“Peek!” Plunk. “Peek!” Plop. “Peek!” Plip. These were the sounds I heard as I walked around a small pond in Amherst, Massachusetts last week, looking for dragonflies, listening for birds. The “peeks” were loud and high-pitched. I knew the plunks, plops and plips were the sounds of frogs, green and black, jumping into the water, so camouflaged, it looked as if the grass and mud were in action. I wasn’t quite sure exactly which frogs the Peeks belonged to, they were exceptionally high-pitched. Most probably Green Frogs, I thought, as I spied prominent eyes peering out of the water. Maybe Pickerel Frogs too, those would be the small, brown ones I sometimes managed to spot before they disappeared. Like Blue Dasher dragonflies, this is what I tended to see at small vegetative ponds in mid-summer. And, I started daydreaming about encountering something a little different, maybe a Horned Frog, Ceratophrys cornuta, a large, squat green and brown frog of South America, with a wide mouth large enough to eat other frogs as well as reptiles. Or, Pygmy leaf-folding frogs, Afrixalus brachycnemis, from Tanzania, tiny climbing frogs who lay their eggs in leaves and then fold the leaves over them for protection, sealing the nest with secretions. Or, one of the 145 species of Glass frogs living in the Cental and South American rainforests, I could look through the transparent skin on their undersides and see their internal organs. This is what happens when you read a book like Frogs and Toads of the World, by Chris Mattison. You learn about all the weird and wonderful possibilities beyond your patch, and your imagination goes sparking off.
A book about all the frogs and toads of the world is an ambitious undertaking. There are over 5,000 species of frogs in existence (5,858 at the time the book was written, the exact number changes as research dictates re-arrangements of taxonomy and new species are discovered). All species of frogs and toads share the fact that they are amphibian creatures, they have two types of skin gland, four legs, and, well, they jump. And, they look like frogs. As Mattison says, “Frogs are unlikely to be mistaken for any other type of animal.” But, within the frog group there is a tremendous range of diversity. For example, I was going to add “no tail” to the list of features above, what all frogs share, when I remembered that there are indeed a small family of Tailed frogs, four species in New Zealand and two in North America (though, the tails are quite tiny). This seemingly boundless diversity comes through in every chapter of this book, and is both its strength and its weakness.
There are ten chapters: Origins and classification; Size and shape, colour and markings; Interactions with the physical environment; Enemies and defence; Food and feeding; Reproduction; Life-cycles; Habitat and distribution; Frogs and man; and The families, a 54-page section which describes the characteristics of the 49 families of frogs. Descriptions of a few will give you an idea of the range of fascinating details crammed into this relatively brief book (192 pages).
Origins and classification describes the evolution of frogs from lobe-finned fishes; there are some gaps in the stages from fish to frog, but scientists have identified the earliest frog-like fossil as Triadobatrachus massinoti, a creature which lived in the area we know as Madagascar about 230 million years ago. The chapter also spends time discussing classification, explaining how scientific naming works and providing a chart of Frog families and their geographic ranges. It is useful as a general introduction as well as for amphibian organization. Mattison also helps solve what for some of us has been a mystery, the difference between frogs and toads. It turns out there is no scientific difference! These are terms of usage. There is a large family of frogs, Bufonidae, that includes most of the warty, hoppy creatures we think of as toads. But, some people may call toads that belong to Bufonidae “frogs” because of the way they look, and similarly, they may call frogs not in that family “toads”. I do love the scientific name for the European common toad: Bufo bufo. I’m also happy to know that I can now say “frog” or “toad” in the field as the spirit moves me.
Chapter 2, Size and shape, colour and markings, explores the physical diversity and variability of frogs (and toads). Now, last December I took my young nephews, Jake and Zach, to a terrific exhibit, Frogs: A Chorus of Colors at the American Museum of Natural History in New York City. This exhibit has been making the rounds of science museums, and if comes to your area I highly recommend it, not just for kids. If you don’t live near a science museum, then read this chapter. The range of sizes and colors and shapes amongst frogs is just amazing! There’s the Goliath frog from South Africa—up to one foot in length and over 6 pounds in weight. Balance that next to the Brazilian golden toad, one-third of an inch long. Shapes range from the streamlined rocket frogs to the squat bullfrogs to the perkey, long-limbed leaf frogs to the bulbous, squishy-looking, snouted Indian purple frog. If you’ve been to the Amazonian rainforest on a birding tour, then you have probably seen the brilliant colors of the tiny Poison dart frogs, the deep brilliant reds and blues and yellows. The poison dart frog pictured here is the Golden poison dart frog, Phyllobates terribilis, known as the world’s most poisonous animal; its skin secretions are used by South American Indians from the Colombian Andes for their blowgun darts. The colors are nature’s way of saying, “Beware!”
My favorite chapter has to be Chapter 6, Reproduction, possibly because so much time has been spent on 10,000 Birds lately talking about the subject. If in the past I thought about frogs and mating at all, it was along the lines of the princess kissing the frog and getting her prince. Now I know that frogs call to attract females, that some call individually and some call in choruses, that most species call using vocal sacs, but some don’t have any at all, and that the bigger the vocal sac the louder the call, and the louder the call, the more apt the frog is to attract a mate. And, I’ve also learned that frogs may look like they are copulating, but they really aren’t, it’s the process I mentioned earlier, axillary or inguinal amplexus. The male and female position themselves close to each other, on top or in back, so that the eggs are fertilized as the female releases them. Amplexus can last from a few seconds to a few hours to a few months. And then, there are the tadpoles, who all have their different ways of feeding. Or, not feeding. It is all as amazing and as diverse as the ways in which birds mate and reproduce. Sadly, no princes are involved at any stage.
Frogs and Toads of the World is profusely illustrated with photographs of frogs and toads in their colorful, dull, smooth, warty glory. The photographs emphasize the variety of shapes and colors as well as situating the frogs and toads in the diverse habitats that determine this variety—ponds, trees, reeds, ruts in the road, burrows in the ground. They are great photographs, particularly the close-ups of frog irises and eyelids. I want to give credit to the publishers, Princeton University Press and the Natural History Museum of London, for the quality of the printing. It’s not easy producing a thousand shades of green. Green-boxed inserts treat specific subjects, such as Polymorphism and Convergent Evolution. The photo above is from a box about Polymorphism, the occurrence of two separate forms in one population. The frogs are both Madagascar Reed frogs, and they were photographed living in the same tree.
Most of the photographs are by the author, Chris Mattison, a British nature photographer and writer. Mattison has written over 20 books, most of them on reptiles and amphibians, ranging in style from reference to children’s books, most published in Great Britain. You can see a selection of his photographs on his web site, including many from this book. You may also end up wondering, as I did, what it’s like to travel the world photographing amphibians and reptiles, creatures who live in the ground, often so camouflaged that most people never see them. Birders look up, frog and snake photographers look down.
The last few pages of the book offer Further Information, a list of selected books and websites, and a very good Index. I was happy to see the list of additional sources because I realized as I finished the book that the one thing I did not learn is which species of frog was making the high-pitched Peek sound I was hearing at that pond in Amherst. This is not a field guide. It is a book to read to give context to field guides. The Further Information section is therefore worthy of perusal if you don’t already have your frog and reptile field guide (the two seem to be often treated together), and I only wish the type was bigger and the list was lengthier. There is still a lot of work to be done in this area.
There is also a lot of work that needs to be done for the conservation of frogs. Mattison writes that in 2008 the International Union for Conservation of Nature (IUCN) identified 30% of all amphibian species as endangered, including 1,626 species of frogs. Thrity-seven species are probably already extinct. The reasons are many–habitat destruction, over-exploitation of frogs for meat, pollution, alien predators, climate change, and the chytrid fungus epidemic, a recently discovered threat that is killing frogs all over the world and which is not totally understood yet. It shouldn’t be a surprise that frogs and toads are experiencing the same threats so many other species are going through, but somehow, it is. Maybe because they are so prevalent everywhere we go, and so much a part of cultures around the world. An organization named Amphibian Specialist Group (ASG) is coordinating conservation initiatives; Mattison recommends their online magazine Froglog.
Frogs and Toads of the World is, like many of Princeton University Press’s offerings, a serious book about the natural world disguised as a small coffee table book. Reasonably priced for a hardcover book with quality binding and photographs, it has a lot to offer the general naturalist and the birder interested in amphibians and learning what else is in that local patch pond. My only caveat with the book is the amount of information it offers. Some readers will eat it up, others might find it overwhelming. This is where the photos and information boxes help, they create entry reading points which can be expanded to the more lengthy texts at a later time. I think it is important to keep in mind that a book like this can be read sequentially or in selections. Which makes it educational and fun, whatever suits your reading style.
Take a look at frogs this month, both in the field and on the written page. It is shorebird migration time, there must be some frogs nearby! Also, added bonus, children really like these creatures, and it is a great way to get them interested in nature. Take a photograph when you hear that Peek Plop Croak (that’s my photo of a Green Frog in that Amherst pond); read Frogs and Toads in the World to find out how exactly they make that sound. And then, let me know–what kinds of frogs are you seeing? Green, Tree, Leaf, or Poison Dart?
Frogs and Toads of the World
By Chris Mattison.
Princeton University Press, 2011, 192 pp. 200 photos.
All photographs, with the exception of the last, are used with the permission of Princeton University Press.