Saturday, April 16, 2011

Updated bat activies for May 2011 (year of the bat!)

An updated list of bat related activities around the world in May to celebrate the 'Year of the Bat'!

Unfortunately activities seem restricted to Europe for the time being...


Germany (Frankfurt)

11 May Nachtscwaermer-guided tour (Frakfurt Zoo)

18 May- Nachtscwaermer- guided tour (Frankfurt Zoo)

21 & 22 May- Experiencing bats (Frankfurt Zoo)

25 May- Lecture "night Flight- Fascinating bats" (Frankfurt Zoo)


17 May Bat walk, Bryngarw County Park, Bridgend, South Wales

20May- 16 September Cambridge, 'Bat Safari' river tours

Friday, April 15, 2011

Back to field planing! (and milking bats)

Ah it is 'that time' again the birds are singing, the bees are buzzing and the bats are lactating! Yes, considering that the Artibeus were all pregnant (late-stage) during my mid-march visit if I plan on collecting milk it is time once again to schedule a trip to the field for the 'last' milk collection of my dissertation (assuming all going according to plan). This next trip my lab mate will accompany me which will be an added bonus. Now all that said I imagine one question came to mind rather quickly 'wait... milk bats?' Yes... this is actually not as difficult as it sounds. Basically the mother and pup are captured, kept away from each other for a short while (~1 hour) so she accumulates milk which is natural if the mother is away from her baby. (Also the mother and pup are accustomed to being separated from each other for longer periods of time because the baby that cannot fly must stay behind while its mother is out for several hours every night searching for food.) After about an hour, I inject the mother with a small amount of a hormone called oxytocin. Oxytocin increases milk let down (i.e. lactation) so this combined with what is essentially a miniature version of milking a cow allows me to collect milk from the female before letting her and her baby return to their roost. I then upon returning analyze many nutritional components in the milk (dry mass, protein, fat, and carbohydrate (sugar) content).

Thursday, April 14, 2011

Flight (Part 2)

Continuing on the topic of flight... The physics of flight include 4 forces. 2 of these (in bold) are generated by the flying animal (in this case a bat) and 2 of them (drag and gravity) are natural properties that the animal must negotiate (fight) in order to fly. 1. Lift (i.e. upward force) 2. Thrust (i.e. forward force) 3. Drag (backward force (resistance)) 4. Gravity (i.e. downward force)


The shape of wings causes air to move over the wing-surface in a unique way. Specifically, air flows faster over the upper curved surface of the wing and slower over the cupped (concave) surface. This causes negative pressure on the upper side of the wing and thus the wing begins to rise. In principle this is what happens when as a child you cupped your hand and played with the wind outside the open car window. Remember how the air would suddenly PUSH your hand upward? That is 'lift'! Additionally that is about the time you were reminded to not put your arms out the window.

Take home: the shape of wings (think of a bird or bat wing) is what causes air to move in a way that LIFTS the wing upward. The opposing force is gravity... without lift (like you or I flapping our arms, sorry to say but we are not going to generate sufficient lift) gravity 'wins' and we stay stuck to the ground. Gravity is complex for despite the fact that physicists can tell us its value (9.81 m/s2) how it 'works' and why it exerts force on objects was perplexing even to Einstein who wrote extensively on the topic. Incidentally, Einstein apparently also noted "Gravity cannot be held responsible for people falling in love." ______________ (I will insert an awkward pause here as you ponder that and why he might have felt it necessary to declare such a fact, if he made this statement in English or German and if it would have been funny regardless). Back to flight: The wings of bats are more flexible than birds because the wing itself is formed by a thin layer of skin rather than stiff feathers. However, birds are able to more easily change their wing area by moving their wings closer to their bodies because bats require the full extension of their 'fingers' i.e. the wing to have it function because of its thin nature. In searching for an analogy the best I have for you follows. This is similar in a way to how airplanes have rigid wings (like bird wings) while a para glider that uses a flexible surface (like a bats wings) is less able to change the shape of the 'wings' or they will loose lift.


Basically thrust is the power from a wing-stroke that pushes back against air and results in a force propelling the animal FORWARD. Indeed to understand this idea you must remember that air is made up of molecules and is in actuality a fluid (like water). Thus there is indeed something to 'push upon'.

I will conclude for now and leave you with another Einstein quote as a 'token' physicist

"Science i nothing more than a refinement of everyday thinking".

I refer you to this much more comprehensive explanation of flight (here) and hope you find this topic interesting.

Tuesday, April 12, 2011

The evolution of flight (Part 1)

Many animals are able to fly and most of these are insects. However, when one stops to consider which vertebrates fly (vertebrates are animals with an internal skeleton including a spine and something resembling a spinal chord) only 3 main groups are able to fly.

These are: birds, Pterosaurs and bats.

The wing surface formed in 3 different ways one for each of these groups (see above).

Both bats and Pterosaurs used a wing-surface created by finger elongation (the 'pinkie' in Pterosaurs and all fingers elongated except the 'thumb' in bats).

Meanwhile, birds fly using a surface created by modified scales (feathers) and a strong series of arm and finger bones that are the result numerous bones fusing. Additional details are left out for brevity but are extremely interesting such as skeletal lightening in birds.

Pterosaurs are extinct and so only two extant flying vertebrate groups (extant = animals that are still alive today) are bats and birds. (What is a Pterosaur? Click here!)

Why did flight evolve?

There are two main thoughts about this. Basically either animals were able to flap and lift UP to escape predators etc. OR they were living in trees and started to glide from tree to tree (like 'flying' squirrels) also to catch food (insects) or avoid predators.

Regardless, the sky is (and was) full of potential food and once they were able to fly bats quickly filled a new niche (a niche is the ecological role of an animal generally relating to the food it eats). Both bats and birds were able to eat flying insects but bats as nocturnal animals compete with a fewer set of birds. Indeed this successful niche 'nocturnal insectivore' has since been radically expanded to include other more unusual food-types such as frogs or fish!

You can read more about the evolution of flight here.

Click here for cool videos of bats flying in slow motion.

For my next I will try to summarize the physics required for flight.

Monday, April 11, 2011

Can pregnant bats fly?

I happened upon the above question incidentally and thought perhaps it is a good one to address since I study reproductive bats and many people who do not study bats might have the same question!

(to the right is a photo of a Jamaican fruit-bat late in her pregnancy)

The simple answer is yes, bats fly while pregnant. That said it is very energetically costly for them and they become increasingly awkward as the pregnancy progresses. Indeed they may be more likely to be eaten by predators as they become slower and less-maneuverable.

Not only do they fly while pregnant, but bats give birth to pups that are much larger relative to the mom's size than human mothers give birth to! So, they are still flying when the developing baby is larger relative to the mother than a human would be walking around with.

After bats give birth (upside-down which is yet another difficulty) the mother will occasionally fly with her ever-growing baby (most bats only have one pup per pregnancy although some have twins and more rarely- triplets). The fortunate bats like Mexican free-tailed bats (Tadarida brasiliensis) or other cave dwelling bats usually leave their young in the roost while they forage but some less-fortunate bats may have to move their young nightly or semi-regularly if they inhabit less-permanent roosts.

So next time you hear a pregnant friend or family member saying how their back hurts or it is hard to get around you can tell them to cheer up and remind them they are lucky that they are not a pregnant bat!

Sunday, April 10, 2011

Toothsome (more facts about biologists)

I have come to the conclusion and with increasing confidence that many biologists love to cook. Perhaps you are picturing them throwing some burgers on the grill or making killer chili.... no I mean that numerous biologists I know make on a semi-regular basis and with avid enthusiasm, fancy 4 course gourmet meals and exotic fare.

For example, BOTH of my collaborators in Mexico are involved in a 'gourmet club' that includes a group of several additional Mexican bat biologists who all alternate making and hosting gourmet fancy dinners. My adviser makes pies for fun and attempts to emulate her favorite dishes (generally carne asada comes into play). She may have learned this from an old committee member and bat-biologist of legend 'Mike' who attempts to dis-entangle the exact recipes from his favorite restaurants through rigours and I assume enjoyable experiments. My lab mate is addicted to the food network and is a good cook. Down the hall an undergraduate researcher brings in homemade meringue pies to lab meetings and makes special cheesecakes for birthdays. The field biologist Mike O'Farrell has published a cookbook on how to cook in the field. A favorite evolutionary biologist of mine- Hanna Kokko has a link on her lab page to her 'good food society' which seem very fun. (by the way...I remained strong and did not have a David Letterman trying to get Oprah on his show moment... but really Hanna if I am ever in town....). Even my friend Natalie, the coolest PhD holding biologist I know-who rock climbs and does field work in Alaska after being dropped off by a helicopter field-gear and all by a helicopter. But even cooler: she can fit her material world (mostly books, clothes and ski-gear) into the back of her truck (shes kind of like if Joni Mitchell and McGyver (to return to a recent post) had a daughter). Even she with her bohemian ways stunned me after years of freindship by making me dinner one night and wiping up an amazing and exotic salad (shes vegetarian but I love her anyway...) and admitted she loves to cook. (Mind you as the 'McGyver-esque soul' who's mother may have been a hippie, I imagine she only has one pot and uses it to make tofu stroganoff).

In sum is perhaps no surprise that biology departmental functions are a culinary joy as well as interestingly competitive when it comes to the 'best' stuffing or mashed potatoes.
Why do many biologists love to cook?
I have come up with several possible reasons but I think it has to do with two main things.

1. Cooking is a scientific process: meat turns brown etc. when you cook it in part because proteins are being denatured, bread rises because yeast produce gases, jelly 'sets' i.e. solidifies because a new chemical structure is forming a'la pectin. So there is the main and most obvious 'its because biologists are scientists and cooking is (if you want it to be) scientific.

2. However, I think there is another reason (this is at least how I explain to myself at my sudden affection for cooking). Much of biology is comprised of incomplete days and tasks. Many days you go to the office and read articles to gain knowledge or attend meetings to question it. Some days you write proposals. After several days of proposal tweaks you send it off and wait to see if you get funding. Meanwhile, on another day, you work on getting permits for your research. Days pass and you wait for the permits and if you are lucky you've heard back from granting agency. If you are even more lucky you were funded. More days and you wait on your permits and meanwhile you order your lab supplies and continue to wait. You secure your permits and supplies and start your work. Probably something about your research does not work the first time... you wait. Days and days you may work to perfect an assay to make sure it works before you use your valuable samples that took days and days to collect. Then for days and days you run samples. Days and days you run your statistics (only after days of entering data). You start to make some conclusions and spend a few days talking to others about your results. You spend days or months writing up your results. You send them to co-authors and wait to hear back. You make changes and send the written results to a journal and wait for their decision. So on and so on. This is obviously the less-glamorous version of biology and truly I am happy to be in academia however... with time answering the 'what did you get done today' question wears on a person.

So indeed, most days you do not come home and think 'gee I am so glad I cured cancer and saved the polar bears today.' In fact more likely you don't even think 'Gee I am so glad I finished that side project on why pika prefer grasses over shrubs today'. Nope. So what do you do?

While members of M*A*S*H told jokes and made bootlegged gin in their tents and Zorba the Greek would say 'now... we dance' -my advice?

Now you cook.
Why? When you start you have nothing but....
But then you finish and when you finish you have (hopefully) something delicious to share with your loved ones or at least to eat while you read or watch TV. Suddenly when someone asks "what did you get done today?" you can reply- "I checked e-mail, made a graph, ordered some pipette tips and made stuffed mushrooms and cheese souffle with rhubarb cobbler for desert."
And who can argue with that?

Monday, April 4, 2011

Argentinian ants and yes...a bat would eat that

Possibly the worst (at least most boring) B-movie of all time 'THEM' (view trailer here)

Yesterday I awoke to find my depressed cat gloomily staring at a trail ... make that a carpeting of Southern California's bane; Argentinian ants swarming her food. To those not familiar with these little ants, they are a terrible pest in kitchens throughout the Los Angeles area and this is for a biological nuance the exhibit. Linepithema humile occur in South Africa, Europe, Australia, Japan and The US but originated in Argentina, Uruguay, Paraguay and Southern Brazil, and in 2009 it was discovered that these little ants are part of a super colony spanning from Japan to the Americas and that because of extreme genetic similarities their hydro-carbons which are used by ants to identify enemy ant colonies (such as the same species but a competitor for a clumped food-source say a chunk of candy-bar) were the same between colonies. Thus, separate colonies of Argentinian ants recognize each other as 'kin'. This means that instead of attacking neighboring colonies they join forces as a 'family unit.' Indeed, they join forces and harass innocent cats and soil the previously clean and well-functioning kitchen of many an innocent resident.

They do not just harass humans, these ants are also blamed for the decline of horned lizards in Southern California. While conducting what has become a nearly ritualistic 'wiping out of the ant-attack' which involves several trail washing bouts followed by waiting for them to be convinced the item of interest is truly gone before replacing my cat's food now sitting in a moat she is clearly intimidated by, I contemplated what pay-back might these ants... i.e. what animals eat ants. I will be honest, I really truly like ants and respect them as some of the most interesting animals to embrace sociality. But really... what might keep these little ants in check before they re-group and plan their next attack?

Indeed many mammals have specialized diets focused entirely on what to me seems a non-appetizing fare. These include ant-eaters, pangolins, aardvarks and well I suspect you saw this one coming: bats! Yes bats.

Some bats, I will assume some very desperate ones at that, eat ants. In an article by Eran Levin, Yoram Yom-Tov and Anat Barnea published in Naturwissenschaften in 2008 it was noted that in Israel, female Greater mouse-tailed bats (Rhinopoma microphyllum) are able to 'afford' the expensive task of lactation by adding ants to their diets during periods of ant swarms! (Ant swarms occur when female and male ants hatch and leave their natal nests to mate and for the female to find a new location to establish a colony). During these times of plentiful ants up to 90% of the bats diets include these unsavory treats. Perhaps my favorite part of the article was the pitiful photo of a bat with an dis-articulated ant heat stuck to it's lip (below right).
Mouse-tailed bats in a colony (photo form Arkive)

So if i were to suggest a timely sci-fi B movie, (of better quality relative to 'THEM' pictured above, which I must say is the most boring 'attack of the killer....(fill in blank but make sure it is larger than usual and relentless)' movie, which is especially surprising considering that THEM features giant killer-ants which seems like a winning plot-line) it would involve mutant bats released from a sealed cave that opened during a recent earthquake. These bats would wipe-out the Argentinian super colony of ants of Southern California or at least keep the kitchens and cat food bowls of residents ant-free!

Saturday, April 2, 2011

The value of bats in monitary form no-less than $3 billion dollars and counting

Today I was sent a link to an interesting new article about the value of bats from an economic standpoint. This recent SCIENCE article (summary link here) suggests that bats may be worth at least $3 billion dollars per year in the services they provide (free of charge I am left to assume but if they started charging bats would be rolling in cash to say the least!)

The article 'Economic Importance of Bats in Agriculture' by Boyles, Cryan, McCracken and Kunz was published in Science this month (331: 6025, April 2011) (for link click HERE). A figure (above) from Boyles et al. 2011 (SCIENCE) illustrates the worth of insectivorous bats with warmer (redder) colors indicating higher financial worth relative to cooler colors (yellow) in the US.

Indeed, the bat-services discussed in the article are focused on those of pest-control by insectivorous bats. Because insectivorous bats must eat many insects every night to maintain their high metabolic demands they are responsible for maintaining lower agricultural pests that would otherwise destroy crops. Thus bats are able to save farmers costs in pesticide use. As the horrific White Nose Syndrome moves gradually westward we can hope these services will still be performed by hungry bats in the West not yet impacted by the disease. However, the Eastern bat populations have been drastically reduced in size and we might expect to see an increase need for pesticides in the near-future. Hopefully, funding of research projects aimed and limiting the spread of this disease will increase as the NSF and other funding agencies evaluate the importance of insectivorous bats in North America. This article focuses on the potential impact of White Nose Syndrome bats but it is worth recalling that world-wide bats provide many economically important services.

I would speculate the monetary value of bats in general supersedes that speculated by the authors of the article given other important services provided by bats such as pollination of plants including agaves that result in tequila in the tropics. Furthermore, the dispersal of seeds of remote islands and after hurricanes is another important bat-service. Regardless, the focus of the article is to make people aware of White-Nose Syndrome as something very scary that can impact us all even if we are not bat enthusiasts. I commend the authors for their article that will hopefully help inform the public and legislators while enticing them with considerations of the economic importance of bats.