Frogs by the garden hose

Introduced species play conspicuous roles in any ecosystem, particularly here in south Florida, the gateway to the Caribbean and most of Latin America. Every few years we hear of the potential for ecological harm posed by the latest introduction, either those that have escaped from captivity, like the walking catfishBurmese python, or Purple Swamphen; the Everglades ecosystem is still threatened by the intentional introductions of invasive plant species like melaleuca and Brazilian Pepper.

Another widespread exotic species in Florida is Osteopilus septentrionalis, the Cuban Treefrog. It’s the largest treefrog in North America by far, and it’s considered an invasive species here. According to the USGS fact sheet on this species,

Osteopilus septentrionalis is usually introduced through horticultural shipments and plantings (especially palm trees) (Meshaka, 1996a, b, 2001; Jackson in Meshaka, 1996a; Livo et al., 1998; Mitchell, 1999; Owen et al., 2006; Enge et al. 2008), building materials (Meshaka, 1996b; Dodd and Griffey, 2002; Owen et al., 2005, 2006), and motorized vehicles (Meshaka, 1996a; Enge et al. 2008). In addition to anthropogenic dispersal, it also is possible that they can disperse throughout much of the Caribbean by rafting on floating vegetation (Meshaka, 2001). Several authors have suggested that indigenous Cuban treefrogs may have existed on Key West and the lower Florida Keys since pre-Colombian times (Lazell, 1989; Meshaka, 2001). [All references are at the aforelinked fact sheet]

However they first got here, they certainly feel at home now. (By the way, most experts classify this frog, despite its cubacentric name, as a West Indian species, because it is widely distributed in the islands. It doesn’t have to worry about the wet foot/dry foot policy…) When I came home from work yesterday, M and little e greeted me with the news that one of these alien invaders could be seen at our garden hose, and sure enough, this little guy seemed quite at home there:

They don’t worry about whether they’re supposed to be here or not; they just go on about the business of being a treefrog. Of course, since they’re larger than other treefrogs, and they are frogs, which eat just about anything they can fit in their mouths, the success of the Cuban treefrog has come at the expense of our native frogs, through outright predation and competition for food and breeding resources.

Despite the fact that they are competitors of some of our dwindling populations of native treefrogs, they are still quite interesting little (and not-so-little) creatures, squawking away now and then of a wet evening, calling their call (a fairly raucous scraaaack that sounds a little bit like the call of the Southern leopard frog, except that it’s usually just one note, not several short ones in a row like Rana sphenocephala), looking for love. Dorcas & Gibbons (2008) describe it thusly:

The advertisement call sounds like a rasping version of a cross between an eastern spadefoot toad’s incessant qwaah and a southern leopard frog’s “rubbed balloon” croak.

It’s easy to tell adults of this species from just about any other treefrog on account of their size: they’re almost twice as large as our native species, up to 6 inches in the largest females. It’s hard to tell size from a photograph, and if you don’t have a native treefrog handy to compare, or you’re looking at a small individual, you need to focus on other identifying characteristics. Elliott, Gerhardt, & Davidson (2009) say that you can distinguish smaller individuals from other Florida treefrogs “by its lack of stripes and other markings running from the front of the eye to the rear and sides of the body” (120). They also note that “individuals can change color rapidly, usually from some shade of brown or tan to pale green (or vice versa), and spots may appear or disappear” (120).

Another way you can tell them apart, according to my Dorcas & Gibbons, is by the size of the toepad: it’s “disproportionately larger than those of any other southeastern frog” (103):

Yet another way you can distinguish them from our native treefrogs is their skin: they are usually pretty lumpy bumpy, while our native treefrogs look quite a bit sleeker. Furthermore, according to my Ashton & Ashton (1988),  “There is a fold of skin from the eye over the tympanum and ending on the shoulder” (177). You can see it pretty clearly in this detail:

Cuban treefrogs, at least in my experience, are also pretty blase about being approached; they seem much less shy than, for example, the still unidentified critters I saw at Lake Ida ten days ago. (This could be a sign of how successful they are as a competitor; they don’t fear much, perhaps because they don’t have much to fear?)

This is not to say that they are entirely fearless; this individual eventually tired of all the attention s/he was getting from my camera, and decided to head for greener pastures. As it got going, though, it revealed its signature markings, the wash of color on the sides and back of the legs in this shot:

We’re supposed to euthanize these guys whenever we find them around, but they’re so well established, and the process is such a pain, I never can find it in my heart to do that. So this guy went on his merry, and I went about my business. Cheers!

If you’re curious, here are the instructions from UF/IFAS on how to euthanize a frog:

To euthanize a Cuban Treefrog, hold the frog firmly in your hand and apply a 1 inch bead of benzocaine ointment along the back of the frog. Benzocaine ointment is a topical anesthetic (a numbing agent) used to treat skin pain (e.g., from sunburn) and itching as well as toothaches and sore throats. There are a variety of name brand and generic versions that are available over-the-counter in a tube or spray. If you are able to, using a gloved finger spread the ointment out on the frog’s back. Alternatively, you could use a benzocaine spray. Once the ointment or spray is applied, place the frog in a plastic grocery bag or a sealable sandwich bag for 15-20 minutes so that the benzocaine has a chance to render the frog unconscious (be sure to seal the bag or tie it closed). After the bezocaine has anesthetized the frog, place the bag in a freezer overnight to ensure that the frog is dead and then throw it out in your trash. If you are unable to apply benzocaine to the frog, you can simply put it in a plastic bag, seal or tie the bag shut, then place it in the freezer overnight–dispose of the bag and the frog in the trash the next day. Do not throw a bagged frog into the trash without euthanizing it first. Remember, Cuban Treefrogs have a noxious skin secretion so be sure to wash your hands thoroughly after you handle the frog, even if you wear gloves or use a plastic bag.
Freezing is a humane way to kill amphibians because their bodies go into a state of torpor (metabolism slows way down) — just as they do in cold weather outside. If the cold weather is short in duration, the frogs will come out of their torpor state. However, after an extended time in freezing temperatures, the frogs die.
A good test to determine if a frog is a Cuban treefrog is to grasp the frog firmly, but gently, and try to move the skin around on the top of the frog’s head with your fingertip. The skin on the head of a Cuban treefrog is fused to the top of the skull and won’t move.
Be sure to wash your hands after handling any frog or toad. They all secrete a slimy film to protect their skin, but the secretions of some species, like the Cuban treefrog, can irritate the skin and eyes of some people.

Spring 2010 migration count

Every spring and fall for the past five, maybe six, years, I’ve participated in the North American Migration Count for Palm Beach County. Last weekend I was responsible for two areas: Lake Ida Park and Dog Park in Delray Beach and South County Regional Park in western Boca Raton.

I began well before dawn in my driveway:

and made it to the lake well before sunup; here’s the sun rising over the lake about 20 minutes after I’d already started counting:

A few birds there were:

And many birds there weren’t. The most popular migrants in North America are the warblers, but they always seem to leave our area before the NAMC. I found two individuals, same species, American Redstart.

But despite the lack of migrants, fun was had by all (well, at least me), and it was wonderful to get out in the field a little bit. You never know what you might run across. For example, while setting up to take the pictures of the Limpkin and the Royal Tern above, I noticed a few tiny anurans hopping around in the undergrowth. After leaning up against the tree to steady myself and take those shots, I was able to track down one of those little hoppers, as you can see:

I still have no idea what it is, but it was fun to follow and get a good shot of…

After a couple of hours at Lake Ida, I headed over to South County Regional Park in west Boca, where I got my Bird of the Day, a Swallow-tailed Kite (no pictures; they’re hard to photograph, at least for me). I also saw a Least Tern fishing over one of the many ponds in the park:

All in all, it was a very good day. Hope you enjoyed yours!

Frog Concertos

Lang Elliott, author and coauthor of many fabulous compilations of nature sounds (the Stokes Field Guide to Bird Songs, Frogs and Toads of North America, Songs of Insects, and many more) has just (finally!) released his much-anticipated CD of Frog Concertos. No narration, nothing to get in the way of the sounds of these wonderful little critters. Just 20 tracks, 1.2 hours (118.6MB in my iTunes), of frog recordings.

Downloadable through Amazon, or you can buy the CD from the author’s website. He has also posted descriptions of the songs (where and when recorded, what species are on the track) to the website, for those of you who might like to know more about what you’re listening to. Here is an excerpt of his description of one of my favorite tracks, Track 9 (I like this track because it’s so richly layered, with insect sounds, treefrog sounds, and pig frogs, all of which can be heard in my neck of the woods, in addition to Saint Marks NWR where he recorded it):

Saint Marks Rainfrogs. The rough nasal quank, quank, quank of Green Treefrogs is a signature sound of southern swamps. Green Treefrogs dominate the chorus in this recording made at the Saint Marks National Wildlife Refuge near Tallahassee, Florida (May 8, 1988). Listen also for the throaty grunts of Pig Frogs, the bellowing notes of Bullfrogs, and the high-pitched trills of crickets.

You have to admire someone who puts this much love and attention to detail into his work. Well, you don’t have to, but I sure do.

I just downloaded the set this morning, and am already on my second listen-through. It’s so much more conducive to the type of work I do than the radio that our office is constantly playing. My coworkers have asked me what “that squeaking noise” is, and I’ve already started spreading the gospel. Give it a listen! You’ll be glad you did.

To find out more about the frogs we have here in Florida, click here or here.

Boca Beaches

One of the things that I admire about Boca is that, despite its many faults, it does have some semblance of a commitment to environmental practices. For instance, it isn’t supposed to groom the beach above high tide during turtle nesting season. So the beach gets a little ugly, but it keeps those gigantic machines off the turtle nests. Well, apparently no one told the operator of the giant beach groomer that we saw a few weeks back, chugging south along the beach well above the tide line. You can see how neat the beach above high tide looks in the picture below:

Thing is, this crawler was not limiting itself to the tide line. Unfortunately, I didn’t get any pictures of its path (it wasn’t something I was thinking of as I was concentrating on taking pictures of the boy and his lovely mother), but trust me: the adherence to this regulation is mighty loose…

It did manage to swerve around the marked turtle nests, but what if (heaven forbid!) the volunteer turtle nest spotters missed a nest? See below for a few shots of the nests and the metal mesh that is supposed to protect them from raccoon predation before hatching (nothing can protect a newly hatched turtle, or tern for that matter. I’ve heard heartbreaking stories of crows waiting outside tern exclosures for the hatchlings to emerge, and gobbling them down one by one as they do). Note how deliciously untidy the beach is around them, with bits of seaweed everywhere. That’s what a beach is supposed to look like!

Not being a turtle expert, I’m not sure what kind of turtles are involved in these nests, but the most common turtle along our shores is the loggerhead, followed by green, then leatherback. If you had the hi-res photos, you could zoom in and see a CC on most of the signs. I assume that’s shorthand for Caretta caretta, the loggerhead turtle. The numbers would be the number of eggs in the nest, and the date, well, I would hope that’s self-explanatory: the date the nest was laid. So most of the nests I’ve seen have been loggerhead nests until I hear different from the people who conduct the research on the turtles of Boca. The studies are conducted by the Gumbo Limbo Nature Center, in conjunction with Florida Atlantic University.

The best books on sea turtles are still Archie Carr’s, particularly The Windward Road. The recent title by James Spotila updates Carr, but can’t match his prose. For an epic look at the leatherback, there’s the recent account by Carl Safina, Voyage of the Turtle.

Turtles race, now?

Well, I’ve been posting regularly here for nearly a week now, and rather than break the streak, I thought I’d at least cross-post an article from last month in Science Daily about Leatherback turtles. I’m still stuck on that book review. Maybe tomorrow… For more on the turtle race, visit National Geo’s website about the race. Of course, the race is no longer live; it finished earlier this month. Read more

Cubans in Florida

With Fidel Castro’s health in serious decline the last few years, the media here in south Florida are waiting with bated breath to hear of the long-reigning leader of the island nation, and its communist government, to expire. Waves of human and animal exodus from the island have marked Florida, though. I discovered one in my garden this morning. Read more

Why Herptiles? Some recent books…

If you’re like me, you might never have really wondered why the word herptile was invented. After all, “Reptiles and Amphibians” is easy enough to say. And besides, “reptiles” aren’t such a simple class, anyway: lots of reptiles have no business being included in the class Reptilia. Until recently, though, no one like me has really had to care about this, because until recently there hasn’t been anything like the slew of high-quality books about the herpetofauna of North America, and particularly of the Southeast, where I live, that has recently hit the market. Read more

Limbless lizards

It was a dry winter here in subtropical Florida, with quite a bit less rain than normal since November. The temperatures haven’t been too unbearable, but the weekend before Easter brought a taste of summer: mid-80s, humid, and plenty of sun. That weekend also happened to be one of the few that I had time to get my hands a little bit dirty in the garden. So, there I was, weeding the cocoplum/palm/oak islands in the front yard. And then, when I couldn’t take it any longer and moved over to a shady corner of the house, I discovered an Eastern Glass Lizard (Ophisaurus ventralis) hanging out in the cocoplum.

As you can see from the picture, I was actually getting my gloved hands dirty:

Eastern Glass Lizard, dorsal view

Eastern Glass Lizard, dorsal view

Readers of this blog may remember that finding a glass lizard is a fairly rare occurrence around our house; I’d only seen one of these little beasties previously. Read more

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