Big, beastly and very extinct birds

In the right circumstances birds can evolve into giants. In the vast majority of cases they have done this on oceanic islands in the absence of any large land predators and most of these extinct giant birds are decidedly lacking when it comes to predatory ferocity, as birds like the moa and elephant bird attest; big, but decidedly vegetarian animals. However, a long-legged bird living in South America several million years ago, probably very similar to the living seriemas (Cariama cristata and Chunga burmeisteri), gave rise to a group of birds collectively known as terror birds (, technically known as phorusrhacids) and as their name suggests they were not the sort of feathered critters you would find nibbling nuts at a bird-table. They were big birds; the smallest of the 17 known species were at least 1m tall, while Brontornis burmeisteri stood as high as 3m and may have weighed as much as 350–400 kg, but even B. burmeisteri may have looked a bit pathetic next to an even bigger species, the skull of which was discovered by a high school student in Patagonia in 2003. There’s every possibility these animals were the largest birds ever to have lived and all of them were undoubtedly fierce predators. Why these nightmarish birds came to evolve in South America is not fully understood, as no other place on Earth has ever produced a group of predatory giant birds. Gigantism in birds is normally associated with herbivory, yet whatever conditions prevailed in South America many millions of years ago allowed the evolution of a varied group of feathered carnivores that were around for a huge stretch of time; from around 60 million years ago to about 1.8 million years ago, which goes to show how successful these birds were.

A selection of terror birds. A - Brontornis burmeisteri; B - Paraphysornis brasiliensis; C - Phorusrhacos longissimus; D - Andalgalornis steuletti; E - Psilopterus bachmanni; F - Psilopterus lemoinei; G - Procariama simplex; H - Mesembriornis milneedwardsi and the silhouette of a man (1.75 m high) for scale (Herculano M.F. Alvarenga)

Following the extinction of the dinosaurs, many niches in the Earth’s ecosystems were left wide open for the vertebrate survivors – the mammals, birds, and remaining reptiles to evolve into, and for a while, apparently, the terror birds had a power struggle with the mammals for the dominance of the terrestrial ecosystems in South America. Many of them were big and powerful enough to have been the top predators at the time, and many mammals were definitely their prey.

All but one of the terror birds paleontologists know of today have been unearthed in South America. One species (Titanis walleri) managed to reach North America, and it appears to have been quite a success, surviving for more than three million years until it disappeared around 1.8 million years ago – the last of its kind to become extinct. Even though this American species was not the biggest terror bird it must have still been a terrifying animal. Its vital statistics are impressive: 1.4 – 2.5m tall and 150kg in weight. It also had an immense, hooked bill and with such an impressive beak it could have probably swallowed a lamb-sized animal in one gulp.

Although we can piece together the skeletons of the terror birds it’s impossible to know what their plumage was like. However, we can look at living birds for clues, and if the other flightless birds are anything to go by, the terror bird’s feathers may have been rather hair-like. Like the vast majority of flightless birds, terror birds had stubby little wings, but what they lacked in the wing department they more than made up for with their long, powerful legs that ended in large feet and long claws. These legs gave these animals a good turn of speed and it has been estimated that some species of terror bird could reach speeds of 100kmh – comparable to a cheetah. The combination of running, big talons and a monstrous beak made the terror birds very effective predators. It is possible to imagine one of these birds snapping at the hooves of ancient mammals as it pursued them across the grasslands of the Americas. Smaller animals were probably immobilized with the sharp talons before being torn apart by the fearsome hooked bill or even swallowed whole after having their skull crushed in the bird’s vice-like grip. Larger prey animals may have been disemboweled with Kung-Fu styles kicks and it is even possible that crushing kicks may have been used to crack the larger bones of big prey to get at the nutritious marrow within.

Skull of a terror bird (Titanis walleri). This is about 50cm long (Ross Piper)

Even if the last terror bird became extinct around 1.8 million years ago, these were successful animals that, as a group, survived for more than 50 million years, some of them even taking on the mantle of top land predator in the ecosystems in which they lived. However, around 2.5 million years ago (during the Pliocene epoch) something happened that completely changed the course of life for South America’s unique animals – the Great American Interchange. The land bridge that eventually appeared between North and South America, what is now known as the Isthmus of Panama, allowed animals from the north to migrate into South America. Among them were lots of predatory cats and it has been proposed these animals were so effective as predators that they outcompeted the terror birds. The talons and beaks of the terror birds were no match for the teeth, claws, and hunting prowess of the invaders from the north. This is a very neat answer for the cause of the extinction of the terror birds, but, the extinction of successful animals is very rarely due to one factor, but a combination of events. Perhaps climate change directly affected the terror birds by changing their habitats and the populations of their prey. Although there is a great deal we don’t know about the life and times of the terror birds we do know that one of their number somehow managed to cross into North America and spread through the southern states. For a long time it was assumed that the American terror bird spread north via the land bridge, but analysis of its ancient bones paints an alternative picture as they appear to have reached the southern states of America before the land bridge formed. Perhaps falling sea levels, due to the growth of the polar ice sheets, revealed a path of ‘stepping stones’ across islands in the gap of open ocean in what would become the Isthmus of Panama, allowing the giant birds to colonize the prehistoric North America. Maybe other species of terror bird, the remains of which are as yet undiscovered, also reached North America before following the rest of their amazing kind into the pages of earth history.

Terror bird (Paraphysornis brasiliensis) reconstruction (Renata Cunha from Extinct Animals, Greenwood Press)

Read more about the terror birds and other beasts that have long since ceased being extant in the book Extinct Animals

Further reading: Marshall, L.G. The terror birds of South America. Scientific American 270 (1994) 90–5; Alvarenga, H.M.F. and Höfling, E. a systematic revision of the phorusrhacidae (aves: ralliformes). Papéis Avulsos De Zoologia 43 (2003) 55–91; MacFadden, B.J., Labs-Hochstein, J., Hulbert, R.C., and Baskin, J.A. Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange. Geology 35 (2007) 123–126.

Scoundrel – #4

The paussine beetles (see scoundrels – #6) are very good at mimicking the odour of ants in order to run amok in the nests of their hosts, gorging themselves on eggs, larvae and pupae. This is the sort of behaviour we’ve come to expect from ground beetles, the dark, scuttling creatures that they are. If someone suggested that a butterfly was capable of the same unpleasant behaviour, your initial course of action might be to take the cad by the lapels and rough him up a bit so that he repents for blackening the good name of such charming insects. Unfortunately, they would be right, so you’d have some apologising to do.

Anyway, butterflies are capable of behaving in some very despicable ways, especially the larvae. The adults are fleeting, shallow, lustful creatures, only interested in getting it on with the opposite sex, but the larvae have the difficult task of eating as much as possible in the shortest amount of time and to do this some species have found they can get the job done very successfully if they pull the wool over the beady eyes of ants.

The alcon blue butterfly (Maculinea alcon) is one such interloper and the story begins around the end of July in the European summer when the female alcon blues deposit their white eggs on the flowers of marsh gentian. A few days later the tiny caterpillars hatch out of the bottom of their egg and munch a tunnel straight into the closed flower of the gentian and here it remains for around two weeks, safe from its predators, eating some of the flower tissue and developing seeds, but not growing very much. In the flower, the caterpillar sheds its skin three times and after the final time it’s ready to take its leave of this safe house, so in the early morning or evening it chews its way from the base of the flower and shuffles along the petals to the apex of the bloom. Apparently tired of its nursery it releases its grip and falls to the ground on a silken thread and waits.

And so the ruse begins - a female alcon blue butterfly laying eggs on a marsh gentian flower (David Nash).

This is the riskiest time of its short life. Predators abound amongst the short turf and all of them would make short work of a tiny, plump caterpillar; however a small, foraging red ant (Myrmica spp.)gets a whiff of the caterpillar and goes for a closer look. The ant, seemingly intrigued and mesmerized by the caterpillar, strokes it all over with its quivering antennae. If it could, the caterpillar would be breathing a huge sigh of relief as this is exactly what it was waiting for. This is a result. To express its relief the ant produces a drop of sweet fluid from its rear end, which the ant immediately starts suckling. This can go on for some time, until the caterpillar flattens the middle or rear of its body, a simple act that is apparently enough to completely fool the ant that the caterpillar is a grub from its own nest that has somehow gone walkabout. It tenderly picks the caterpillar up in its jaws and makes for the nest.

Get in! This is just what the caterpillar was hoping for (David Nash).

The caterpillar is deposited in the nursery of the ant’s nest alongside the countless young of the colony. Here, it blends right in. It smells right and smell to ants is all important. The ants feed the caterpillar by regurgitating nutritious fluid and somehow these tiny tricksters persuade the ants to give them preferential treatment so that they receive more attention and food than the ant grubs. To add insult to injury, the caterpillars also supplement their liquid diet by scoffing the odd ant grub or two. On such a nutritious diet the caterpillar grows quickly, increasing its weight by amount 100 times during its first month in the nest. The caterpillar stays put in the nest for some time, living it up in the safety of the nest at the expense of the trusting ants and only when the following summer arrives does it begin the transformation that will turn it into a fine butterfly.

The alcon blue caterpillar lives it up in the nest with the ants at its beck and call (Darlyne A. Murawski).

When it emerges from its chrysalis as an adult butterfly deep underground the tricks used to deceive the ants have long since worn away. It no longer smells like an ant and it certainly doesn’t look like an ant larva, albeit a massive one. At this point, the ants are probably beginning to twig: “Wait a minute… is that the fat sister we’ve been feeding for ages…isn’t she a looker?…must have got her dad’s genes.” “Saying that though she does look a lot like those weird fluttery things we see on the outside……..but what’s it doing in here?” As the penny drops it’s time for the butterfly to leg it. The ants see the butterfly they have nurtured for the best part of a year as nothing more than an intruder and if they get hold of the low-down mimic they’ll do unspeakable things to it. Fortunately, the butterfly has one last trick to avoid being held to account and as the angry ants try and bite the fleeing charlatan all they come away with is a mouthful of scales. The whole body of the newly emerged butterfly is densely covered in loose scales and the ants cannot get a grip on it, so by the scales on its behind it manages to give its trusting guardians the slip and leaves the nest by the nearest exit without so much as a bye or leave. Above ground it makes for a perch among the lofty vegetation of the meadow where its wings will inflate and harden in the summer sun until it is ready to flutter off like butter wouldn’t melt on its proboscis.

Who'd have thought a butterfly would be capable of such things (Pieter C. Brouwer).

For the sheer audacity of these butterflies they’re at number four in the scoundrel chart.

Scoundrels – #5

Most animals are content with mimicking one species or a group of species, indeed that’s all they can do because their ruses are based on the way they look. However, there is one animal that’s a master of many disguises – the mimic octopus (Thaumoctopus mimicus), which is such a wily beast it’s at number five in the scoundrel run-down.

This eight-limbed trickster is a denizen of the estuarine and shallow coastal waters of the Indo-Malaysian archipelago, a habitat that’s not the safest for a large, succulent invertebrate. To protect itself in these hostile waters this octopod has evolved some very sophisticated mimicry that hinges on its sinuous limbs and colour-changing abilities.

The mimic octopus, not mimicking anything, poking its head from a burrow (M. Norman and R. Steene).

This mimic octopus isn't fooling anyone. It's not trying to - this is the species' normal foraging look when they're not pretending to be something else (M. Norman and R. Steene).

Should the octopus spy danger then it draws its arms into a leaf-like shape, changes colour to match the sea-bed and swims off with undulations of its body. The posture, colour and particularly the movement are startlingly similar to a number of flatfish found in the same area. These flatfish have venom glands at the base of their dorsal and anal fins and many predators steer well clear of them.

Do you like my fish impression? The mimic octopus (left) pretending to be a flatfish, the real mccoy of which is on the right (M. Norman and R. Steene).

In situations when the predator isn’t fooled by the old flatfish trick, the octopus swims up from the sea bed and splays its arms wide. Cruising slowly through the water in this posture it looks for all intents and purposes like a lion fish brandishing its venomous spines. The approaching predator has dealt with lionfish before, knowing their stings to be particularly painful so it swims off and searches for easier pickings.

Another fish impression, this time a lion fish (M. Norman and R. Steene).

The mimic octopus continues on its foraging rounds and then accidentally swims through the breeding ground of a damselfish, which happen to be fiercely territorial. The fish doesn’t take kindly to this intruder and it goes on the offensive. With an angry damselfish bearing down on it, the octopus uses yet another of its impersonations and bolts for the nearest hole. It changes colour and pattern and sticks six of its arms into the hole, leaving two at the surface heading off in different directions, waving sinuously in the water. Hey presto – a convincing impersonation of a banded sea-snake, a reptile that will quite happily scoff a damselfish. The aggressive fish gets the message and backs off.

I'm tired of fish. How about a banded seasnake (M. Norman and R. Steene)?

As splendid as these impersonations are they are not the entire repertoire of this mollusc. Some predators may be invulnerable to the poisonous spines of flatfish and lionfish and unfazed by the venomous bite of a sea-snake. In these circumstances the octopus may swim to the surface, fully extend its many arms and float slowly back towards the sea-bed in much the same way as certain jellyfish found in the same waters. Even if the stinging cells of a large jellyfish are not enough to deter a hungry predator, the octopus has one more trick up its mantle: it takes to the sea-floor and on a mound of silt it raises its arms above its body to give a very convincing impression of a large, stinging anemone.

 

Reference

Norman, M. D., Finn, J., and Tregenza, T. Dynamic mimicry in an Indo-Malayan octopus. Proceedings of the Royal Society (Series B) 268, (2001) 1755-1758.

Win a book

Time for a small competition I think. Win a copy of my book, Extinct Animals, by telling me what organism is in the photo below.

What the devil is this? (Photo courtesy of Prof. R Lester)

If there are any answers, ideally right ones, send them to me at naupilar@googlemail.com and I’ll pick a winner at random. Happy guessing.

Scoundrels – #6

As we’ve seen with the ant-mimicking spiders (see scoundrels – #8), the imitation of ants is often very elaborate because of the fringe benefits of living with these industrious insects, namely being able to taunt your predators safe in the knowledge that the worker ants around you are a pretty potent repellent. The relationship of the ant-mimicking spiders with ants is a rather benign, albiet one-sided one, i.e. they pretend to look like ants for the sake of defence, but there are some insects that have taken the ruse to a more devious and abhorrent level.

There’s a group of ground beetles, the paussines, that make little or no attempt to look like ants, but they have evolved other, more subtle disguises allowing them to live deep in the ant’s nests where they are free to come and go as they please.

This is what a typical paussine beetle looks like. See the massive antennae - probably important for producing ant odours (www.entomology.lsu.edu/lsam/inquilines/InquilineHetaeriine.htm)

Another paussine beetle, but with even more elaborate antennae. Apart from their odd appearance, these beetles can also fire boiling-hot noxious chemicals from their rear end - useful if they ever find themselves away from the protection of an ant's nest and confronted by a predator (www.entomology.lsu.edu/lsam/inquilines/InquilineHetaeriine.htm)

These wily beetles mimic the smell of ants, and because odour is so important in ant colonies the beetles are simply accepted, no questions asked.  Any animal that manages to live inside an ant’s nest without being hounded and pulled apart like soft bread by the workers is on to a winner.  The nests of these social insects are miniature fortresses and, as an added bonus, they’re chock-full of toothsome morsels. There are abundant eggs, larvae, pupae and waste heaps to keep even the greediest predators and scavengers busy. Paussines are predators and like malevolent house-guests they wander through the galleries and chambers of the nest, smelling of ant, helping themselves to their host’s brood. Occasionally, a worker ant will grow suspicious as the greedy beetle demolishes yet another plump larva, but under ant interrogation the paussine simply exudes more L’Eau de Ant from its bulbous antennae and the numerous pores on its body and the suspicions of the worker are quickly allayed.

For the sheer underhandedness of the paussine beetles they are at number 6 in the scoundrel chart.

Scoundrels – #7

Some predators found hunting to be something of a real chore, so over the eons they evolved means of getting their food to come to them. All they have to do is sit perfectly still and wait. Perhaps the most intriguing of these lazy predators is the alligator snapping turtle, one of the most fearsome and beastly-looking reptiles on the planet and one that also happens to be number 7 in the scoundrel chart.

"And where do you think you're going?" www.dausettrails.com

This North American brute spends most of its time loitering on the bottom of lakes, rivers, swamps and canals. They’re very well camouflaged and in the murky depths its favoured prey, fish, probably have no idea of what terrible things lie in wait until it’s too late and they end up sliced in two by the turtle’s bolt-cropper jaws. If the turtle were to simply open its mouth and wait, it would be waiting for a very long time for a fish to blunder within range. This wouldn’t do. No, it needs something devious, something that will tempt fish within scoffing range. To this end evolution has equipped the turtle with a modified tongue that bears more than a passing resemblance to a juicy worm.

Here's the 'worm' - the bright pink tip of the turtle's tongue (Jesús Mendoza)

The deliciously pink ‘worm’ stands out against the dark maw like a beacon, a too-good-to-be-true snack, the ruse further enhanced by the turtle making the ‘worm’ wriggle by twitching its tongue. Sooner or later, a greedy, albeit dim fish, sees the ‘worm’ and swims over for a closer look. It edges closer and closer to the plump ‘invertebrate’, positively salivating at the mouth, and just when it’s about to close in for the kill, the impossibly patient turtle lunges and snaps its heavy jaws shut. Who knows the last thought that went through the hapless fish’s tiny brain, but I bet it never banked on ‘that worm’ being the business end of a 50kg devil turtle.

In the above video you can see the turtle wiggling its ‘worm’.

Scoundrels – #8

Ants are pretty mean animals. They bite, some of them sting and individuals from the same nest can co-ordinate their activities to repel and even kill much larger animals. For these reasons, most animals leave them well alone making them excellent subjects for mimicry.

There are lots of invertebrates that pretend to be ants, but perhaps the most impressive are the jumping spiders, some of which behave and look like ants to such an extent that it’s often difficult to tell them apart when all you catch is a quick glimpse. Below is a particularly impressive female ant-mimicking jumping spider alongside the weaver ant it pretends to be:

The jumping spider (Myrmarachne plataleoides) (left) and the ant (Oecophylla longinoda) it's pretending to be (right) (Sean Hoyland and Alex Wild)

Often, these spiders have the cheek to pretend their front legs are antennae, waving them about in the air like they are actually doing something. It has the distinctive thin ‘waist’ of an ant. It scurries around like an ant and to top off its disguise, it has a pair of dark eye-spots well behind its big, forward-looking eyes. It’s an incredible little animal that blends in with the ants for protection from predators, some of whom are the ants themselves.

The male ant-mimicking spider’s disguise is not quite as effective thanks to its massive mouth-parts (chelicerae). Here is the male of the species shown above and just take a look at it’s ridiculous chelicerae:

Look at the jaws on that (Challiyil Eswaramangalath Vipin)

The grossly exaggerated feeding gear is used to despatch prey, but their primary use is in courtship, hence their enormously inflated dimensions. The males joust with their chelicerae to win the right to mate and because bigger is better when it comes to male adornments they run the risk of blowing their cover. Amazingly, these spiders have evolved a way of incorporating their incredible adornments into their disguise. Worker weaver ants often carry their smaller nest mates (minor workers) around and this is what the male jumping spider is mimicking – an ant giving another ant a lift. The photo below shows this more clearly:

Male jumping spider hiding its massive chelicerae by pretending to be a weaver ant carrying a smaller weaver ant (Sean Hoyland)

So, despite their grossly exaggerated chelicerae, even the male ant-mimicking spiders are superbly disguised and therefore protected making them number 8 in the scoundrel chart.

Scoundrels – #9

Not content with pretending to be other animals, some insects have taken to mimicking inanimate objects, namely various parts of plants. Among the most adept plant mimickers are the insects known as treehoppers (membracids) and leafhoppers (cicadellids) – in at #9 in the scoundrel chart. Take a look at the photo below.

This is a treehopper and what better way to dupe your enemies into leaving you alone by pretending to be a withered, partially chewed leaf. No insect predator worth its salt is going to look twice at a gnawed bit of vegetation, so the treehopper can sit in the open in the relative safety.

The treehoppers have really gone to town with plant mimicry and there are very few parts of plants they don’t have a go at pretending to be:

There are buds and blisters…

This treehopper is pretending to be a bud

This treehopper is trying to blend in by looking like a bud or plant blister

Flowers and thorns…

Lots of these colourful Brazialian membracids are normally found together, sitting around trying to be flowers

This treehopper is trying to convince everyone it's a thorn

More fake thorns - this time another Brazilian treehopper

And Christ knows what this is supposed to be…

I'm still trying to work out what this one's trying to be. Maybe poison loaded spines?

Scoundrels – #10

Nature is full deception. There are loads of animals that live their life by pretending to be something else. Over the next few days we’ll take a look at ten of the animal kingdom’s best deceivers, starting with this one at number 10:

The little insect below is a native of Southeast Asia, but for the past few years it has been submerged in alcohol, not because it’s a heavy drinker, but because it blundered into a malaise trap that was left out to see what insects inhabit the Cameron Highlands in Malaysia.

Mutant leaf-beetle or body-concious fly?

What’s so special about this then you may be thinking? It’s just another little insect. True, but what type of insect is it? If you think it’s a beetle then good effort, alas, no cigar. It does look like a beetle, but it’s really a celyphid fly pretending to be a beetle. Its disguise is convincing, all the way down to the fake elytra (wing covers).

Why pretend to be a beetle? What’s wrong with an honest, albeit irritating, good old fashioned fly? Plenty. Flies get eaten by lots of things, because apart from being nifty in the air they’re pretty defenceless. On the other-hand, the beetles these flies mimic, chrysomelids (leaf beetles), taste foul thanks to their ability to harness a plant’s chemical defences to protect themselves. By looking like these beetles, the flies are given a wide berth by the predators that would otherwise quite happily scoff them.

What devilry is this?

Let’s start this post with a picture:

"No thank you. I'm not partial to stationary. And anyway, can't you see I've got a bloody frog in my throat"

What’s going on here? Some photoshop jiggery-pokery? An amphibian version of Russian dolls? A severe case of indigestion? Sadly, none of the above. Even more sadly, it’s the first and last picture of a gastric-brooding frog (Rheobatrachus silus) ‘giving birth’.

Like the Stephens Island wren, the gastric brooding frog was in the extinction fast-stream and a little over seven years following its discovery it was gone forever. Reasons for its demise are numerous and varied, including meddling scientists shoving paper-clips down their throats, killer fungi and greedy gold-miners.

Discovered in 1973 in the mountains of southeast Queensland, Australia, this little frog was a biological wonder because the female nurtured its young in its stomach, hence the catchy ‘gastric-brooding’ moniker. At some point following the fertilisation of her eggs the female swallowed as many of them as she could and safe in the confines of their mother’s belly, the eggs hatched into tadpoles and the tadpoles grew into tiny froglets. The stomach, what with its acids, etc. is not the first place that springs to mind as the ideal place to raise the kids, but fortunately, this amphibian had a splendid little trick. When the young were in the stomach the secretion of the powerful acids was blocked by a chemical known as a prostaglandin and the eggs and tadpoles could develop without the fear of being digested. Naturally, this stomach-brooding trick wasn’t without a price and for the duration of her ‘gestation’, the female frog had to go without food.

Apart from this singular adaptation, very little else is known about this amphibian as the last specimen was seen in 1981 and repeated searches of its old haunts have drawn a blank, so, it’s presumed to have hopped into the big dusty book of Earth history.

Read more in Extinct Animals:

www.greenwood.com/catalog/GR4987.aspx