I study how invasive reptiles adapt to new environments. AMA!

Iguanas and pythons are the obvious invasive species based on people buying them and then letting them go when they get too big (I'm thinking about Florida specifically)- are there any species that surprised you? Something you didn't expect to find, or didn't expect to do well in its new environment?

The pet trade is one of many routes that a non-native vertebrate can arrive through. The most common species are most likely to be released- especially if they get too large (such as iguanas and pythons). Reptiles are also notoriously good at escaping enclosures from first-time pet owners who aren't ready for it. If multiple people release them into a suitable climate (or if a gravid female is released and offspring survive), they are likely to establish. However, the more releases of the species in an area, the more likely it is to establish. This is known as "propagule pressure".

I'd say I am surprised at some of the established species that are less popular in the pet trade - such as the Peters's Rock Agama (AKA red-headed agama, Agama picticauda, introduced from West Africa) or the Cuban Knight Anole (Anolis equestris). They both come from similar climates as Florida, however.

a gravid female

I had to look up "gravid." It seems like it means "pregnant," except for reptiles. Is that about right?

Yes! Gravid is similar to pregnant for reptiles. Reptiles do not have a true placenta. Some species lay eggs, some give live birth to offspring that developed within the mother- I use gravid rather than "pregnant" or "full of eggs" because it encompasses both types of reproduction.

What’s the solution to the Python problem in the Everglades?

That's a billion-dollar question! The ultimate goal would be eradication of the species in the Everglades, but this task would be very difficult to accomplish. Currently, there is sustained management and culling of the species where it is accessible. The Everglades is a vast environment and would be nearly impossible to comb-through for python removal without causing more damage to the ecosystem. Even with a comb-through, pythons are very cryptic and can be difficult to detect in plain sight. They also can hide underneath solution holes in limestone karst throughout the Everglades.

There are many avenues being explored for control of the pythons. One is attaching radio-transmitters to male pythons and using them as 'sentinels' to find and remove large females. Another is allowing the public to hunt them on some managed lands. Unfortunately some of the techniques used in the insect world (releasing sterile males, or releasing a parasitoid) aren't feasible with vertebrate species like pythons.

The current solution then, is keep exploring new avenues to add to the management techniques we have, and teach others from this lesson to prevent harmful species from establishing in the Everglades and other sensitive ecosystems worldwide.

I've always wondered why drones aren't used. These snakes need to sun themselves during certain parts of the day. Could some sort of heat detection software be used on a large scale?

For the most part, python body temperature closely matches that of its environment, so heat-seeking technology may not be as useful as it is with endothermic animals like mammals or birds, because the thermal difference is not as large.

What’s your opinion on cats? Outside cats and stray cats specifically, Australia has a huge cat problem for example. But it seems every where else in the world they are socially accepted and never seen as an issue because they are cute.

Edit: No I don’t hate cats, no am not a dog. I have a 2 year old orange Tabby cat that I love very much. He neutered and stays inside.

Cats and dogs are both invasive species that establish feral populations and impact native wildlife. Like many of the invasive reptiles, they arrived via 'pet trade', but are more common pets, so their roaming around outdoors have somehow become normalized. They are both disease vectors and predators and it is important to treat them as such when managing wildlife. That being said, I have a pet cat that I took inside (formerly feral) and he has adopted his cozy, all-indoors life very easily. It's also safer for him indoors, for many reasons. Sometimes people don't think wildlife biologists and cat-owners can get along, but oftentimes we are both at the same time!

Have you heard about Chicago’s Humboldt Park Gator? Thoughts?

It sounds like this gator is a released pet. Alligators are very cute when they are hatchlings, but quickly grow to a dangerously large size that most people cannot accommodate, and subsequently release the animal.

It is unlikely that the alligator will be able to survive the bitter cold winter in Chicago. The animal may pose a risk to people before then, though, especially if it associates people with food, and could become aggressive if people feed it. I expect most Chicago residents don't know how to behave safely around alligators because they are not native there, which makes this a potentially dangerous situation, especially for folks who don't expect alligators in public water bodies like we do here in Florida. Hopefully they will be able to safely capture and relocate the alligator to a captive facility.

What do you think will happen with the tegus in south Florida?

I bought a captured invasive Tegu from Rodney at Tegusonly and she’s the sweetest little chomper. Do you support what he’s doing down here?

Thanks

Tegus are certainly an invasive species to be concerned about- they are omnivorous and seem to have a preference for eggs. This means they could be a threat to American Crocodiles, which listed as an endangered species in Florida. They could also impact many other egg-laying species. As with other invasive species, the goal is to at least contain them to the areas they are found, and to eradicate them from the invaded populations.

I am not familiar with Tegusonly, but will speak based on my experience. While tegus can make good pets when socialized, a wild adult tegu is not going to be a suitable pet for a first-time keeper. It is difficult to find homes with advanced keepers with the space for these animals. There are definitely ethical issues with removing and culling invasive species, and one issue is whether they can be 're-homed'. While some certainly can, potentially hatchlings, it is not likely possible for all invasive animals to find suitable homes, and logistics are especially difficult for housing all these animals and finding a 'suitable home' that is not likely to re-release the animal and exacerbate the problem.

Do you like turtles?

I like turtles!

Does every environment have a chance of getting an invasive species? I live in the Mid-Atlantic and it’s kind of hard to imagine iguanas in the same ecosystem as the squirrels and rabbits and cardinals.

I would say, yes! Every environment has the chance of getting an invasive species. Perhaps not every environment could support an invasive reptile, however....

By definition, an invasive species arrives by anthropogenic means (i.e., a human moved it, whether intentionally or unintentionally). After it arrives, if it successfully establishes in the new environment, it is considered non-native. To be invasive, the species has to have demonstrated impacts (usually quantified in terms of economic or ecological harm). The impacts are sometimes obvious, but can be difficult to demonstrate or measure when the species has just arrived. As long as the 'invader' is able to successfully establish and breed in the new environment, an invasive species could technically occur anywhere. The mid-atlantic region has some 'infamous' non-reptile invaders: European Green Crab in the Chesapeake Bay, Northern Snakehead, Hemlock Wooly Adelgid, and many species of invasive plants.

Has climate change led to an increase in invasive reptiles?

Climate change is changing thermal environments. For the most part, reptiles regulate their body temperature through behavior- moving throughout the environment to heat up or cool down. When the thermal environment changes, it may benefit certain species, including invasive reptiles.

When temperatures increase, reptiles are generally good at finding cooler refuges to prevent overheating. Invasive reptiles' ranges are typically limited by their critical thermal minimum- the minimum temperature they can withstand before dying. Species that are not behaviorally adapted to respond to cold weather would benefit from increases in mean temperatures at the edges of their invaded range, and may be able to invade further North (in a North American context).

It is difficult to attribute climate change alone to overall increases in invasive reptiles because there are other anthropocentric factors that feed into this. Increasing popularity of reptiles in the pet trade led to increased imports and increased probability of escapees/releases. Increasing global connectivity and trade also increases the chances of 'hitchhiking' reptiles. Climate change may have improved the thermal suitability for establishment and spread once reptiles arrive.

It's always been fascinating to me that a species could have outsize success not because it's had a long time to adapt to its environment, but rather specifically because it has NOT been part of its environment for long. It's very counter-intuitive on the face of it.

One obvious advantage of being transplanted to a new environment is that predators and parasites will not necessarily be "interested" in you - are there other advantages that an invasive species can have when entering a new environment?

One example of an invasive species at advantage in a new environment is when it becomes the predator. In the native range, prey species that have co-evolved with it are likely adapted to detect or avoid the predator. If there is no similar predator in the invaded range, the prey are not adapted to avoid the invasive predator, and may be more likely to be depredated. If prey is easier to catch in the invaded range, the predator may grow faster and reproduce more often. Also, there is no competition for these resources, so the invader can "boom". The classic example of this is the brown treesnake on Guam, which was introduced and essentially wiped out the avifauna of the island, which were not adapted to snake predators. This situation can be translated to any situation where an abundance of resources exist and there is an unfilled niche: iguanas as large, arboreal herbivores in south Florida... an insect that finds a host plant similar to its native range, but the invaded range plant does not have a similar insect that feeds upon it...

The African rainbow lizards have invaded the upper part of South Florida now. I’m talking about Palm Beach/Martin/St. Lucie county. They’re everywhere and they are gorgeous. But how does their presence affect the regular, small lizards that have always been here like the anoles?

This species (Agama picticauda) is part of my dissertation research, and they are very abundant where they have established. It is difficult to guess at impacts, mostly because we don't have much data on "before" they arrived. In general, we don't have much data on urban wildlife communities- and this species is establishing in mainly urban areas. They definitely eat other, smaller, lizards, such as the (also non-native) Brown anoles, or native green anoles. I found a female agama that had even cannibalized two hatchlings. They have also been observed eating bread, strawberries, and other 'human food' that is left around dumpsters. It seems like they will eat anything they can chase down or fit in their mouths.

how much do you know about how the lizard people adapted to our planet? thank you for your service.

I only study "alien species" that originate on earth.

How and why would stress/immunity play a part in a successful invasion? Is the implication here that stress causes the reptile to migrate to a new location, or for it to thrive in a new environment under stress? I don't seem to understand what you mean by either of those two topics.

I live in the keys and am curious about your research given the recent explosion of iguanas and to a lesser extent crocodiles (although technically not invasive).

While stress can trigger dispersal, this would be considered a 'natural' event. Invasive species arrive through human transportation, whether intentional or non-intentional. I'm interested in how stress and immunity play a role in the establishment of a non-native species. This can be just as it arrives from the native range, or how it establishes in a new location within the invasive range.

The stress of transport could alter an individual's physiological state, and could also affect how it responds to stressors in its new environment (such as predators or competitors). This may cause a long-term change in the individual which could be heritable to offspring. There is some evidence of stress-induced traits passed to offspring in other species- arctic hares and even humans. Thus, an invasive population, although typically the same species as a native population, may have changed to become physiologically distinct from it's original source.

As for immunity- when a species arrives in a new location, it leaves many of its co-evolved pathogens behind. In the new range, it is exposed to many novel pathogens- and these immune responses may determine whether the individual survives. The first defense for a new pathogen is to mount an inflammatory response, which can be very self damaging (think to your last bad cold...fever, swelling, lethargy) and leave the individual vulnerable to death and depredation. Reptiles have to change position to achieve body temperatures, and many will induce 'fever' during inflammation by moving into warmer habitats. In order to establish, though, the species has to reproduce! It needs energy to do so. So there is a trade-off... invest in reproduction, and less in immunity, and risk disease/parasite load to produce offspring before succumbing to an infection, or invest in fighting off pathogens and assume the symptoms of inflammation and risk of recovery time, being less likely to reproduce.

Additionally, stress can affect the immune system's functioning, and can regulate immune responses to some extent. I'm interesting in how these processes are connected in determining a successful invasion.

How is the florida government taking action on Green Iguanas this year?

The state wildlife agency has employed an iguana removal team, but the scale of the problem is too wide to manage with the current funding. Taxpayers would have to get involved by contacting their representatives to confirm they are willing to pay more for management. Currently, iguanas are an issue in the Southern part of the state, so local government action may be more effective (voters in Tallahassee are unlikely to want to pay taxes for an issue they are not affected by in their lifetime). Some local governments employ private iguana removal companies. The agency is also encouraging people to remove and humanely kill iguanas from their properties. There are several public lands where hunting iguana is allowed without a permit

I loved to pick up lizards (podarcis muralis) when I was a kid, keeping them in a quite big terrarium aiming to reproduce their habitat and feeding them with crickets or spiders, I found a lot of behaviors I didn’t expect from a small reptile like that, what is the behavior/thing that you discovered about reptiles do that surprised you the most?

I find reptiles are much more social than people give them credit for. When studying (native) rattlesnakes in California for my masters, I noticed a smaller male followed the same larger male to different areas of my field site on multiple occasions. I'm not sure if they were kin or not. I also noticed curly-tailed lizards will "greet" each other by licking one another before settling at a basking site.

Is there evidence of multiple introductions for most of the invasive reptiles in Florida? Were any the result of a single introduction? Also, are you skeptical about the enemy release hypothesis? It seems like if you do discover that these stress and immune response metrics are important in explaining invasive success, it might chip away a bit at the ERH.

It is difficult to make a generalization for most invasive reptiles' having multiple introductions, simply because we do not have the fine-scale genetic data for many of them in their introduced and native ranges to do these comparisons. Continuous imports of different species for the pet trade imply some species should have multiple introductions. But, single introductions and subsequent dispersal is also possible.

The enemy release hypothesis is somewhat central to my dissertation's questions. By leaving enemies (pathogens) behind, the invader may not need to invest as much in immune responses, and can divert energy to reproduction and dispersal. If I confirm this, I will have some support for ERH. On the other hand, the reaction to novel stressors and pathogens may be more important for establishment success than the release from native enemies. They could both be important, but at different time scales in the invasion (ERH more important during first stages, perhaps). It is difficult to disentangle the two without limiting study to a controlled laboratory environment. That's what I like about looking into 'natural' experiments... asking whether the patterns fit the ideas of invasion biologists!

Hello!

What got you started in this field? Very cool job! :)

I was always interested in reptiles from a very young age. As an undergraduate, I studied to prepare for a career in veterinary medicine, focusing on exotic species. I became very interested in physiology of animals at this point, and decided after working at an exotic veterinary clinic that the client-doctor career was not the path for me. I learned that it is possible to have a career in animal physiology (with a focus on reptiles) through research. I went on to pursue a Master's at Cal Poly on rattlesnake physiology, where I gained experience developing and implementing research projects. I ended up in Florida because this project joined my interests in exotic/pet reptiles, wildlife, and physiology.

I live in central florida and i often see on community facebook pages that there is a need to kill any cuban tree frogs/any other invasive frogs that we come across. I luve next to a wooded area, so lots of wildlife. Does culling these species as an individual actually make a difference?

There are certainly ethical issues with invasive species management. It is difficult to justify culling animals when their establishment is due to human means, it's not "their fault". Many people would like to rely on wildlife agencies and other government organizations for control. In many cases, it is not feasible for these organizations to achieve this because 1. they are understaffed for issues like this 2. they are alerted after the species has become unmanageable and 3. the species is on private property and the time and effort required to get permissions needed to attempt eradication is beyond the ability of these agencies. As an individual, it is important to be positive with your identification (so you do not harm native wildlife) and your efforts may help. Community-organized efforts would have a greater impact. Some communities organize 'Invader Rally' weekends where they remove invasive plants or animals. In short, invasive species management requires involvement on many levels, but as an individual, your involvement definitely counts!

Any cases of leopard geckos in the wild in the states? I have a few and well they don’t seem like the sharpest tools in the shed... I feel like they would stare blankly at a predator lol, my bearded dragon on the other hand.....

It is interesting that some of the more common reptile pets have not established invasive populations. There are sometimes reports of single individuals of leopard geckos, ball pythons, bearded dragons, but I don't know of any confirmed established populations of these. One reason might be they stay a manageable size and people are less likely to release them, so they never establish reproductive populations in the wild. Another might be that when they are released, they are unable to cope behaviorally or physiologically where they are released.

Why can't the invasive pythons in the Everglades be attracted to traps using sex pheromones? Barring that, why not use females to attract males and either kill or neuter all of one sex?

Great question. Deploying pheromone scent trails in a classic sense is logistically difficult in a mostly aquatic environment such as the Everglades. There are current efforts investigating the use of pheromones to attract pythons, but there isn't enough information to implement at a large scale yet.

Female snakes have been fitted with telemetry equipment and males removed when found with them. Males have also been fitted with this equipment, leading researchers to females (and sometimes other males), which are also removed. While neutering/killing all of one sex would potentially help eradicate pythons, the issue is that we are currently limited to hand-capturing all pythons of any sex to implement this, and this species is difficult to find/capture in the Everglades.

Can't believe no one has asked the most important question: how do invasive reptiles adapt to new environments?

There is not much information on both invasive/native populations of reptile species, as opposed to other invasive species, which prompted my research.

Some ways reptiles could adapt, which there is evidence for in non-reptile invaders: Different investment in physiological processes than native counterparts, such as immunity/reproduction/dispersal. Longer breeding season in response to more a mild climate in the invaded range. Increased numbers of eggs/offspring produced per individual Better endurance or improved traits for dispersal, such as longer limbs. Changes in morphology to the new habitat, such as greater variation in limb lengths in the invaded range due to lack of competition or depredation that restricted them to a specific morphology to inhabit certain area in the native range. Loss of anti-predator behaviors or phenotypes as similar predators do not exist in the invaded range.

It is important to note that adaptation occurs over several generations, so long-term studies are required to investigate adaptation in any species.

Whats your opinion about how the situation with pythons specially in the everglades have made it really difficult to transport certain species of snakes across states, if I'm not mistaken, like burmese and reticulated pythons? Do you think it is justifiable or do you think it only hurts the pet trade without really improving things?

The transport restrictions make it difficult to move species that are demonstrated to cause harm, or likely to cause harm to native ecosystems. These restrictions certainly prevent the likelihood that more will be established, but mostly have come after the damage has begun. It is difficult to predict which species are likely to be most harmful before that damage occurs- and it is also not feasible to place bans on species without justifications. I am exploring an avenue of research that might predict which species are likely to establish beyond climate-matching and other current metrics.

Regulations cause changes in any industry, but as a society we place value on native ecosystems that justifies regulating exotic species trade. The pet trade is dynamic and resilient (and has been, based on the changing demands of consumers), and those that are invested in the business will move to focus on different species, as any other industry would do.

Do feel like we'll be able to successfully remove even one invasive species from Florida and if so which one do you think we have the best chance at success?

The best chance for success for complete removal of an non-native species would be one that is in the very early stages of establishment, or a species that is not yet confirmed established. This early-strike is the most cost-effective, feasible way to remove an non-native species. "Invasive" implies there is a measurable impact, though- and unfortunately, the time it takes to measure an impact may be the time it takes for an invasive species to establish and increase beyond eradication efforts. Due to limited funding, however, the current system restricts most action until after impact assessments to justify spending taxpayer dollars on a given species.

Removal of already-established invasive species is possible, but will require a lot of funding and support from private and public entities to ensure success.

I work in immunology; how are you characterizing immunity? Is this from a more epidemiological standpoint or are you doing some form of sequencing of the non-natives or molecular bio to quantify the types of pathogens they carry?

I am looking at functional immune responses in terms of bacterial killing capacity of plasma and natural antibody capacity to agglutinate red blood cells. I am also looking at cellular surveillance via leukocyte counts. I'm most interested in innate immune responses as these are the first defense against novel pathogens. I have collected tissue samples and hope to do some quantification of TLRs and other immune gene expression in the future for a broader picture of immune investment in different invasive populations. I have a collaborator who is investigating the ectoparasites (ticks, mites) I find to understand whether these pose a risk to native species.

So I'm guessing you guys catch a lot of reptiles, what do you do with them when you've studied them? Do they get maybe radio tagged and released to see how their levels change over time? Is it preferential to just euthanize them or put into captivity?

For my study, I euthanize the animals I capture. I then preserve them and they are curated at the Florida Museum of Natural History so they can be studied by future scientists. Museum specimens act as a 'snapshot in time' which may be important for learning about long term adaptation in invasive species.