Tag Archives: invasive species

Invasive Pythons Decimating Native Species in the Everglades

By Kim Smiley

Have you ever dreamed of hunting pythons?  If so, Florida is hosting the month-long 2016 Python Challenge and all you need to do to join in is to pay a $25 application fee and pass an online test to prove that you can distinguish between invasive pythons and native snake species.

The idea behind the python hunt is to reduce the population of Burmese pythons in the Florida Everglades.  As the number of pythons has increased, there has been a pronounced decline in native species’ populations, including several endangered species.  Researchers have found that 99% of raccoons and opossums have vanished along with 88% of bobcats, along with declines in nearly every other species.  Pythons are indiscriminate eaters and consume everything from small birds to full-grown deer.  The sheer number of these invasive snakes in the Florida Everglades is having a huge environmental impact.

The exact details of how pythons were released into the Everglades aren’t known, but genetic testing has confirmed that the population originated from pet snakes that were either released or escaped into the wild. Once the pythons were introduced into the Everglades, their number quickly grew as the python population thrived.  The first Burmese python was found in the Florida Everglades in 1979 and now there are estimated to be as many as 100,000 of the snakes in the area.

There are many factors that have led to the rapid growth in the python population.  They are able to live in the temperate Florida climate, have plentiful food available, and are successfully reproducing.  Pythons produce a relatively large number of eggs (an average of 40 eggs about every 2 years) and the large female python protects them.  Hatchling pythons are also larger than most hatchling snakes, which increases their chance of surviving into adulthood.  There are very few animals that prey on adult pythons.  Researchers have found that alligators occasionally eat pythons, but that the relationship between these two top predators can go both ways and pythons have occasionally eaten alligators up to 6 feet in length.  The only other real predators capable of taking down a python are humans and even that is a challenge.

Before a python can be hunted, it has to be found and that is often much easier said than done. Pythons have excellent camouflage and are ambush predators that naturally spend a large percentage of the day hiding.  They also are semi-aquatic and excellent climbers so they can be found in both the water and in trees.  Despite their massive size (they can grow as long as 20 feet and weigh up to 200 pounds), they blend in so well with the environment that researchers even have difficulty finding snakes with radio transmitters showing their locations.

The last python challenge was held about 3 years ago and 68 snakes were caught.  While that number may not sound large, it is more snakes than have been caught in any other month.  The contest also helped increase public awareness of the issue and hopefully discouraged any additional release of pets of any variety into the wild.  For the 2016 contest, officials are hoping to improve the outcome by offering prospective hunters on-site training with a guide who will educate them on swamps and show them areas where snakes are most likely to be found.

To view a Cause Map, a visual root cause analysis format, of this issue click on “Download PDF” above.  A Cause Map intuitively lays out the cause-and-effect relationships that contributed to the problem.

You can check out some of our previous blogs to view more Cause Maps for invasive species if you want to learn more:

Small goldfish can grow into a large problem in the wild

Plan to Control Invasive Snakes with Drop of Dead Mice

Small goldfish can grow into a large problem in the wild

By Kim Smiley

Believe it or not, the unassuming goldfish can cause big problems when released into the wild.  I personally would have assumed that a goldfish set loose into the environment would quickly become a light snack for a native species, but invasive goldfish have managed to survive and thrive in lakes and ponds throughout the world.  Goldfish will keep growing as long as the environment they are in supports it.  So while goldfish kept in an aquarium will generally remain small, without the constraints of a tank, goldfish the size of dinner plates are not uncommon in the wild. These large goldfish both compete with and prey on native species, dramatically impacting native fish populations.

This issue can be better understood by building a Cause Map, a visual format of root cause analysis, which intuitively lays out the cause-and-effect relationships that contributed to the problem.  A Cause Map is built by asking “why” questions and recording the answers as a box on the Cause Map.  So why are invasive goldfish causing problems?  The problems are occurring because there are large populations of goldfish in the wild AND the goldfish are reducing native fish populations.  When there are two causes needed to produce an effect like in this case, both causes are listed on the Cause Map vertically and separated by an “and”.   Keep asking “why” questions to continue building the Cause Map.

So why are there large populations of goldfish in the wild?  Goldfish are being introduced to the wild by pet owners who no longer want to care for them and don’t want to kill their fish.  The owners likely don’t understand the potential environmental impacts of dumping non-native fish into their local lakes and ponds.  Goldfish are also hardy and some may survive being flushed down a toilet and end up happily living in a lake if a pet owner chooses to try that method of fish disposal.

Why do goldfish have such a large impact on native species?  Goldfish can grow larger than many native species and they compete with them for the same food sources.  In addition, goldfish eat small fish as well as eggs from native species.  Invasive goldfish can also introduce new diseases into bodies of water that can spread to the native species.  The presence of a large number of goldfish can also change the environment in a body of water.  Goldfish stir up mud and other matter when they feed which causes the water to be cloudier, impacting aquatic plants.  Some scientists also believe that large populations of goldfish can lead to algae blooms because goldfish feces is a potential food source for them.

Scientists are working to develop the most effective methods to deal with the invasive goldfish.  In some cases, officials may drain a lake or use electroshocking to remove the goldfish.  As an individual, you can help the problem by refraining from releasing pet fish into the wild.  It’s an understandable impulse to want to free an unwanted pet, but the consequences can be much larger than might be expected. You can contact local pet stores if you need to get rid of aquarium fish; some will allow you to return the fish.

To view a Cause Map of this problem, click on “Download PDF” above.

Plan to Control Invasive Snakes with Drop of Dead Mice

By Kim Smiley

Brown tree snakes are an invasive species that was inadvertently introduced to Guam where they have decimated native bird populations and done massive environmental damage.  It’s estimated that there are about two million of these snakes  on the island.  The newest plan of attack in the battle to control the brown tree snake population is to poison the snakes by parachuting dead mice laced with pain killers onto Guam.

The problem of invasive brown tree snakes can be analyzed by building a Cause Map, a visual root cause analysis.  A Cause Map is built by asking “why” questions and adding the causes to intuitively show the cause-and-effect-relationships.  The first step is to identify the goals that are impacted.  In this example, the environmental goal is impacted because the balance of native species on Guam has been altered.  This has happened because the native bird population has been decimated because they have been eaten by an invasive predator, the brown tree snake.  The spider population has also exploded because many of the birds, their main predator, have disappeared.  The snakes also cause significant and expensive power outages on Guam as they climb into electrical equipment.

Brown tree snakes have taken over Guam for several reasons.  First, the snake was accidently introduced to the island, likely as a stowaway in military cargo after World War II.  Once the snake was on the island, it thrived because the species had no major predator on the island, there was little competition for resources, and there was an abundant food source.  There was little competition because Guam had only one other snake species prior to the introduction of the brown tree snake.  The native snake species is blind and significantly smaller, preying mostly on insects.  The brown tree snake had ample food because it is a pretty flexible predator happy to eat birds, lizards, bats and small mammals.  In fact, the brown tree snake has found Guam so hospitable that the snakes grow larger on Guam than in their native habitat where predators are more plentiful and food is more limited.

Presence of these snakes on Guam has caused massive damage.  Nine of twelve native bird species are extinct on the island.  The snakes have also eaten a significantly amount of the small mammal population.  There has also been a huge impact on vegetation on Guam since the snakes have wiped out many of the pollinators.  Scientists have been trying to find ways to improve the situation.

The newest plan involves dropping dead mice laced with pain killers onto Guam.  The pain killers are deadly to the snakes if ingested.  The mice will be attached to something called a flagger, which is two pieces of cardboard attached with a streamer.  The flagger should act like a parachute and catch in the tree canopy, which is where the snakes predominately spend their time.  The hope is that the snakes will then eat the pain killer laced mice, thus reducing their population.  The current plan is to drop about 2,000 mice over an enclosed area to determine if this is an effective method of brown tree snake population control.  If it works, more dead mice could be headed Guam’s way in the future.

To view a Cause Map of the brown tree snake problem and a Process Map of the plan to drop dead mice, click on “Download PDF” above.  To view a similar example about controlling feral cats on Macquarie Island, click here.