Monday 25th January 2016
A Sinister New World Emerges
Once the sun sinks low on the horizon and the light levels fall to dusk then the daytime animals return to the safety of their nightly abodes. There is not much twilight this close to the equator, the sun seems to fall from the sky and before you know it darkness has descended and the world around you takes on a very different atmosphere. The calls of birds ceased some hours ago. Those cicadas whose constant high pitched hiss has permeated throughout the hot sunlit day have now gone quiet. Even the sundown cicadas, the white noise of which replaces their daytime cousins, have called to a crescendo the fortississimo now having fallen silent too. The blackness that was the green lawn starts to flicker here and there with small green flashes of light as the male fireflies emerge, the twinkling stimulating a response from the females which live higher in the vegetation. In the background a Spectacled Owl, (Pulsatrix perspicillatus), calls sounding for all the world like a distant muffled laugh. Not too far away a ground roosting night hawk, the Common Paureque, (Nyctidromus albicollis), calls with a series of plaintive whistles. The night shift has begun.
All the Better to See You
From somewhere hidden for the day deep in the depths of the undergrowth nocturnal snakes emerge. There is one with a body long and pencil thin that supports a head seemingly too large and out of scale with the other dimensions. It has large eyes, very large eyes, all the better for seeing its prey. The snout is short and the eyes are directed forwards giving it some perspective. The long slender body is triangular in section which reinforces the skeletal strength of what is little more than a muscular tube. This is the Brown Blunt-headed Snake, (Imantodes cenchoa).
The slightness of the serpent allows it to move unnoticed through the branches and leaves which make no movement in its passing. Like an angel of death it seeks a victim. The tongue flicks in and out constantly sampling the air until it picks up on an odor measured in quantities at the molecular level. The scent plume leads the snake to its source and consequently its prey, a sleeping lizard.
Lying in Peril
This lizard is a Golfo Dulce Anolis, (Anolis polylepis). It has been active during the day waiting head down on a leaf in low lying vegetation for hapless insects to wander by. It jumps from its ambush position, grabs the meal and consumes it in quick time. Bouts of feeding maybe punctuated with territorial disputes of chasing interloping males from its territory or perhaps courting a passing female. With the day’s activities at an end it retires to what would normally be the relative safety of a leaf tip to sleep for the night. Any predator approaching on the leaf would cause vibration which becomes amplified along the length of the leaf thereby warning the sleeping lizard which awakens to the imminent danger. It jumps off and disappears into the leaf litter below.
Tonight however the lizards sleeping position is not so safe as doom is approaching from a different direction. The Brown Blunt-headed Snake is not on the same leaf. Its search has led it to a position on a plant in close proximity. That long strong sinuous body reaches out across the gap. It has already identified where its meal lies. The lizard is oblivious to its presence. The snake’s body draws into a series of s-shaped loops and then with lightning speed and precision the strike is made. The lizard knew nothing of its final moment on earth, dispatched and eaten like the insects that met their fate in a similar way earlier in the day.
Upping the Ante
Not all lizards sleep at night though. There are nocturnal lizards, the most common and noteworthy of which are geckoes. Around the Osa Peninsula there is a very common gecko that can be found in all buildings and on the trunks of garden trees. It is a visitor that became naturalized, the Mediterranean House Gecko, (Hemidactylus frenatus), hitching a ride from Southern Europe courtesy of human transport and wherever conditions were suitable then there it settled, not just here but in tropical conditions everywhere. They are familiar to most people as those small creatures hanging around by house lights to catch the insects attracted in by the incandescent glow.
Asleep or not the gecko is still a meal that does not escape the attention of the Brown Blunt-headed Snake. With a similar stealthy approach it closes in on a gecko which remains perched head down on a tree trunk waiting for insects to land. But this hunter is about to become the hunted, the difference being this one is wide awake and alert to the danger
The snake slithers into position, the tongue confirms the gecko’s presence, the eyes focus forward and the scene is set. The snake strikes out, the jaws agape but the gecko’s reaction is rapid and it moves just in time. The snake does not miss its target but rather than hitting the body the jaws close and the teeth sink into the tail. Here the gecko has another defense, the tail breaks and the snake is left with little more than a wriggling piece of tail section, not much of a meal but better than nothing.
Meanwhile the gecko has scuttled off post haste up the tree trunk, the missing tail section being little more than a minor inconvenience. The most important thing is that it is still alive. That missing part of the tail will regenerate over the coming months and apart from the fact that it will be of a slightly duller color than the original there will be nothing else to show for the encounter.
Philip Davison is a biologist, writer and photographer based in Costa Rica.