Tag Archives: fish

Five Feet High and Rising

The creek behind my uncle’s house here in Western Ohio is flooding; normally a laconic and nameless little tributary with quietly dipping mallards, last night’s thunderstorm and rapidly melting snow has raised the water level almost twelve feet and transformed it into a swollen, churning torrent. As I sit here watching the lawn furniture and Fisher Price playsets rush downstream, I thought it’d be appropriate to talk about animals for whom floods are home.

I’ve written before about the flooded forests of the Amazon basin, the Amazon river dolphin in particular, but it’s worth another visit. The Amazon is sometimes referred to as the River Sea, and the reason why becomes clear when the water level rises 30 feet and covers three times its already substantial area. During the Spring floods, a gondola navigating the trees in the rainforest might come upon a pair of giant otters chasing each other through the water, or glide into a mysterious pool of shimmering gold which, on closer inspection, turns out to be a school of piranhas. Here in the varzea, the underwater forest, the Amazonian manatee does the dead man’s float while grazing on submerged meadows, and the anaconda rolls like water boiling. And if you’re lucky, you may find the dragon of the Amazon: the arapaima.

Continue reading

The Fish That Climb Trees

All children are essentially monkeys. Ever since I was tall enough to reach the lowermost branches of a tree and strong enough to swing myself up, arboreal life was the life for me. I remember climbing the mastheads of swaying pines, reading books in the crooked elbows of maples, and challenging myself to steal the most unreachable apples. I felt safer in trees; they seemed less like a high wire and more like a net to me. They held me safely out of sight of real siblings and imaginary enemies. They put me closer to the birds I loved. Throughout my childhood, I felt myself pulled up into the treetops by some plant magnetism, and pushed up there by some rambunctious animal urge.

I may need a boost.

I want to go to there.

When I went to college, I decided to study canopy ecology. And one of the things that sparked my interest was a story I heard from a professor about fish living in the trees. It went like this: when the Amazon River floods, the water level can rise enough to temporarily cover the lower branches of trees. Small fish, my professor told me, will sometimes lay their eggs in the submerged bromeliads on the tree branches, and when the floodwaters subside, the eggs hatch in a leafy fishbowl of water, replenished by rain and oxygenated by the plants themselves. Voila, fish in the trees.

Of course, I can find ZERO evidence to support this claim. And if fish ever do wind up imprisoned in tree branches, it would be by accident; after all, guppy fry in an epiphyte would soon make a nice snack for a hungry coati. But it turns out that there are a few fish in the world who head for the trees on purpose. Their existence challenges the public preconception about the definition of “fish,” and serves to help us understand the soul of a tree.

Continue reading


Fans of the Hitchhiker’s Guide to the Galaxy will remember Slartibartfast, the planet architect who was very proud of his award-winning design for Norway. The fjords, he explained, were designed to give the continent a “baroque” feel. And a fjord is indeed a very splendid thing. A fjord, by definition, is a long and narrow inlet to the sea, flanked by very steep cliffs, and carved by glacial activity. (Or Slartibartfast.) While Norway coined the name “fjord,” they have no trademark on the geological flourish. You will find fjords anywhere there are mountains that meet the sea, and freezing temperatures to support glaciers, including the coast of Chile, New Zealand, and the Northwest coast of North America.

First Prize!

From time to time I like to take electronic expeditions to rare places on Earth, to see what I can find. Readers know I have a passion for fractals, and subscribe to something I call Fractal Earth Theory; the theory that the patterns of the planet are self-repeating ad infinitum. It was thinking about the true lengths of coastlines that led Mandelbrot to discover fractals in the first place; fjords make for rough edges in the world, wrinkling the land into a series of nooks and hidey-holes in which any manner of animal might live.

Today, we look for the unique wildlife of the fjords. I use a basic set of hypotheses as a compass:

1. Wherever life can exist, life will exist.
2. Where ever a habitat is geographically separated in any physical way, unique life will exist.
3. The more severely isolated a habitat is, the greater the number of unique species.

Fjords, however unique as geologic structures, are not very isolated: their cliffs connect with the mainland, and their inlets connect with the ocean. Their main aspects of geographic distinguishment are the steep angles of their cliffs, on which only certain wildflowers can grow, and the murky, silty, brackish water below. Fjords are often estuarine, with freshwater running as a river into their channels, which will certainly exclude many sensitive saltwater animals. The turbid, murky water is caused by violent tidal action, which in turn is caused by the water rushing over the lip of the terminal moraine left by the glacier at the fjord’s edge; this turbulence may also make the habitat even more exclusive, and more unique. But all in all, a fjord is not as isolated as a lake or an island, and we can’t expect a great number of unique species. But a few, sure. Some modifiers to the original compass:

4. The cold temperatures and low salinity will lead to a lower general biodiversity for animals, compared to a tropical habitat.
5. The cold water, with its high level of dissolved oxygen, will nonetheless support a high overall biomass.
6. The prediction of high aquatic biomass makes it more likely that any unique species are aquatic.

With these in mind, we set out to explore the nooks of the fjords, seeking life found nowhere else on Earth. And what we’ll find is a series of ecosystems among the most mysterious and little-known in science.

Continue reading

The Glass Menagerie

“Is there such a thing as an invisible animal? In the sea, yes. Thousands! millions! All the larvae, all the little nauplii and tornarias, all the microscopic things, the jelly-fish. In the sea there are more things invisible than visible! I never thought of that before. And in the ponds too! All those little pond-life things—specks of colourless translucent jelly! But in air? No!… If a man was made of glass he would still be visible.”
–H.G. Wells, “The Invisible Man”.

I have written about invisible animals before, and all the ways in which one can become invisible, of which transparency is only one. I’ve spent some time thinking about transparent animals, from the Glass Frog of Central America:

to the Glass Squid of the deep oceans:

The transparency of the frog is obvious as a means of camouflage, but it is less certain in the case of the squid. Does its transparency serve to make it invisible? Or is there simply so little available light that producing pigments of any sort is wasteful? A great number of deep-ocean animals are transparent, including the Phronima, a type of amphipod with a glass-like exoskeleton, and the sea cucumbers which make up 90% of the complex animals on the abyssal plain. But the depths are not the only dark places on Earth; in the subterranean grottoes live the “troglobites,” animals adapted to the life in the sub-basement of the world:

The Alabama Cave Shrimp:

The Transparent Cave Crayfish:

And the Glass Goby:

Where these animals live, there is not even a stray photon bouncing off the stalactites, and so even the term “invisible” is inherently useless. There’s no such thing as “visible” there. To make an admittedly silly pop culture reference, I’m reminded of the character Invisible Boy from the 1999 film Mystery Men. On a team of quirky superheroes with dubious “powers,” Invisible Boy’s abilities are the most useless: He can only turn invisible when no one’s looking. The majority of “invisible” animals have the same superpower: their transparency is just a by-product of another adaptation, because where they live, nobody could see them even if they were day-glo orange.

“Visibility depends on the action of the visible bodies on light. Either a body absorbs light, or it reflects or refracts it, or does all these things. If it neither reflects nor refracts nor absorbs light, it cannot of itself be visible. You see an opaque red box, for instance, because the colour absorbs some of the light and reflects the rest, all the red part of the light, to you. If it did not absorb any particular part of the light, but reflected it all, then it would be a shining white box… A glass box would not be so brilliant, not so clearly visible, as a diamond box, because there would be less refraction and reflection. See that? From certain points of view you would see quite clearly through it… And if you put a sheet of common white glass in water… it would vanish almost altogether, because light passing from water to glass is only slightly refracted or reflected or indeed affected in any way.”

Continue reading

Your Lying Eyes

The sunbittern of Central and South America appears, at first glance, to be a very normal and nondescript water bird. This knee-high, heron-like hunter is cryptically colored to blend in with the leaf litter around the stream beds where it pecks at snails, frogs, and small fish.

But if the camouflage fails, and a predator or rival gets too close, the sunbittern unleashes its full fury:

Suddenly, the bird has disappeared and a bug-eyed beast from hell has materialized in its place. Today, we reconsider an ecological classic: false eyespots.

Continue reading


It is one thing to take flight from the ground. A push-off, a grab of air with your wings, and you’re up. It is another thing entirely to take off from the water. You can get a good running start, but once your body’s airborne you immediately feel the awful gravity of what we land-dwellers call “the real world.” You feel how heavy the sky.

The flying fish takes such a running start at almost 40 mph. It shoots from the water like a bullet and sails like a brief kite. Some of them have pectoral fins shaped like dragonfly wings, some like butterfly wings, but all have curved front edges like those of birds and airplanes. Merely gliding, it can stay airborne for 45 seconds. When it comes down after its initial flight, which may have reached 200 yards in length, it can skate on the surface of the water on the tip of its tail, zigzagging delicately on the waves for another 200 yards.

Continue reading

Buried Alive

You will probably never see a purple frog. In order to see a purple frog, you very much have to be in the right place at the right time. The place: a tiny fraction of a tiny but biologically rich mountain range in Southern India called the Western Ghats. The time: the summer monsoons. If you come to the Western Ghats in October, or go anywhere else but that few hundred square miles of wet plateau in June, you and the purple frog will miss each other entirely.

It is a great round blob of an animal, the purple frog, with a hard, beak-like nose for breaking into termite tunnels. Its eyes seem too small, its stance pigeon-toed, its call sounds like that of a chicken. It is such an unusual animal that it’s surprising it wasn’t discovered until 2003. The reason it remained hidden so long is that the purple frog is subterranean, burying itself alive for most of the year until it hears the drumming of the monsoon rains on the earth above, and clambers up to the surface to mate.

The Art of being Buried Alive is not an easy one to master. It requires you to slow your metabolism to a crawl, to live as if hibernating, but without being asleep. It is a self-imprisonment during which you cannot dare to plan your escape, or you will go mad. I imagine you can’t think at all. The purple frog is not in complete stasis: it hunts termites, its heart beats. But mainly, it squats in the dirt and listens. Who knows if the purple frog’s mind remains safely dreamless and null as it waits in the earth. Perhaps it does nothing but dream.

This waking hibernation has a name: estivation. For most animals that employ it, estivation happens during the dry summer months, but the Indian monsoon season starting in June makes the purple frog’s cycle unusual. Consider the lungfishes, those ancient and air-breathing fish whose shallow ponds which, for much of the year, do not exist. That’s right: there is a fish that can survive in a lake with no water. During the dry season, the lungfish buries itself in the mud, coats itself in a mucus cocoon, slows its breathing rate down to next-to-nothing, and estivates. It is awake. It waits for rain.

It’s been a long, dry summer.