Tag: frogs

Toad rescue

August 18, 2016 • 1:30 pm

by Greg Mayer

I’ve mentioned in previous posts how I periodically engage in turtle or frog and toad “rescues”, taking animals that had fallen into human made traps, such as window wells and stairwells, and releasing them, sometimes after feeding them for a while in captivity to fatten them up prior to release. A couple of days ago I decided to stop and check a stairwell on my campus, the University of Wisconsin-Parkside, where I’ve previously found toads and a turtle, and sure enough I found a young American toad (Bufo americanus), about 30 mm in snout-vent length, hunkered down in some leaf litter at the bottom of the stairs. I took the little fellow’s picture with a lady bug, the type of beetle made famous by Jerry’s academic grandfather Theodosius Dobzhansky.

American Toad with ladybug in stairwell, University of Wisconsin-Parkside, Somers, Wisconsin,16 August 2016.
American Toad with ladybug in stairwell, University of Wisconsin-Parkside, Somers, Wisconsin, 16 August 2016.

The beetle of course was not trapped, and could just fly away when it wanted to. I checked the same stairwell again the next day. It had rained in the general area the previous night, which might encourage toads to be moving about– and thus fall down the stairs– but I wasn’t sure if it had rained on campus.  There were two more American toads. These were smaller, about 18 mm snout-vent length. (A penny is about 19 mm in diameter.) These two were hopping about— they had just fallen in, and were in good shape. The toad from the previous day, although it looked good, may have been stuck in the stairwell for some days during a generally dry period, and was not active, but rather hiding in the leaf litter.

American Toads from stairwell, University of Wisconsin-Parkside, Somers, Wisconsin,17 August 2016.
American Toads from stairwell, University of Wisconsin-Parkside, Somers, Wisconsin, 17 August 2016.

Here’s the stairwell, on the northern side of the Communication Arts building, in which the toads (and last year a painted turtle) got trapped. This year’s larger toad was under the leaves on the far right. Once they go down a step, they cannot climb back up, and they get ratcheted to the bottom.

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Stairwell at UW-Parkside, NE corner of Comm Arts extension, 16 August, 2016.

I released these toads immediately after photographing them in Greenquist Woods, shown in the photo below, approximately under the large basswood leaves visible at the right. You can see how the ground slopes down to the left– just behind that screen of bushes is Greenquist Pond, which is where the toads breed, and the painted turtles live.

Greenquist Woods, University of Wisconsin-Parkside, Somers, Wisconsin,16 August 2016.
Greenquist Woods, University of Wisconsin-Parkside, Somers, Wisconsin, 16 August 2016.

Here’s Greenquist Pond looking north, with Greenquist Woods to the north and east, a lawn area (not well seen) behind bushes to the west, with a sidewalk and lawn edging to the south (from where the photo was taken).

Greenquist Pond, University of Wisconsin-Parkside, Somers, Wisconsin,16 August 2016.
Greenquist Pond, University of Wisconsin-Parkside, Somers, Wisconsin, 16 August 2016.

The smaller toads were recent transformlets from tadpoles this season. The 30 mm toad was a bit puzzling. Either it’s a transformlet from earlier this year which has grown quite a bit, or it’s a one year old from last year’s brood. It seems too small, based on my experience of toad growth in captivity, to be a year old, yet it seems odd to have in just one breeding season such a wide size range in the season’s transformlets (18 to 30 mm). I’ve not quite worked out the breeding phenology of the toads– perhaps I should figure this out.

After releasing the 30 mm toad in the woods the first day, I stopped at the Pond with the colleague who accompanied me, and there we found many small frogs that jumped in the water. At the size of those we saw, you need to get a good look at them to tell bull frogs (Rana catesbeiana) from Green frogs (Rana clamitans)– both species occur in the Pond. They all were diving quickly in the water, and we had no binoculars to get a close look at those that surfaced in the water, but one large individual sat still and let me approach. It was a large adult male green frog:  a green frog, because the dorsolateral ridge extends from the eye over the ear and along the side toward the groin (in bull frogs, the ridge curls round the ear); and a male, because the ear is larger in diameter than the eye.

Large male Green Frog in Greenquist Pond, University of Wisconsin-Parkside, Somers, Wisconsin,16 August 2016.
Large male Green Frog in Greenquist Pond, University of Wisconsin-Parkside, Somers, Wisconsin, 16 August 2016.

Frog defense: hiding, fighting, or both

June 4, 2016 • 7:30 am

JAC: Instead of “Readers’ Wildlife” today, we’ll have a report on frogs by Greg Mayer, who’s just visited Costa Rica.

by Greg Mayer

Although quite cryptic on the forest floors it calls home, the smoky jungle frog (Leptodactylus pentadactylus) in the photo below is too obvious to be a candidate for “spot the frog”. This large species of frog (reaching over a 150 mm in snout-vent length) sports what in the military would be called “defense in depth”– a series of defensive behaviors and adaptations that help the frog avoid becoming someone else’s meal. The one in the photo below I encountered at the Lapa Rios Ecolodge, near the tip of the Osa peninsula, on my recent trip to Costa Rica.

Smoky Jungle Frog (Leptodactlyus pentadactylus), Lapa Rios Ecolodge, Osa, Costa Rica
Smoky Jungle Frog (Leptodactlyus pentadactylus), Lapa Rios Ecolodge, Osa, Costa Rica

It was a large individual (well over 100 mm), and we found it at night in the rainforest. Its first line of defense is that it’s quite hard to see against the variegated mixture of brownish leaves, twigs, and mud of the forest floor. (The red shine of the eye is more noticeable, but fortunately for the frog, natural predators don’t carry flashlights!) When first seen, the frog was sitting up at attention, but when we approached, it pushed itself down flat against the substrate, and as I moved around in front of it for a picture, it really pushed its face into the ground, making itself less noticeable.

Smoky Jungle Frog (Leptodactlyus pentadactylus), Lapa Rios Ecolodge, Osa, Costa Rica
Smoky Jungle Frog (Leptodactlyus pentadactylus), Lapa Rios Ecolodge, Osa, Costa Rica

Since all we wanted was pictures, the frog did not move to its further lines of defense. Had we provoked it, it would have assumed an elevated defense posture, with the back raised, also inflating its body and expelling air to make a hissing sound, similar to what is seen in some toads (Leptodactylus is not a true toad).  I haven’t seen (or at least can’t recall seeing) this in Leptodactylus— the behavior was described in this species by Jaime Villa (1969)– but I have seen it in giant toads.

Elevated defensive posture of Leptodactylus pentadactylus (Villa, 1969: Fig. 6).
Elevated defensive posture of Leptodactylus pentadactylus (Villa, 1969: Fig. 6).

This of course draws a potential predator’s attention to the frog– having hidden, why would it now face up to its foe? This is where the next lines of defense come in. First, the frog is big, and this behavior makes it look even bigger. For some predators, the frog is a mouthful too far. Next, if the frog is touched, it exudes a copious and toxic mucus. This mucus induces a strong allergic response in humans, and presumably others, at least mammals if not all other vertebrates- intense sneezing, watery and itching eyes– the unpleasantness of which I can attest to from personal experience. It is said that people merely in the vicinity, who have not touched the frog, can, through aerial transmission of toxin droplets, get the same symptoms. The mucus can irritate the skin, and cause pain to any scratches or open wounds (which I fortunately did not have when catching the frogs). And the frog will also emit a loud, piercing shriek, which might well startle a predator into releasing its grip. Norm Scott reported that caimans were attracted to this cry, and even speculated that that was its function– to attract caimans to dispatch the frog’s predator– sort of like a bugle call to the cavalry!

More straight forward than the multi-layered defenses of the smoky jungle frog is the defense of poison dart frogs– aposematic, or bright, warning coloration, accompanied by very toxic skin secretions. We encountered two species at Lapa Rios. Phyllobates vittatus, with bright orange stripes, is a member of the genus which contains the three species of the poison dart frog family, Dendrobatidae, that are actually used by Indians to make poison darts.

Poison Dart Frog (Phyllobates vittatus), Lapa Rios Ecolodge, Osa, Costa Rica
Poison Dart Frog (Phyllobates vittatus), Lapa Rios Ecolodge, Osa, Costa Rica

We found three of them, during the day, along the Rio Carbonero. We also found three Dendrobates auratus along the paths at the Lodge itself, wandering about during the day, bold as brass, as is their wont. I’ve seen them quite abundant in other parts of Costa Rica, but we saw only three during 4.5 days at Lapa Rios. For neither species of dart frog was I able to get a very good picture; there’s a better picture of auratus in an earlier post, and, in another earlier post, more details and references on poison dart frogs. BBC Earth has a nice explainer on poison dart frogs, with links to interesting papers

Poison Dart Frog (Dendrobates auratus), Lapa Rios Ecolodge, Osa, Costa Rica
Poison Dart Frog (Dendrobates auratus), Lapa Rios Ecolodge, Osa, Costa Rica

Savage, J.M. 2002. The Amphibians and Reptiles of Costa Rica: A Herpetofauna between Two Continents, between Two Seas. University of Chicago Press, Chicago

Scott, N.J. 1983. in D.H. Janzen, ed. Costa Rican Natural History. University of Chicago Press, Chicago

Villa, J. 1969. Comportamiento defensivo de la “Rana Ternero”, Leptodactylus pentadactylus. Revista de Biología Tropical 15:323-329. pdf

Their names should be legion

April 5, 2016 • 11:30 am

by Greg Mayer

Following up on Matthew’s linguistic investigation of larval amphibians, I’d like to address another amphibian linguistic conundrum: the English words for adult members of the order Anura. Just as we have two standard words for a larval anuran in English, we have two standard words for the adults: frog and toad. But this linguistic duality comes nowhere near encompassing the biodiversity of anurans. There are, by many estimates, over 40 families of anurans. I myself consider this taxonomy a bit oversplit, but even a conservative taxonomy would have more than two dozen families. There are thus many more sorts of anurans than there are English words to name them. Why is this so?

The answer, I believe, is simple. In Great Britain, where the language developed, there are four native species: two frogs (Rana temporaria and Rana lessonae), and two toads (Bufo bufo and Bufo calamita). So in England, there are indeed only two sorts of anurans. Here’s one of the frogs, the common frog (North American readers will note the resemblance to our wood frog, Rana sylvatica, which also has a tympanic dark spot and dorsolateral folds):

The Common Frog (Rana temporaria), near Bad Kohlgrub, Bavaria. Photo by Richard Bartz (Wikimedia).
The Common Frog (Rana temporaria), near Bad Kohlgrub, Bavaria. Photo by Richard Bartz (Wikimedia).

And here’s one of the toads, the common toad (the green flecks are duckweed or some other plant):

Common Toad (Bufo bufo), Broomscroft, Kent. Photo by Peter K. Moore. http://www.petermoorewildlifephotography.co.uk/Peter%20K%20Moore%20Wildlife%20Photography/index.html
Common Toad (Bufo bufo), Broomscroft, Kent. Photo by Peter K. Moore.

We can distinguish frogs from toads, because frogs are more aquatic, with long hind limbs for jumping, webbed toes (easily seen above), and moist, smoother skin. Toads are more terrestrial, squat with short legs for hopping, and have dry, warty skin. And this distinction works for the anurans of Britain– the frogs are members of the family of “true frogs”– Ranidae, while the toads are members of the family of “true toads”– Bufonidae.

As the English encountered more kinds of anurans around the world, each new anuran was shoe-horned into being either a frog or a toad. Thus the long limbed, arboreal, jumping anurans of the family Hylidae (which English nobility would have encountered in their Continental estates) were called, aptly enough, tree frogs. And in the North American colonies, the squat, warty burrowing members of the family Pelobatidae were called spadefoot toads. But with dozens of families of anurans, and a great diversity of ecological habits and body forms, the distinction breaks down, and our English common names wind up forcing an exuberant diversity into just two names.

I wonder to what extent the biodiversity of a language’s native land influences the language’s naming diversity. In the only other language I (sort of) speak, Spanish, I know three words– rana (for frogs), sapo (for toads), and maco. The latter is a word I learned in the Dominican Republic, and it has a very different meaning in standard Castilian, as given by the Real Academia Española: it means ‘knave’ or ‘rogue’ if converted to a noun (in Castilian it is an adjective). It’s possible that the Dominican word is of Taino or West African origin, rather than Spanish.

So, I’d like to ask our non-Anglophone readers, how many words for kinds of adult anurans are there in your language? And how does this compare to the biological diversity?

[The title of the post refers of course to a story about demons in the Gospels. A Roman legion had 6,000 men (and there are about 6000 species of anurans). If each family of anurans should have a common name, there names would not be quite legion, but there would be a lot more than two!]

The anurans of autumn

September 29, 2015 • 12:30 pm

by Greg Mayer

In a previous post here at WEIT, I’d reported on some toads and a painted turtle that I’d rescued from stair and window wells, and then released back into the wild last spring. I’d mentioned at the time that I periodically check these places, especially a deep (ca. 20 feet down) window well on the west side of the building my office is in, because it faces a pond and woods, and animals coming out of the woods regularly fall down into it. So at the beginning of the semester in early September, I took my vertebrate zoology class out during our first lab period, and we investigated the window well. There was a pretty good ‘crop’ this fall– eleven American toads (Bufo americanus), and 23 green frogs (Rana clamitans).

Bufo Kenosha 1
American toads just outside Greenquist Woods, Kenosha, Wisconsin, 17.ix.2015. There are clearly six of them, the same ones as in “Spot the toads“.

The toads fell into two size classes: medium (in picture above), about 55 mm snout-vent length, and small, about 40 mm. The green frogs were all about the same size– 35 mm. These latter were probably all a single age class, having metamorphosed from tadpoles earlier in the summer, and then hitting the building and falling in the window well as they began to disperse away from their natal pond. Bullfrogs (Rana catesbeiana) are also common in the pond, but we’ve never found them in the window well– they must have different dispersal behavior.

Chrsi Noto Bufo release
Chris Noto helps to release American toads in Greenquist Woods, 17.ix.2015.

Frogs and toads are collectively known as anurans— it means “not having a tail”– and adult frogs and toads do, of course, lack tails. The anurans we rescued from the window well had been there varying lengths of time, but most were in at least decent shape, though some were thin and dehydrated. We kept them in the lab for a couple of weeks, feeding them and rehydrating them. We then released them on two warm days just as autumn was about to begin. My colleague Chris Noto was teaching a lab on a floor looking out over the woods, and he saw me encumbered with toads as I attempted to take their pictures and carry them back out to the woods. He came down and helped with the pictures and the release (which were featured in two “Spot the __” posts, on frogs and toads).

Bufo Kenosha 3 20150917_162944
Small American toad, about to be released into Greenquist Woods, 17.ix.2015.

The green frogs were released a few days later.

Rana Kenosha 1 20150920_153340
Green frogs anxiously await their transfer to the pond, 20.ix.2015.
Rana Kenosha 3 20150920_153446
One last picture.
Rana kenosha 3 20150920_153507
Well, maybe just one more.
Rana Kenosha 6 20150920_153811
And then it’s time to re-enter the pond.
Rana Kenosah 4 20150920_153724
Green frogs queue up to enter Greenquist Pond, 20.ix.2015.

[JAC: a video of the release. I have to commend Greg for both taking the time to rescue these frogs and also calling them to our attention. Frogs are not only underappreciated animals, but are harbingers of human damage to the environment, climatic and otherwise. And I’ve always said that if frogs hadn’t evolved, we simply wouldn’t be able to imagine them!]

There are at least a dozen or more different sorts of anurans around the world that are worthy of their own vernacular name, but because only two sorts occur in England, we are stuck with calling them all either “frog” or “toad” in English. The American toad and the green frog do, however, correspond to the two sorts found in England (what are sometimes called the “true toads” and the “true frogs”, respectively).

Anurans are amphibians, and like most amphibians, have a complex life cycle. The word “amphibian” alludes to this– it means “both lives”, because a typical amphibian lives both on the land and in the water. Reptiles and their descendants (the amniotes, including birds and mammals), do not have this dual life cycle. One of the former candidates for the title of “first reptile” was the 270 million year old Seymouria, which has reptile-like features; but when it was found that its close relatives had aquatic larvae with gills, it was clear they were not reptiles, but rather led the “both lives” of an amphibian.

“Both lives” does not seem to adequately summarize the life of a typical amphibian, such as the American toad. They begin life as eggs in water, hatch out as tailed, gilled, tadpoles, that then swim about, eventually losing their tails and gills and sprouting legs to transform into toadlets, which then move onto land. After sexually maturing, they return to the pond each spring, to resume an amphibious existence, there to mate and reproduce. The adults then leave the pond for the summer to live wholly on land, while their eggs begin the complex cycling again. To paraphrase The Who, “Amphibians? They’re bleeding Quadrophibians.”

Spot the frogs

September 22, 2015 • 10:15 am

by Greg Mayer

As a preview of an upcoming post on frogs and toads, a chance to practice your spotting skills. No real difficulty here, but you need to spot all of them.

Green frogs (Rana clamitans about to enter Greenquist Pond, Kenosha, Wisconsin, 20 Sept. 2015.
Green frogs (Rana clamitans) entering Greenquist Pond, Kenosha, WI, 20.ix.2015.

As we’ll see in the upcoming post, these are “rescue frogs”.

Spot the wood frog

June 16, 2014 • 10:00 am

by Greg Mayer

Well, it’s not that hard to spot, but you can see how the wood frog (Rana sylvatica) is aptly named.

Wood frog, near Lake Superior, Minnesota, 6 June 2014.
Wood frog, near Lake Superior, Minnesota, 10 June 2014.

My Minnesota correspondent found this fellow along Caribou Trail (a road) and Jonvick Creek near Lutsen, Cook County, Minnesota, about a half mile from the north shore of Lake Superior, on 10 June 2014. The region is mixed spruce and maple forest; the frog was in a “mapley” area. The great herpetologist Robert C. Stebbins thought the species’ distribution tracked, for much of its range, pretty closely to the distribution of spruce.

The distribution of wood frogs is interesting for at least two reasons. First, they are the most northerly distributed of any North American amphibian (or reptile, for that matter), and extremes are always interesting. They can survive for weeks at temperatures below freezing, in part through elevated levels of blood glucose acting as an “anti-freeze”.

Range of the wood frog (Rana sylvatica), from USGS via Wikipedia.
Range of the wood frog (Rana sylvatica), from USGS via Wikipedia.

They’re not immune to freezing though—I once found, during an early spring field trip near Northampton, Massachusetts, a dead female who had laid her eggs in a small pond. She was perfectly intact, and I suspected she had frozen, as contact with ice crystals (from the pond) makes them more vulnerable to freezing.

Second, there are a number of outlying populations to the south of the main range (which, as shown above, crosses northern North America from the Bering Strait to the North Atlantic, descending into eastern North America along the Appalachians). In particular, note the outliers in Colorado and Wyoming. These are almost certainly relicts from cooler glacial times when the frog occurred further south in the Rockies; it moved northward as the glaciers retreated, leaving behind populations in some favorable southern localities. The isolated Colorado-Wyoming population was named as a distinct species (maslini), but currently it is not recognized, not even as a subspecies.

Wood frogs are are also famous for another “non-subspecies”: cantabrigensis, a short-legged form from the northwestern part of the range, versus the longer legged ones to the east. While the variation in leg size is real, there is a gradual cross-continental gradient (a cline, in technical terminology), with no break in leg size, and most systematists do not distinguish such clinal patterns of geographic variation with nomenclatural recognition. So cantabrigensis is not recognized either, and the wood frog has become a classic case of clinal variation.

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Bagdonas, K.R. and D. Pettus. 1976. Genetic compatibility in wood frogs (Amphibia, Anura, Ranidae). Journal of Herpetology 10:105-112 (jstor)

Costanzo, J.P., M.C.F. do Amaral, A.J. Rosendale and R.E. Lee. 2013. Hibernation physiology, freezing adaptation and extreme freeze tolerance in a northern population of the wood frog. Journal of Experimental Biology 216:3461-3473. (pdf)

Dodd, C.K. 2013. Frogs of the United States and Canada. Johns Hopkins University Press, Baltimore (publisher) (Google books)

Porter, K.R. 1969. Evolutionary status of the Rocky Mountain population of wood frogs. Evolution 23:163-170. (jstor)

Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians. 3rd ed. Houghton Mifflin, Boston. (publisher)

NASA launches a frog, and experimental biogeograhy

September 13, 2013 • 9:07 am

by Greg Mayer

On Sept. 6, NASA launched the Lunar Atmosphere and Dust Environment Explorer (LADEE) towards the moon, where it will go into orbit to gather data on the thin lunar atmosphere. But along with the rocket, a frog, apparently resting on the rocket or launch pad, was taken spaceward, before being thrown free.

An unidentified frog is launched along with the LADEE rocket (NASA photo).
An unidentified frog is launched along with the LADEE spacecraft on Sept. 6, 2013 (NASA photo).

NASA’s dry caption is priceless:

A still camera on a sound trigger captured this intriguing photo of an airborne frog as NASA’s LADEE spacecraft lifts off from Pad 0B at Wallops Flight Facility in Virginia. The photo team confirms the frog is real and was captured in a single frame by one of the remote cameras used to photograph the launch. The condition of the frog, however, is uncertain.

The photo reminded me immediately of a famous biogeographic experiment performed by Thomas Barbour (1884-1946) and Philip Darlington (1904-1983), who differed over the importance of land bridges (favored by Barbour) versus overwater dispersal (favored by Darlington) in the distribution of animals on islands. The experiment and its results are handed down from one generation of graduate students to the next by a well-known oral tradition at the Museum of Comparative Zoology, but the only published account I know of is by Bob O’Hara (1988):

A how-possibly experiment performed by Philip Darlington and Thomas Barbour at the Museum of Comparative Zoology has become legendary. Darlington and Barbour were disputing the possibility of frogs being dispersed in the West Indies by hurricanes. Darlington, who believed such dispersal was possible, took a bucket of live frogs up to the roof of the Museum, and, with Barbour standing on the lawn below, proceeded to throw the frogs to the ground, one by one. As each one hit the ground, Barbour examined it and called up “That one’s dead,” “So’s that one,” and so on. But after a few minutes, much to Barbour’s disappointment, the frogs all revived and started to hop away. Darlington had thus shown that hurricane dispersal was possible, or at least had removed one of Barbour’s objections to it, namely that it would be too rough on the frogs.

To Bob’s account I would add that the MCZ is 5 stories tall, which gives you some idea how far the frogs fell in their journey to the courtyard below. Bob used the experiment to illustrate his notion of a “how possibly” experiment, which demonstrates the possibility, though not the actual occurrence, of a phenomenon.

I thought of the experiment because I wondered about the “uncertain” fate of the frog. The frog appears to be outside the plume of hot gas escaping form the rocket engine. If so, and if the clear air around it has not been super-heated, the frog could well survive the fall. Many tree frogs are adept at jumping long distances, bodies flattened and limbs spread, so that they reach a terminal velocity more dependent on aerial friction than gravity. The so-called “flying frogs” are ones that have gotten very good at this, usually with both morphological and behavioral specialiazations (see Wallace’s flying frog, an apt example for Wallace Year).

I’m not sure about the identity of the frog. My guess is that it’s a tree frog of some sort. [Note: I’d originally guessed it was a  Cuban tree frog (Osteopilus septentrionalis), a large, introduced species in Florida, but that’s before I realized the rocket was launched from a facility at Wallops Island, Virginia, on the Delmarva Peninsula, and not from NASA’s more usual Florida launchpads.]

h/t Christian Science Monitor

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O’Hara, R.J. 1988. Homage to Clio, or, toward an historical philosophy for evolutionary biology. Systematic Zoology 37:142–155. pdf

Frogs!

June 30, 2011 • 5:31 am

by Greg Mayer

As an Everton supporter, I am loath to praise anything Mancunian, but Andrew Johnson, a Manchester zoology graduate, has a marvelous website on the Amphibians of Borneo, which was brought to my attention by Matthew (yet another praiseworthy Mancunian).

Ansonia leptopus (Bufonidae) by Andrew Johnson

The site contains excellent photographs of many species of Bornean frogs. What struck me most is the resemblance of many of the depicted species to Central American frogs, especially the Costa Rican ones with which I am most familiar. Our toad friend above reminds me of the gracile-limbed Central American toads of the genus Atelopus. (Superb photos of the various Costa Rican frogs mentioned can be found in Jay Savage’s magisterial The Amphibians and Reptiles of Costa Rica [see references] and at Costa Rican Frogs, a site I just discovered.). The following one is a more typical-looking toad, resembling various Central American Bufo.

Duttaphrynus melanostictus (Bufonidae) by Andrew Johnson

The following species resembles the Central American toad Bufo haematiticus in its cryptic forest-floor dress, but is in fact not a true toad, but a member of a different family.

Kalophrynus baluensis (Microhylidae) by Andrew Johnson

The resemblances between the Bornean and Central American frogs is a mixture of convergence (in this case, adaptation to the varied niches of tropical rain forest) and common ancestry (in some cases, a toad is a toad is a toad). Convergence is indicated when similar species are in different families, but it’s also possible within families. Both American Atelopus and Bornean Ansonia are members of the family Bufonidae (true toads), but their gracile form may have evolved independently from more squat ancestors (that’s why phylogenetic studies are so important for elucidating evolutionary phenomena– we need to know who’s related to who, and what the likely ancestral conditions were).

Here are several other of my favorites. The first resembles Central American Leptodactylus, especially pentadactylus.

Limnonectes ingeri (Dicroglossidae) by Andrew Johnson

Our friend above is named in honor of my esteemed colleague Robert Inger of the Field Museum, the dean of Bornean amphibian studies (see references below). The following species, in the same genus, Limnonectes, resembles various Central American Eleutherodactylus, a very species-rich genus with more than 40 Costa Rican species.

Limnonectes laticeps (Dicroglossidae) by Andrew Johnson

We’ll finish with some treefrogs, none of which are in the “true” treefrog family, Hylidae (which has many genera and species in Central America), but rather the Old World Rhacophoridae. The first resembles some of the the Central American Smilisca.

Rhacophorus cyanopunctatus (Rhacophoridae) by Andrew Johnson

The next resembles various Hyla.

Rhacophorus dulitensis (Rhacophoridae) by Andrew Johnson

And finally, a flying (actually gliding) frog; note the large webs. Some Costa Rican hylid treefrogs of the genus Agalychnis are capable of gliding, too.

Rhacophorus nigropalmatus (Rhacophoridae) by Andrew Johnson

A more academic site devoted to Bornean frogs, also beautifully illustrated and with a great range of useful information, is Frogs of Borneo, by Alexander Haas and Indraneil Das. The American Museum of Natural History is currently hosting a traveling exhibition entitled Frogs: a Chorus of Colors, featuring live (not preserved) frogs, which I saw when it was at the Milwaukee Public Museum, and is worth seeing if you’re in the New York area.

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Behler, J. and D. Behler. 2005. Frogs: A Chorus of Colors. Sterling Publishing, New York. (book to accompany the exhibition)

Inger, R.F. 1966. The systematics and zoogeography of the amphibia of Borneo. Fieldiana Zoology 52:1-402. (downloadable as pdf)

Inger, R.F. and R.B. Stuebing. 2005. A Field Guide to the Frogs of Borneo. 2nd ed. Natural History Publications (Borneo), Kota Kinabalu, Sabah, Malaysia. (available here)

Inger, R.F.  and F.L. Tan. 1996. Checklist of the frogs of Borneo. Raffles Bulletin of Zoology 44(2): 551-574. (pdf)

Savage, J.M. 2002. The Amphibians and Reptiles of Costa Rica | A Herpetofauna between Two Continents, between Two Seas. University of Chicago Press, Chicago.

… breeding mulleins out of the dead land.

April 11, 2010 • 12:43 am

by Greg Mayer

March continued its cruelty, and less than two weeks after they emerged in Virginia, mulleins emerged from the dead land of Wisconsin as well.

Mullein, Saukville, Wisconsin, 23 March 2010. Photo by Eric Hileman.

The above was one of a number of mulleins Eric Hileman and I found and photographed while reconnoitering his Butler’s garter snake (Thamnophis butleri) study site at the University of Wisconsin-Milwaukee Field Station. The plywood board against which the mullein nestles is one of several hundred in a 15m mesh grid that the snakes use as cover, enabling Eric to find them and track their numbers and movements.

Eric Hileman and a snake cover board amidst the dead land, Saukville, Wisconsin, 23 March 2010.

The progress of spring continues apace. Earlier tonight, in Franskville, Wisconsin, I passed a chorus of chorus frogs (Pseudacris triseriata) in wet fields and sloughs calling so loudly that I could hear them in my car with the radio on and the windows closed at 45 mph!

Polymorphism in vertebrates

March 26, 2010 • 1:04 pm

by Greg Mayer

Darwin’s theory of evolution (and ours), unlike that of Lamarck, is variational, rather than transformational: the process of evolution is a change in frequency of different variants within a population, not a transformation of the individuals.  Darwin thus made the origin, nature, and inheritance of variation key problems for biology; indeed, for much of the 20th century, evolution and genetics were often taught as a single course at universities.

One of the most distinctive sorts of variation is polymorphism, in which two or more discontinuous forms are found in a single species (this is distinct from sexual or age related variation). Darwin himself pioneered the study of polymorphisms. Such discontinuous variation often has a simple genetic basis, with allelic variation at one genetic locus accounting for all (or most) of the variability.The color polymorphism in peppered moths (Biston betularia) is a well known and well studied case involving industrial melanism, in which light and dark forms are adapted to polluted and unpolluted environments, respectively. A well known case of polymorphism in vertebrates are the two color phases of Cuban sparrow hawk (Falco sparverius sparverioides). This case is not well studied, though, and we know nothing about the genetics, nor the adaptive significance (if any) of the polymorphism.

Light and rufous phase male Cuban sparrow hawks (Falco sparverius sparverioides).

A polymorphism in vertebrates that many Americans and Canadians are familiar with are the melanistic and gray forms of the gray squirrel (Sciurus carolinensis). The most frequent color form is gray, but blackish or dark brownish individuals are widely distributed, and in places quite frequent. I have seen them in Illinois (Cook County), Wisconsin (Racine and Kenosha Cos.) and Michigan (Ingham Co.), and also on the campus of Princeton University. (I was told at Princeton that, during football season, black squirrels are captured, and orange stripes applied to them, so that they resemble diminutive arboreal tigers, the tiger being Princeton’s mascot.)

A demonic gray squirrel (locally known as 'yard dogs'), Annapolis, MD, 23 June 2008.

A much less common color morph is the leucistic or albinistic form, which is whitish, cream or yellowish. They are famously common in Olney, Illinois (due to an introduction of two albinistic individuals to an area previously lacking any gray squirrels at all), and also occur regularly in Stevens Point, Wisconsin, but I had never seen one before my recent trip to Washington, DC, where I saw one on the tree right across from the steps on the Mall entrance to the USNM.  (The picture was taken through a bus window.)

Leucistic or albinistic gray squirrel, Washington, DC, 16 March 2010.

Vertebrate polymorphisms are often less well understood than those of invertebrates, because their generally greater size and longer generation times make experimental study more difficult. Melanism in squirrels, for example, has been related to thermoregulation and fire frequency, but no thoroughly compelling explanation has been found. One exception to this is coat color variation in mice of the genus Peromyscus, where coat color seems to be an adaptation for camouflage in varying environments.

Light and dark forms of Peromyscus polionotus from sandy and dark soils (P. p. leucocephalus on the left, P. p. polionotus on the right, I think).

In the 1930s, F.B. Sumner conducted classic field and lab studies on light colored mice living on sandy soils and dark mice on dark soils. Unlike the melanistic and albinistic squirrels, which are variant individuals within a populations, there is an element of geographic variation in the mice, which live in distinct, though adjacent, places. Sumner’s studies showed that there were several (not just one) genetic loci involved in coat color, and the color forms intergrade where their habitats meet and they interbreed. Hopi Hoekstra of the Museum of Comparative Zoology is currently conducting exciting studies of some of the same species studied by Sumner.

Although the mice occur in distinct modal forms (white vs. brown), the intergradation where they meet shows an underlying continuous variation. The frogs below show that although we can pick out distinctly different individuals, the range of pattern from plain to mottled to striped makes it difficult to recognize a small number of discrete color morphs, and the variation approaches a continuous dictribution. Such continuous variations were thought by Darwin, and most biologists today as well, to be important raw material for the evolutionary process.

Leotpdactylus albilabris from Isla Vieques.