Native Delaware: Seasonal Symphony of Frog Calls Returns

April 19, 2013 under CANR News

On April nights, Holly Niederriter can be found driving slowly down the back roads of New Castle County. Although she appears to be meandering, her excursions are quite purposeful.  A wildlife biologist with the Delaware Department of Natural Resources and Environmental Control, Niederriter is listening for frog calls.

She is one of dozens of Delawareans who drive around after dark searching for frogs as part of the Delaware Amphibian Monitoring Program. The first survey period kicked off in late February, the second starts in a few days, and the final survey occurs in June. Participants are volunteers from the community; most don’t have Niederriter’s wildlife savvy. But they all receive training, and before their debut, take an online quiz to ensure they can distinguish the calls of Delaware’s 16 species of frogs.

American toad by Jim White“Frog calls are an important way to determine where different species occur and how populations are doing over time,” says Niederriter.  “Because most amphibians need both aquatic and upland habitats, they can serve as important indicators of water quality and other aspects of environmental health.”

A colder-than-average early spring made for a slow start to the frog-calling season.  Early April is often the peak of spring peeper season, when the sleigh-bell-like chorus of these tiny frogs reaches maximum volume in vernal pools and marshes. But the beginning of this month was so chilly that the peepers didn’t want to peep.

“Male peepers call to attract a mate but if the weather isn’t warm enough they hunker down and wait it out,” says Jim White, associate director for land and biodiversity management at the Delaware Nature Society and an adjunct herpetology instructor at the University of Delaware. “I didn’t hear a single peeper during the first few days and nights of April.”

Now that temperatures are more seasonal, the spring peepers are out in full force. Recently, they’ve been joined by the pickerel frog, with its snore-like call, and the American toad, which boasts a musical trill. In the Coastal Plain region (Kent and Sussex, plus a sliver of New Castle County), you also can enjoy the throaty croak of the Southern leopard frog.

You need a sharp ear to recognize the call of the American toad, notes Jake Bowman, a UD professor of entomology and wildlife ecology.

“American toads are frequently heard all over our area but rarely do people realize what they are hearing,” he says. “Unlike the commonly recognized sleigh bell call of the spring peeper, the American toad has a high pitched trill. Here on the UD campus, you can find them in most of the wetlands on our farm.”

A father of two sons, Lee, 10 and Ethan, 5, Bowman likes the fact that frogs are “kid-friendly.”

“Probably the nicest thing about toads is that it’s often the only amphibian kids have a chance to handle. My boys love the chance to chase and capture American toads and learn more about them,” he says. “After the boys have checked out the toads, we release them back where we found them.”

Like the Bowman boys, James White, Jr. grew up playing with frogs with his father, Jim White. Now a UD freshman, White is majoring in wildlife conservation and hopes to become a national park ranger.

“For as long as I can remember, I went looking and listening for frogs every rainy, spring night,” says White. “We had a marsh only a few yards from our house so it was never difficult to hear them.”

“I will go herping with my father but because of college it probably won’t be until school is out,” he says. “My favorite frog of spring is the pickerel frog. I always found them pretty frogs and very jumpy, making them a challenge to catch.”

If you want to catch frogs with your kids (or at least see and hear them), Bowman has a few suggestions. Look for terrestrial species on the ground in woodlands and other land habitats. Semi-aquatic species can be seen on the shoreline or surface of freshwater habitats. To find breeding frogs, head to vernal pools and marshes. Warm, rainy nights make for the very best frog-watching. Pack a bright flashlight and plenty of patience.

A spring peeper, for example, is only about an inch long and its brown, gray and green colors don’t stand out, especially at night. “You can practically be on top of them and still not see them,” notes Bowman.

But it’s worth the wait to see a peeper, especially a male one. Males have large vocal sacs under their chins that they pump full of air until they look like balloons about to burst, When they peep, the air is discharged and the shiny sac deflates.

How to Help

To learn more about volunteering with the Delaware Amphibian Monitoring Program, contact Vickie Henderson at 735-8651 or vickie.henderson@state.de.us

Article by Margo McDonough

Photo by Jim White

Share

Tunisian Fulbright Scholar studying beneficial bacteria for legumes

May 29, 2012 under CANR News

At first glance, it wouldn’t seem like Delaware and the Sahara Desert have a lot in common. However, on closer inspection, the mid-Atlantic state and the arid regions of southern Tunisia in Africa are more similar than they first appear.

That is one reason why Mokhtar Rejili, a professor from the University of Gabes in Tunisia, is excited to be at the University of Delaware on a Fulbright Scholarship working with UD’s Janine Sherrier on the study of legumes native to his home country.

Of the similarities between the two seemingly disparate locations, Sherrier, a professor in the Department of Plant and Soil Sciences in UD’s College of Agriculture and Natural Resources, explained that Delaware has sandy soil and shoreline salt stress. “Our sandy soils dry out very rapidly and our crop plants can be subject to salt stress. There are also common stresses experienced by plants grown in the two locations, albeit to different levels of severity,” she said.

The scientists are collaborating on research to identify beneficial bacteria to help the plants grow more successfully under conditions of drought and salt stress. Rejili specifically studies legumes that grow in conditions of extreme drought and severe salt stress, and his Tunisian team identifies bacteria that interact with the plant roots growing on the outskirts of the Sahara.

Sherrier is recognized internationally as a scientific expert on bacterial interactions with legumes, and together, the two scientists are working on a research project that will help farmers in Tunisia and Delaware.

The scientists are conducting research that focuses specifically on the type of beneficial bacteria that associate with legume roots and provide nitrogen to the plant. Nitrogen is an essential nutrient for plant growth, and it is often provided to the plant by the application of chemical fertilizers or manure. This is costly for growers and contributes to environmental pollution.

The beneficial bacteria studied by the team can convert a small amount of the nitrogen that is naturally abundant in the Earth’s atmosphere into a form that can meet the nutritional needs of the plant. This reduces the cost of crop production for the grower and also protects the environment from damage caused by fertilizer runoff from agricultural fields.

“The plants form close relationships with the beneficial microbes. They develop a new organ on their roots for the bacteria to reside and provide the right environment and all the energy required for the bacteria to convert atmospheric nitrogen into fertilizer,” Sherrier said. “At a practical level, that means plants growing in soils without sufficient nitrogen can still have productive growth.”

Benefits to health and the environment

Rejili explained that this is especially important for extremely hot and dry areas, like southern Tunisia, where a chemical fertilizer would be of little help to the plants. Such fertilizers are often too expensive to even consider using and, worse, can be detrimental to human health.

“The fertilization of crops is limited to only the well-developed countries,” said Rejili, noting the high costs involved in producing fertilizer, only a small fraction of which is used by the plant. The remainder goes deep into the soil, where “it will contaminate the soil and the water, or it will evaporate into the atmosphere, leading to pollution,” he said, adding this poses “a big question to our health.”

Sherrier said that fertilizer use doesn’t pose a health risk just in Tunisia, it does so in America as well.

“The overuse of fertilizer impacts human health,” said Sherrier, explaining that a recent Environmental Protection Agency (EPA) survey of well water quality in Delaware’s southern counties showed that more than 50 percent of the wells had nitrogen contamination above the levels recommended for drinking water and required remediation.

Sherrier said that while Rejili is interested in helping out his home country, he is also concerned about improving crop production and health for Delawareans.

“People from Delaware love their lima beans, but the beneficial bacteria are not present at very high levels in our soils. Our growers add fertilizer to ensure a good yield. That’s expensive for them, and it’s not good for our environment,” said Sherrier, adding that Rejili has taken on a leadership role on one of her projects to identify beneficial bacteria from Delaware soils that could be added to the soil early in the growth season instead of chemical fertilizer.

Sherrier also explained that the damage to the environment is not just in the fertilizer application, it’s also in the way fertilizer is made. “There’s a huge energy cost associated with making fertilizer,” said Sherrier, explaining that the process requires high pressure and high temperatures, and uses 4 percent of the world’s natural gas supply annually.

“When you burn that natural gas, it releases carbon dioxide into the atmosphere,” she said, adding that there are additional environmental costs in transporting the fertilizer.

Inexpensive option

Besides the environmental and health considerations of cutting down on fertilizer use, the beneficial bacteria could also be an inexpensive option for growers, something that is of particular importance in developing countries.

“We would like to provide whatever help we can to allow the people of Tunisia to support their own food production,” Sherrier said. “Food security is a huge concern for any country. This inexpensive approach to food production protects their environment and helps provide the people with a basic level of security that every human being deserves.”

Providing an inexpensive and reliable food source for developing countries is not the only benefit of this research, however. Being able to grow legumes in areas that have harsh landscapes, like southern Tunisia, will enable the growth of forage crops in areas prone to desertification. This will allow livestock to graze in the area, and will help stabilize a sandy landscape that is prone to degradation from unforgiving winds.

“If you have a few plants that can survive in that area, they can protect soils and prevent the region from converting into desert. This will help preserve the land for food or forage production,” explained Sherrier.

Beneficial bacteria

Sherrier worked closely with the U.S. Department of Agriculture (USDA) and the Delaware Department of Natural Resources and Environmental Control (DNREC) to arrange for the team to study Tunisian plants in her Delaware laboratory. For some of the species, it is the first time that these legumes will be studied outside of Tunisia.

Rejili is evaluating the diversity of bacteria associated with these plants and performing experiments to determine which ones provide the most benefits. In a laboratory setting, the team is inoculating plants with individual strains of beneficial bacteria and evaluating the plant’s performance.

“The bacteria infect the plant root,” Sherrier said, “and when you talk about an infection, most people think, ‘Oh, no! You need to spray something to get rid of that.’ However, in undisturbed natural environments, the bacteria normally infect the plants, boosting their immune systems and helping the plants acquire essential nutrients. This is very similar to the benefits people gain from the bacteria which naturally reside in our digestive tract.”

Said Rejili of the plant interacting with the bacteria, “We can say they are beneficial interactions. So the plants give carbohydrates to bacteria and bacteria gives nitrogen to the plants. So there is an exchange.”

The two hope that when Rejili’s 10-month stay concludes, they can continue their collaboration. “This is a great starting point, and it’s really what the Fulbright progam is all about,” said Sherrier. “It’s helping to build bridges scientifically and culturally.”

Article by Adam Thomas

Photo by Danielle Quigley

This article can also be viewed on UDaily

Share