Bullfrogs and other Super Species – Will They Soon Dominate Our Planet?

Super species are the phenomenally successful invasive creatures—animals, plants, and microbes—that are dominating ecosystems around the globe. Feral pigs are relentlessly trampling across Europe, North America, and Australia. Jellyfish are dominating the world’s oceans, clogging fishing nets. Not to mention the invasive species that are in our own backyards:  house sparrows and eastern gray squirrels.

In Super Species: The Creatures That Will Dominate the Planet (Firefly Books, published October 2010) Garry Hamilton details the fascinating stories of the species that seem to have won the natural selection sweepstakes. Some of these super species include the European green crab, the giant African land snail, the Argentine ant, nutria, zebra mussels, the chytrid fungus, and killer algae.

One of the species he describes, the invasive American bullfrog, especially concerns us at Frogs Are Green. Hamilton contends that bullfrogs are more invasive than Australia’s notorious cane toads. The reasons are many—bullfrogs were shipped around the world for use as biological control agents, as pets, or for sport.

Frog farms have also led to their introduction to nonnative areas. In the late 1800s after gold miners out West ate their way through native frogs, entrepreneurs imported American bullfrogs from back East to satisfy the increasing demand. Eventually farming bullfrogs spread to other parts of the world as well.

As Hamilton describes it, bullfrog farming isn’t easy and many of the frogs in these “farms” were let loose. Most frogs wouldn’t have survived. But like many invasive species, bullfrogs are highly adaptable. Bullfrogs like deep, stable, non-moving aquatic habitats. This describes many human-modified environments: reservoirs, farm ponds, irrigation channels, and even garden water features.

Bullfrogs can survive through cold Ontario winters and the extreme heat of Southern U.S. summers. Female bullfrogs can produce between 6000 and 7000 eggs and as they mature, up to 25,000 eggs per clutch. As carnivorious amphibians, they prey on fish, water beetles, snails, turtles, bats, voles, ducklings, snakes, lizards, and salamanders.

Bullfrogs compete with and prey on native frogs. This is one of the contributing factors to the worldwide decline of amphibians. Bullfrogs may also be helping to spread the deadly chytrid fungus, which is devastating frog populations around the world.

Attempts to deal with invasive bullfrogs have been challenging. But scientists have found that their numbers are fewer in waterways that haven’t been altered by people. As Hamilton writes, “By changing the physical parameters of a freshwater wetland, humans also change the playing field for all life-forms in the ecosystem, and this results in a cascade of ecological readjustments.”

The answer, Hamilton contends, is not to use the old methods such as killing the frogs and draining ponds. Rather, he says that in order to save native frogs, we need to save their habitats. Altering habitats is conducive to an invasion of bullfrogs.

I had mixed feelings reading about invasive bullfrogs. I like coming across them in ponds in the woods of upstate New York (one of their original habitats), their eyes peering just above the water, as they croak a bass jug-a-rum sound. One of my favorite frog books, The Frog Book, written in 1906 by naturalist Mary Dickerson, describes the bullfrog:

If we go rowing on river, lake, pond or park lagoon,  some moonlit night late in late June, we are certain to hear the deep-toned call of the Bullfrog many times. Coming as it does at unexpected intervals  and from unexpected directions, it seems startlingly weird in the quiet of the night. For June nights are quiet. The insect orchestras are not in full swing and the frog choruses have disbanded.

During Dickerson’s time, bullfrogs were less common than other frogs. At that time, they had many natural predators to keep them in control: snakes, otters, hawks, owls, herons, and turtles, and frog farming was mainly in the future. But human intervention tipped the balance.

In Super Species, Hamilton documents the story of many species like bullfrogs in which human intervention and alterations of habitats led to an imbalance. But his tone isn’t hysterical. Some invasive species like the plant kudzu, he contends, don’t actually have much of an impact on local biodiversity despite alarmist news stories. These species may actually be creating a new biosphere from the “rubble of our own destruction.”

This review is part of Ecolibris’s  Green Books Campaign.  Today at 1:00 p.m. ET, 200 bloggers will take a stand to support books printed on recycled or FSC-certified paper by simultaneously publishing reviews of 200 such books. By turning a spotlight on books printed using environmentally-friendly paper, Ecolibris wants to raise the awareness of book buyers to this issue and to encourage them to take it into consideration when purchasing books.


U.S. Agency Proposes Legislation to Help Stem Spread of Chytrid Fungus

In an effort to stem the spread of the deadly chytrid fungus that is wiping out amphibian populations, the U.S. Fish and Wildlife Service (FWS) is considering banning the importation of amphibians and their eggs without a permit certifying the animals are disease-free. The chytrid fungus has caused the extinction of at least 200 amphibian species and continues to be one of the greatest threats to amphibians.

Northern Leopard Frog, a North American native species

In a statement, Rowan Gould, Acting Director of the U.S. Fish and Wildlife Service, said,

The worldwide decline of amphibians is of great concern to us. Chytrid is attributed as a major cause of this amphibian mortality. We understand that halting the spread of the fungus or eradicating it will take more than just regulating importation and transportation of infected amphibians, but it is a major step in the right direction.

According the the FWS website, under the Lacey Act, the Department of the Interior is authorized to regulate the importation and interstate transport of wildlife species determined to be injurious to the welfare and survival of native wildlife. Current regulations prohibit the release into the wild of all species of live amphibians or their eggs, except as authorized. But, of course, this law isn’t easily enforced. Many pet frogs are let “free” in local ponds, potentially infecting native species.

A listing under the Lacey Act would not affect a person or institution that currently owns an amphibian and does not transport it to another state or U.S. territory.

At FROGS ARE GREEN, we applaud this proposed legislation and feel it would be a huge step toward controlling the spread of the chytrid fungus that threatens the survival of so many amphibian species, including native species listed under the Endangered Species Act.

The FWS is seeking input from the public. You can leave a comment until December 16, 2010. Please take a few minutes to comment and to show your support for a measure that will genuinely help amphibians.

More information: Statement from the U.S. Fish and Wildlife Service

Information from Save the Frogs about the frog legs trade and the spread of infectious diseases.


Teach Your Children Well (about nature): Father's Day Thoughts

A couple of months ago, we received a lovely email from a reader named Marty who lives in in Eastern Pennsylvania (Lehigh County) one hour south of the Pocono Mountains.  Here’s part of the email:

What’s  the best thing I can do as a Dad to teach my children to preserve these treasures [frogs and salamanders] that are so dear to me. My grandfather taught me the love of wild places and I want to pass that on to them.

I wish more dads were thinking about how they could introduce nature to kids. My sons are in their twenties and still love learning about wildlife and animals. I think most of this love of nature came from their father. So I’m offering a few suggestions. But we’d like to open this up to readers of Frogs Are Green and get your ideas also. How did your father encourage your love of nature? What are you doing as a dad to instill a love of nature in your kids.

photo by Mary Jo Rhodes

Here are some ideas:

• take them on short hikes or walks into the woods, starting when they are very young. (Here is a list of state parks). Young children need no encouragement to love nature—everything around them is still magical and interesting (bugs, stones, flowers).  The key is to keep taking them on walks in the woods throughout their childhood, even when they start saying it’s boring (the preteen years). You might have to add other incentives during the rougher times (a trip to an ice cream store afterwards or some other treat).

• Your child might start to like one animal and that may become their animal. Encourage this by buying books about the animal, plush toys, trips to see the animal in the wild (whale watching trips, for example), or in zoos or aquariums.  You can adopt various wild animals for $25 or so, and this will give your child a personal connection to the animal (we adopted a whale when our sons were young).

• Plan family vacations around national parks rather than amusement parks. We’ve visited a number of national parks over the years. These are fun because the trails through them are easy and well worn, there’s a certain familiarity to them (the park rangers, the gift shops, etc), and the scenery is spectacular. You can buy a passport for your child and have it stamped in each national park you go to.

• Share you enthusiasm about nature, but don’t be too heavy handed about it. If kids feel you are always teaching them, they might get turned off. Instead, share your sense of wonder. Point out a cardinal (look at that red bird!), but don’t turn it into a lesson about birds.

• The National Wildlife Federation has ideas about enjoying nature with children, including setting up a tent in your backyard and sleeping outside. I did this a few times as a kid in my suburban backyard (without the tent), and loved it. If you’re lucky enough to live in a place far from cities, you can stargaze with your children, pointing out a few constellations.

• as far as our amphibians friends….the best places that we’ve found to see them are state parks. Unlike Marty, we live in an urban area and it’s tough to find amphibians in a region where all the land has been developed. But state parks and wildlife refuges that have been left untouched, with ponds and swamps, are great places to see them. Tell your kids to look out for frogs, toads, and salamanders. Kids are closer to the ground and have sharper eyes and will most likely see them before you do. You can also build a frog pond in your backyard.

Dads: Please send along your ideas as well for introducing children to nature! Happy Father’s Day!


Cane Toads Invade Sundance!

Susan and I are both eager to see filmmaker Mark Lewis’s Cane Toads: The Conquest, which has received good reviews at the Sundance Film Festival. This film, in 3-D,  is a follow-up to his cult favorite of 25 years ago, Cane Toads: An Unnatural History.

Here’s a description of the film from the website:

Shot against the harsh and beautiful landscape of northern Australia, Cane Toads: The Conquest tracks the unstoppable journey of the toad across the continent. Director Mark Lewis injects his trademark irreverence and humor into the story as he follows a trail of human conflict, bizarre culture and extraordinary close encounters.

Filmed with high-resolution 3D technology, Cane Toads is the first Australian digital 3D feature film.  Custom designed equipment allows viewers to get up close and personal with these curious creatures like never before. The unique viewing experience is like being immersed in the world of the toad.

Cane Toads were introduced to Australia in 1935 to control sugar cane larvae. Unfortunately they didn’t do that—instead this adaptable toad has thrived without natural predators and now numbers in the millions. The toads are poisonous when eaten by other animals, including native species and pets. They’ve caused other problems as well (for example, they eat the insects that other animals, such as skinks, depend on). Clearly, the importation of cane toads into Australia has been a huge ecological disaster.


Cane Toads: The Conquest isn’t a conventional animal documentary.  According to the film’s website:

[Cane Toads] is a truly poignant environmental cautionary tale on the issue of invasive species and human folly. Some will see this story as a tragedy, some a comedy of errors, and still others a heroic journey across a harsh yet beautiful continent. As the world wrestles with the idea that we have irretrievably altered our own ecosystem, these bulbous creatures may be the ultimate metaphor for the inevitable path upon which we have set ourselves.

For more information, watch Anne Thompson’s interview with Mark Lewis on her blog TOH! Thompson on Hollywood. Susan I and hope a major distributor picks up the film so we can see it in our area!


Pacific Chorus Frogs Spend the Holidays in Alaska

This holiday season, some Alaskans found “live” ornaments on their Christmas trees—Pacific Chorus frogs that hitchhiked in the trees to Alaska.

Coutesy of the Alaska Department of Fish and Game

Courtesy of the Alaska Department of Fish and Game

Unfortunately, these little stowaways were not warmly received by the Alaska Department of Fish and Game. They are considered invasive species as they might carry fungi and viruses that could harm native frog species.

I imagine these frogs would be happier if they were sent home. Pacific Chorus frogs are native to Pacific coastal areas from Baja California up to Washington State. According to Lang Elliott in The Frogs and Toads of North America, its familiar two-part call, rib-bit, is the one most associated with frogs because they have provided the background “music” for so many Hollywood movies and TV shows.

Here’s the call of the Pacific Chorus frog in its native habitat—far from Juneau.