The Savage Death of a Velvet Cat   2 comments


Philip Davison Nature Diaries. Bosque del Cabo Rain Forest Lodge.

Sunny Days are Back Again

The weather has most certainly turned a corner.  After the record-breaking deluge that occurred continually over the course of the last five weeks we now have the opposite situation, no rain.  Not a single drop of rain has fallen over the past week.  The skies have been clear and bright blue.  The sun has been shining brightly.  The temperatures are on the rise.  The night skies have been clear and filled with stars.  Just within the space of seven days, the formerly soft muddy trails have started to harden up.  There are, of course areas where the ground is stiff soft and in places water continues to run off but these are now few and far between.  One trail had a new lake form as the water was unable to run off.  Walking along a familiar path I was finding myself waist deep in water.  I imagined that this new water feature may persist for months before the ground was exposed once more.  I was wrong.  Walking the trail a few days ago, all the water had gone.  The path was very muddy but no longer submerged.

Bosque del Cabo Rain Forest Lodge. Osa Peninsula. Costa Rica.

Zapatero Trail at Bosque del Cabo Rain Forest Lodge.

It was fortunate that the heavy rain stopped as the flowering season for many of the trees commences in December.  Should the trees bloom and then become bombarded with persistent downpours, the flowers can be knocked from the trees before they have been pollinated.  The result of this is a lack of fruit later in the dry season as the plants have not set seed.  There are many animals whose lives depend on the bounteous supply of mixed fruits that comprise their diet that should the flowering and fruiting seasons fail then they simply starve to death.  This happened in 2005 when substantial numbers of Spider Monkeys and Toucans were, quite literally, just dropping out of the trees.  Necropsies carried out by veterinarians showed that they were suffering from very low body fat.  They were starving to death.  Everything looks good at the moment for a bumper harvest as I have seen many trees starting to produce blooms.

Golfo Dulce. Cabo Matapalo. Osa Peninsula. Costa Rica.

The Sun is Shining Over the Golfo Dulce Once More.

Caught in the Eye of a Cat

The frogs are still out in numbers but those numbers will start to dwindle as we head into the dry season.  There are creatures that feed on frogs and they too have been out and about at night, the snakes.  One of the commoner snakes around the pond after sunset is the Cat-eyed Snake, (Leptodeira septentrionalis).  It feeds on frogs at all stages of their life history.  More particularly it searches out clumps of Red-eyed Green Tree Frog eggs which it finds suspended beneath the leaves overhanging the water.  The gelatinous masses are stuck in position and when the tadpoles reach about 7 or 8 days in age, the jelly liquidizes allowing the tadpoles to drop into the water where they complete the initial stage of their life history before emerging as froglets.  Frogs eggs make a perfect meal for the snake, they don’t run away or fight back and are packed with protein.  At the height of the amphibian breeding season, May, June and July, there are so many egg masses that the snakes start to look well fed and bloated.  Now, because there is little amphibian reproduction taking place, the snakes also fish for the tadpoles from beneath the water surface, take froglets as the emerge from the water and if they get the opportunity they will eat the adults too.

Red-eyed Green Tree Frog.

Red-eyed Green Tree Frog, (Agalychnis callidryas)

Agalychnis callidryas eggs

Red-eyed Green Tree Frog Eggs

Cat-eyed Snake

Cat-eyed Snake, (Leptodeira septentrionalis)

Leptodeira septentrionalis

Cat-eyed Snake. Close up.

The Fatal Velvet Kiss

Whereas the Cat-eyed Snakes feed on the smaller frogs, there is a much larger snake which feeds on the larger frogs.  One of the largest frogs in Costa Rica is the Savage’s Thin-fingered Frog, (Leptodactylus savagei).  A huge amphibian might make a satisfying for meal for any number of creatures.  To lower the risk of being predated upon Savage’s Thin-fingered Frog has several defenses.  It has a toxic skin secretion that can cause intense irritation of mucus membranes.  Should this prove ineffective it has a secondary defensive measure.  When it is caught, it issues a loud cry not dissimilar to a crying baby.  More importantly the call resembles the distress call of young caiman.  If there any adult female caiman in the area they charge in to defend their young, which means hopefully as far as the frog is concerned, it can then make its escape as its attacker is attacked.

Savage's Thin-fingered Frog

Savage’s Thin-fingered Frog, (Leptodactylus savagei)

But there are predators from which there is generally no escape.  It is not uncommon to see by the pond at night some substantially large sized Terciopelos, (Bothrops asper).  They are large pit-vipers in the same subfamily as rattlesnakes.  Like rattlesnakes they have a venomous bite that spells certain death for any prey victim it strikes.  An adult female can reach up to 6 feet, (2 meters), in length.  A snake that size demands a big meal and the Savage’s Thin-fingered Frog fits the bill.

Once the sun sets out come the Terciopelos.  They place themselves around the pond where an encounter with a frog is likely.  They are ambush predators; the cryptic coloration of muted browns and greys camouflage them perfectly against the background.  They remain motionless, camouflage works best if it is still.  Frogs, being mostly nocturnal, have large light gathering eyes.  They rely on movement to find food which is usually anything smaller than themselves, particularly arthropods, but sometimes smaller frogs too.  But the only movement they will detect from a hungry coiled Terciopelo will be one that is over in a flash.

Terciopelo. Crotalinae.

Terciopelo, (Bothrops asper)

The pit-viper is not so visually acute especially at night although its eyes will detect close movement.  Once the feeding response has been stimulated then the tongue comes into play, slowly flicking out then in again, each time tasting the air.  The tongue can detect parts per million of scent particles in the air and because it is forked it can pick up the gradient of a scent plume.  You and I may not know what a frog smells like but the snake does.  Then there are the pits that give it the sinister name pit viper.  These lie one on either side of the head between the eye and the nostril.  They are lined with cells that detect minute differences in background infra-red radiation.  They work best at responding to the presence of warm blooded prey such as rodents but their efficiency could also differentiate the small difference in body heat of even a cold-blooded creature such as a frog against the background temperature.

The unsuspecting frog passes by.  The snake has already drawn its head and neck into tightly sprung S-shaped.  The strike happened so fast that it would probably have been unaware, there would have been no time to react, no chance of escape.  As the snake’s head shoots forward and the jaws open, two long hinged fangs that lie flat against the upper part of the mouth now swing down.  They are simply two hypodermic syringes attached to glands that contain virulent life-ending cytotoxic venom.  The fangs puncture the skin like two needles, the force of the bite pushes them deep into internal tissues and organs.  The snake quickly recoils to avoid any retaliatory action by the victim in its final moments, not that a frog could inflict any damage but the bite of a rodent might.  The quantity of venom injected will spell doom and instant death for the unfortunate amphibian.  It probably would not feel anything from this lethal injection, the effects of which would most certainly be instantaneous.

The frog takes one or two steps forward then collapses dead in its tracks.  The snake is in no hurry.  The meal is ready whenever it would care to dine.  Lying patiently in the shadows the Terciopelo begins to smell the air with its tongue once more.  Once it is feels secure in the demise of its victim it slips forward, the tongue constantly flicking in and out over the cadaver.  It is searching for the head.  Snakes have no way of rendering a meal into small pieces and must swallow the prey whole.  Savage’s Thin-fingered Frog is a giant among amphibians, its body larger than the snakes head.  To deal with this inconvenience the snakes lower jaw disengages at the midpoint as do the upper and lower jaws where they hinge together at the side of the head.  Now the snakes gape can accommodate the huge frog body.  The snakes skin is highly elastic allowing it to stretch as it moves forward over the meal and with continuous backward moving S-shaped waves the feast is delivered finally to the stomach.  The snake moves away back into the shadow of the undergrowth where it will lie motionless for some time until it has digested the hearty dinner.

Terciopelo. Leptodactylus savagei

Terciopelo eating a Savage’s Thin-fingered Frog

Payback Time

There are times when even the top predators can become prey.  Where there are snakes then there might be snakes that eat snakes.  Sure enough on occasion by the pond where the Terciopelos lie in wait there is a hunter that actively seeks them out.  A hunter that is immune to the deadly venom.  A hunter that can overpower with impunity its adversary.  That hunter is the Mussurana, (Clelia Clelia)..

The Mussurana is a snake with a solidly muscled body.  It has a beautiful deep gloss grey color which radiates a fabulous deep blue iridescence.  The underside is a soft eggshell cream.  It is a powerful constrictor.  The teeth at the back of the jaws are strong and allow it to hold onto its writhing victim while it throws around it those ever-tightening coils.  This is a non-contest, the Terciopelo has little or no chance.  Finally, it succumbs and expires.  The hunter has become the hunted and the frogs have one less problem in their territory.

Mussurana.

Mussurana, (Clelia clelia)

Philip Davison is a Biologist, Writer and Photographer Based In Costa Rica

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2 responses to “The Savage Death of a Velvet Cat

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  1. Wow Philip, great action shot of the Terciopelo eating the frog. Did you see the whole encounter or just the aftermath? Either way, a great read.

    Like

  2. I was impressed that a frog,(Savage’s Thin-fingered Frog) that if captured will call out mimicking a young caiman in distress. What an amazing evolutionary defense.
    Such beautiful and sharp photos Philip, thanks.

    Like

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