All posts by Sean Giery

About Sean Giery

Postdoc in the Department of Ecology and Evolutionary Biology at the University of Connecticut. My research focuses on food web ecology, sexual selection, and the evolution of communication.

Knight Anoles Eat Fruit and Pass Viable Seeds

knight anole

Figure 1. Knight anoles (Anolis equestris) are large, arboreal, and highly frugivorous lizards native to Cuba and introduced to Miami, Florida in the mid-20th century. This adult female was found perched on the trunk of a strangler fig (Ficus aurea) in Miami, Florida, a common sight in south Florida. Strong jaws and a large gape enable knight anoles to consume a range of large food items including snails, locusts, small vertebrates (occasionally), and some moderate-sized fruit. Photo by S. Giery.

I remember the first knight anole (Anolis equestris) I ever caught. Details about how I caught it are gone, but I certainly remember the resulting bloody thumb. I was impressed and intrigued by the force and stamina of its bite – I needed to study this critter (fig. 1). Motivated by the recent publication of a short paper on knight anole  diets, below, I break down a few years of research into the trophic ecology of the knight anole into a brief recount of what my collaborators and I have found.

Preliminary observations on knight anole trophic ecology
Following that first encounter I conducted a simple study of anole diet and habitat use around the Florida International University (FIU) campus in North Miami. In general, the findings showed some sensible results: Cuban brown anoles (A. sagrei; trunk-ground) perched low and ate a wide variety of terrestrial insects, Hispaniolan bark anoles (A. distichus; trunk) skittered up and down the trunk and ate – almost exclusively – ants, and Cuban knight anoles (A. equestris; crown-giant) ate larger food items than the other two species and tended to stay in the canopy (Giery et al. 2013). Again, this pattern of diet and habitat use was expected except for one thing – the composition of knight anole diet. Prior to embarking on the study, I had expected, based on their large size, strong bite force, the abundance of smaller anoles, and a few anecdotal accounts, that these powerful lizards would be eating lots of anoles. Surely these were the T-Rex of the trees and their direct interaction with other anoles was a predatory one. Yet in all the knight anoles that I dissected in this first study (n =21), not a single one contained vertebrate remains. Instead, nearly half of the diet (by volume) was fruit, specifically strangler figs (Ficus aurea; look to Supplemental table 1 for summary diet data). Our stable isotope data corroborate these observations – rather than the enriched 15N signature we‘d expect from an anole predator, the isotope data suggested similar trophic levels for brown, bark, and knight anoles. So what gives? Where was the evidence for a swaggering, arboreal meat-a-saurus?

Years later, James Stroud and I assessed the stomach contents of more knight anoles (n = 10) from a different site in Miami (Fairchild Tropical Botanic Gardens. James had directly observed knight anoles eating three different species of anoles there (1,2,3,4) and so we thought another look at their diet would be interesting. Once again, the majority of gut contents consisted of fruit, this time from royal palm trees (Roystonea regia). In fact the only evidence for vertebrate prey in this population was a 1 cm section of green anole tail. These data supported earlier observations (Brach 1976; Dalrymple 1980, Giery et al. 2013) demonstrating that fruit is a major component of knight anole diet, and vertebrates aren’t. It seemed that the canopy superpredator role I’d imagined for knight anoles was increasingly less likely. In fact, in all three previous examinations of knight anole diet, few instances of vertebrate predation by knight anoles are observed (table 1). The evidence spoke, knight anoles were sharp-toothed, veggie-sauruses with a deliberate, powerful bite.

Table 1. Knight anole (Anolis equestris) diet summaries (number of individuals assessed, ‘n’, are included below each study reference). Data presented in columns are the proportion of individual knight anoles with prey taxa in their stomach, P(n). For this study we also present the proportion of total stomach contents by volume, P(vol).

An opportunity presents itself
Understanding the trophic ecology of anoles has been an ongoing project of mine for some time, the paper that we’ve just published in Food Webs (Giery et al. 2017) would not have come without the serendipitous post-capture … deposition … of a few seeds. An adult male passed two royal palm seeds which were planted post-haste in the greenhouse at FIU. It took a few months but the seeds eventually geminated, demonstrating that seeds consumed by knight anoles are viable and suggesting a role as seed dispersers (fig 2).

seed dispersal in knight anole

Figure 2. Adult knight anoles (Anolis equestris) often inhabit the crowns of royal palms (Roystonea regia) in Florida and Cuba. Note the numerous ripe fruits above this displaying male photographed at our study site in Coral Gables, Florida (A). Roystonea regia seedlings resulting from seeds passed naturally by a wild-caught A. equestris. Both seeds were planted at the same time, but germinated nearly 130 days apart (B). Adult royal palms can reach 30m high and are an ecologically and economically important plant throughout their range (C). Photos by J. Stroud (A & B) and S. Zona (C).

We felt that these data filled an important gap in our understanding of how anoles interact with other species. Certainly, the literature (e.g., Herrel et al. 2004; Losos 2009) and our data from Florida (Giery et al. 2013, 2017), Bermuda (Stroud, unpublished), and The Bahamas (Giery, unpublished) show that frugivory is widespread and sometimes quite common in anoles. Yet, the fact that seeds remain viable after passing through the guts of anoles presents a new facet to their interactions with plants. For more about what we know about lizard-plant interactions go ahead and check out the references in our paper (there’s good stuff from Europe, and recently, the Galapagos).

Whether the interaction we illustrate in our paper is ecologically important (i.e., increasing germination rates via ingestion and/or dispersal) requires substantially more study. Yet, the relationship between knight anoles and royal palms has been noted for nearly a century in Cuba suggesting their interaction is more widespread than just Florida. For example, Barbour and Ramsden (1919) remarked on the frequent coexistence of royal palm and knight anoles in Cuba. Interestingly, these early works often focused on the potential consumption of vertebrate prey, despite reports from Cubans that knight anoles often ate fruit – a bias matching my own preconceptions about the nature of this great anole:

As to the food of the great Anolis [equestris] we know but little; it is surely insectivorous and Gündlach records that he once heard the shrill scream of a tree frog Hyla and found that it had been caught by one of these lizards. The country people all declare that they feed largely upon fruit, especially the mango; it is not improbable that this idea arises from the fact that they are frequently found in mango trees. We have always imagined that this circumstance was due in part at least to the excellent cover offered by the splendid growth of rich green foliage of the Cuban mango trees; it, however, has been seen eating berries (Ramsden). With good luck one may occasionally see two males of this fine species chasing one another about, making short rushes and charges at each other, accompanied by much tossing of heads and display of brilliant dewlaps When this mimic battle takes place about the smooth green top of the trunk of a stately Royal Palm, it is a sight not easily forgotten.” from Barbour and Ramsden 1919.

Anyways, we hope our short paper does two things. First, we hope that our summary of knight anole diet in Florida accurately illustrates their trophic ecology. Second, seed dispersal of native trees (royal palm and strangler fig) by an introduced vertebrate represents an interesting contrast to the negative effects usually attributed to introduced species (e.g., brown anole). We hope our observations highlight the diverse relationships between anoles and plants in the Caribbean region. Finally, we realize that our data are merely suggestive and effective seed dispersal by anoles has yet to be demonstrated. Nevertheless, we’re excited by the potential for new research directions stimulated by our observations.

Giery, S.T., Vezzani, E., Zona, S., Stroud, J.T. 2017. Frugivory and seed dispersal by the invasive knight anole (Anolis equestris) in Florida, USA. Food Webs 11: 13-16.

Winter Activity in North Carolina Green Anoles

Green anole from Robeson Co. NC

Green anole from Robeson Co. NC

Winter activity by reptiles has always intrigued me. Growing up in NY, I was confronted with long reptile-free stretches. However, on occasion, a little hope for the coming spring could be found. For example, at least once, a painted turtle passed slowly under the ice, which was obviously reason for major excitement…and surely portended an imminent spring like an auspiciously overcast February 2nd. More typically, during those times of scarcity I satisfied my herpetological curiosity by dip-netting tadpoles and red-spotted newts through holes punched in the iced-over pond behind my house.

This same impatience motivated me to stop at the side of the road on a warm (63F), sunny, winter (Jan 18) afternoon in southeastern North Carolina. The previous night, I had heard a small, lackadaisical spring peeper chorus down near Myrtle Beach, and during my afternoon drive back to Raleigh, a few turtles were basking in roadside swamps. So, I pulled off the road near the Lumber River in Robeson County and took a short stroll.

A big cypress at the edge of the river was lit by a patch of late-day sun and instantly caught my attention. Sure enough, about 1 minute after getting out of my car, an adult male green anole was found, plenty active and warm to the touch, resting at the base of said cypress. These little anoles are tough! Surely this must be an anomaly. Nope, 5 minutes later, I found another adult male by the edge of the forest! I wanted to look more, but the sun was getting low and the temperature dropped below 60. I got in my car and drove back to Raleigh encouraged by this observation – spring is on the way!

Does anyone know what these anoles are doing during these winter days? From talking to folks with longer histories in NC, winter activity is not that uncommon in green anoles up here at the northern limit of their range. For example, I saw my last one up here in Raleigh in late November. And last year they were active into December!

What’s the benefit of winter activity?

Are Bark Anoles (Anolis distichus) Native to Abaco Island, Bahamas?

Bark anole, A. distichus

Bark anole, A. distichus

I’ve been working on Abaco, in The Bahamas for several years now. The Bahamas, Abaco in particular, is famous for the abundance of terrific science that originates there. Currently, Abaco has three species of anole: A. sagrei, A. smaragdinus, and A. distichus. However, only A. sagrei has been considered native to the island, the others likely introduced relatively recently from islands of the Great Bahama bank such as New Providence or Bimini. However, a recent study reports fossil evidence of A. distichus in peat deposits from about 950 YBP supporting a long history of A. distichus on Abaco.

One interesting aspect of this find is that the contemporary distribution of A. distichus on Abaco appears to be limited to the main port town of Marsh Harbour. I always suspected that this limited distribution suggested that A. distichus was not native to the island, but rather came in on landscaping plants over the last several decades.

So why are there conflicting observations here? Is it possible that A. distichus was extirpated on Abaco due to settlement by indigenous peoples (seems to be contemporaneous with the fossil sediment formation)?  While it might seems rather hard to extirpate such a small, abundant animal, there is growing evidence that the Bahamas were reptile-dominated ecosystems at the time of human arrival. Therefore, the coincident extirpation of tortoises, Cuban crocodiles, and rock iguanas places the modern hiatus of A. distichus in a different light. I am guessing that the altered (intensified) fire regimes initiated by ancient human civilizations may have contributed to the absence (rarity) of A. distichus from contemporary, natural ecosystems. This is admittedly, a lot of conjecture, but how else might one explain their ancient presence, yet contemporary confinement to a human-dominated habitat?

I look forward to hearing more from the interesting work that Dave Steadman, Janet Franklin and Nancy Albury are doing on these ancient Bahamas communities. And it looks like there is a lot more to come! Also, the name of the journal is The Holocene. How cool is that?!

Steadman DW, NA Albury, P Maillis, JI Mead, J Slapcinsky, KL Krysko, HM Singleton, and J Franklin. 2014. Late-Holocene faunal and landscape change in the Bahamas. The Holocene. DOI: 10.1177/0959683613516819.





Anoles Link Spatially Distinct Terrestrial Food Webs – Part 1 Of 2


LIke all the anoles in our study, a considerable fraction of A. equestris’ diet was derived from the flow of allochthonous resources into its habitat.

A. sagrei, probably the most common vertebrate in Florida perch low on trees making occasional forays to the ground to feed.

A. sagrei, probably the most common vertebrate in Florida perch low on trees making occasional forays to the ground to feed.

The ecological importance of small, terrestrial insectivores such as litter frogs and small geckos is a topic that I’ve been curious about for years. While my dissertation research does not include anything about it, I am still quite curious about how these small, diverse and abundant vertebrates fit into ecosystems. Anoles possess all of the attributes that seem to predispose them to strong interactions and soon after arriving in Miami to begin my Ph.D., I decided to launch a small, side-project using tried-and-true food web tools, stable isotopes and gut content analysis to try to illustrate if and how these small, rather inconspicuous predators might affect ecosystem structure and function. The results of this study were just published online in Functional Ecology.

Basically, we found that anoles couple adjacent food webs by consuming insects that move across habitat boundaries. While food web linkages are a potentially important ecological dynamic and our study yielded some unique findings, there are other bits of information for those more generally interested in anole biology. Therefore, I’ve decided to break this post into two parts. Part 1 deals with our primary findings and contextualizes them within current understanding of food web ecology linkages. It’s sort of a geeky treatment of the subject. Part 2 will illustrate some of the other data that we’ve collected that were not dealt with explicitly in the paper that will be of interest to, I suspect, AA readers.

Bidirectional trophic linkages couple canopy and understory food webs

Sean T. Giery,Nathan P. Lemoine, Caroline M. Hammerschlag-Peyer, Robin N. Abbey-Lee, and Craig A. Layman

1.  Cross-system resource flux is a fundamental component of ecological systems. Allochthonous material flows generate trophic linkages between adjacent food webs, thereby affecting community structure and stability in recipient systems.

2.  We investigated cross-habitat trophic linkages between canopy and understory food webs in a terrestrial, wooded, ecosystem in South Florida, USA. The focal community consisted of three species of Anolis lizards and their prey. We described interspecific differences among Anolis species in the strength and routing of these cross-habitat flows using stable isotope analysis, stomach content analysis, and habitat use data.

3.  All three Anolis species in this study consumed different prey, and occupied vertically distinct arboreal habitats. Despite these differences, carbon isotope and stomach content analysis revealed strong integration with understory and canopy food webs for all Anolis species. Modes of resource flux contributing to the observed cross-habitat trophic linkages included prey movement and the gravity-driven transport of detritus.

4.  Our study shows that terrestrial systems are linked by considerable bidirectional cross-system resource flux. Our results also suggest that considering species-specific interactions between predator and prey are necessary to fully understand the diversity of material and energy flows between spatially separated habitats.


The study system was dominated by St. Augustine grass and isolated Ficus trees.

Some basics – The community was composed of four anole species, Anolis sagrei, A. distichus, A. carolinensis*, and A. equestris. The study site was recently featured in AA. Generally, the purpose of the study was to describe variation among species in resource use using stomach contents, habitat use, and stable isotope analysis. But based on some initial observations and a bit of stable isotope data, we had considered that there might be a role for anoles in ecosystems via linking spatially distinct food webs. That is, anole diets might be sourced, in part, by primary production originating outside their respective microhabitats. Basically, we knew that anoles occupy distinct arboreal habitats, but when we examined the stomach contents of each, we found that some prey were from habitats spatially distinct from the ones used by each anole species (e.g., How do terrestrial grasshoppers get inside a canopy giant anole such as A. equestris?),which spawned a more in-depth investigation. Additionally, some initial stable isotope data strongly supported the same interpretation – that is, anole diets might be at least partially derived from allochthonous resources. Continue reading Anoles Link Spatially Distinct Terrestrial Food Webs — Part 1 Of 2

Nesting Knight Anoles

Female Knight anole digging nest at the base of an oak.  April 2013

Female Knight anole digging nest at the base of an oak. April 2013

On my way to teach biology lab the other day, I ran into this female knight anole (actually, my buddy Zack is the one who spotted it).  She was obviously spooked by us and after snapping a few photos I backed off to see if she would continue nesting.  After a few seconds she returned to her task.  I don’t know why I imagined anoles would dig with their hind legs, but for some reason I did. However, she continued to excavate with alternating strokes of her front feet.  Unfortunately I had to run to a meeting, but when I returned a few hours later her hole was still there.  Zack had stayed behind to watch her progress and reported that she had aborted the endeavor when a bicyclist whizzed past a bit too close. The hole was about 4 centimeters deep and 5 wide into the mineral soil when she left.

Female Knight anole observed digging nest at the base of a large fig tree.  Note the soil under her front claws and on her snout.  Observed July 2012.

Female Knight anole observed digging nest at the base of a large fig tree. Note the soil under her front claws and on her snout. Observed July 2012.

This is the second time I’ve seen nesting knight anoles in Miami.  The first was last summer when I found a very healthy looking female at the base of a fig tree.  There was dirt on her snout and a small hole where she had been.  In both cases, the nesting females were within 1 meter of a tree, and both were excavating with their front feet and possibly their snout.  Also, the dates of each observation show that there is a protracted nesting season in South Florida that includes April 10th to July 20th.  Such a long season explains the variable size of first year knight anoles that I find during the spring.

Red In Beak And Talon: A Few Observations Of Birds Consuming Anoles In Urban South Florida

Boat-tailed Grackle

A few years ago I asked an ornithologist friend of mine what urban birds such as starlings and house sparrows ate.  His answer was that it was probably a mix of bottle caps, cigarette butts, and McDonald’s French fries.  I’m only partially satisfied with that answer, and so try to keep an eye on what urban birds eat wherever I go.

Since moving to Miami four years ago, I’ve observed several cases of birds consuming anoles.  After watching a Common Grackle feed an anole to a fledgling a few days ago, I thought I’d compile and share these observations with AA readers.

Continue reading Red In Beak And Talon: A Few Observations Of Birds Consuming Anoles In Urban South Florida

Orange sagrei

I saw the recent posts about orange/red sagrei and I thought I might contribute another observation of orange-colored brown anoles.  A few years ago while assisting another grad student with his dissertation work I spotted a few orange-colored brown anoles in a suburban yard in S. Florida.  What I thought was most interesting about the observation was that: 1) there were multiple males (2-3) with orange color, and 2) many of the palms on which lizards were perched were a similar orange color.  It got me thinking that it could be more than a coincidence.

The orange color on the trees, sidewalks, and other hard substrates in the area is from ground water with a high concentration of iron.   When sprayed on the surface with sprinklers it mixes with oxygen and leaves an orange color.  Many houses, signs, sidewalks, and even cars in S. Florida are graced with an arc or two of orange residue.  I’ve yet to revisit this lawn or surrounding houses, but I bet there are quite a few more houses with orange lizards.  For what it’s worth, I see and catch a lot of brown anoles further south in the Miami area and this is the only case of red/orange brown anoles I’ve seen yet.  It’s possible that these lizards were covered in rust, but it didn’t look like it when I got one in my hand.  It’s also interesting that all of the photos I’ve seen of orange-colored brown anoles are male, however I’ve only seen about 4 cases including this observation.  Oh, and the dewlaps on these males were normal(ish), not like the cool one recently posted by Joe Burgess.