Wednesday, February 24, 2010

Chiropterophily: Bat Pollination

I see you!
Geoffroy's tailless bat (Anoura Geoffroyi) - photo by Nathan Muchhala

Ever since coming across this word, I can't stop saying it: chiropterophily. Chiropterophily, or pollination of plants by bats, is very common in the tropics. Hundreds of tropical plant species are exclusively or at least partly pollinated by nectar-feeding bats.

Many tropical flowers are night-blooming, specializing in attracting bats. Bat-flowers are typically white, cream, or pale green in color, making them easier to see in the dark. They usually have a musky, fermented odor - like that of the bat - or sometimes a fruity odor. They have a large, sturdy, open shape with long, bushy anthers so that the bat's head and chest get coated in pollen when it visits. In return for the bat pollinating the flower, the flower provides the nectar that these high-energy flying mammals need.*

Tube-lipped nectar bat (Anoura fistulata) - photo by Nathan Muchhala

Nectivorous bats have both good eyesight and a keen sense of smell, which helps them locate the flowers. They also have evolved adaptations to the flowers, including long muzzles, less teeth, long bristly tongues, and the ability to hover - all of which help them get to the nectar.

Geoffroy's tailless bat - photo by Nathan Muchhala

The bats also ingest the pollen of the flowers, which is higher in protein than the pollen of flowers not pollinated by bats. It contains two amino acids that are useless to the plant but useful to the bat - for making the connective tissue of its wings and tail membrane and for producing milk.

calabash flower, Bosque del Cabo, Costa Rica

In addition to the colors, smells, and flower structures a plant evolves to entice bats, the position of the flowers on the plant are also bat-friendly. For example, the flowers of the calabash tree (see above) grow on the tree's trunk - this is known as cauliflory. The mucuna and the sausage tree have flowers that hang from whiplike branches, which is known as flagelliflory. Flowers that are penduliflory hang down as streamers. And finally there are the brush-type flowers, like that of the agave (see below) and baobab. In all of these cases, the flowers are positioned in a way that allows the bat easy access.

Mexican long-tongued bat (Choeronycteris mexicana) - photo by Joe Coelho

While more common in the tropics and subtropics, Chiropterophily also occurs in the southwestern United States and Mexico, where bats pollinate the night-blooming cacti of the deserts, including the saguaro cactus, the organpipe cactus, and the agave. In this set of photos a Mexican long-tongued bat (Choeronycteris mexicana) is pollinating an agave. (Looks like he's had his fill of nectar - has a bit of a pot belly in the photo above!)

photo by Joe Coelho

photo by Joe Coelho

*Nectar-feeding bats have an incredibly fast metabolism - faster than any other bird or mammal on earth! So if they don't find nectar every day, they will starve. Glossophaga soricina, a small nectivorous bat in Central and South America, can consume 150% of its body weight in one flower visit! Read more (and see a funny picture of this bat covered in pollen) in "Nectar-feeding Bats Live on Energetic Knife Edge" (Cosmos).

related links:

Tuesday, February 23, 2010

Animal Pollination in the Tropics: Hummingbirds to Hawkmoths

Inside a tropical rainforest, there's not a lot of wind, apart from high up in the canopy, and plant species tend to be very rare and quite far away from each other. Therefore wind pollination is not an effective means of plant reproduction. The preferred method is animal pollination, and many fascinating processes have evolved both in the pollinizer (the plant) and pollinator (the animal).

It's a coevolutionary process - both plants and pollinators become specialized to attract each other. Tropical plants have evolved flowers that entice their preferred pollinator - be it hummingbird, insect, or bat - so that the pollinator will hopefully carry the plant's genes, via the pollen, to another plant of the same species. Sometimes it entices by rewards like nectar - making it a mutualistic relationship - sometimes by trickery,* but it will match its characteristics to the characteristics of a specific pollinator and discourage all other pollinators. At the same time, the pollinators have evolved traits - like a long beak or a long tongue - to better pollinate certain flowers.

photo by Danny Perez
For instance, hummingbird-flowers are usually bright red or orange (hummingbirds have excellent eyesight), non-odorous (they don't have a good sense of smell), and tubular. They produce nectar that is high in sugar but low in nutrients, supplying the highly-active hummingbird with a source of energy. (It's not the hummingbird's primary food source though - that would be insects.) The tubular flowers and the hummingbird's long, thin beak are a perfect match and because the flowers don't have a landing platform, the hummingbird must hover to feed. These characteristics discourage other would-be pollinators.

hummingbird hawkmoth - photo by Sue Snowdon

On the flip side of this we have the hawkmoth - the nighttime version of the hummingbird - who is also capable of hovering. Flowers pollinated by hawkmoths are also tubular - to accommodate the hawkmoth's long tongue - and do not provide a firm place to land. These jasmine-scented flowers bloom at night and are white, making them easier for the hawkmoth to see and smell in the dark. (Not sure what kind of flower the hawkmoth is pollinating above.)

Then we have the bees and the butterflies...

photo by Danny Perez

Bee-flowers are typically yellow, blue, or ultraviolet (colors they can see) and sweet-scented (which they can smell).

Bosque del Cabo, Costa Rica

Butterfly-flowers are usually brightly colored and odorless - butterflies have good vision but a weak sense of smell.

So we have the birds, bees, butterflies, and moths, but it's the bats - very important rainforest pollinators - that will get their own post... "Chiropterophily: Bat Pollination"

* There's a species of orchid that tricks male tachinid flies into believing it is a tachinid female so that when the male fly copulates with the "female," he is actually just pollinating the orchid.

Note: Though the text is about pollination in the tropics, the only photo actually taken in the tropics was my butterfly pic - but the others are oh so beautiful.

Friday, February 12, 2010

The Disk-Winged Bats of Lapa Rios

Spix's Disk-Winged Bats (Thyroptera tricolor) roost upright in rolled Heliconia and banana leaves.

You can see the little suction discs on the thumbs and ankles. These lightweight little insectivores use these to cling to the leaves.

The other bat species found at Lapa Rios are the Greater Fishing Bat (Noctilio leporinus), Thomas' Fruit Eating Bat (Artibeus watsoni), and the Greater White-Lined Bat (Saccopteryx bilineata), which is seen but uncommon.

These pictures were taken on 6/29/08 along the Osa Trail at Lapa Rios. Link to "Costa Rica: Day 11 - Lapa Rios Osa Trail."

Read about the Sucker-Footed Bat (Myzopoda aurita) that also roosts head up in "Sucker-Footed Bats Don't Use Suction After All" (Science Daily).

Wednesday, February 10, 2010

Eyeshine in Nocturnal Animals

Peters' Epauletted Fruit Bat (Epomophorus crypturus), Kruger National Park - photo by Peet van Schalkwyk

Have you ever noticed how under certain lighting conditions some animal's eyes seem to glow? Animals that are nocturnal hunters - and a few of them that are not - have something called eyeshine. Eyeshine is the light that we see reflected back from the animal's tapetum lucidum (a membrane behind the animal's retina). Light enters the eye, passes through the retina, strikes the reflective membrane, and is reflected back through the eye toward the light source. This phenomenon makes the most of what little light there is at night for these nocturnal creatures.

a moth with pink eyeshine

Humans can display the red-eye effect in flash photography, but we do not have a tapetum lucidum, and thus, do not have eyeshine.

Eyeshine is best observed by wearing a head lamp or holding a flashlight at eye level against your temple because the light is reflected right back into your line of vision. In the wild, many times, if not for this eyeshine, an animal would otherwise go undetected by us at night.

Many biologists can identify animals in complete darkness based on the color of the eyeshine. Cats, deer, and raccoons are typically yellow and green; alligators are typically red-orange; and spiders are said to be "sparkling". It is not known why certain kinds of animals have a certain eyeshine color.

Other eyeshine-related characteristics that help identify an animal include the distance between the pupils, the manner of blinking, the movement of the eyeshine, and the height at which it is coming from.

"Eyeshine" (Texas Parks & Wildlife Young Naturalist)
photos of "Wild Animals With Glowing Eyes" (The Firefly Forest blog)

Tuesday, February 9, 2010

The Sucker-Footed Bats of Lapa Rios

The Sucker-Footed Bats, though sometimes referred to as such, are actually Spix's Disk-Winged Bats. Their scientific name is Thyroptera tricolor, Thyroptera meaning "disk" (thyro) "wing" (ptera).

Be Kind to the Googlebots!

As I posted last week, I am currently working on optimizing this blog. In doing so, I came across something that I am now completely fascinated with (and mostly because of its name and how I imagine it to look in my head): the Googlebot.

(I think I imagine it to be something like the little obsessive-compulsive robot M-O that cleans things in WALL-E.)

So there's not actually a Googlebot - it's Google's search bot - or spider - software that searches the web and indexes the information it finds in the Google search engine. Here are some of the things the Googlebot likes:
  • Relevant and descriptive titles (blog title bar, blog post titles, titles in the permalinks)*
  • Relevant and descriptive labels (categories, tags)
  • Relevant and descriptive anchor text
  • You updating your blog often!
Anyway, these are some of the things I'm implementing in an effort to be kind to the Googlebots, so, again, please bear with me while I'm changing some things around (like titles, labels, and permalinks) and making new, shorter posts out of long, older posts.

* Followup: You should avoid changing post titles/permalinks, especially if your blog post has already been indexed. What happens is that somebody may do a search that brings up your blog post, but when he/she links to the page, the page no longer exists. So think through your blog's intention (if you're serious about your blog, of course) and try to get everything right the first time.

Wednesday, February 3, 2010

Bat Anatomy and Behavior

Bats are the only true flying mammals. They belong to the order Chiroptera (coming from the Greek words for "hand" and "wing"). They are further divided into 2 suborders: Megachiroptera (megabats) and Microchiroptera (microbats).

Bats account for 20% of all of the world's mammals. They are present on every continent except Antarctica. They are integral in seed dispersal and the pollination of certain flowers, and they help keep the insect/pest populations down.

Being a mammal, the skeletal structure of a bat's wing is more like a human arm than a bird's wing. In fact, a bat's wing very closely resembles a human arm - the difference is in the proportions. (Imagine your arm with extremely elongated fingers - link to bat wing anatomy).

Monteverde Bat Jungle

Also, the difference between bat and bird flight is that bats do not flap their entire forelimbs like birds, but rather flap only their spread-out "fingers".

bat skeleton, Monteverde Bat Jungle

The anatomy of a bat is perfectly adapted to hang upside-down. Their hindlimbs are rotated 180 degrees so that their knees face "backwards". This helps them navigate in flight and hang by their feet.

Straw-colored fruit bat (Eidolon helvum), Houston Zoo

They have also evolved specialized tendons that hold their toes in place, enabling them to cling to the roost surface without exerting any energy and must actually flex their muscles to let go of the roost surface.

Straw-colored fruit bat (Eidolon helvum), Houston Zoo

These adaptations allow them to instantly drop off into flight from their roost and to occupy roost sites that no other animal could occupy.

* * *

Of the 1,100 different species of bats, 70% are insectivores, with most of the rest being frugivores and nectar-feeding species. Additionally, there are a handful of species that are carnivores and 3 species that feed exclusively on blood.

Bats are nocturnal - they hunt at night to avoid competition with birds. The microbats navigate and find prey using echolocation, while the megabats rely on their keen vision and smell. Bats spend their days sleeping, resting, and grooming. (An interesting note: they rarely fly in the rain because the rain interferes with their echolocation.)

Honduran white bats, La Selva, Costa Rica - photo by Christopher L. Wood

Bats can live over 20 years (which makes them the longest-lived mammal for their size). Some species of bats live solitary lives while other species have colonies of over a million bats. Then there's everything in between. For instance, the Honduran white bats (Ectophylla alba) live in small groups of up to 6 individuals.

A large number of bat species migrate hundreds of miles to winter hibernation sites. Some will go into a state of torpor during cold weather and rouse only when it is warm enough for the insects - which they feed upon - to be active. Others will hibernate for 6 months.

Most bats give birth to only one pup per year - which is an incredibly low reproductive rate for an animal of that size! The mother will nurse the baby until it is nearly adult size and can forage on its own (6-8 weeks for microbats, 4 months for megabats). Females have strategies (delayed fertilization, delayed implantation, and delayed fetal development) for timing their pregnancy and timing when they give birth so that environmental conditions and food availability are optimal.

mother and juvenile fruit bats (Epomophorus crypturus), Kruger National Park - photo by Peet van Schalkwyk

BCI's "All About Bats" page
Wikipedia entry on bats

Tuesday, February 2, 2010

Shuffling and Optimization

Please note that I will be shuffling some things around because I am currently doing some site optimization. This will involve reworking some of the posts already up and hopefully adding more posts regularly, especially those bat- and Costa Rica-related. (My husband and I visited Costa Rica a second time over the holidays!)

One reader commented about the blog's colors and fonts, saying it was kinda hard to read. I don't have a problem with it (but different monitors display things so differently) and no one else has commented on this; but if it is a problem, I don't want to turn people away with my color and font selections. So let me know.