Big Problem in the Big Easy: Invasive Cuban Treefrogs Move into Louisiana

iStock
iStock

Louisiana is now home to one more frog species, and that's a problem. According to Popular Science, scientists have found invasive Cuban treefrogs at a New Orleans zoo, marking the first toehold the amphibians have been able to make in the U.S. outside of Florida.

Cuban treefrogs are native to Cuba, the Cayman Islands, and the Bahamas, but they came to the U.S. in the 1920s by way of the Florida Keys. They have since spread as far north as Jacksonville. The massive frogs—females can grow up to 6 inches long—are major pests, hunting several species of native Floridian frogs and out-competing others, clogging drains and setting up camp in toilets, and occasionally causing power outages when they decide to hide in utility boxes.

Now, the species is showing up in New Orleans, more than 430 miles away. They may have stowed away on a 2016 shipment of palm trees from Lake Placid, Florida bound for the elephant exhibit at New Orleans's Audubon Zoo.

A U.S. Geological Survey in the fall of 2017 captured hundreds of the frogs on and around the zoo's grounds. Over the course of four surveys, USGS scientists found 367 frogs and 2000 Cuban treefrog tadpoles. They drained the two pools where the tadpoles were swimming in the hopes of killing off any they missed, but the likelihood of reversing the spread of the frogs is low. The USGS warned in a recent press statement that "eradicating the recently discovered population in Louisiana is improbable." The frogs reproduce quickly and will eat almost anything. Based on the results of these surveys, it seems they have already driven out all the native frogs in Riverview, the section of Audubon Park where the tadpoles were found.

Brad Glorioso, the lead USGS ecologist on the study, explained that while stowaway treefrogs have trouble surviving when they make their way to higher latitudes, the climate around New Orleans seems to be more hospitable to them. "They often end up in places with unsuitable climates, but in south Louisiana, Cuban treefrogs appear capable of withstanding seasonal cold spells by seeking appropriate refuge," he said.

For now, the best scientists can hope for is keeping the frogs from moving across the river from the zoo into one of the large public nature preserves nearby.

[h/t Popular Science]

Elephants Are Evolving Without Tusks Thanks to Poaching

iStock.com/LeighGregg
iStock.com/LeighGregg

Natural selection can take millions of years to shape a gene pool, but in parts of Africa, the extreme pressures of poaching may have changed elephants in just a few decades. As National Geographic reports, more tuskless elephants have emerged in regions where their ivory has made them a target.

Elephant poaching has long been in a problem Africa, but the crisis reached a fever pitch during Mozambique's 15-year civil war. Between 1977 and 1992, 90 percent of the elephants living in the country's Gorongosa National Park were slaughtered for ivory used to fund the conflict.

The diminished numbers aren't the only thing that looks different about Gorongosa's elephants today. Poachers often kill male elephants first because they have bigger tusks, and once they're eliminated, the hunters will go after females. Typically, about 2 to 4 percent of all female African elephants never develop tusks—but among female elephants that survived Mozambique's civil war, that number is 51 percent. The effects of poaching can also be observed in the next generation. Roughly 32 percent of female elephants born after 1992 are tuskless.

The trend can be seen in other parts of Africa where poaching has ravaged elephant populations. In Ruaha National Park in Tanzania, elephant behavior researcher Josephine Smit has observed that over one fifth of female elephants older than 5 years lack tusks. Tusklessness rates reach about 35 percent in females over 25.

The statistics are even harder to ignore in South Africa's Addo Elephant National Park, where tuskless animals made up 98 percent of all female elephants in the early 2000s. South Luangwa National Park in Zambia, Lupande Game Management Area in Zambia, and Queen Elizabeth National Park in Uganda each reported higher-than-average rates of tusklessness immediately following the ivory wars of the 1970s and '80s.

Though poaching is on the decline thanks to bans on the ivory trade and other conservation efforts in Africa, its impact can still be felt. In East Africa, the elephant population was nearly halved between 2008 and 2018. The establishment of wildlife preserves, DNA tracing, and GPS tracking are just a few of the ways conservationists are working to crack down on poachers and restore the species.

[h/t National Geographic]

This Map Shows All the Trees in New York City

Tim Wallace/Descartes Labs
Tim Wallace/Descartes Labs

Trees may not be the first thing that comes to mind when you picture big cities, but they're an essential part of many urban landscapes. By maintaining a healthy tree population, a city can clean the air, provide shade to buildings, and improve the quality of life of its residents.

To quantify the impact trees have, officials first need to keep track of how many grow within city limits—a task that's harder than it sounds. Even with thousands of volunteers working on the ground, tallying all the trees in a city like New York can take years, according to City Lab, and such surveys often don't account for the trees growing in parks or on private property. Using artificial intelligence, researchers at the geospatial analytics startup Descartes Labs have found a way to map all the trees in major cities without taking to the streets.

To make the New York tree map below, Descartes programmed a machine learning model to identify tree canopies from satellite images. This isn't as easy as pinpointing green spots: The program had to be taught to distinguish trees from other greenery, like grass and shrubs, using artificial intelligence. This sets it apart from other tools used to map vegetation like the Normalized Difference Vegetation Index (NDVI), which only accounts for light wavelengths, not height.

Map of New York City's Trees.
Tim Wallace/Descartes Labs

When applied to New York, the tree-mapping technology provides a different view of the city. Some of the most heavily trafficked areas, like downtown Brooklyn and Times Square, are blank spaces on the map. Not surprisingly, parks like Forest Park in Queens and Central Park in Manhattan have the densest concentrations of trees, but some affluent neighborhoods, like the West Village and the Upper East Side, also have plenty of greenery.

New York's vegetation may be impressive by some city's standard, but it's nothing compared to what it was 400 years ago. Here's what Manhattan looked like in 1609.

[h/t City Lab]

SECTIONS

arrow
LIVE SMARTER