A recent issue of the journal, International Reptile Conservation Federation (IRCF), contains two short articles featuring recent observations of two new species introductions to Abaco. Below, I relay these findings and offer a few thoughts on what these recent observations suggest for the future of Abaco’s fauna.
The first article is a brief account of the establishment of a small frog, the eastern Narrowmouthed toad (Gastrophyrne carolinensis) on Abaco and it’s expansion throughout the Caribbean region (link to paper). This paper is largely a follow-up of previous Abaco Scientist blog posts that some of you might have already seen (link). However, the final product has some additional information that is worth checking out.
The second paper is a report by Scott Johnson and David Knowles of some recent sighting of another herp species, the knight anole (Anolis equestris) in Marsh Harbour (link to paper). Scott and David provide photographic evidence of one adult lizard from the Port Building in Marsh Harbour and report that another two were seen by Marsh Harbour residents in the previous two years. While this is probably only three knight anoles, with no evidence of reproduction, it seems possible that establishment of this large lizard on Abaco has occurred, or is imminent.
Recent introductions to Abaco, including the red corn snake, are symptomatic of a emerging pattern describing the spread of reptiles and amphibians in The Bahamas. In the last few years several new reptile and amphibian introductions have been noted in Abaco. Yet, each of these species was previously established on New Providence and Grand Bahama. What does this pattern say about how these species arrive on Abaco, and what additional species can Abaco expect to see in the near future?
Where do they come from?
Well, I can say that we don’t know exactly where these animals originated from. However, there are two primary suspects: Florida, and The Bahamas.
Florida: High volume trade between south Florida and The Bahamas is undoubtedly a vector of invasive species in the Caribbean region. Trade in landscaping plants seems to be the most likely route of species transportation. Frogs, lizards, and snakes abound in Florida nurseries where palms and shrubs are grown and sourced to The Bahamas. Corn snakes and narrow-mouthed toads burrow into loose soils and are likely to hitch a ride in root balls and pots. Similarly, knight anoles frequently use palm crowns where they can stowaway during transport. Alternatively, knight anoles lay eggs in the soil underneath tress that could persist through the journey across the channel.
The Bahamas: Once introduced populations establish within an area they often spread from the point of introduction. This phenomenon sometimes termed the ‘beachhead effect’ results in subsequent introductions called ‘secondary invasion’. Under a secondary invasion hypothesis the source of the recent invasions to Abaco would be from within The Bahamas. All three of the recent herp invasions to Abaco include species already established on Grand Bahama and New Providence, as well as Florida which muddles any easy attempt at determining the origin of corn snakes, narrow-mouthed toads, or knight anoles arriving in Abaco.
Of course, it’s also possible, if not more probable, that Abaco’s recent introductions are sourced by a combination of secondary and primary introductions. Nevertheless, the route of introduction is likely the same – trade in ornamental plants.
So what else can we expect to disembark on Abaco? That is, what other species can we expect to see on Abaco in the near future? Well, the pattern emerging suggests that Abaco’s new fauna follows their establishment in other islands of The Bahamas, Grand Bahama, and New Providence in particular. So, what other species are there?
Rather than go into depth why, I’ll just offer a few predictions, guesses really, as to which species are likely to arrive in Abaco in the coming years.
- Squirrel treefrog (Hyla squirella) – Introduced from Florida to Grand Bahama, these small, adaptable treefrogs are adaptable and seem a likely invader.
- Red-eared slider (Trachemys scripta) – A popular pet, these tough turtles rapidly outgrow their tanks and are often released. I’ve seen a few around Abaco over the years, including one that I fished out of the ocean off of eastern shores. But luckily, I’ve yet to see any signs of reproduction there. However, these are one of the world’s most invasive species. Certainly it’s the world’s most invasive and damaging turtle species. Keep an eye out, this one might already be established in Abaco.
- Brahminy blind snake (Rhamphotyphlops braminus) – These small, shiny black snakes are often called thread snakes. Currently established in New Providence and introduced from who-knows-where, these are a likely, if not already introduced, component of Abaco’s fauna. Sometimes called ‘Flowerpot snakes”, these little snakes have been introduced throughout the tropical and subtropical regions of the world. My guess is that they’re already on Abaco. However, these worm-like snakes are easy to overlook because, 1) they are tiny, look like worms, and live underground, and 2) they resemble a native species of blind snake (link).
- House geckos (Hemidactylus spp.) – There are a few different species of gecko introduced to The Bahamas. At least one has already been introduced to Abaco. Take a look under your outdoor light at night and you’ll know what critter I’m talking about. Note, these are also the lizards that leave little turds around your house. They’re a bit difficult to distinguish from one another, and I admit, I’ve never tried to differentiate the various species likely inhabiting Abaco: H. mabouia, H. garnotti, and H. frenatus. However, these adaptable nocturnal lizards with vertical pupils and extraordinary climbing abilities are able invaders and likely to continue to arrive in Abaco. The recent introduction of another invasive island tramp gecko, the mourning gecko (Lepidodactylus lugubrious), to the Caribbean from the Pacific suggests that this species may one day arrive in The Bahamas.
- Cane toad (Rhinella marina) – Recent establishment of this invasive species on New Providence has raised alarms throughout the archipelago (link). Native to tropical South America, these invasive amphibians have (been) spread throughout the Caribbean. They’ve been linked to a variety of ecological injuries, which has raised the alarm for The Bahamas (link). While control efforts are underway in New Providence, large populations of these large, fecund amphibians in Florida and throughout the Caribbean suggest that their appearance in Abaco is likely.
What seems obvious from these recent observations is that new species are arriving in Abaco every few years. As mentioned previously, the geographic origins of these introductions is unclear, but is likely tied to shipments of landscaping plants from Florida. This flow of species into Abaco will continue. As it is now, Abaco currently includes at least: 2-4 non-native lizards (it’s complicated), 1 non-native snake, and 1 non-native frog. My guess is that most of these introductions will not affect the Abaco landscape to any appreciable degree. However, the introduction of the corn snake is a potentially serious threat to ground nesting birds such as Abaco’s parrots. Conventional knowledge suggests that the potential for ecological harm grows with each new introduction – a thought worth keeping in mind.