A celebration of wrinkles!! The esthetics of the Wrinkle-faced Bat

It is safe to say that Tracie and I love bats. Fortunately for us Costa Rica has massive diversity when it comes to these flying mammals. Scientists have identified around 240 mammals in Costa Rica of which 113 are bats. The Osa Peninsula has the highest bat diversity in the country with 80 identified species.

Even so, bats can be elusive during the Night Tour. Most of our sightings are fleeting views of bats flying by at breakneck speed. At times we are also approached by insectivorous bats capitalizing on the insects attracted by our headlamps.

Occasionally we are fortunate enough to encounter roosting bats which we can observe in detail. These prized encounters, although usually brief, are always memorable. By far the most memorable bat encounter we have had is with the Wrinkle-faced Bat, Centurio senex. Wrinkle-faced Bat - Centurio senex

This bat is so different from other bats it is the only member of its genus: Centurio. The binomial name is derived from the Latin words centurio, meaning 100, and senex, meaning old or aged, because its face looks like that of a 100 year old person.

It is not known why these bats evolved such a wrinkly face, but it is though that perhaps the wrinkles act as canals to channel juices into the bat’s mouth as it feeds on ripe fruit.

Male bat’s faces are wrinklier than the females’ faces and they also have chin folds which they stretch over their faces while roosting. A swollen ridge along the bat’s foreheads prevents the face mask from slipping and, incredibly, the masks are complete with transparent “window panes” over the area covering the eyes!!

Wrinkle-faced Bats have a very short and wide skull which allows them to apply about 20% more force in their bite compared to other similarly sized bats. Scientists believe that this allows Wrinkle-faced Bats to feed on harder fruits than other frugivorous bats. They also have pouches in their mouth where they can store spare fruit.

Wrinkle-faced Bat - Centurio senex

Wrinkle-faced Bat feeding on fruit. Notice its massive thumbs!!! Click on the photo for a larger image

Another impressive feature about these bats are their massive thumbs. It seems this is an obvious adaptation which allows the bat to grip and feed on large fruit, although their feeding habits are poorly understood. Very little is actually known about these handsome bats. Roosts are rarely found and scientists think they may roost high in the canopy.

The facial features of the Wrinkle-faced Bat make it one of the most unusual mammals in Costa Rica. Some may say they have a face only a mother could love. To us, though, their unique looks represent the beauty and diversity awaiting discovery in the tropical rainforest.
Wrinkle-faced Bat - Centurio senex
References:

LaVal, R. & Rodríguez, B. 2002 Murciélagos de Costa Rica / Bats Editorial INBio
Wainwright, M. 2002 The Natural History of Costa Rican Mammals Zona Tropical

In the Presence of the Jaguar

There is no question that the most elusive, imposing and impressive mammal in Costa Rica’s rainforests is the Jaguar, Panthera onca.  The word itself, Jaguar, is derived from the Guaraní Indian word yaguara meaning “he who kills with one bound”.  Native Americans throughout their range have venerated these apex predators for their power, stealth and beauty.  In many cultures they are treated as god-like entities and their presence has been woven into many mythologies.  Their likeness graces the walls of many temples, carvings, paintings, and ceremonial masks all over America.

Indigenous Vessel with Jaguar Image Discovered in Nicoya, Costa Rica
Image Sourced from the Wikimedia Foundation – www.commons.wikimedia.org

It is easy to see why these animals are so revered.  Jaguars are the third largest cats in the world, behind the Lion and the Tiger, and they are the largest cats in the Western Hemisphere.  To the native people that share its range, the Jaguar is the ultimate hunter.  It symbolizes fear, respect and reverence.

Jaguars are now extremely endangered throughout their once great territory and have been completely wiped out in many areas where they once thrived.  Encounters with these magnificent beasts are rare and often fleeting.   Though I had been intrigued by these cats for most of my life, I had never been close to a Jaguar until my late twenties.

It was then, while working as a canopy tour guide in Rincón de la Vieja, that I first began to understand their power.  One night, a Jaguar attacked and killed a cow on the farm where I worked. At the time, the farm was in a legal dispute and the police were called in to inspect the kill.  They needed to do so in order to make sure it had not been illegally slaughtered for food by the people in possession of the land.  When the police showed up the next day and were taken to the kill site, to everyone’s surprise the Jaguar had returned overnight and dragged the carcass 50 meters to the base of a tree, where it had been feeding on its prize!  This is an awesome display of power, considering that the average cow can be up to three times as heavy as the average Jaguar.  Jaguars have been known to take down bulls weighing up to 800 pounds and are considered a pest by cattle ranchers throughout Latin America.  It was hard to imagine such a powerful creature lurking in the forest, living among us.

Jaguar – Panthera onca
By USFWS [Public domain], via Wikimedia Commons
http://commons.wikimedia.org/wiki/File%3AStanding_jaguar.jpg

A couple of years later, in 2001, I was hiking with a friend from Carate to Sirena Station, in Corcovado National Park.  It was here that I had my first face to face encounter with a Jaguar. We left Carate very early in the morning and embarked on the 20 km hike to Sirena Station.  The hike was amazing, with an abundance of wildlife.  Gigantic, scattered whale bones littered one beach giving this primeval place a prehistoric aura.  It felt as though we had stepped back in time.  About half way through our trip we arrived at a long beach called Playa Chancha.  As we rounded the rocky outcrop at the beginning of the beach, we stopped to rest, get a drink of water, and soak in the raw beauty of Corcovado National Park.  We were sipping our water bottles, when my friend said “What the hell is that!”  I turned to look behind me and saw a large, black figure walking down the beach, towards us, about 500 meters away.  We watched it for a while when, suddenly, it turned.  We got a full, profile view of an adult, all-black, or melanistic, Jaguar.  After a few seconds the cat literally took two leaps and disappeared into the forest.  Stunned by what we had seen, we walked down the beach until we came across these massive paw prints sunk deep in the sand. They were twice as wide as my size 41 feet (about 8.5) and about half as long. Impressive!

Jaguars often patrol the beaches of Corcovado and Tortuguero National Parks in search of sea turtles.  As unsuspecting sea turtles arrive on the beach to lay their eggs, marauding Jaguars pounce and turn them into an easy meal.  Their bite is the strongest of all the world’s wild cats – almost twice as strong as the Lion, and the second strongest of all mammals, after the Spotted Hyena.  They can pulverize even the sturdiest of bones and can perforate a turtle’s shell as easily as we would bite through a banana.  Elated by our encounter, we continued on to Sirena Station where we spent the next two nights.  The remainder of our trip was overshadowed by the 15 or 20 seconds we spent in the presence of the Jaguar on Playa Chancha.

Corcovado National Park – Sirena River Mouth

Six years later, I was to meet this elusive cat again.  Tracie and I were walking back home from Drake Bay Wilderness Resort after a tour.  My eyes were killing me because, although I didn’t know it at the time, I had sustained a scratched cornea that night that would take me on an emergency flight to San José the next day for treatment.  As we headed up the hill towards La Paloma Lodge I looked up and there was this massive black Jaguar about 10 feet in front of us, right in the middle of the trail!  Before I could say anything, the cat took two leaps and was gone.  The most amazing thing about this encounter was how, despite its size, this animal moved in complete silence.  We were not very far from it when it leapt into the forest.

Melanistic Jaguar – Panthera onca
http://commons.wikimedia.org/wiki/File%3AMelanistic_panthera_onca.jpg

We looked for it for some time afterwards, but there was no sign of the cat.  We didn’t hear even the slightest sound – not a leaf crinkling, not a twig breaking, just absolute silence.  It was as if we had imagined the whole thing – or had just seen a ghost.   Thick pads on the bottom of their feet allow Jaguars to move silently through the forest.  They move so silently, that people often don’t realize a Jaguar is nearby until they see their tracks.  As I sat on the plane with my aching eyes closed the next day, my thoughts were haunted by this silent predator.  Was it flesh and bone or was it some ghostly jungle spirit we had seen that night?

Last Saturday night, November 24th, 2012 we were out on The Night Tour with guests from Finca Maresia and La Paloma Lodge.  It was an amazing night filled with great encounters. We saw a Leaf Katydid (Mimetica sp.), an incredible brown and green morph that we had only seen one other time before, about ten years ago.  Other highlights included a Gaudy Leaf Frog, a Giant Walking Stick, an incredibly rare Ray Spider, an Emerald Glass Frog and an Eyelash Pit-viper. Towards the end of the evening we also encountered a pair of Granular Glass Frogs (Cochranella granulosa) in auxiliary amplexus.  They were on a tree next to the hanging bridge that spans the Agujitas River.  Since Tracie and I had never seen these tiny frogs in their breeding position before, we decided to stop back after the tour to get some photographs.

Granular Glass Frogs in Axillary Amplexus – Note the eggs clearly visible in the female’s abdomen
Cochranella granulosa

We managed to locate the frogs and even though they were on a leaf about ten feet from the bridge, and their maximum size is about 31 millimeters (about 1 ¼ inches), I managed to get some shots with a telephoto lens as Tracie lit the frogs up with her handheld flashlight.

After a while Tracie said: “Maybe, if we turn off our lights, they will start laying their eggs.”  We waited in complete darkness.  By now it was nearing midnight.  After some 15 minutes with our lights off we suddenly heard a low, guttural growl coming from the river’s edge, about 6 feet from the bridge.  We stood silently, not quite knowing what to make of this menacing sound, when we heard it again! (Click here to listen to the Jaguar’s Growl: Jaguar Growl ) A rock then rolled down the bank and fell into the river making a small splash. I turned to Tracie and said: “There’s an animal down there!” and we simultaneously turned on our headlamps.  As the light pierced through the darkness, it lit up a shadowy figure standing on the river’s edge.  The Jaguar’s identity was revealed by the incredibly intense, bright golden glow of the animal’s eyeshine.  It, too, was an all black cat.  We looked at each other for a second and then it disappeared.  We ran about five feet to the trail and managed to catch a glimpse of the Jaguar’s tail and rear end, about 20 feet away at this point, as it was swallowed up silently by the dark forest.  Though it was a shocking sight for us indeed, it is not so surprising to find a Jaguar at a river’s edge.

By Bruce McAdam from Reykjavik, Iceland (Panther Uploaded by BruceMcAdam) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
http://commons.wikimedia.org/wiki/File%3ABlack_Panther_by_Bruce_McAdam.jpg

Jaguars are quite aquatic and regularly hunt in or around rivers.  They have been observed fishing, by tapping their paws on the water and luring fish to the surface.  They are also known to wrestle and eat Cayman and small Crocodiles!

After a few minutes of frantically searching the forest, yearning for another glimpse, we gave up our search and started walking home.  As we looked back on what had just happened and assimilated our time in the presence of the Jaguar we couldn’t help feeling blessed to live in a place where an encounter like this is still possible. The thought of sharing a moment of space and time with such an amazing creature, to hear its growl and meet its gaze as we crossed paths in the forest gave us an uplifting thrill – a thrill hard to match, except while staring into the mysterious eyes of the jungle’s top predator.

Posted by Gianfranco and Tracie