TARANTULAS AND THE DANCE OF DEATH   2 comments


Wildlife, nature, fauna and flora of Costa Rica.

The weather on Cabo Matapalo continues to favor the visitor.  Over the past week the days have been dry and sunny, there has been little rain at all.  The rain that has fallen has been at night after everyone has returned to the comfort of their cabins.  There was one afternoon when an electric storm developed over the tip the tip of the peninsula.  Thunder echoed loudly throughout the forest, the rumbles seemingly shaking the ground beneath your feet, whilst simultaneously lightning sizzled and cracked overhead illuminating the surrounding area with blinding flashes of light.  The rain poured vertically down from the heavens and within no time the paths had turned into running rivers.  The whole event lasted little more than an hour and ended as abruptly as it began.  The thunder rolled off into the distance, a herald of the deluge that was about to be visited upon the neighboring areas.

There would appear to be no letup in the enthusiasm of the breeding amphibians.  Each night the number of calling males remains constant.  The vegetation around the pond is covered in the eggs of many species.  It is strange that this year should have seen a surge in the population of Small-headed Frogs, (Dendropsophus microcephala), which previously have been present in small numbers but this year have exploded to the point where they are the most vocal of nightly serenaders.

This has also been an exceptional year for the White-nosed Coatis, (Nasua narica).  They are normally to be found around the gardens and throughout the forest and therefore are easily encountered.  One of the first animals people see upon arrival are the coatis with their striped tails, slightly curved at the tip, stuck directly up in the air.  The males are solitary and tend to bolder in their approach to people.  The females, which band together in large groups with the young, until recently were more shy and retiring, they would run if you got too close.  At least that is how it used to be.  Now they are not so inclined to move out of the way.  They will look at you with furtive glances, on their toes ready to run if you make a fast movement towards them, but if you move slowly they will continue about their business just maintaining a wary watch.  It could well be that after so many years of being watched in this fashion that they have become familiarized with their human observers and no longer perceive them as an immediate threat.

A Touch Too Much

The sun is setting, its last red glowing rays now only picking out the top of the trees, creating the illusion that the canopy is on fire.  You grab your flashlight knowing that the fire will rapidly fade into the burnt-out embers of dark red and ultimately dampened into darkness.  With this darkness an awakening occurs, creatures of the night are beginning to emerge.  Before all becomes blackness, the silhouettes of bats can be seen against the sky, leaving their daytime roosts to feed on all manner of food.  Here the bats feast on a sumptuous banquet, each of the 80 species on the Osa Peninsula having its own preferred diet.  There are insectivorous bats, nectar-feeding bats, fruit-eating bats, carnivorous bats, fish-eating bats and yes, even blood-feeding bats, the vampires.

In the background, the plaintive whistle of a Great Tinamou can be heard, its three ascending sad notes announce that the day has ended and the night has begun.  As if on a collective cue, the insects start to call.  The soft but rhythmic pulsating sound of katydids and crickets fills the still nighttime air.  The shrill call of parrots and macaws fill the darkening sky as they pass overhead returning to their nightly roosts.  Now, adding to the white noise of the insect symphony comes the call of the amphibians.  They have been tucked away, hidden during the day from the harsh and drying effects of the sun’s rays, not good for creatures that breath through a delicate moist skin.  But as the air cools it becomes damper, perfect for males to begin to emerge, set up a territorial platform and start to call.  If he is lucky, a female will be attracted to the tone of his voice, oblivious to our ears, but sweet music to hers conveying the potential genetic quality that she would wish for her offspring.  Finally the deep roars from the male Howler Monkeys as they settle down for the evening are telling you it is time to venture out.

You step out into the darkness, flashlight up by your eye scanning the area immediately in front of you looking for eyeshine.  You are familiar with the various colors and the distinctive way the eyes of different animals reflect back at you.  There is something.  Fiery orange eyes on the ground, it blinks so it is not a snake, it hops up and down and then it calls and flies off.  That you could identify quite easily as one of the nighthawks, a Common Paureque, (Nyctidromus albicollis). Now over there in a tree, more bright orange eyes staring down at you.  You walk over to see what might be observing you.  Before you get close enough to make out its form it calls, a Spectacled owl.  It opens its wings, leans into the night and silently slips away, gliding like a feathered phantom into the blackness.  So not a bad start to the evening.

There are diamonds sparkling everywhere, on the ground, in the vegetation, all colors, red, orange silver, green and blue.  Anything with a diamond sparkle eyeshine you know is a spider and there are hundreds, no thousands of spiders, in whichever direction you look.  Most of them are little more than the size of a pinhead.

Your free hand is resting on the low branch of a tree sticking out horizontally from the trunk at about hip level.  You are glaring into the tangled vegetation in front of you looking for some of the amphibian choristers that you hear calling when you feel something lightly brush against your hand.  You don’t retract you grasp quickly but rather gingerly lift your hand away and turn the flashlight in the direction of where it was resting.  There you see the creature that had inadvertently made contact with you before withdrawing.  Its body is large and hairy, it has eight stout and hirsute legs.  Your pulse races and a bead of sweat rolls down by your eye from your brow.  It could be due to the heat of the night but it is probably because you are looking at a tarantula.

Tarantula. Rainforest Spider. Mygalomorphae. Therasophidae.

Unidentified Tarantula species in the Costa Rican rainforest

Tarantulas And The Dance Of Death

Now mistakenly putting your hand on a tarantula in the dark would increase the heart rate of most people but like so many other maligned creatures, the poor tarantula has a reputation it does not deserve and nor can it live up to.   Despite their size and grotesquely fearsome appearance, tarantulas are shy and mostly harmless creatures.  They are however venomous and a large, hairy, many-legged venomous arthropod is generally going to suffer bad press amongst their misinformed human observers.

Costa Rican Tarantulas. Mygalomorphae. Theraphosidae. Tarantula.

A rather shy Tarantula does not want its picture taken

Venom is a complex cocktail and quite often it can be very different and peculiar to different types of spiders depending upon their preferred dietary prey species.  Once a spider catches its prey, the victim must be rendered immobile very rapidly, especially if it is not caught in a web and then swaddled in restraining silk.  Most venoms therefore contain fast-acting metabolic toxins that kill or paralyze the prey rapidly.  In this respect, tarantula venom is very weak and does not have much effect on humans but it will kill dogs.  Spiders do not have mouthparts capable of mastication so essentially they have to drink soup, that soup being the digested internal organs of their prey.  The venom contains proteolytic enzymes that break down and liquidize the tissues so that the spider can suck up the rich protein meal and finish the process of digestion within its own alimentary canal.

So why does the tarantula have a reputation of being so dangerous.  The story has its origins in a city located in mediaeval southern Italy called Taranto.  Here lives a wolf spider, (Lycosa tarantula), one bite from which would drive the victim into a state of frenzied madness more commonly known as tarantism.  The unfortunate sufferer was prone to dizziness, vomiting and a heightened sensitivity that compelled them to lose all inhibitions and dance in a wild state of abandon trying to release themselves from the effects of the venom.

Due to these effects, it has been suggested that the spider responsible was Latrodectus tresdecimguttatus, closely related to Black Widow of the U.S.A and the Red-back Spider of Australia.  It may well have been that in a mediaeval Italy gripped by religious fervor that most cases of tarantism were little more than the result of a pious mass hysteria and not a spider induced dance of death.  However the story travelled with European settlers to tropical America and from thereon  the poor tarantula was saddled with the name and its resulting reputation from its smaller, deadlier European cousins.

Tarantula. Mygalomorphae. Theraphosidae.

Tarantula sp – look closely and you can see the fang-tipped chelicerae

The tarantula in these photographs was found last week on the grounds here.  It was not very co-operative and shied away from having its picture taken.  When I tried to get a close-up on the fangs, it pulled all of its legs up against the body.  I did manage to get low down and in front to get an image that if you look closely reveals the two fangs, which in the case of tarantulas are parallel to each other and face forwards.

Small But Deadly

Talking of smaller spiders, there is one species I see commonly around the buildings of the area that could be quite easy to miss.  It prefers dark corners where two walls meet at right-angles.  It is dark ruddy-brown and spends the day with its legs tucked up under the body.  The web is little more than a few silken strands strung between the two wall faces.  What draws your attention is not the spider itself but the size of prey it captures and consumes.  I quite regularly see everything from large kaydids, beetles and moths dangling helplessly from the sticky diaphanous cords as a tiny spider cautiously approaches to deliver the coup de grace.

Although I do not profess to being an expert with regards to spiders, (nor with anything in fact), I think these tiny assassins belong to the family: Theridiidae, which includes the notorious Black Widow, (Lacrodectus mactans).  The venom of the spiders in this family is highly neurotoxic which would explain why prey so much larger than the spider rapidly succumb to its bite.  I don’t know anyone who has been bitten by one of these individuals I commonly find lurking in places like bathrooms and have no great desire to try and find out for myself.

Tangle-web Spider. Araneidae. Araneae. Theridiidae.

Tangle-web Spider female guarding egg cocoon

The individual in the photograph sat guarding a grey sac for many days.  This is the egg cocoon.  She will mate with a male then lay her eggs which she will wrap in silk in order to protect them against the environment and parasites.  When these ones hatched I would see them swarming all over a prey item along with the mother.  I never saw her wrap a victim in silk, they just remained suspended in death pose from the strands upon which they had initially and unfortunately become caught.

Choking On A Poisoned Thorn

One more spider that I found last week in the gardens is so distinctive that it can be identified immediately, at least to genus level.  This is one of the Spiny-bodied Spiders, (Micrathena sp).  They are small but tend to be dressed in bright and contrasting colors so you should not have too much trouble finding them if you are diligent in your searching.  They are orb-weavers but the web, just as its maker, is relatively small.  Spiny-bodied Spiders are more commonly found in the open areas rather that within the depths of the forest.  Their webs can be found strung between the twigs and branches of bushes and small trees.

Once you have located one of the Spiny-bodied Spiders you will quickly appreciate why is bears that name.  The rear of the abdomen is drawn out into two long vicious-looking thorns at the base of which are two shorter spines.  The dorsal surface of the abdomen has a pair of upward pointing spines while the ventral surface has one downward pointing spike.  This whole appearance is not an appetizing prospect for a potential predator.  The coloration of bright vivid primary colors against darker background colors actually make the spider stand out in contrast to its surroundings.  If it is visibly obvious then it is patently not trying to hide.  It is using warning, (aposomatic), coloration to advertise its presence to a predator.

Spiny-bodied Spider. Araneidae. Araneae. Micrathena sp. Rainforest Spiders

The spines covering its body are a clue to the naming of the Spiny-bodied Spider, (Micrathena sp)

Should a naïve predator such as a bird or lizard ignore that warning signal and try to feed on the spider, those thorns and spines will lodge it in the unfortunate creature’s mouth from which it is very difficult to displace.  The spider meanwhile produces a noxious secretion that tastes foul and the hapless predator, rather than relishing a tasty meal, is now stuck with spiny vile dietary experience.  One the spider is dislodged, the predator will never, ever go near anything sporting aposomatic colors again.

Shadowy Parasites – Not Green And Not Seen

While walking the trails I found a weird little plant that could easily be mistaken for a fungal fruiting body.  It grows from the ground with a short fleshy stalk holding up the flowering head.  The overall color is the same as the ground, a ruddy-brown, there is no green to be seen.  In appearance it looks like no other flowering plant.  It contains no chlorophyll because it is an obligative parasite.  It taps into the roots of trees from where it extracts all its nutritional requirements.  This is Helosis cayennensis of the family: Balanophoraceae.  They can be found in northern and southern hemisphere tropics.

Parasitic plants. Balanophoraceae. Rainforest plants. Helosis cayennensis

Strange acorn-shaped inflorescence of Helosis cayennensis

The main body of the plant is an amorphous underground tuber attached to the root it is parasitizing.  The flower head produces both male and female flowers both of which are small in size.  Quite often they can be found in large clusters, especially this time of year, the wet season, growing out from the base of the tree they are sucking the life from.

Balanophoraceae. Helosis cayennensis. Parasitic rainforest plants

No green to be seen – the parasitic Helosis cayennensis

Philip Davison Is a Biologist, Writer and Photographer Based in Costa Rica

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2 responses to “TARANTULAS AND THE DANCE OF DEATH

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  1. Those last two shots are pretty cool, Phil. You keep learning,
    and thus, so will my wife and I. Looking forward to seeing you once again in December

    Like

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