Resisting Venomous Skeletons   4 comments

Felipe del Bosque Blog August 6th 2012

Sun Shade

This week started cloudy and overcast but soon gave way to glorious sunshine which in turn gave rise to more rain.  The rain has been quite light though, we have not experienced the storms that occurred last week.  Having said that, there has been thunder rumbling around for a while, but as is so often the case it doesn’t amount to anything.

Stripped to the Bone

On one of the primary forest tours last week as the group I had out with me came towards the end of the trail I could hear the soft trilling call of a male Golfo Dulce Poison Arrow Frog, (Phyllobates vittatus).  We were approaching the creek which at this point is crossed by a small wooden foot bridge.  I stopped to listen and ascertained that the frog was calling from just the other side of the bridge in the creek bed.  Sometimes the frogs call from under the leaf litter and other times they appear to be master ventriloquists, their calls seemingly coming from a location while the frog appears to be in another.  On this occasion this one was not too hard to find and photograph.

After securing the images, we scrambled back on to the bridge and one of the group, Ian Linnett, who was visiting Bosque with his wife, and their 2 sons, asked me the identity of a skeleton that was lying in the stream bed but back around the bend behind us that I had missed.  I jumped down into the creek again and found a perfectly clean, polished white skull somewhat removed from the rest of the intact skeleton.  The shape of the cranium and the dentition were diagnostic of a cat.  It was not a big cat and looking at all the bones together I concluded it was a Jaguarundi, (Hepailurus yagouarundi), skeleton.  That same evening there was a tremendous downpour and so the next day when I walked the trail the skeleton that 24 hours earlier had been complete was now broken up and the bones littered the banks.  When something the size of a medium sized mammal dies in the forest it can be reduced to cleanly picked bone in as shorter time as 36 hours.

I brought the skull back to add to the Bosque bone collection in the lodge’s museum.  There is a small collection of bones that visitors have found on walks over the years.  When I placed the new skull amongst them it occurred to me that it might be an entertaining idea by way of a change to photograph some of the specimens we have as most of the time I take pictures of living not dead things.

Mug Shots for the Boneyard

I started with a skull most people would instantly recognize as they are so similar the human skulls, that of a primate; the Spider Monkey, (Ateles geoffroyi).  The first and most notable feature is the large forward facing eye sockets.  For arboreal monkeys, (all of Costa Rica’s monkey species are arboreal), it would be of great benefit while moving through the trees tops to be able to gauge depth and distance.  Forward facing eyes with overlapping binocular vision, such as we as primates have, allow for that perspective.   This is especially true of the Spider Monkeys which are natural born acrobats spending their lives swinging from branch to branch and free falling from upper to lower levels of the canopy.

Spider Monkey         Spider Monkey         Ateles geoffroyi

All of the 4 monkey species found in Costa Rica also live in the grounds of Bosque del Cabo.  They all live in different parts of the forest and they all feed on different types of food.  Howler Monkeys, (Alouatta palliata), and Spider Monkeys both inhabit the higher regions of the canopy but Howler Monkeys are essentially leaf-eaters while the diet of Spider Monkeys consists largely of fruit.  White-faced Capuchin Monkeys tend to stay in the mid levels of the forest.  They have a very mixed diet; flowers, fruit and young leaves.  But 65% of the Capuchin diet is insects, frogs and lizards.  However, the Capuchins will take bigger prey and have regularly been seen on the grounds of Bosque catching and eating the Chestnut-mandibled Toucans, (Ramphastos swainsoni).  The smallest of the monkey species at Bosque is also the most carnivorous; the Squirrel Monkey, (Saimiri oerstedii).  Squirrel Monkeys prefer the denser cover of secondary forest rather than primary forest, they tend to stay low down near forest edges and 90% of their diet is insects, frogs and lizards, all that small stuff they find by gleaning as they move through the forest.

Ateles geoffroyi

Although the dentition of most primates is rather unspecialized when compared to other mammals, there is still a variation dependent on dietary requirements.  Howler Monkeys have small incisors but high crested molars designed for shearing leaf material and males have larger canines than females.  Spider Monkeys on the other hand have large incisors with small molars to deal with a fruit diet.  Capuchins have large incisors as well as large, thickly enameled premolars and premolars to enable the cracking of nut shells.  Squirrel Monkeys sharply crested premolars and molars to slice open insect exoskeletons.

Next is the Jaguarundi skull.  It has a short snout typical of cats which rely more on sound and vision to locate prey rather than scent.  They have reasonably large eye sockets placed more on the side of the head.  But look at those teeth; they leave no doubt as to their carnivorous nature.  The upper and lower canines are lethal stabbing weapons designed to hold the prey.  Typical of carnivores are the carnassials, the rearmost premolar of the upper jaw and forward most molar of the lower jaw which fit together like the blades of a pair of pinking scissors, designed to shear through flesh.

Jaguarundi         Jaguarundi         Hepailurus yagouarundi

You can also see the large zygomatic arch through which the large temporal muscle passes.  Running along the top of the skull is the sagittal crest, a bony ridge to which the temporal muscle is attached in carnivores, (and some other mammals), allowing greater muscular strength in delivering a very strong bite.

Hepailurus yagouarundi

Whereas cats have short snouts, the dogs have long snouts which house an amazing olfactory sensory apparatus that give them abilities way beyond our comprehension.  Although not dogs, the Procyonids or Raccoon family have that same ability.  The White-nosed Coati, (Nasua narica), familiar to most visitors to Bosque as they can be quite easily observed walking nonchalantly around the grounds, has an acute sense of smell that more than compensates the creature for its apparently hopeless sense of sight and hearing.  Anyone who has ignored the lodge advice or inadvertently left food in the cabin will have probably been paid a visit by a coati.  As with the Jaguarundi skull, the dentition points to a more carnivorous diet but coatis are not fussy eaters; they will take anything from fruit, grubs, crabs, reptiles, amphibians, rodents and chocolate bars.

White-nosed Coati         White-nosed Coati         Nasua narica

Nasua narica

Finally the largest skull in the collection belongs to a distantly related member of the pig family, the Collared Peccary, (Tayassu tajacu).  The peccary has that long skull which like the coati houses wonderful olfactory sense organs.  The lower jaw is long and narrow, typical of animals that crush or grind food in their molars rather than the short curved lower jaw of carnivores which exerts more pressure at the front of the mouth where the incisors and canines are housed.  Peccaries eat a lot of vegetative material including large nuts which are crushed directly in the molars.  But the most noticeable feature are the large and fearsome looking canines.  Peccaries eat very little by way of meat so they are not used in the same fashion as a dog or cat.  These ferocious tusks grow continuously until the animal is about 5 years old.  The upper and lower canines rub against one another thus sharpening the edges but also they interlock resulting in reduced sideways motion of the jaw and action required more by grinding animals than crushers.

Collared Peccary         Collared Peccary         Tayassu tajuca

Tayassu tajuca

Philip is a biologist, writer and photographer as well as the onsite naturalist guide at Bosque del Cabo Rainforest lodge on the Osa Peninsula, Costa Rica.

 Photo Feature

 Bite Me, Eat You

One night last week I went out early in the evening to get photographs of the male frogs as they emerge from their daytime cover, set up their territories and start to call for females, at least that was the initial plan.  On my way over to the pond, a large dark shape moving in front and away from me on the lawn caught my attention.  It was a large snake of about 6 feet in length and of substantial girth.  Although there are many snakes that live here it is not always easy to find them but there are some creatures that are experts at doing just that.  They have to be as snakes form the main basis of their diet.  This was one of those creatures, a snake eating snake, the Mussurana, (Clelia clelia).

Mussurana         Mussurana         Clelia clelia

I had found them around the pond in the past.  There are a lot of frogs that breed around the pond and consequently there are a lot of snakes which specialize in eating frogs and frog’s eggs.  At night it is common to see large numbers of Cat-eyed Snakes, (Leptodeira septentrionalis), and during the day their diurnal counterpart, the Parrot Snakes, (Leptophis ahaetulla).  On the odd occasion I will find a Terciopelo, (Bothrops asper), by the pond as they too are not averse to eating some of the large frogs such as the Smoky Jungle Frog, (Leptodactylus savegei).  It is hardly surprising then that all this serpentine activity might attract a Mussurana on the hunt.

Clelia clelia

The Mussurana is a robust and fearsome predator.  The body is solid, muscular and strong.  It can attain a length just somewhat short of 9 feet.  The coloration is a beautiful blue grey with a uniformly cream belly.  They tend to be nocturnal but if observed during the day the highly polished scales resembles cabochons of opalescent moonstones set by a master jeweller into its long sinuous body.  With each twist and turn of the coils the fabulous blue iridescence gives the impression of a scintillating yet cold azure flame enveloping the entire length of its body.

But what is beauty to us spells death for its legless cousins.  The Mussurana actively seeks out other snakes and when it finds what it is looking for; it strikes and holds the prey in its powerful jaws.  Those muscular coils are wrapped around the unfortunate victim is less than a blink of the eye.  The constricting force they apply begins to asphyxiate the immobilized prey.  All the while, the Mussarana is chewing into body of its captive, the jaws house rear fangs that inject venom that will quickly dispatch the quarry.The Mussurana is a robust and fearsome predator.  The body is a solid, muscular and strong.  It can attain a length just somewhat short of 9 feet.  The coloration is a beautiful blue grey with a uniformly cream belly.  They tend to be nocturnal but if observed during the day the highly polished scales give a fabulous blue iridescence that flickers like a cold azure flame enveloping its body scintillating with each twist and turn of the coils.  But what is beauty to us spells death for its legless cousins.  The Mussurana actively seeks out other snakes and when it finds what it is looking for; it strikes and holds the prey in its powerful jaws.  Those muscular coils are wrapped around the unfortunate victim is less than a blink of the eye.  The constricting force they apply begins to asphyxiate the immobilized prey.  All the while, the Mussarana is chewing into body of its captive, the jaws house rear fangs that inject venom that will quickly dispatch the quarry.

The Mussurana is held in high regard in Latin America due to its predilection for feeding on highly venomous pit vipers such as the Terciopelo.  For most predators trying to feed on another predator that is potentially more dangerous than yourself is a hazardous existence but the Mussurana has evolved immunity to the venom of pit vipers.  It has not, on the other hand, developed immunity to the venom of coral snakes.

The individual that I now had in front of me tried to make a rapid escape but it was too late, I had already seen it.  I bent down and picked it up.  It offered no resistance at all.  Some species of snake are renowned for their irascible natures, here the Tropical Bird-eating Snake, (Pseustes poecilinotus), which will lash out at the slightest provocation.  Other species have individuals that are miserable and others that are placid, the Boa, (Boa constrictor), for example.  The Mussurana is noted for its disinclination to bite.  They do however sometimes display the strange behavioral trait of swinging violently round and hitting you with their heads, a tendency I have observed in some other snakes too.  Just by way of interest, I have handled many Terciopelos here and despite their reputation as an aggressive serpent, I have never experienced one that ever acted in an aggressive manner.

One final point of interest is that the young Mussuranas are a blood red in color and only later develop the blue grey of the adults.  I find the large ones every now and then but have never come across one of the small ones.

Text and Photographs are taken from the forthcoming book:

The Natural History of Bosque del Cabo by Philip Davison

Temperature and Rainfall

Average Daily Rainfall 0.19 ins.  Total Weekly Rainfall 1.30 ins

Average Daily Rainfall 4.7 mm.  Total Weekly Rainfall 33.0 mm

Highest Daily Temp 89°F.  Lowest Daily Temp 75°F.

Highest Daily Temp 31.7°C.  Lowest Daily Temp 24.0°C.

Species List for the Week


  • Central American Squirrel Monkey
  • Howler Monkey
  • Spider Monkey
  • White-faced Monkey
  • White-nosed Coati
  • Agouti
  • Red-tailed Squirrel


  • Mealy Amazon
  • Red-lored Amazon
  • Scarlet Macaws
  • Great Curassow
  • Crested Caracara
  • Laughing Falcon
  • Roadside Hawk
  • Wedge-billed Woodcreeper
  • Rufus Piha
  • Pale-billed Woodpecker
  • Chestnut-backed Antbird
  • Black-hooded Antshrike
  • Short-billed Pigeon
  • White-tipped Dove
  • Blue-crowned Motmot
  • Long-billed Hermit
  • Red-capped Manakin
  • Chestnut-mandibled Toucan
  • Grey-headed Tanager
  • Bright-rumped Atilla
  • Great Kiskadee
  • Great Tinamou
  • Black-throated Trogon
  • Black Vulture
  • Turkey Vulture


  • Barred Ameiva
  • Cat-eyed Snake
  • Central American Whiptail
  • Clawless Gecko
  • Common Basilisk
  • Four-lined Ameiva
  • Golfo Dulce Anolis
  • Litter Skink
  • Mussurana


  • Banana Frog
  • Black and Green Poison Arrow Frog
  • Fitzinger’s Rain Frog
  • Gladiator Frog
  • Golfo Dulce Poison Arrow Frog
  • Marine Toad
  • Olive Tree Frog
  • Red-eyed Green Tree Frog
  • Smoky Jungle Frog
  • Tink Frog


  • Anartia fatima
  • Anartia jatrophae
  • Archeaoprepona demophon
  • Caligo eurilochus
  • Dryas iulia
  • Glutophrissa drusilla
  • Heliconius erato
  • Heliconius hecale
  • Heliconius ismenius
  • Heliconius sapho
  • Hermeuptychia hermes
  • Junonia evarete
  • Morpho helenor
  • Morpho menelaus
  • Metacharis victrix
  • Opsiphanes tamarindi
  • Pareuptychia ocirrhoe
  • Philaethria dido
  • Phoebis argante
  • Pierella luna
  • Pyrrhogyra crameri
  • Saliana longirostris
  • Siproeta stelenes
  • Urbanus tanna


  • Alamandra  cathartica Flowering
  • Alpinia purpurata Flowering
  • Apeiba tibourbou Flowering
  • Arachis pintoi Flowering
  • Arundina graminifolia Flowering
  • Aspidosperma spruceanum Fruiting
  • Astrocaryum standelyarum Fruiting
  • Asterogyne martiana Flowering
  • Atrocarpus heterophyllus Fruiting
  • Averrhoa carambola Fruiting
  • Cascabella thevetia Flowering
  • Chamaedorea costaricana Fruiting
  • Cocos nucifera Flowering andFruiting
  • Crestentia alata flowering and Fruiting
  • Costus speciosus Flowering
  • Couroupita guianensis Flowering and Fruiting
  • Dypsis lutescens Flowering and Fruiting
  • Etlingera elatior Flowering
  • Ficus citrifolia Fruiting
  • Ficus insipida Fruiting
  • Gustavia brachycarpa Fruiting
  • Heisteria accuminata Fruiting
  • Heliconia chartacea Flowering
  • Heliconia latispatha Flowering
  • Heliconia pogonantha Flowering
  • Heliconia psittacorum Flowering
  • Heliconia rostrata Flowering
  • Hibiscus rosa-sinensis Flowering
  • Hymenaea coubaril Fruiting
  • Hymenocallis littoralis Flowering
  • Ixora coccinea Flowering
  • Lacistema aggregatum Fruiting
  • Lacmellea panamensis Fruiting
  • Lantana camara Flowering andFlowering
  • Lagerstroemia speciosaFruiting
  • Mangifera indica Fruiting
  • Miconia argentia Fruiting
  • Morinda citrifolia Fruiting
  • Musa acuminate Flowering andFruiting
  • Naucleopsis ulei Fruiting
  • Nephelium lappaceum Fruiting
  • Pandanus tectonus Fruiting
  • Piper auritum Flowering and Fruiting
  • Piper nigrum Fruiting
  • Piper umbellatum Flowering and Fruiting
  • Pleiostachya pruinosa Flowering
  • Plumeria rubra Flowering
  • Psidium guajava Fruiting
  • Stachytarpheta frantzii Flowering
  • Terminalia catappa Flowering
  • Thunbergia grandiflora Flowering
  • Virola guatemalensis Fruiting
  • Virola koschnyi Fruiting
  • Zammia sp Flowering

4 responses to “Resisting Venomous Skeletons

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  1. Hi Phillip – am so much enjoying receiving your blog. Your tour at Bosque del Cabo was wonderful and so very insightful. I’m really looking forward to your book when it’s published. Your photography is amazing. Looking at these snakes makes me think of what was lurking out there at the pond at night. Yikes!
    Oh…have to report a puma sighting. Dennis saw one on our very early Sunday morning drive to Puerto Hemenez – right near the road in an area our drive said there have been a number of sightings. Sadly, i missed it, but exciting to know he was so close by.


  2. I, too, had a collection of bones and skulls in my home in the Amazon Rainforest.
    I find them fascinating.
    Enjoyed your blog.


  3. Phillip,

    In January I was at Monteverde, Costa Rica, with my family. After doing a canopy walk we decided to visit the serpentarium. As we approached the entrance we saw a coral colored snake about 18” long. We had been escorted there by a guide and he went in to get one of the people inside. When the guy came out he was very excited, and as he picked the snake up he told us it was a young Mussurana. He related how it was unusual to find them, and told us that Mother Nature was smart enough to make them red so that the parents could recognize them and not dine on them.

    When trying to find out more about this interesting critter I came across your Website.I really enjoyed your story about your Mussurana by the pond.

    I have a picture if you would like me to send it. Just email me so that I will have your address.

    Central Oregon


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