrieved from http://www.northern.edu/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.