Understanding the Issues with the Highly Invasive Iguanas

Since iguanas were first discovered and recognized as an “Invasive Species” in South Florida in the early 60’s and 70’s their population has continued to multiply. There are three main species of invasive iguanas - the black spiny-tailed iguana, the Mexican spiny-tailed iguana, and the green iguana. All 3 are highly invasive and seriously problematic for Florida. They are all ravenous herbivores and highly destructive. Another common denominator is they are every sensitive to cold.

In the past 60 years (+/-) since their discovery (pre-2010), there have been several “kill off” events where the recorded temperature at Miami International Airport was below 39 degrees. Many of these events were in back-to-back years and none were farther than 5 years apart. 23 years in total between 1964 and 2010 recorded day(s) with temperatures below 39 degrees, averaging a “kill event” every other year. These weather conditions have served Florida well in keeping the iguana population in check more or less and the population more of a nuisance than a pressing economic emergency.

Unfortunately, since 2010 there has not been a weather kill event. The closest was in 2021 when temperature reached 40 degrees for a short period of time. The event was widely reported in the news as “Falling Iguanas”. The next coldest recorded temperature was 42 degrees. Other than that, there has not been another natural event that has had a negative impact on the iguana’s population in the last 12 years. 

The current total population of all species of iguanas in Florida is estimated to be well over several 100,000. This number is calculated from the number of “reported sightings” and a calculation of their breeding. Based on many other reports and the simple empirical data, the population is believed to be much greater, and could be into the hundreds of thousands, especially with their expansion into central Florida. 

It is fair to say that the State can no longer count on the weather as a means of population control, especially as evidenced by the last 13 years with no kill events. When the previous average was once every other year. Florida's three warmest years in NOAA records dating to 1895 have all occurred in the last four years, and all the state's 10 warmest years have occurred since 1990. Miami has roughly 75 more days a year in which temperatures reach 90 degrees today than they did in 1970, according to Climate Central. Regardless of “climate change” the data shows that these kill offs are less likely to occur. With the supporting data, if the iguana population goes unchecked any longer, the cumulative amount of destruction will be measured in the billions of dollars. 

There’s now even evidence that Iguanas are “adapting” to cooler weather as they push north through the state. Should that be held true it will make weather events even less likely to impact the Iguana population.

Florida is now at a major tipping point where the iguanas will move from an invasive species to a native species and generally infest every aspect of the Florida economy and forever change the Florida economy. The impact will be felt in every sector of the Florida economy from residential and commercial landscaping, plant nurseries, recreation, and more, with the most significant impact being felt in infrastructure and agriculture. 

The iguanas have now discovered an endless supply of food on the farms of south and central Florida. Between the damage and losses to crops and the damage caused to Florida’s infrastructure, from their burrows under roads, sidewalks, and foundations to the berms, seawalls, dams, canals, lakes, and Florida waterways. Florida is at a serious crossroads that will require a very aggressive approach.

The question is - Does Florida take an aggressive approach to not only slow the growth of the iguana population but greatly reduce their population and protect the economic development of Florida? It is more than obvious that the current solutions/methods of population control are not working and have proven to be completely ineffective.

Taking the current reported population numbers and conservatively “assuming” they are all mature adults and a 50/50 mix male/female, the forecast of their conservative population growth over the next 10 years looks something like the graph above. 

   Facts we know: 

      • A female iguana lays between 15 and 70 eggs, with the widely accepted average being 40     eggs.  For the purpose of this analysis, we’ll assume ONLY 25% of the clutch on average survives to become juveniles, instead of the 30+ average, at which time they will have no natural predators, excluding the occasional alligator. 

      • Newborn iguanas will not reproduce for the first 24-30 months. This example has a 2-year delay in the population explosion due to maturity time for the 2022 clutches. 

      • The other difficult variable to know is how many juveniles are out there reaching adulthood that are unaccounted for in this model.

      • Furthermore, baby male green iguanas often use their own bodies to shield and protect females from the occasional bird. It appears to be the only species of reptile to do this. With their “3rd eye” the Parietal Eye allows them sense birds or other predators while they’re vulnerable and protect themselves by seeking shelter. 

      • Female iguanas can save sperm from mating for her next clutch in case a male is not present making the population growth even more likely

Regardless of the exact population numbers and forecast, the numbers show unquestionably that South and Central Florida are on the verge of serious population explosion. A simple drive along any Florida waterways will highlight hundreds of iguanas, and those are only the ones visible in the open. It is a reasonable assertion that the current reported population could be and likely is seriously understated.

A bigger unknown number is how many iguanas can Florida’s environment support before collapse? What does the devastation look like? How long do we “wait and see” before acting? What is the point of no return?

The forecasted numbers show the State is approaching that tipping point referred to earlier. All the assumptions in this model are significantly below the numbers accepted in all research as to the reproduction of iguanas, including the FWC.

Making these numbers even more critical is the fact that they are the leading indicator of the economic damage (disaster) that will soon be inflicted on the State of Florida. The biggest economic areas affected will be agriculture and infrastructure.

Agriculture is a multi-billion-dollar business in the state of Florida. Except for citrus, nearly every other farm crop grown in Florida is on the menu for iguanas, and many are their favorites. The impact of the Iguana on the farming community will be devastating. These are the most current number from FDACS (2019): 

                               Crop              % of US Prod      Revenue Generated 

                           Tomatoes               60%                   $426 million

                           Bell Peppers           45%                   $235 million

                           Watermelons          29%                   $162 million

                           Sweet Corn              29%                   $141 million

                           Squash                      16%                   $35.4 million

                           Strawberries             12%                   $307 million

                           Peanuts                     11%                   $119 million 

                           Cabbage                    11%                   $58.4 million

Agriculture is a multi-billion-dollar business in the state of Florida. Except for citrus, nearly every other farm crop grown in Florida is on the menu for iguanas, and many are their favorites. The impact of the Iguana on the farming community will be devastating.    

Iguanas will eat apples, pears, bananas, mangoes, grapes, star fruit, peaches, tomatoes, guava, kiwis, melons, figs, apricots, dates, blueberries, raspberries, strawberries and vegetables such as squash, green beans, cabbage, carrots and broccoli cactus, broccoli, bell peppers, green beans & sprouts, sweet potatoes, parsnips, okra, cucumber, asparagus, mushrooms, peas, and corn. Iguanas also will decimate flowers (floriculture) that they love.

These Florida crops alone represent $1.75 Billion for vegetables, melons and berries and $4.45 Billion for Floriculture in 2019 to the Florida economy - tomatoes, strawberries, bell peppers, watermelons, sweet corn, cucumbers, potatoes, snap beans, cabbage, blueberries and flowers. Every single item is on the iguana’s menu with almost all being favorites. Farmers are just now starting to feel the wrath of the iguana.

When the infrastructure damage to sea walls, dams, canal berms is included, it all quickly adds up. One instance alone caused $1.8 million dollars of damage in West Palm Beach, where their digging helped to undermine a dam that controls water flow into the city's reservoirs. 

When analyzing all the approved methods by FWC for “harvesting” iguanas the below it is evident there is only one that will yield the necessary results.

      • Nets, noose poles, snares - simply impractical 

      • By Hand – beyond impracticable 

      • Unofficial shooting – dangerous (to people & property), time consuming, and an iguana needs to be visible and within range. Most iguanas see a hunter coming and run for cover. In addition, most municipalities do not want people running all over with “guns” shooting iguanas.

      • Trapping – this is the most viable solution, but the process will require many improvements and a scale well beyond using simple raccoon traps and commensurate with the need for the population reduction. 

If all the current solutions above really worked, we wouldn't' be having this conversation. Something needs to chance!!  "INNOVATION!"