Saturday, February 28, 2009

I <3 the BBC

I already preferred BBC for the quality of their international reporting, but they just took it to a whole new level. Accompanying a straight-forward article on the Zimbabwean dictator Robert Mugabe's latest abuse of power and his birthday party, they posted a photo of a cake-scarfing Mugabe glaring with evil intent at a very young girl, with the caption "The birthday cake reportedly weighed 85kg (187lb)". The article may be neutral but their opinion is clear. I am totally in love with the BBC.

Thursday, February 26, 2009

The cute little ugly one: Engystomops pustulosus

I end my Venezuelan frog posts with one of the more interesting species: Engystomops pustulosus, the Tungara Frog. This is another Leptodactylid, related to the Leptodactylus and Pleurodema I've already covered. Engystomops is a small little frog that is quiet abundant and very vocal every night on the ranch. It produces a weird two-part call that sounds very much like two different frog species calling at the same time - check it out in my frog call video.

I was surprised to discovered very similar photos of this species in an animal communication textbook. It turns out this is a fairly well-studied neotropical frog (mostly under its former genus Physalaemus), with papers on its odd call and sexual selection, and its foam-nesting habits.

A pair in amplexus

Wednesday, February 25, 2009

Endless frogs most beautiful: Hypsiboas crepitans

First off, forgive my punny title. To make up for that, I'll keep the words to a minimum on this one. Here are my vast collection of photos of Hypsiboas crepitans, a treefrog (Hylidae) that was one of the most abundantly encountered anurans on Hato Masaguaral. They are highly variable in pattern, with lots of plain browns but some are quite nice. The best part are the eyes. Don't get sucked in.

As the season progressed into November and the rainy season began winding down, the frogs begin showing up more and more in our parrotlet nest boxes, in our homes, in our clothes. I'm not really sure why, but it sure is hilarious to open a nest box and not see the bottom.

That's over twelve Hypsiboas crammed in there. I just wish I got the photo that evening. When I walked up on the box in the twilight, a big dark mass bulging out of the entrance hole startled me. I shined my light on it and saw two dozen eyes staring back at me as they were all scrambling out for the night.

During the breeding season, they call from elevated perches over wet areas. Before I learned their call I spent fifteen minutes sifting through a flooded patch of pasture before I happened to look up and see the calling frog just over my head in a shrub. To hear their call, check out my frog video compilation.

Tuesday, February 24, 2009

South America's Spadefoot Look-alike: Pleurodema brachyops

Any examination of world Anuran diversity will come across many examples of convergence in body form and function. Just examine one functional class of frogs - the burrowers. Many different frog families on all continents have evolved burrowing members. They vary in their method of burrowing, general shape, habitat, and behavior, but two broad groups emerge.

There are the flat, pointy-nosed type, frequently the front-limb diggers. These include:

Rhinophrynus dorsalis - the Mexican Burrowing Toad, only member of the family Rhinophrynidae (see awesome photo here)

Hemisotidae - 9 species in the genus Hemisus from Africa (photo)

Nasikabatrachus sahyadrensis - a recently discovered purple frog from India, only member of the family Nasikabatrachidae

Nasikaba.... oh, the ugly purple one (source)

Microhylidae - many species in many genera found worldwide, including the North American Gastrophryne and others

Gastrophryne carolinensis - Eastern Narrowmouth Toad (source)

Then there are the fat round ones (okay, so Rhinophrynus and the ugly purple one kind of bridge this artificial class system). They are characterized by a short, squat body, big bug eyes on the top of the head, hard digging spades on the limbs, and an episodic lifestyle of spending most of the year buried underground in aestivation, only coming up during rains to breed. These include:

Microhylidae - another member of this large family is the genus Breviceps from Africa (split into the Brevicipitidae in some taxonomies). These frogs are some of the most hilarious looking of all amphibians. I can't help but laugh everytime I see one. You MUST see photos here, here, here, here, here, and here.

To see these frogs in action, check out this clip from Life in Cold Blood:

Myobatrachidae - this diverse family takes up many convergent niches in Australia, including burrowers in the genera Neobatrachus, Opisthodon, Notaden, and more.

Neobatrachus sudelli (source)

Opisthodon spenceri (source)

For Notaden - another MUST see photo can be found in this fieldherping thread. I guarantee you will burst out laughing on seeing it - look at that frowny face!

Notaden are referred to as 'spadefoots' for their digging apparatus, as are some species well known in North America and Europe:

Scaphiopodidae, seven species in two genera (Scaphiopus and Spea) in North America

Spea hammondii (source)

The hard black spade on the foot of Scaphiopus couchii (source)

Pelobatidae, four species in the genus Pelobates

Pelobates fuscus (source)

These last two families are closely related and probably don't truly represent convergence.

Finally, I discovered during my stay in Venezuela that some members of the diverse Neotropical family Leptodactylidae deserve to be labeled spadefoots (spadefeet?) - particularly the 12 species of Pleurodema.

Pleurodema brachyops

Pleurodema brachyops inhabit Hato Masaguaral, where I saw them on several different nights after rain. Like so many of the other species listed above, Pleurodema is a burrower that lives in the loose sandy soils of the llanos. They emerge after rains to breed in the pools that form during the wet season, then disappear underground again. While I never personally saw emergence, the description of this behavior in Staton and Dixon (1977) is perfect:

This ubiquitous frog was invariably seen on sandy soil and apparently stayed beneath the soil throughout the day. This species was observed emerging from sandy substrates between 2300-2330 hrs on several nights. Their emergence from a sandy substrate with sparse vegetation between the above hours reminds one of "popping popcorn". Almost simultaneously, several will emerge by a sudden eruption of sand, head & eyes appear first, followed almost immediately by a short jump which clears them from their daytime retreat. They appear as lumps of damp sand with only the eyes visible, but shortly the condensation on surrounding grass leaves washes away the sand particles leaving the frog almost the same color as the sand. The only visible color to the eye is the bright orange "flash marks" of the groin as they jump from place to place. Calling and breeding began immediately after the first heavy rain of the wet season and extended throughout the rainy season. It called from shallow water.

Unfortunately, this Pleurodema chose to emerge in a less-than-glamorous location all too common on a working cattle ranch:

The orange flash marks mentioned by Staton and Dixon actually form big bright eyespots when the frogs are floating in the puddles, calling. Also check out the mosquitos feeding on the floating frog (click to zoom).

Here you can make out two hardened digging spades on the rear foot:

Finally, I leave you with Pleurodema love. To hear their calls, see my frog calls video.


Staton MA, Dixon JR (1977) The herpetofauna of the central llanos of Venezuela: noteworthy records, a tentative checklist, and ecological notes. Journal of Herpetology 11(1):17-24.

Monday, February 23, 2009

The always difficult Leptodactylus

The neotropical frog family Leptodactylidae is a massive one, and the most prominent among its members is the genus Eleutherodactylus, the largest vertebrate genus with over 700 species (of course, the recent flurry of systematic changes in amphibians has begun carving up these groups, so neither statement may hold true anymore). These are small nondescript brown frogs whose identification makes Empidonax seem incredibly simplistic.

Another member of this group is Leptodactylus, a genus of larger species who are convergent on our northern frogs in the genus Rana (actually, that name may have changed too!) in habits and shape - long-legged jumping species of wet areas and edges. In my research before herping in Venezuela I narrowed down a list of about eight possible Leptodactylus and relatives that I could potentially see. Even with this pared down list, details on identification were sketchy, and I still had a rough time sorting out these frogs. When I compiled enough photos of all of Leptodactylus I saw on Hato Masaguaral, I could break it down into two groups. With some help from fieldherpforum, I confirmed the ID on these two species:

Leptodactylus wagneri (probably a species complex, so look for that name to change too)

Leptodactylus macrosternum

I would say these identifications are more tentative than the others I post, so don't run off and claim these as a taxonomic authority on the subject!

For video of the wagneri calling, see my frog video post.

Are these the only two species I saw on the ranch? Probably not, but they are so difficult to catch many got away.

Sunday, February 22, 2009

I got milked by the Rana Lechera: Trachycephalus venulosus

One frog I didn't get to film while calling is Trachycephalus venulosus, a Hylid treefrog (I wish I had - check out their ridiculous vocal sacs!). I did get to witness the origin of the common name of some frogs in this genus - Rana Lechera, or Milk Frog. Poisonous skin excretions are a common defence among many amphibians. Trachycephalus are a group whose secretions are obvious and include a bit of physical defense as well as chemical.

The very first T. venulosus I encountered on Hato Masaguaral put this defense to good use. I found this big guy roosting inside a parrotlet nest box. I shook him out into the box cap so I could catch him (he was a lifer, after all) and he got rather upset about it. Out oozed the milk!

Their skin secretion was very sticky and glues my fingers together, much like that of Slimy Salamanders (Plethodon glutinosus complex) in the US. It is undoubtedly toxic or distasteful, but I wasn't about to go licking unknown skin secretions in the field. Instead I just played with this big charismatic treefrog for a few minutes, then let him go.

I encountered T. venulosus fairly frequently over my three months at Hato Masaguaral, but none ever milked me to the extent of that first big one.

This one lived in a whole in our gate

A smaller individual in a parrotlet nest box

Did you eat any parrotlet eggs? (Photo courtesy Rae Okawa)

Digging in the nest boxes (Photo courtesy Rae Okawa)

(Photo courtesy Rae Okawa)

(Photo courtesy Rae Okawa)