Taking Care of Business While Hanging Upsidedown

Have you ever wondered how a bat can poop and pee, while upside down, and not end up a filthy mess? I must admit the thought had never occurred to me. I guess I just assumed that sometime during their evolution that issue would have sorted itself out.

It is thought that bats began roosting upside down early in their evolution because dropping head first from their roosts makes it easier for them to take flight. By hanging from their feet bats are able to spread their wings before letting go of their roost and are poised for flight as soon as they hit the air.

Notable exceptions to this rule are Disk-winged Bats, which roost right side up. These tiny insectivores roost in groups inside rolled Heliconia and Banana leaves. Suction cups on their thumbs and heels enable them to stick to the sides of the leaves.

Thyroptera tricolor Disk-winged Bat

Disk-winged Bat, Thyroptera tricolor, roosting in a Heliconia Leaf. Click on the image for a larger picture

But I diverge…back to the pooping and peeing. About a week ago we came across a Tent-making Bat, Artibeus watsoni, and as we watched the little bat began to pee….and it was amazing! It didn’t get a single drop on itself!

A few days later, while on the tour, I spotted a bat feeding in a tree about 7 meters off the ground. I knew right away it was not one of the typical fruit bats we tend to see. It was quite small and had very light colored fur. I got it on the scope and we watched it as it fed.

Then suddenly, without releasing its fruit, the little bat arched backward and took a big poop followed by a lengthy pee! Once again its form was impeccable and it managed to keep itself and its fruit feces free. After it finished, it went right back to what appeared to be a very enjoyable meal. Fortunately, while we were watching the bat I shot some video. I have posted an excerpt of the video, which Tracie set to a catchy tune, below…

It turns out that this cute little bat, Chiroderma villosum, is not a common one to see at all. During all the years of doing the Night Tour we have only seen it a couple of times. Their common name, the Hairy Big-eyed Bat, is quite fitting. They have really big eyes for a bat and long shaggy fur. They are quite distinctive from other fruit bats as they have light colored fur and very faint, barely visible facial and middorsal stripes.

Hairy Big-eyed Bat, Chiroptera villosum

Hairy Big-eyed Bat, Chiroptera villosum. Click on the image for a larger picture

Next to nothing is known about these little bats. Their roosting sites are unknown and they are only known to feed on 3 species of fruit. They are rarely captured in mist nets and it is thought that they dwell mainly in the canopy. We feel fortunate to have observed this little guy and to have gotten a glimpse into its otherwise secretive life; including its feeding and toilet habits.


LaVal, R. & Rodríguez, B. 2002 Murciélagos de Costa Rica / Bats Editorial INBio

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

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

The Mysterious Velvet Worm

Velvet Worms are small, elusive and secretive creatures. Because of their size and

Velvet Worm photographed in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

Velvet Worm photographed in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

semi-fossorial lifestyle they are not easy to find.

Guests on the tour are sometimes a bit puzzled as to why this strange little worm-like animal should cause their guides so much excitement, but a glimpse into the life history of Velvet Worms reveals a creature nothing short of phenomenal.

The first line of the scholarly paper: “A new giant species of placented worm and the mechanism by which onychophorans weave their nets (Onychophora: Peripatidae)” by Bernal Morera Brenes and Julián Monge Nájera puts it all into perspective by stating:

Onychophorans, or velvet worms, are small 
invertebrates that most biologists study in theory, but due to their rarity, 
never see in the real life“.

Encounters with these enigmatic creatures are always special because of their rarity and because of these organisms’ ancient legacy.

The origin of Velvet Worms is still not well understood. One thing that is not in contention, though, is that these little creatures are living fossils. Due to the soft structure of their bodies, Velvet Worm fossils don’t preserve very well. Even so, fossils have been found dating as far back as 500 million years ago when Velvet Worms were marine

By Gunnar Ries Amphibol (Own work (own photo)) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

animals. The fossilized creature pictured right, which was discovered in Cambrian Burgess Shale, looks remarkably similar to the Velvet Worms that roam the earth today. They are thought to have crawled out of the ocean about 430 million years ago where they evolved in the inter-tidal zone until eventually colonizing land.

One of the things that make Velvet Worms so special is simply how different they are from any other animal on the planet. In fact, they are so different that they are grouped in their own Phylum: Onychophora. Mammals, for example, belong to the Phylum Chordata. It is made up of about 60,000 incredibly diverse species including sea squirts, fish, birds, amphibians, and reptiles. Taking this into consideration, it is remarkable to think that Velvet Worms have been placed into a Phylum of their own containing less than 200 species. Onychophora is divided into two families: Peripatidae and Peripatopsidae. Only Peripatidae is represented in Costa Rica.

Velvet Worm photographed in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

Velvet Worm photographed in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

The word Onychophora is derived from the Greek words onyx, meaning nail or claw, and phoros, meaning to carry or to bear. They are given the name “claw-bearers” because Velvet Worms are equipped with a pair of claws on each one of their feet. Velvet Worms found in Costa Rica usually have between 22 and 43 pairs of legs. Their skin is covered with very fine “papillae”, or tissue projections, which are covered by tiny scales. These papillae give Velvet Worms their “velvety” appearance and account for their common name.

Perhaps Velvet Worms’ most remarkable feature is a pair of slime glands present on either side of the head. This feature is unique to Velvet Worms and represents their foremost weapon for hunting prey.  While hunting, Velvet Worms use their antennae and chemosensory organs near their mouth to identify prey.  

Once they decide to attack, Velvet Worms shoot white, sticky slime from glands located below their antennae. Velvet Worms have the astounding ability to shoot their slime at a rate of 5 meters per second!! This is a world record in the animal kingdom, as there is no other animal capable of propelling anything at a faster rate. As the slime ensnares their prey, the Velvet Worms pounce and inject digestive saliva before starting to consume it. The slime is also re-ingested in order to recycle valuable protein.

Velvet Worm giving birth. Photograph taken in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

Velvet Worm giving birth. Photograph taken in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

The many reproductive cycles known to occur among Velvet Worms are also fascinating. One species of Velvet Worm  reproduces by parthenogenesis and no  males of that species have ever been discovered.

Some species, all of which are found outside of Costa Rica, reproduce by laying eggs. Most Velvet Worms are “ovoviviparous”, meaning that they develop as eggs in the mother’s uterus and hatch from the eggs only a short time before birth.

Finally, some Velvet Worms are live-bearing and the young develop as embryos in the mother’s uterus. They are nourished via secretions released from the mother’s uterus or via a placenta. These are the only placental invertebrates on the planet. The diversity of reproductive cycles occurring within Velvet Worms is astounding, especially considering there are less than 200 species.

A few nights ago, on March 13, 2013, we had what was by far our most amazing Velvet Worm encounter. We were walking back to Jinetes de Osa

Velvet Worm giving birth. Photograph taken in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

Velvet Worm giving birth. Photograph taken in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

towards the end of a Night Tour. We stopped to look at a Burrowing Tarantula when I noticed a Velvet Worm not far from the Tarantula’s burrow. As I leaned in to get a closer look, I saw what I thought to be the Velvet Worm feeding on something. I had a closer look, trying to identify the prey item, but something seemed to be off. Suddenly I realized, to my disbelief, that I was

looking at the Velvet Worm’s rear end and it was actually giving birth! Blown away by what we were witnessing, I took out my camera and started clicking shots off. We watched in awe as the tiny little baby Velvet Worm was born and I stayed behind to capture the newborn’s first few minutes on earth.

The newborn Velvet Worm crawled cautiously, exploring this brand new world but never straying too far from its mother. The mother, seemingly exhausted by the birth process, stood motionless as its newborn examined the surrounding area. Amazing! For us to have witnessed this ancient creature bringing this tiny being into our modern world was truly a privilege.

Velvet Worm with newborn offspring, minutes after birth. Photograph taken in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

Velvet Worm with newborn offspring, minutes after birth. Photograph taken in Drake Bay, Costa Rica on the Night Tour © Gianfranco Gómez

After several minutes we left the two little Velvet Worms and headed home. We walked back silently, still reeling from what we had seen. Lost in thought, I could not help wondering how this small, delicate, soft bodied creature had outlived so many others during the last 500 million years.

How could this tiny creature have managed to survive so many mass extinctions, natural disasters, ice ages, the shifting of the continents, to outlive the dinosaurs and so many other creatures and still be with us today?  I suppose the only answer is that Velvet Worms, small and fragile as they might seem, are perfectly adapted for the environment they live in. As long as they have undergrowth and leaf litter to inhabit, they may well survive the current mass extinction brought on by humans and outlast us all.

We are currently working with researchers at the Universidad Nacional de Costa Rica on identifying a couple of new species of Velvet Worms from Drake Bay as well as studying their ecology and behavior.

posted by Gianfranco