Archive | October 2012

Scary, scary stuff

As the tradition dictates, every year on this day we like to scare the living crap out of each other. One common way of doing it is to pick a random, small animal, and pretend that it is somehow dangerous or deadly. The top of this list of innocent victims is usually occupied by bats, spiders, cockroaches, or pretty much anything that is way too small to do us any harm. Unfortunately, the stereotypes hammered into everybody’s head on Halloween stay with us much longer than just one day, and the poor creatures suffer the undeserved bad reputation for the entire year.

But the really scary, dangerous animals are those that nobody suspects of being evil, and none more so than the creepy Giant panda. Sure, they look cute. But under the cuddly exterior hides a vicious, mean monster. My friend Corey, who used to work in the Panda Base in Chengdu, China, told me about about one particularly nasty, psychotic individual who used to attack people all the time, completely unprovoked. In fact, panda attacks are quite common, and there is even a blog devoted to this topic (“When Pandas Attack”). While in China I heard stories of people being killed by these vicious animals. In any case, I would rather be assaulted by a cockroach or run across a bat or a spider while walking alone in the forest, then meet one of these giant, black and white monsters. I know that they try to appear sweet by hiding their beady eyes in black patches of fur, but they are not fooling me!

A disappearing Goliath

Quickly vanishing forests of West Africa are still home to one of the most magnificent members of the beetle order—the Goliath beetle (Goliathus regius).

Despite their bulky appearance, Goliath beetles are excellent fliers, frequenting flowers blooming in the forest canopy. Adult beetles feed also on ripe fruits and sap, while their giant grubs, which can exceed 150 millimeters in length, develop in the decomposing wood of naturally fallen large trees. It is the increasing shortage of large rainforest trees that may ultimately spell the demise of this and other giant beetles. Their development depends on the availability of old-growth trees, the very same ones that are the principal target of the logging industry. I was lucky to run into this coleopteran wonder on Mt. Bero in Guinea. [Canon 10D, Nikon 17-35mm (yes, a Nikon lens on a Canon body)]

[Read more about the wonderful world of beetles in my book “The Smaller Majority.”]

Upside-down world

Notice anything wrong? For some reason we are able to accept that bats like to live upside-down, but we find it difficult for other animals. (Fruit bat, Myonycteris torquata, from Ghana)[Canon 5D, Canon 180mm, speedlight Canon 580EX]

“Men it appears would rather believe than know” wrote E.O. Wilson in his seminal book “On human nature”, and this sad truth is evident in many aspects of our life, including, strangely, the world of nature photography. One of my pet peeves has always been the tendency of some editors to rotate pictures of animals that prefer to look at the world with their heads pointing down, so that in the modified photo their posture appears more similar to ours. Somehow, this fakery to make animals more anthropomorphic has always been considered pretty innocuous and, to my dismay and outrage, on many occasions my photos were modified in this way without consultation.

Most praying mantids, like this Epitenodera sp. from Mozambique, spend most of their lives hanging with their heads towards the ground. [Canon 7D, Canon 14mm, Canon MT-24EX twin light]

Why is it that such a blatant distortion of the natural world is considered acceptable? If I Photoshopped a giant panda so that its fur is pink, everybody would be up in arms, but if a photo shows a praying mantis molting with its head pointing up then all is fine and good. The first is conceivably possible with a simple mutation, the second would require turning off the gravitational forces of the planet in order to happen.

Hanging, rather than standing, is less costly energetically, and allows praying mantids to invest more resources into their large raptorial legs (Empusa capensis from South Africa) [Canon 7D, Canon 100mm]

And yet, we prefer to go along the easier path of believing that all animals have the same preference to hold their heads high, and that this is somehow the “right” way. But for many organisms, especially those that make a living by being sit-and-wait predators, keeping the head pointing down makes far more sense.

Sloths can achieve their large body size on nutritionally poor diet of leaves because they spend little energy on walking. [Canon 1D MKII, Canon 16-35mm, speedlight Canon 580EX]

First, hanging from a branch, as opposed to standing on it, is much more efficient energetically. All you need is sharp claws to grasp the branch, and gravitation will make sure that these are firmly embedded in the bark, and no muscle power is required to keep the animal from falling. If you look at animals that spend their lives in this way – praying mantids, sloths, bats – you will notice that their leg muscles are severely reduced, and some can barely walk if forced to stand with the head pointing up. The energy that would otherwise go into legs can be diverted into other parts of the body: the powerful raptorial arms of the mantis or wings of the bat. (Sloths are a special case – the fact that they don’t need to walk allows them to grow really large, considering how nutritionally poor their food is. Any walking mammal their size would quickly starve if its diet were as meager as that of the sloth. )

Second, by hanging upside down, sit-and-wait predators are better able to blend in among the vegetation, which also tends to droop towards the ground. Relatively few arboreal sit-and-wait predators walk on branches, rather than hanging from them (chameleons are one of the examples.)

Molting is the most dangerous time in the life of an insect. Using Earth’s gravitation to slip out of the old exoskeleton is the fastest and safest way to do it. (Katydid, Teleutias sp., from Suriname) [Canon 1Ds MkII, Canon 180mm macro, speedlight Canon 580EX]

And finally, molting. A molt is a very special time in the life of an arthropod, a moment that we, mammals, cannot possibly identify with. It is a moment of ultimate weakness and vulnerability, and the faster you can go through it the better. So why don’t most insects use their legs to quickly crawl out of their old exoskeleton? The reason is that while the muscles of a molting insect or spider are fully functional, their points of attachment are not. Our muscles rest on the always rigid internal skeleton, and when we flex a muscle we don’t run the risk of bending a bone. But a molting insect does, because its exoskeleton, which contains points of attachment of all muscles, is at that point very soft. It can be easily distorted if any muscle is engaged while chitin, the polysaccharide that makes up the bulk of the skeleton, is still hardening. If an insect bends a leg during the molt, its exoskeleton may solidify in the bent position, making it unusable in the future. For this reason most terrestrial arthropods prefer to molt by slowly slipping out of their old, smaller exoskeleton, using the gravitational forces of Earth to their advantage.

And so, next time you see a photo of a butterfly emerging from the chrysalis towards the sun, or a praying mantis standing on its stick-like legs and holding a giant grasshopper towards the sky, don’t believe it. The truth may be a little more difficult to grasp, but it will give you a more beautiful picture of the world.

Nearly all spiders that are sit-and-wait predators prefer to wait for the prey with their heads pointing down. [Canon 1Ds MkII, Canon 180mm macro, speedlight Canon 580EX]

Arboreal lizards, like this forest dragon (Hypsilurus modestus) from New Guinea, often wait for their prey while sitting upside-down on tree trunks. [Canon 1D MkII, Sigma 15mm]

Tasty silk weavers

Australian green weaver ants (Oecophylla smaragdina) guarding a lycaenid caterpillar, which repays this service with honeydew rich in amino acids. [Canon 1D MkII, Canon MP-E 65mm macro, Canon MT-24EX twin light]

I gently squeezed the little green bulb between my teeth, and a lemony flavor flooded my mouth. I savored it for a second – Hmm, not too bad, I can totally see myself adding it to rice or some other bland food.
I shook off my arm the remainder of the insects who were aggressively intent on avenging the untimely death of their sister. I was in the Northern Territory, giddily soaking in myriad of natural history facts about Australia. These tasty ants, which feature prominently in the aboriginal cuisine, were definitely one of the highlights.

African weaver ant workers pulling leaves closer together, while others bind them with larval silk. [Canon 10D, Canon MP-E 65mm macro, Canon MT-24EX twin light]

Weaver ants are exceptional, even by the standards of a group of organisms that rival humans in the complexity of their social interactions and sophistication of their engineering. Only two species of the genus Oecophylla are known: in addition to the Australasian green weaver ants (O. smaragdina), the African weaver ant (O. longinoda) is found throughout most of sub-Saharan Africa. Both live in large arboreal colonies, and both exhibit an interesting behavior that has earned them the distinction of being silk weavers.

A worker of African weaver ant (O. longinoda) using a larva as a tube of glue to stitch together leaves (Guinea). [Canon 10D, Canon MP-E 65mm macro, Canon MT-24EX twin light]

When we think of silk, the first thing that comes to mind is of course underwear. The second is silkworms, and the ancient Chinese who first employed these insects to produce sophisticated garments. But weaver ants can also produce silk, yet, rather than spinning protective cocoons like moths, they use it in a way that is remarkably similar to the way we use crazy glue.
Being arboreal animals, weaver ants cannot build expansive underground galleries to protect their brood and queen. Instead, they pull together leaves and stitch them with sticky silk threads produced by their larvae – since adult workers do not have silk glands, some carry small larvae like tubes of glue, and squeeze them gently as they move back and forth between edges of two leaves. The leaves are temporarily held together by other members of the colony, often hundreds of them. The resulting arboreal nest is usually about the size of a football, and holds everything an ant colony needs – the queen’s chamber, a nursery for the larvae, and a larder full of prey.

African weaver ant (O. longinoda) from Mozambique. [Canon 7D ,Canon MP-E 65mm, 3 speedlights 580EXII]

Weaver ants are voracious hunters – I have seen them attacking grasshoppers, beetles, snails, even snakes, and they are not opposed to partaking of carrion. I have also felt them attacking me, and this is one of the reasons why these ants are not popular among gardeners in Australia – having them rain on you from a tree and spray formic acid on your skin is not one of the most pleasant experiences. But at the same time weaver ants can be quite beneficial. It has been shown that their presence increases fruit production of some plants, and reduces the amount of pesticides needed to control pests. Unfortunately, like most ants, they have a weakness for sugar, and will protect aphids and scale insects that cause damage to plants. In the end, their impact on agriculture is probably about neutral.

An ant-mimicking katydid Polichne sp. resembles a green weaver ant worker. [Canon 1D MkII, Canon MP-E 65mm macro, Canon MT-24EX twin light]

Some insects take advantage of the aggressive nature of weaver ants and, by assuming a similar appearance and hanging around their nests, gain protection from predators who dare not to get close to the ants. Katydids of the Australian genus Polichneare some of them, and it is still unclear how they manage to convince the ants not to eat them (chemical mimicry is the most likely explanation.)

African weaver ants carrying a live snail to their nest (Mozambique). [Canon 7D, Canon 14mm, Canon MT-24EX twin light]

Since my initial encounter in Australia, weaver ants have been my favorite social insects, both off and on the plate. I have had them with rice and sweet cakes, and they always add to the experience. Sometimes ants on your picnic table are a good thing.

African weaver ants carrying a live snail to their nest (Mozambique). [Canon 7D, Canon 100mm, Canon MT-24EX twin light]

Dwarfs of Lovane

Cape Dwarf Chameleon (Bradypodion pumilum) at Lovane near Stellenbosch; the name of this vineyard is derived from a Xhosa word “U’Lovane”, which means Chameleon. [Canon 7D, Canon 16-35mm, Canon MT-24EX twin light]

Yesterday I wrote about the Mt. Gorongosa Pygmy Chameleon, a species endemic to a single mountain in central Mozambique. But if you travel towards the southwestern corner of South Africa, you are likely to encounter another lineage of these amazing lizards, the Dwarf Chameleons (Bradypodion). About twenty species of these small but incredibly colorful chameleons are known from South Africa, and they are all endemic to this country.

Last year Kristin and I met one of the species, the Cape Dwarf Chameleon (B. pumilum), in a picturesque vineyard near Stellenbosch, as we were walking, glasses in hand, among rows of grapevines before sunset. A biologist’s life is sometimes so tough.

Western Dwarf Chameleon (Bradypodion occidentale) from Namaqua National Park in the Northern Cape province of South Africa [Canon 1D MkII, Sigma 15mm]

Pygmies of Mt. Gorongosa

Mt. Gorongosa Pygmy Chameleon would look right at home walking alongside a triceratops. If  triceratops were the size of your pinky, that is. [Canon 7D, Canon 14mm, MT-24EX twin light]

“You should not be there at night,” said Tonga, “it is not recommended.”

Since doing things that are not recommended is what I like to do, I dully noted my assistant’s objection, waved him goodbye, and began a hike towards the top of Mt. Gorongosa. I was in Mozambique, a member of a group of biologists working on a survey of the Gorongosa National Park. The mountain had only recently become a part of the park, and its mysterious, unknown katydids beckoned me ever since I had arrived in the country a few weeks earlier.

But katydids, being cryptic and all, are not easy to find, and the only sure way to get them is to quietly follow their calls at night. This activity benefits from the lack of company, hence my decision to spend a few days on the mountain by myself.

As soon as I got to the rainforest that envelops the mountain below the peak, I pitched my tent and set out to see what was out there. By then it was already dark and insects were beginning to sing. I scanned the vegetation with a headlamp and immediately noticed a tiny creature hugging a branch, an animal whose shape seemed both unexpected, and yet oddly familiar. It took my brain a second to pull together disparate threads of superficial knowledge, and then… Sweet Merciful Jeebus, this is the Gorongosa Pygmy Chameleon!

The tongue of the pygmy chameleon rarely misses. [Canon 7D, Canon 100mm macro, 2 speedlights Canon 580EXII]

I had read about this nearly mythical lizard, discovered only in 1971 and seen since by only a handful of people, and never expected to chance upon it during the first few minutes of my foraging. The Gorongosa Pygmy Chameleon (Rhampholeon gorongosae) is a member of a group (Brookesiinae) that has radiated extensively in Madagascar, but has only a few members in Africa. Unlike the “non-pygmy” chameleons (Chamaeleoninae), which live high on trees and bushes, pygmy chameleons spend most of their life in the leaf litter, and climb branches only at night to avoid being eaten by shrews and other nocturnal predators. And since few night predators are equipped with good color vision, at night they shrink their color-producing chromatophores in the skin, and turn ghostly pale. This of course makes them easy to spot by somebody carrying a powerful flashlight, and soon I started noticing dozens of them, sleeping on trees and bushes all around me. One was perched about three feet from my tent, and I decided to get up early to see its descent and the beginning of its daily routine. I was hoping to photograph it throughout the day as it hunted insects in the leaf litter. Alas, although I got up just before dawn, the chameleon was already gone. I spent the entire day looking for these lizards, and found none, but right before sunset the chameleon was back on its perch in exactly the same spot as before.

I found this female and a newly hatched baby sitting close to each other on the same branch, and soon the young chameleon climbed the adult and stayed on top of her for a while. Pygmy chameleons generally take a few months to hatch from eggs, and thus it is not certain that she was the baby’s mother. Still adorable, though. [Canon 7D, Canon 100mm macro, MT-24EX twin light]

The following morning I got up even earlier, just in time to see my chameleon make it slowly to the forest floor. It was a female, and I spent several hours tracking her every move, watching and photographing her as she fed on termites and other small insects. Every now and then I threw a tiny grasshopper in her direction, and almost invariably she caught it with her incredibly long tongue. At some point I took my eyes off her for a few minutes, and she vanished.

Crypsis is these animals’ only defense, but they managed to turn it into a form of art. Not only do they resemble a piece of wood but, like all chameleons, they are incredibly good at changing their body color and pattern to match the substrate on which they are sitting or walking. Although most of the time the Gorongosa chameleons display various shades of brown to match dead leaves on the forest floor, if they find themselves climbing a vine or another live plant, they turn green. It is rather entertaining to watch them climb things, which they do very skillfully, if very slowly, despite  the lack of a prehensile tail that defines their larger cousins.

Brown Leaf Chameleon (Brookesia superciliaris) from Madagascar, although Yoda Chameleon might be a more apt name for this species. [Nikon D1x, Nikkor 17-35mm, flash Nikon SB-28DX]

My encounter on Mt. Gorongosa was not the first time that I met pygmy chameleons. Nearly a decade earlier I spent some time in Madagascar, and there I saw several species of the genus Brookesia. They were similar in shapes and sizes to the Gorongosa chameleons, and also lacked the prehensile tail, but these features turn out to be the result of convergent evolution, rather than true close relatedness of African and Malagasy species. They also exhibited one quite unexpected behavior that I did not see in the African species. Just like their cousins from Mt. Gorongosa, brookesias drop to the ground and remain motionless until the danger passes. But if it does not, such as when I picked one of the lizards with my hand, they suddenly turn into a really pissed off, loudly buzzing bee! Or at least that’s what my sympathetic nervous system told me, forcing my hand to drop the animal almost as soon as I touched it, even though my brain knew that it was a bluff, and that I was still holding a small, harmless lizard. Such buzzing defensive behavior has been seen in a few species of chameleons, but its mechanism is poorly understood.

Vadon’s Leaf Chameleon (Brookesia vadoni) from northeastern Madagascar [Nikon D1x, Sigma 180mm macro]

The Mt. Gorongosa Pygmy Chameleon may be smaller than your pinky finger, but it is a magnificent symbol of Mt. Gorongosa’s unique ecosystem, and it is not alone. During the few nights that I spent on the mountain, in those moments when I wasn’t giggling with delight at the sight of the most adorable lizard on the planet, I found several new to science species of katydids. It is quite likely that, like the chameleon, they are endemic to Gorongosa, and I absolutely must go back to learn more about them. Even if it is not recommended.

A male Mt. Gorongosa Pygmy Chameleon on my hand [Canon 7D, Canon 100mm macro]

The other whipscorpions

A rainforest vinegaroon (Thelyphonus sp.) from Cambodia. [Canon 1Ds MkII, Canon 100mm macro, 2 speedlights Canon 580EX]

It never ceases to amaze me how excited everybody gets about the prospect of finding life elsewhere in the universe, even if that life is likely to be in a form of thin layer of slime somewhere deep in the rocks, while our own planet is bursting with forms that would be considered figments of drunk imagination, if not for the fact that they actually exist. Among them, few possess a more fantastic combination of features than vinegaroons (Thelophonida), also known as tailed whipscorpions.

The mouthparts of the giant vinegaroon (Mastigoproctus giganteus) from Arizona are an efficient machinery for catching and crushing prey. These arachnids produce no venom, and must rely on their strength alone to overpower their victims. [Canon 1Ds MkII, Canon 180mm macro, speedlight Canon 580EX]

I first saw a live vinegaroon in Arizona. It just happens that the southern US has the world’s largest species; one who also has a strange preference for dry habitats. Normally, vinegaroons have little tolerance for water loss, and most species are found in tropical rainforests. Vinegaroos have poor vision, and thus their picture of the world is pieced together mostly from the input of thousands of chemical, vibrational, and pressure receptors that cover their entire body. The first pair of legs acts as sensitive antennae, smelling and feeling for prey. At the opposite end of the body a long “whip” (telson) constantly scans the world around the animal like a super-sensitive aerial searching for signals from space. It can detect the faintest odors or movement of air molecules that may signify danger, and the sensors that cover its surface send a constant stream of information to the vinegaroon’s central nervous system. If a potential attacker is detected, the animal snaps into action. But rather than trying to use its formidable pedipalps, which can easily crush large prey insects, the vinegaroon engages its chemical warfare.

The “whip”, or flagellum, of a vinegaroon act as an extremely sensitive antenna that collects information about the world around the animal. It its base the pygidium has two small nozzles that spray a defensive acid cloud. [Canon 1Ds MkII, Canon 100mm macro, ambient light]

At the base of the “whip” a small segment known as the pygidium opens up to a gland filled with a powerful mixture of acetic, octanoid, and caprylic acids (the mix contains 83-84% acetic acid, which is also present in vinegar, hence the animal’s common name; vinegar, however, has only 5-8% of the acid.) The moment a threat is detected, the pygidium, guided with the signals from the “whip”, sends a precisely directed acid spray, smack into the face of the attacker. Being sprayed with concentrated, foul-smelling vinegar is no fun, but even worse is the aftereffect – the caprylic acid in the spray, if it lands on an arthropod’s exoskeleton, destroys the lipids that cover its surface, which not only increases its permeability to the vinegar, but also causes accelerated dehydration. To a desert spider or a ground beetle this may mean death. (Thankfully, our bodies don’t have the exoskeleton, and thus vinegaroons’s chemical weapons have little effect on us; after all, we put vinegar in our food.)

A female shorttailed whipscorpion (Hansenochrus sp.) from Saba, West Indies. [Canon 1Ds MkII, Canon MP-E 65mm macro, Canon MT-24EX twin light]

Like their close cousins, tailless whipscorpions, vinegaroons are rather peaceful creatures, with elaborate mating rituals and extensive maternal care. Although they are solitary predators, they are known to share large items of prey, and up to six individuals have been seen feeding at the same time on a particularly large millipede or beetle. Recent phylogenetic work on the relationships of vinegaroons confirms a long-held belief that their closest relatives are tiny, enigmatic shorttailed whipscorpions (Schizomida). They look like ant-sized, pale vinegaroons, but lack the long “whip”. They do, however, employ similar chemical defenses, albeit little is known about the specifics of this behavior.

During their mating ritual the male of the giant vinegaroon uses his large pedipals to gently caress and steer the female. [Canon 1Ds MkII, Canon 180mm macro, speedlight Canon 580EX]

Considering how incredible vinegaroons and their relatives are, it is not surprising at all that creatures in scifi movies often borrow heavily from their morphology. But if there is one thing that is certain, it is that nowhere else in the universe will you find anything like these remarkable creatures.

Vinegaroons use their first, long pair of legs as sensory organs to detect prey. The large “pincers” (pedipals) are mouthparts. (Thelyphonus sp., Cambodia)[Canon 1Ds MkII, Canon 100mm macro, 2 speedlights Canon 580EX]