Calling Activity of Gray Treefrogs: Circadian Patterns of Activity and the Role of Environmental Factors
Mentor 1
Dr. Gerlinde Höbel
Location
Union Wisconsin Room
Start Date
28-4-2017 1:30 PM
End Date
28-4-2017 4:00 PM
Description
Temporal patterns of breeding activity in frogs are highly variable, and species can be classified as either explosive (breeding <14 days), or prolonged breeders (breeding >1 month). Eastern Gray Treefrogs (Hyla versicolor) breed for 2-3 months, which should classify them as prolonged breeders. Using data from a long-term recorder stationed at our study pond, we tested the hypothesis that Gray treefrogs indeed show a chorusing pattern typical for prolonged breeders We predicted that (i) calling activity is concentrated in nightly choruses, that (ii) choruses form each evening, and that (iii) interruptions to chorusing would be brief and caused by cold fronts or storms. We scored the recordings (1min every hour) for chorus intensity using the 1-3 point North American Amphibian Monitoring Program (NAAMP) index; non-chorus calling (1-3 individuals) was also scored (as <1). In addition, we gathered weather data from the UWM Field Station weather station. Some of the results deviated considerably from our predictions: (i) Calling activity was not constrained to nightly choruses - rather, 40% of calling activity occurred outside choruses. (ii) Peak chorusing is from 8PM-12PM, but can extend up to 13 continuous hours. As predicted, gray treefrog calling activity was impacted by weather, particularly temperature; males call more around 200C, while calling activity was reduced below 150C or above 250C. This Wisconsin population of Gray Treefrogs shows a temporal pattern of breeding activity more similar to explosive than prolonged breeders. Variation in the temporal pattern of reproduction has important implications for the operation of sexual selection; among other aspects, the opportunity for female choice should be limited in explosive breeders. Future research should examine whether populations in areas with more stable weather conditions show chorusing patterns more typical for prolonged breeders, and whether the strength of sexual selection differs between them.
Calling Activity of Gray Treefrogs: Circadian Patterns of Activity and the Role of Environmental Factors
Union Wisconsin Room
Temporal patterns of breeding activity in frogs are highly variable, and species can be classified as either explosive (breeding <14 >days), or prolonged breeders (breeding >1 month). Eastern Gray Treefrogs (Hyla versicolor) breed for 2-3 months, which should classify them as prolonged breeders. Using data from a long-term recorder stationed at our study pond, we tested the hypothesis that Gray treefrogs indeed show a chorusing pattern typical for prolonged breeders We predicted that (i) calling activity is concentrated in nightly choruses, that (ii) choruses form each evening, and that (iii) interruptions to chorusing would be brief and caused by cold fronts or storms. We scored the recordings (1min every hour) for chorus intensity using the 1-3 point North American Amphibian Monitoring Program (NAAMP) index; non-chorus calling (1-3 individuals) was also scored (as <1). In addition, we gathered weather data from the UWM Field Station weather station. Some of the results deviated considerably from our predictions: (i) Calling activity was not constrained to nightly choruses - rather, 40% of calling activity occurred outside choruses. (ii) Peak chorusing is from 8PM-12PM, but can extend up to 13 continuous hours. As predicted, gray treefrog calling activity was impacted by weather, particularly temperature; males call more around 200C, while calling activity was reduced below 150C or above 250C. This Wisconsin population of Gray Treefrogs shows a temporal pattern of breeding activity more similar to explosive than prolonged breeders. Variation in the temporal pattern of reproduction has important implications for the operation of sexual selection; among other aspects, the opportunity for female choice should be limited in explosive breeders. Future research should examine whether populations in areas with more stable weather conditions show chorusing patterns more typical for prolonged breeders, and whether the strength of sexual selection differs between them.
