Tag Archives: equestris

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.

Crown-giant habitat overlap

Spring is the season for spotting crown-giant anoles in Miami!

I was hosting (recently graduated Lacertid-ophile, although closet anologist) Dr. Robert Heathcote for a few days this week, and after his failed attempt at catching a Cuban knight anole (A. equestris) a fortnight previous, I had promised to deliver him another! Now, I imagine many AA readers may chuckle at someone foolish enough to promise a crown-giant observation (myself included). Much to my relief luck was on our side and we managed to spot not one, but TWO species practically on top of each other!

test 2

A Cuban knight anole (A. equestris) and Jamaican giant anole (A. garmani) perched within 1-2m of each other in Miami FL – April 2nd 2014, JStroud

Cuban knight anoles (A. equestris) and Jamaican giant anoles (A. garmani) are both non-native introduced species to south Florida.

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A. equestris (left) and A. garmani (right) – habitat overlap in Miami FL, JStroud

Miami Anole Safari (Part III)

Firstly, let me start by offering my sincere apologies for the standard of photography you are about to view. As you AA readers have become accustomed to Jonathan’s flowing prose, and other members’ excellent use of modern photographic equipment, I must warn you not to expect either here!

As has been mentioned previously, the IBS Conference was a tremendous success, and firstly huge congratulations must be passed on to (a potential anologist in the making?) Ken Feeley for all the hard work and effort. The lack of talks concerning arguably one of the world’s most studied vertebrate biogeographic systems did not detract from the high levels of anole hunting that ensued over the course of the conference!

After a wonderful afternoon visiting Miami’s most bizarre lizard community, the following day provided an opportunity for conversations to be followed up from the previous night’s conference dinner (as some graduate students’ memories may have appeared a little hazy on Saturday morning). Much of the day was spent wandering around FIU’s Biscayne Bay Campus eagerly trying to find the dozen knight anoles that were promised to us the previous night by resident expert, and thoroughly nice guy, Sean Giery.

Sean has spent the past 3 years observing the A. equestris community on this campus, and has assured me that he will bless AA readers with a synopsis of his eagerly awaited dietary analysis paper in the near future. The day started brightly, with two juveniles being found in close proximity to each other; however with just he and I as the only observers, it was tough to include these individuals in the promised dozen.

Juvenile knight anole found on a horizontal branch ~2m high. Photo by JStroud

Juvenile knight anole found on a horizontal branch ~2m high. Photo by JStroud

At the start of lunch, and confronting the midday heat with the enthusiasm of schoolboys on a day trip, we regrouped with some extra eyes and headed back out to continue on our quest. Although A. sagrei, A. carolinensis and A. distichus were abundant, these were still not the target species. A loud thump behind us saw us all swivel in synchrony, like a troop of sunburnt and slightly dehydrated Michael Flatley fanatics, to be confronted by a rather startled green iguana that had just plummeted 10 feet after submissively losing a dispute to a larger male. The campus had previously been awash with a healthy population of green iguanas; however the big freeze of 2009 reduced this significantly so that the only survivors were those small enough to retreat underground. Continue reading Miami Anole Safari (Part III)

Anoles in the Blogosphere

It turns out that Anole Annals isn’t the only member of the WordPress.com stable that has a thing for our favorite lizard. While recently doing some tag surfing, we came across the following posts.

Catholic mom tells the gripping (or not) story of a green anole that went for a ride on the minivan windshield. You can probably guess the outcome, but the photos are nifty. Continue reading Anoles in the Blogosphere