Gray treefrogs provide clues to climate change-Females' interpretation of mating calls may not be affected by climate change, could help provide clues to ecosystem management – via Herp Digest

Date: February 2, 2016

Source: University of Missouri-Columbia

According to the National Aeronautics and Space Administration (NASA), and the National Oceanic and Atmospheric Administration (NOAA), 2015 was the hottest year on record. According to a University of Missouri researcher, increasing temperatures and climate variability might have an effect on the sounds produced by gray treefrogs. According to a recent study, scientists found that a female's interpretation of male mating calls may not be affected by climate change; however, knowing how breeding habits are affected can help predict the health of ecosystems. These findings will contribute to the enhanced management practices of ecosystems by federal and state officials.

Gray treefrogs are a common species found in North America and throughout the eastern two-thirds of the country, including Missouri. They're marked by their sticky toe pads that help them cling to windows and by the male mating calls, or trills, which distinguish them on warm, summer evenings.

"In a way, the decline of the polar bear has become the face of climate change; yet, gray tree frogs located in our own backyards might give us better clues about changes in the environment," said Sarah C. Humfeld, a postdoctoral fellow of biological sciences in the MU College of Arts and Science. "Our team wanted to take a look at how rising temperatures might affect how female gray tree frogs interpret the signals given off by males and whether or not that might interrupt their breeding habits."

During mating season, male treefrogs produce calls to attract potential female mates. Females interpret various characteristics of the trilled call to help them locate a high-quality male of the correct species. Scientists have long known that the pitch and rate of trilling can be temperature-dependent, often corresponding to rising or falling temperatures experienced by these cold-blooded animals.

"We already know that there's an optimal range for male mating calls," Humfeld said. "When temperatures rise, the pitch and trill rate of the calls can increase. What we didn't know, was whether or not females' interpretation of those calls were dependent on temperature as well. We were interested in studying whether or not the responses of the female's auditory system shifted in tandem with the male's calls at different temperatures."

The researchers gathered female treefrogs from the field and brought them to the lab. In a controlled environment, they elevated the temperature slightly to simulate a warmer climate. Then, using computer-synthesized sounds, they played back various types of calls to see how the females responded.

"We found that temperature didn't have a great effect on females and their interpretation of the mating call; however, these are still important findings," Humfeld said. "Amphibians are the veritable 'canary in the coal' mine, an indicator species that can send signals to scientists who study the effects of rising global temperatures. Knowing more about how their mating habits are affected by climate change can help us study the ways rising temperatures are affecting biodiversity. Findings from our study help add to the knowledge base needed to study thermal tolerance levels for various species and the steps conservation managers can take to maintain various ecological systems."

The study, "Effects of Temperature on Spectral Preferences of Female Gray Treefrogs (Hyla versicolor)" recently was published in Herptological Conservation and Biology. It can be found at: http://www.herpconbio.org/Volume_10/Issue_3/Humfeld_Grunert_2015.pdf

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The above post is reprinted from materials provided by University of Missouri-Columbia. Note: Materials may be edited for content and length.

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University of Missouri-Columbia. "Gray treefrogs provide clues to climate change: Females' interpretation of mating calls may not be affected by climate change, could help provide clues to ecosystem management." ScienceDaily. ScienceDaily, 2 February 2016. <www.sciencedaily.com/releases/2016/02/160202143743.htm>.

Pesticide Exposure: Is It Reducing Amphibian Populations? - via Herp Digest

PRWeb ,August 20, 2015 2:01pm  

A new study in the journal Herpetologica was conducted to test if the development and survival of Gray Treefrogs would be influenced by a fungal pathogen, an insecticide, or a combination of both. The results demonstrated that larval survival rates were not affected by either malathion or B. dendrobatidis.

(PRWEB) August 20, 2015

Herpetologica – There have been noticeable population declines in both reptiles and amphibians because of habitat destruction and disease. In addition to immune-suppressing insecticides, the fungal pathogen, Batrachochytrium dendrobatidis, continues to invade the natural environment of amphibians and cause widespread disease. A study was conducted to test if the development and survival of Gray Treefrogs would be influenced by B. dendrobatidis, malathion (an insecticide), or a combination of both.

The researchers of an article published in the journal Herpetologica raised Gray Treefrogs from eggs to determine at which larval stage they are affected by B. dendrobatidis and/or malathion. They hypothesized that (1) survival, mass, and time to metamorphosis of the larvae would all be negatively affected by exposure to malathion and B. dendrobatidis; (2) there would be more negative effects with B. dendrobatidis exposure at metamorphosis compared to other subadult periods; and (3) exposure to malathion would increase the impact of B. dendrobatidis during all developmental periods.

The researchers monitored the Gray Treefrogs for 28 days. At 1 week, 3 weeks, and at the time of metamorphosis, frogs were exposed to B. dendrobatidis alone or in combination with malathion. The researchers documented the larval frogs' growth rate, time to metamorphosis, mass at metamorphosis, and time until the tail was completely absorbed. This data was compared to that of healthy Gray Treefrogs.

The results demonstrated that survival rates were not affected by either malathion or B. dendrobatidis. Malathion caused negative effects at metamorphosis, however, that persisted into the frogs' terrestrial phase. On the other hand, B. dendrobatidis did not have a negative effect on the larval growth rate, nor did malathion exposure appear to increase the frogs' vulnerability to fungal disease following exposure to B. dendrobatidis.

The researchers concluded that Gray Treefrogs exposed to insecticides during larval stages do not have a greater risk of disease as a result of exposure to the fungus B. dendrobatidis.

Full text of the article, "How Time of Exposure to the Amphibian Chytrid Fungus Affects Hyla chrysoscelis in the Presence of an Insecticide," Herpetologica, Vol. 71, No. 3, 2015, is now available.