Archive for the ‘Dendropsophus ebreccatus’ Tag

Sun and Moon, Bananas and Lichen.   2 comments


Philip Davison. Costa Rica. Blog. Nature Diaries

Sunny September

The clement weather conditions are continuing to prevail.  The rain we are receiving is most certainly intense but by no means prolonged.  If there is one day of rain it is being followed by two days of sun.  This time of year there are very few visitors.  September and October are not big holiday periods.  For anyone who does want to visit Costa Rica at this time of year you can certainly avoid the crowds but you also run the risk of being confined to your cabin unless you want to suffer a constant soaking.  For those of us who do live here then the quiet time and unseasonably dry and sunny conditions give us time to go and explore a little more or in my case catch up with the writing.

I’m Lichen That

One night when I was out doing my nightly frog counts I came across one of the Anolis lizards that I see more often up in the canopy, a Lichen Anole, (Anolis pentaprion).  This individual was sleeping but when I turned the lights on to video the creature in its state of slumber the instant change from night to apparent day woke it.  Not only did the lizard stir but the increase in light levels drew in some of the insects including one of the few species of night-flying wasps, Apoica pallida.  It landed near the lizard’s head so presenting itself as an easy meal the advantage of which it was not going to refuse despite having only just being disturbed from its sleep.  With a quick snap of the jaws the wasp was caught, chewed up and down the body and then swallowed.  The Anolis then soporifically walked up the small branch on which it was clinging, climbed atop a leaf into a darker location than it was now finding itself, closed its eyes and went back to sleep.

Anolis lizards are a very diverse genus with many closely related genera belonging to the family: Polychrotidae.  There are well over 200 species of Anolis and each species quite often is divided into a number of subspecies.  Anolis lizards are similar to geckos in that they have an anatomically specialized structure to the toes, (lamellae), that allow then to climb with ease including smooth vertical walls and even panes of glass.  Anolis lizards are generally small and unless you notice some movement as they jump through the vegetation then they can easily be overlooked.  In terms of ecology smaller species inhabit the lower levels of the forest and conversely larger species the higher levels.

Anolis pentaprion

Lichen Anole

Although the family is species rich, it is not always easy to identify the individuals to species level.  One factor that does help is the males have a loose flap of skin under the chin called a dewlap.  Thankfully each species has a different color dewlap, particularly pronounced in this area.  The loose skin is attached to a rod of cartilage fixed at the jaw over which the lizard has muscular control.  The lowering of the cartilage extends the skin revealing the brightly colored flag which is in stark contrast to the more usual body color and it is used to intimidate and scare rival males from the territory or used to court females.  Certainly if you see that bright flash of color appear as if from nowhere then there will be a second individual you may not be so aware of but it will be somewhere close by in the vicinity.  The dewlap of the Lichen Anole is a deep purple edged with magenta and is not as large as in some other species.  Most females do not possess a dewlap and because there is a strong sexual dimorphism can prove a little more difficult to identify.  Here on the Osa Peninsula there are only seven species of Anole and they are all fairly distinct in appearance both male and females.

Many Moons

There are two particular species that seem to have reacted to this year’s slightly abnormal weather conditions.  One is a butterfly and the other is a frog.  They have both been recorded in numbers in excess of those normally found.

The Luna Satyr, (Pierella luna), is a largish brown butterfly that is normally found throughout the year but for the most part as solitary individuals or in small groups.  It is found flying very close to the forest floor in the dark, dank, shady conditions beneath the forest canopy.  You will quite often only notice it when it momentarily passes by your feet, wings beating slowly, as it moves from one side of the path to the other.  It will disappear under the vegetation and when it settles the muted grays and browns of its now still wings blend it immediately into the background.  It prefers the denser aspect of secondary forest as opposed to the more open situation beneath primary forest.  This may have something to do with the distribution of its larval host plant, species in the family: Heliconiaceae, many of which can be found in secondary forest habitat.

This year when walking along trails through secondary forest Luna Satyr could be found in huge numbers much larger than experienced before.  I am not sure what triggered the population explosion but the adults have not been hard to find, sometimes in groups numbering ten or more.  The slightest disturbance caused by your footfall will have them momentarily take to the air before quickly alighting once more on the ground.

Pierella luna

Luna Satyr

A Big Bunch

The Banana Frog, (Dendropsophus ebreccatus), is one of those small tree frogs that you can more or less guarantee you will see if you go to the pond at night.  They are ever present throughout the year.  At the height of the amphibian breeding season which starts when the rains arrive in April, gets into full swing in May and draws to a close by the end of August, the Banana Frog males can be both seen and heard in reasonably large numbers every night.  Those numbers reduce outside of the breeding season to the point where during the dry season it might only be one forlorn male out calling but there will always be one.

The males emerge as the sun slowly sinks beneath the western horizon.  They set up their territories on the Water Lettuce or Water Hyacinth and call vigorously with a protracted “Eeeack”.  The larger egg bearing females emerge a little later, select a male on the quality of his call, makes her way over to the male of choice, they pair up and later she lays a sheet of small jelly coated eggs on the surface of a leaf which the male fertilizes.  The eggs develop here for 7 or 8 days, the tadpoles wriggle free and slip below the surface of the water from where they will emerge about 8 weeks later as small froglets.

Whereas this time of year when all the other frog species have either disappeared from the breeding pond or are present in only small numbers, the Banana Frog has seen a surge in numbers.  There are presently in the region of 20 calling males every evening.  It could well be that they are taking advantage of the lack of competition from other species, although there are not too many other species that do use the Water lettuce, (Pistia stratiote), and Water Hyacinth, (Eichhornia crassipes).  The tadpoles of other frogs do have to compete for space and food once they have entered the water, some of which may be larger and/or more voracious than D. ebreccatus tadpoles.  It may simply be the fact that there is still a lot of rain which is perfect for the eggs but that is the norm every year.  Whatever the reason if you could down to the pond at the minute after sunset you will be greeted by a vociferous chorus of amorous Banana Frogs.

Dendropsophus ebreccatus

Banana Frog

Seeing You Walk for the First Time

Last week I happened across an insect that has proved to be somewhat difficult to identify.  What initially caught my eye were the colors, most strikingly the bright yellow.  The head was small but the body was long and soft.  The wings too were brightly colored but in green.  My first thoughts were that it was some kind of Phasmid or Walking Stick, more precisely a winged walking stick.  It did not seem to be disturbed when I moved it from the bare white stucco wall where its colors were making it rather conspicuous to some nearby vegetation where it was less obvious.  Not moving is part of a Phasmids game plan though.  I took some photos and headed off to my reference library.

Phasmid

Winged Walking Stick

As with most insects that I see for the first time after 16 years of living here I just know the identification is going to be difficult.  Insects are so prohibitively numerous in number of species, especially tropical insects.  The reference material available is limited and by no means exhaustive.  So after some searching I was not really any further forward than still being confident it was a winged phasmid.  Time to scour that great resource the internet.  Scrutinizing photo after photo all I could conclude that it was a winged phasmid but there was nothing I could see that looked remotely like this individual.  So if there are any phasmid experts that may be reading this and could enlighten me as to a genus or species I would love to hear from you.

Phasmid

Winged Walking Stick

Philip Davison is a biologist, writer and photographer based in Costa Rica.

 

Eyelash Viper and Tropical Frogs   2 comments


Local weather conditions may differ drastically from year to year and during 2009 the Osa Peninsula experienced a particularly rainless dry season.  Normally, from December through to April, there is at least some rain, not much; it is after all the dry season, but last year, barely a drop.  This was then followed by a very dry wet season.  When the rains should have arrived in May, they did not, and this condition carried on unabated throughout June and July.  For visitors to the Osa Peninsula, the conditions could not have been more perfect, lots of hot, sunny days, perfect vacation weather.  But that interruption in the natural rain cycle was having a profound effect on the fauna and flora of the area.

Rain forest trees are very dependent on their water source and if this becomes limited in supply, they begin to suffer environmental stress.  The first obvious sign is that they will shed leaves.  Should the stress continue, they begin to shed branches.  Finally, if we end up, as we did in 2009, with a drought in a rain forest, the trees divert a lot of energy into reproduction to ensure the passing on of their genetic material lest they themselves die.

That is exactly what we saw in 2009.  Visitors were treated to a canopy high display of flowering, rarely equaled, with a veritable kaleidoscope of color; yellows, reds, purples and pinks painted like a pastel infusion among the normal mix of greens at the treetops.  Some of the trees did not just flower once; they produced blooms two or three times throughout last season.  The exuberant flowering display led in turn to a profusion of fruiting, the trees were quite literally hanging with fruit.

This series of events led in turn to a very good reproductive year for those animals whose diet depends to a greater or lesser extent on nectar or fruit, such as Spider and Howler Monkeys, Toucans, Hummingbirds and Manakins.  This year visitors have been treated to the sight of huge flocks of toucans and a great many of the female Spider and Howler Monkeys carrying young ones.

But what a difference a year makes.  In a complete reversal of last year, 2010, so far, has been a wetter than normal year.  Rather than the tired looking yellows and browns evident in last year’s vegetation, this year has remained luxuriously verdant and that bodes well for another group of animals; the amphibians.  Despite a myriad of problems causing global declines in amphibian populations, here on the Osa Peninsula, the frogs are still holding their own.

Veridion-Adventures Red-eyed-Green-Tree-Frog Agalychnis-callidryas Nature Photography Travel Adventure Holidays

Mating pair of Red-eyed Green Tree Frogs, (Agalychnis callidryas)

There are certain species that one can almost rely upon to be present right throughout the year; Marine Toads and the picture postcard child of Costa Rica, the Red-eyed Green Treefrog.  With the onset of the rains though, all those species that have been noticeable by their absence for the previous five months emerge once again, sometimes in numbers so large that it begs the question, “Where has such a biomass of amphibian life been hiding for almost half the year?”

When they do emerge, it is with only one thing in mind; reproduction.  Around the breeding pools, the cacophony of the calling males renders it all but impossible to make yourself audible.  The initial heavy rains of the season immediately encourage a response from Costa Rica’s largest treefrog, the Milky Frog.  Within hours on the evening of the first downpour a full breeding choral congregation of males, in numbers upwards of fifty will have accumulated in the pond.  The deafening din of their ardor can be heard from great distances.  After several nights of this repeat performance, they once again decline in numbers until it is only a very occasional chance sighting that you will experience during the remaining rainy months.

Now is the time of the frog though and during the next seven months we are treated to a nightly chorus of serenading males of different species, some of them more melodious than others; the jackhammer mating call of the Marine Toad, the chuck of the Red-eyed Green Treefrogs, the sound of little metal bells tinkling from the Tink Frogs, clipped chirps of Banana Frogs and what you would swear sounded like two blocks of wood being knocked together that announce a Gladiator Frog male is looking for a mate.

Veridion-Adventures Banana-Frog Dendropsophus-ebreccatus Nature Photography Travel Adventures Holidays

Banana Frog, (Dendropsophus ebreccatus)

Yet there is one more amphibian phenomenon that only a lucky few experience; the explosive breeding display of Parachuting Red-eyed Green Tree frogs.  This is the second species of Red-eyed Green Tree frog to be found on the Osa Peninsula.  They are rarely, if ever seen, living as they do at the tops of the trees, but several times during the rainy season following several days of concerted torrential rain out they come, and they come in their hundreds.  They receive the parachuting part of their name from having large hands and feet that are extensively webbed.

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Parachuting Red-eyed Green Tree Frogs, (Agalychnis spurelli). Mating pair

Taking the monsoon-like conditions as their cue, they launch themselves from above, opening the hands and feet, spreading the webbed fingers and toes, allowing them to effectively ‘glide’ to the lower levels.  The males and females pair up and then not long before dawn they start to lay eggs, everywhere, covering the surfaces of the leaves overhanging the ponds.  The eggs develop for seven to ten days, liquidize, slip off the leaves and plop into the water which is where the normal tadpole stage will then take place.  The explosive breeding frenzy has to end before sunrise; the frogs need to take shelter from the drying effect of the sun’s harmful rays on their delicate skin.

If you are out early enough you will be awestruck by the sight of hundreds of pale green frogs trying to climb up into shadowy parts on the underside of leaves.  Sometimes the weight of such huge numbers will snap the vegetation in which they are attempting to seek refuge.  It really does have to be seen to be believed.

Eyelash Viper Feature

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Eyelash Viper, (Bothriechis schlegelii). Gold phase – Oropel

In all my years living on the Osa Peninsula I have seen the elusive Eyelash Viper, (Bothriechis schlegelii), on only four occasions.  It is not necessarily because they are rare but more to do with the fact they are very cryptically colored, the point of which being, to avoid being seen by both predator and prey.  Although they come in several color forms, the ones I have seen at Cabo Matapalo have all been the green mottled morph. The camouflage coloration blends the contours of the body perfectly against the moss covered branches of the plants where they sit as ambush predators awaiting the approach of a small lizard, frog, bird or rodent on which they feed.

The most distinguishing feature of this small pit viper are the two spine-like scales protruding over the eye giving it the name Eyelash Viper.  There is no definitive answer as to why it has these scales, possibly to push vegetation out of the way which may scratch the snake’s unlidded eyes.  One other eponymous feature  to the pit vipers is the small hole on the front of the face between the nostril and the eye.  These house acute sensory apparatus that detect very small changes in background infrared radiation allowing the snake to detect the presence and location of it prey.

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Eyelash Viper, (Bothriechis schlegelii). Motteld phase- Bocaraca

The Eyelash Viper is a small snake, especially given the size some other vipers can grow to.  It is a nocturnal predator and will take a variety of prey ranging from frogs, lizards, birds and mammals. Unlike terrestrial vipers which envenomate their prey, release it, then seek it out after it has died, the arboreal vipers have a strongly prehensile tail and tend to hold on to their prey after biting.

Eyelash Vipers are distributed from Mexico down through Central America into Venezuela.  They prefer shrubby vegetation found in secondary growth.  In Costa Rica the yellow morph is know as the oropel, (golden skin), while the mottled morph is known as the bocaraca.

Due to its size, cryptic coloration and preference for resting during the day in the lower areas of vegetation it is responsible for biting those people who work in those areas.  Although deaths from the bite of an Eyelash Viper are rarely fatal, there can be some long term issues with impairment of movement particularly if bitten on the hands.  Viper venom varies between species and can be quite complex in chemical make-up.  Generally they contain a cocktail of fast acting proteolytic enzymes that cause a multitude of effects including tissue necrosis and death.

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