Todd McLeish: Pandemics threaten amphibians, too

Green frogs

— Photo by Todd McLeish

From ecoRI News (ecori.org)

As frogs and salamanders emerge from winter hibernation and migrate to their breeding ponds, herpetologists throughout the region are paying close attention to the growing number of diseases threatening amphibians in the Northeast.

The most worrisome is an infectious fungal disease called chytridiomycosis, or chytrid, which has caused major die-offs of frog populations in the tropics and elsewhere and is blamed for numerous frog extinctions in Latin America.

According to University of Rhode Island herpetologist Nancy Karraker, chytrid grows on the skin of frogs, and when it’s found on their drink patch — a site on their belly where they absorb water into their bodies — the fungus makes it impossible for the frogs to regulate how much water they absorb, causing them to become desiccated and die.

“Chytrid has been found in multiple species of frogs in the Northeast, but we haven’t seen massive die-offs here,” said Karraker, a University of Rhode Island associate professor of natural resources science who has studied frogs around the world. “But that doesn’t mean that die-offs haven’t occurred, just that they haven’t been at the scale we’ve seen in South America. So we can’t say it’s not a problem here, and it certainly could become a serious problem.”

Some scientists believe that the disease originated in African clawed frogs, which were shipped around the world for use in human-pregnancy tests from the 1940s to the ’60s. Many of the frogs escaped from captivity and could easily have spread the disease to native frogs in many places. Other scientists believe the fungus was ubiquitous around the globe and that, initially, the only frogs that died were those with compromised immune systems.

“I don’t know where the greatest weight of support is for those ideas today,” Karraker said. “But maybe our frogs aren’t as susceptible because they’re not facing the kinds of stressors that may have impacted frogs in other places. Or it could be something to do with their natural history. We just don’t know, and that’s partly why I’m worried.”

In 2010, Antioch University New England graduate student Mandy Gaudreau, working in collaboration with Lou Perrotti, conservation director at Roger Williams Park Zoo, in Providence, swabbed 47 frogs and toads at 11 sites in Rhode Island and detected chytrid in 21 percent of the samples.

“What struck me about her results is that most of the ponds where she found chytrid were manmade ponds — farm ponds, retention ponds,” Perrotti said. “Why was it in those and not in the natural wetlands?”

He also wonders whether climate has an effect.=

“Frogs in Panama got wiped out. Costa Rica got wiped out. It seems like it’s worst at that certain temperature range,” Perrotti said. “Maybe our winters knock it back and keep it from becoming prevalent. Tropical frogs don’t have the seasonality that we have here.”

Chytrid, however, isn’t the only disease threatening amphibians and reptiles in the Northeast.

Scott Buchanan, a herpetologist at the Rhode Island Department of Environmental Management’s Division of Fish and Wildlife, is particularly concerned about ranavirus, an infectious disease that has caused die-offs of reptiles, amphibians, and fish in 20 states, including box turtles in the Northeast.

In frogs and toads, it especially affects the tadpole stage, causing skin hemorrhages, erratic swimming, buoyancy problems, and the inability to right themselves in the water.

“We know it’s here, it’s in our environment, but if and when it becomes active is hard to predict,” he said.

Buchanan is also tracking a fungal disease in snakes, a herpes virus in turtles, and chytrid in salamanders.

“Salamander chytrid has had devastating effects on salamanders in Europe over the last five to ten years, and it’s considered an eventuality that it will be brought into the U.S. one way or another and run through our salamanders,” he said. “The eastern U.S. is a global hot spot of salamander diversity, and a lot of research is going on now to determine how virulent it is, are particular species susceptible, and what are their natural defenses.”

“What’s notable for us,” Karraker said, “is that it’s usually really hard to change the rules for importing animals for the pet trade, but in 2016, legislation was passed that prevented the import of 201 species of salamanders to prevent the introduction of the disease into the U.S. That’s a landmark bit of legislation to protect our native species.”

Buchanan said it’s up to biologists and others working in area wetlands to follow strict protocols to prevent the spread of the diseases, such as regularly disinfecting their boots, equipment, and tools as they move from site to site around the region.

“We have to be vigilant about potentially transferring diseases from one wetland to another,” he said. “Because we move from one wetland to the next throughout the day and throughout the season, there’s real potential that we could move it around with us, and we often go to the most important sites and monitor the most sensitive species.

“It’s something we take really seriously. We know how quickly things can change here, we know disease pandemics can happen quickly, move around quickly, and cause devastating impacts on populations. And if it doesn’t wipe them out completely, it can take decades for them to recover.”

Todd McLeish, an ecoRI News writer, also runs a wildlife blog.

Tadpoles

Todd McLeish: Be careful -- salamanders, frogs on the march

A spotted salamander.

Via ecoRI News (ecori.org)

During last month’s warm spell, Emilie Holland saw and heard something she seldom detects this early in the year: the first movement of frogs and salamanders from their woodland wintering grounds to their springtime breeding pools. She observed wood frogs, spring peepers, spotted salamanders, and even a rare marbled salamander near her house not far from the Great Swamp Wildlife Management Area in South Kingstown, R.I.

“We often get pretty early activity here,” said Holland, an environmental scientist for the Rhode Island Department of Transportation and a board member of the Rhode Island Natural History Survey. “For whatever reason, the micro-climate is good for them. The problem is that my hot spot is along a road, and the frogs and salamanders are often crossing it.”

During the same warm days last month, other observers reported hearing spring peepers in North Kingstown and Cumberland, and seeing a red-backed salamander in Middletown.

According to amphibian expert Lou Perrotti, director of conservation at Roger Williams Park Zoo, frogs and salamanders don’t typically migrate to their breeding ponds until mid-March in most areas of the state. During the cold winter of 2015, when many ponds were still frozen until April, amphibian migration was delayed by almost a month. But it’s not unusual for rain showers during an especially warm period in late February to trigger an early migration.

“When that happens, the migration period tends to get extended,” Perrotti said. “A snowstorm or cold snap shuts things down for a while, and then it picks back up again. You don’t have the usual massive explosion of breeding activity all at once. It trickles along instead.”

What happens to the frogs in the ponds when the cold returns and the ponds freeze over again? Not much. Perrotti said the animals are adapted to survive such conditions for short periods of time. In fact, University of Rhode Island herpetologist Peter Paton said he commonly sees wood frogs and spotted salamanders swimming beneath the ice of local ponds in late winter. And wood frogs are uniquely adapted to freeze solid and thaw out later with no negative consequences.

The bigger concern, as Holland expressed, is that many frogs and salamanders must cross roads to reach their breeding ponds, and untold thousands of them get run over by vehicles each year in Rhode Island during those journeys.

“It’s a huge problem, one of the biggest threats to amphibians and reptiles in the area,” Perrotti said. “I’ve seen nights where there were hundreds of smashed wood frogs at just one site. Toads get hammered, too, because they typically have huge breeding explosions over a period of two or three nights. And gray tree frogs, too, which are pretty clumsy on the ground.”

Amphibian movement to and from their breeding ponds will likely continue through April – some species, such as green frogs, migrate later than others — but it typically happens at night when it’s raining. Perrotti and Holland recommend driving carefully at night along back roads in wetland areas during rain showers.

“It’s hard to avoid every frog in the road, especially if you catch it on a good night for migration when they’re everywhere,” Perrotti said.

One strategy that Perrotti said has been employed in western Massachusetts to avoid the problem of amphibian roadkill is the installation of what he calls “salamander tunnels” beneath roadways in areas where large numbers of frogs and salamanders migrate across roads. Barriers along the roadside funnel the animals toward the tunnel, which avoids much of the mortality.

The idea has been discussed in Rhode Island, but the cost is high and finding funding in municipal budgets is an impediment. Signage encouraging drivers to slow down at certain locations is another strategy that officials in the state have considered, though few have been installed to date.

Holland noted that homeowners with sump pumps should regularly check the system for amphibians that wander in and can’t escape.

“I’m constantly fishing salamanders and frogs out of mine,” she said. “People should monitor the sump in their basement and maybe they can keep a local breeding population healthy by not letting the adults die in a pitfall trap that they didn't even know they had.”

Those interested in learning more about local amphibians and participating in a related citizen science project should consider signing up for FrogWatch, a national program administered locally by Roger Williams Park Zoo. Volunteers attend a training program to learn the breeding calls of the various frog species that reside in Rhode Island, then visit a designated pond in the evening once a week from March through August to document breeding activity.

Rhode Island resident and author Todd McLeish runs a wildlife blog.