Walking around Redonda

One of our first goals on Redonda was to get a good sense for the density of lizards on the island. This is one of the key metrics that has changed following rat eradications elsewhere in the Lesser Antilles. To do that we used a few different methods, we’re hoping that each will give us a slightly different sense for densities that we can compare one year to the next.

The first was a mark-recapture study in two different locations. We’d survey a fixed area (one of the big fig trees at the north of the island and a boulder field at the south) and catch all the lizards we could find. Every time we caught a lizard we’d write a number on its belly and put a little white dot on its backside (see below). The paint spot will help us see the lizard from a distance without spending lots of time trying to catch a lizard that’d already been caught that day.

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Lizard number 22 getting a number on its belly. Photo credit: Geoffrey Giller

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An anole hanging out on a branch after getting a white spot. Photo credit: Geoffrey Giller

We spent two long days marking all of the lizards we could find in the tree and the rocks. After each site had had a day to rest, we returned. By figuring out which lizards we’d previously caught and how many new lizards had shown up we can get an estimate of just how many lizards are using that area. The lizards in the tree were particularly plentiful – we’re estimating a population of around 50! with unlimited time we’d continue marking, revisiting, and recapturing a few more days but our island time was short so we compromised with a single recapture day at each site. We’ll repeat the survey next year in the same places to see if there are changes in density.

Our next survey method was the tried-and-true walk around, look on both sides of your path, and count ’em up. For this Anthony did a big hike around the perimeter of the island counting all of the lizards he saw. He did this twice and found a lot of lizards! Here’s a page from my notebook showing the track. Unfortunately the map only really makes sense to us, but as you can see, he saw 61 anoles and 65 ameiva that day. The next day he ended up seeing 73 anoles and 118 ameiva! Those are pretty wide margins, but they’ll provide a baseline for next year’s repeat transects.

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Now, I decided to strap a GoPro to Anthony’s head for the second survey. It’s two hours long though so I had to speed the video up. Grab your dramamine, you’re going to need it!

This video is just a short segment of the hike in the vicinity of the “Hanging Gardens.” It’s one of the prettiest parts of the island I think. You can tell too how tricky some of the traversing is. On this section Anthony saw 10 ameiva and 24 anoles. Can you find them? I slowed down the first ameiva so you can get a good look. You’ll also notice a few other surprises along the way.

 

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Reporting on the Reptiles of Redonda

This post is reposted from www.anoleannals.com and so might be a little familiar in its start to readers here.

IMG_4616I’m back from Redonda and the expedition was a great success! I’m happy to report there were many Anolis nubilus boulder-hopping out of the way of the black rats and even blacker ground lizards on the island. In many ways the trip was even more challenging than expected but we came out with quite a lot of data so we have a great sense of the current status of the reptiles on the island and a baseline for comparisons into the future.

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To refresh your memories, Redonda is an island of Antigua and Barbuda and was completely denuded by rats and goats over the last century. Despite the dearth of vegetation, three endemic reptiles had been hanging on: Anolis nubilusAmeiva (Pholidoscelis) atrata, and an as-yet unnamed Sphaerodactylus dwarf gecko. The government of Antigua and Barbuda, in collaboration with Fauna & Flora International and local NGO the Environmental Awareness Group, has decided to undertake a massive restoration effort by eradicating the rats and relocating the goats. My job was to get some baseline data on the current lizard populations so we can figure out how they change into the future.

Helicopter inside

Helicoptering to the island was every bit as exciting as I’d hoped. The Jurassic Park theme was playing through my head the whole way down. See that grassy patch with slightly fewer large rocks – that was the little tiny helipad, but our pilot was a pro and set us down perfectly. Almost as soon as we were out of the helicopter, we deposited our bags by our tents and set about catching Anoles.

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Anolis nubilus is at first blush a relatively innocuous member of the genus. They’re perfectly camouflaged in this environment, which is to say they’re drab gray and brown. Their dewlaps are cream-colored (which is really just my nice way to say drab gray-yellow) and the most elaborate of the females sport faint dorsal stripes. Males did fairly regularly display impressive crests behind their heads, but nonetheless, the species at first and second glance is considerably less flashy than many of their cousins on nearby islands.

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Photo: Geoffrey Giller

All that said, there’s still a lot of cool stuff going on with nubilus. As Skip mentioned in his article 45 years ago, there’s a casuarina tree right next to the remains of the mine manager’s house that hosts an abundance of the few Redonda tree lizards living up to their name. The tree is still there and the lizards are still eagerly defending their precious few branches (see above).

There are actually quite a few trees still on Redonda, some of which are native Ficus trees. For the most part they’re in fairly inaccessible areas, but that really just means you need to bring a longer noose pole and don’t look down. I caught a lizard on this tree below with a perch height of approximately 350 meters (that’s really going to mess with the averages). Truth be told, after catching the lizard my knees were so wobbly I had to go find a nice big boulder and just had Geoff and Anthony shout me data for a while.

fig cliff

After a week on the island and many many Anoles, we got morphometric and performance data, diet data, extended focal-animal behavior videos, two mark-recapture density studies and two permanent transects established, thermal ecology data, habitat use data, and flight behavior data. We even exhaustively determined whether nubilus likes Chuckles! (But that’s a story for another post).

I know this is an Anole blog, but there were some pretty cool things going on with the other reptiles on the island, too. The ground lizards were jet black and really big. Here’s a picture of Anthony Herrel trying to get a tail measurement:

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Photo: Geoffrey Giller

The atrata spent their days cruising around scavenging. We saw one eating a hermit crab, and we heard rumor of another that managed to get a sardine away from one of the crew working on the eradication effort! Analyzing the stomach contents of these guys is going to take quite a lot of detective work.

We also were able to gather the first natural history data on this unnamed dwarf gecko species. They’re strangely beautiful with an unlovely shovel-face and semi-transparent, too-squishy, gelatinous body. You wouldn’t guess it but they’re quick! 1D4_1226editlarge

In all, the reptiles of Redonda were fascinating and getting to explore the island was a unique privilege. I can hardly wait to return next year, and many years after, to see how the lizards change with the island.

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“What about us?” Technically these guys are reptiles too, but c’mon, the lizards are so much cooler. Photo: Geoffrey Giller

Redonda

I know this is a bit last minute notice but it seems like that’s how this whole project has been. I’m headed to Redonda in a week!

Redonda you ask? Never heard of it? Yeah, well, neither had I. Redonda is a little tiny island in the Lesser Antilles and to save you the trouble of searching for it, here it is on a map:

(you’re going to have to zoom out a few clicks to get some context)

Redonda is owned by the government of Antigua and Barbuda. Up until a few days ago the only residents on the island were goats, rats, and three species of endemic lizard. (Alright, there are a few avian reptiles too but my mother’s the birder of the family and the four-legged ones are just so much cooler). I say up until a few days ago because the government of Antigua and Barbuda have decided to designate a beautiful, massive new marine sanctuary with Redonda as the jewel in the center. The only problem being that that jewel is currently crawling with goats and rats and that just won’t do!

In partnership with some great conservation organizations (Flora and Fanua International [FFI] taking the lead) the goats are being ferried off the island (they are a rare breed) and the rats are being removed somewhat less ceremoniously with a highly targeted poison that won’t hurt any of the native species. You can read more background on the project here. The removal of goats and rats is going to change the face of Redonda.

Judging from other islands in the neighborhood, Redonda probably used to be covered with lots of vegetation and was definitely a lot more lush than it is today. Unfortunately, after goats and rats were introduced a little over a century ago all of that vegetation has been nibbled down, making Redonda into a barren boulder moonscape. Conditions are so harsh now that the goats are actually dying of starvation (you know it’s bad when even goats can’t find something green to nibble) and the rats have turned into diurnal apex predators, stalking lizard prey even in daytime!

This is particularly problematic because the only place in the whole world these three lizard species are found is on this island. There’s a little tiny gecko that’s so rare it doesn’t even have a formal scientific name yet. There’s a large “ground lizard” called Ameiva atrata that is almost completely black and looks really awesome. And there is an anole called Anolis nubilis, known as the Redonda tree lizard. That name is unfortunately ironic because there is exactly one tree left on the entire island. It’s a non-native Casuarina species from Australia that was planted on the island decades ago and was so unpalatable that even the starving goats let it be!

It’s for these lizards that I’m headed to Redonda. I’m teaming up with FFI and the government of Antigua and Barbuda to put together as comprehensive a dataset as possible on these lizards in the wild. Our goal is to see how they change as Redonda recuperates following the rat and goat removal.  I’m flying to Antigua in exactly 1 week and I’ll be in Redonda 2 days after that. Over the next few days I’ll post a few more times with details of the trip. I’m extremely excited but my brain is fairly bursting with packing lists and contingency plans. I’m looking forward to filling you in on the details.