Monday, December 16, 2019

Answer: Does anything live deep in the earth?

Let's go deep.  

As discussed, I have NO IDEA what animals might live deep in the earth. But... 

Anyone down there? 

Does anything live down there?  How far down in the earth does life extend?  

You can see where this is going.  Our Challenge for this week was:   

1.  What, if anything, lives deep in the earth? I know moles, earthworms, ants, and gophers live in the earth--but they don't go very deep.  Are there any creatures that live REALLY deep in the earth? If so, what are they like?   

I started my quest with a straightforward search: 

     [ life deep in the Earth ] 

I was pleased to find some interesting reports about life deep in the crust of our planet. and reports that there's life, specifically nematodes, that life about 1 miles (1.6 m) underground in South African mines. 

Unidentified nematode (Poikilolaimus sp.) in a biofilm of microorganisms, from under Kopanang
gold mine in South Africa. By Gaetan Borgonie/Extreme Life Isyensya, Belgium.

This report is from the Deep Carbon Observatory (DCO), a collaborative network of geologists, chemists, physicists and biologists searching for life deep underground.  

That's great!  Not only is there small life way underground, but there's an entire network of people looking for it.   

First question to ask:  Who / what is the DCO?  It's easy to find the DCO home page, which describes them as  

"...a team of scientists...with the support of the Alfred P. Sloan Foundation [investigating] how the deep carbon cycle drives our world.
The DCO brings together a multidisciplinary group of scientists, including geologists, chemists, physicists, and biologists.
The DCO Science Network, is made up of more than 1200 scientists from 55 countries..."  

I've heard of the Sloan Foundation. That's a well-known research support foundation that does large grants to further science throughout the world.  They're credible, and when I check the Sloan site, I see their initial grant to Oxford to start up the DCO.  And I see their management team at the Carnegie Institute.  (Another well-known research place.)  

I clicked through on the link to the original report from DCO and found more data.  I didn't know that they also have a project that has drilled 2.5 kilometers into the seafloor, and found microbes in boreholes more than 5 km (3.1 miles) deep.  

In addition to nematodes, two types of microbes—bacteria and archaea—dominate the deeper parts of Earth. There are millions of distinct types of bacteria, most yet to be discovered or characterized, that form a kind of microbial “dark matter.” Deep Life scientists say about 70% of Earth's bacteria and archaea live in the subsurface.  

That's astounding.  

Deep microbes are often very different from their shallower relatives, often with life cycles on near-geologic timescales.  

In some cases, they exist on nothing more than rocks.  No organic materials input required.  They directly digest and get energy from the minerals themselves.  

What's more, the
 genetic diversity of life below the surface is comparable to or exceeds that above the surface.  

Luckily, the DCO page (above) links to their peer-reviewed work.  Here's a sample from that page: 

The biomass and biodiversity of the continental subsurface. (2018) Nature Geoscience Magnabosco C, Lin L-H, Dong H, Bomberg M, Ghiorse W, Stan-Lotter H, Pedersen K, Kieft TL, van Heerden E, Onstott TC

Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floor. (2015) Science Inagaki F,  (et al.)  

What this tells me is that indeed, life DOES exist way down deep into the earth, and that it's remarkable.  

One of the terms I picked up as I read through these reports is microbiome--that is, the collection of microscopic bacteria and other organisms that live together in a particular environment.  Learned that term led me to do this query: 

     [ deep underground microbiome ] 

which leads to all kinds of articles.  In these articles we find that: 

* deep earth life holds 15 to 23 Billion tonnes of Carbon, 245 - 385 times the carbon mass of surface-living humans
* that is, up to ~70% of Earth's bacteria and archaea live underground... not out where we can see it!  
* deep underground microbes are very different than surface microbes, living life on near-geologic timescales, in some cases consuming nothing more than energy from digesting rocks, 
* the genetic diversity of life below the surface is comparable to or exceeds that above the surface,
* microbial community richness relates to the age of marine sediments where cells are found—suggesting that in older sediments, food energy has declined over time, reducing the microbial community

The absolute limits of life on Earth in terms of temperature, pressure, and energy availability have yet to be found. As we learn more, the records are continually broken. 

A frontrunner for Earth’s hottest organism is Geogemma barossii, a single-celled organism living in hydrothermal vents on the seafloor. Living in hydrothermal vents on the seafloor, this microscopic spherical bacteria survives at 121 degrees Celsius (251 Farenheit; that's 21 degrees above the boiling point of water).   

And... the depth? 

The record depth at which life has been found below the surface is approximately 5 km (3.1 miles).  Meanwhile, the record below the ocean is 10.5 km from the ocean surface at 4000 meters depth below the sea floor.  (That's nearly 11 km (6.8 miles).)  

Admittedly, these are only microbes--but they're amazing and live under extreme conditions (which is why they're called, collectively, extremophiles , but also, hyperthermophiles for those that like it hot).  

Ultimately... I think we've found our answer--at least for the moment.  Nematodes (multicellular life) can exist down to 2.57 km (1.6 miles) underground, while bacteria can make it to nearly 11 km (6.8 miles).  

But I'm sure we're find more, deeper, probably hotter in the coming years.  

Other notes: 

SRS Regular Reader found some great content as well.  Arthur Weiss found this superb BBC documentary about deep life focusing on nematodes (including the remarkable  Monhystrella parvella, which lives at 2.2 miles (3.6km) down.  See also the article in Nature (a very well-known scientific journal) about the deep-living nemtodes of South Africa.  

SRS RR Jon (the Unknown) found that CBS 60 Minutes had done a segment on this: What lies two miles beneath the Earth's surface?  (It's a bit painful to watch--you can't skip through the ads--but it's got some great visuals.) 

Research Lessons 

While it wasn't hard to do this piece of research, there's certainly a lot of stuff to wade through.  

1.  Keeping all of the research findings straight takes notetaking.  I know that I needed to keep a set of notes (in a handy Google Doc) with just the URL, a word or two about what's relevant, and whether it was from a reputable source, a peer-reviewed journal, or simply a news site.  

2.  Pick up specialized terminology as you read.  Once again we found that as you read, you should pay attention to the specialized language of the articles you see.  That's how I picked up the term "microbiome," which led to many excellent articles.  (Why did that work so well?  Because it's kind of a technical term that's used in kind-of-technical articles, which is what I was looking for.) 

Excellent job this week.  

Search on!  

P.S.  Sorry about the delay in finishing this SRS answer.  It's the end-of-the-year... what can I say?  There's a lot going on!  

Wednesday, December 4, 2019

SearchResearch Challenge (12/4/19): Does anything live deep in the earth?

As you know, I love diving... 

... and although I never go much below 100 feet (33 meters), I'm fascinated by the creatures that live way down deep in the sea.  They're interesting, wonderful, and exceedingly strange.  

But... as I was talking with a friend yesterday I realized that while I have a pretty good idea of the animals that live in the bottom of the sea, I have NO IDEA what animals might live deep in the earth. 

Any creatures down there? 

That made me curious:  Does anything live down there?  

You can see where this is going.  It's time for us to go deep.   

1.  What, if anything, lives deep in the earth? I know moles, earthworms, ants, and gophers live in the earth--but they don't go very deep.  Are there any creatures that live REALLY deep in the earth? If so, what are they like?   

How would you start a search like this?  

I'm really curious about two aspects of this: 
     (a) How far down in the earth does life exist?
     (b) How do you (the researcher) know? 

What counts as a credible source for an SRS Challenge like this?  (Few of us are going to actually go check it out, so what makes you believe a particular source?)  

I'm really curious to see what we can discover.  

How far down into the planet does life exist?  

Let us know what you find.  Be sure to say HOW you found it, and WHY you believe the source!  

Search on!  

Tuesday, December 3, 2019

Why connected people are also better searchers!

I bet you’re a skilled online searcher... 
....if you’re reading this, you might even be an expert at online search. 
Note:  This post originally appeared in the blog, Connected Learning.  
But improving your search skills is one of those things that will pay dividends way beyond your expectations. That’s what this post is really all about—how to be much better at digging up the content you need to find fast, accurately, and with skill.
This is the premise of my new book, The Joy of Search: A Google insider’s guide to going beyond the basics (MIT Press, 2019)

There are the tips and tricks that you’d expect from a book like this—the tactics that great online searchers know, but there’s much more to know about search than knowing about when to use double quotes. That’s just a little tactic you should have under your fingertips. Instead, knowing the big strategies of search can shift your searches from merely okay to truly great.
At the heart of this book are 17 compelling search stories—each one starting with a question that you (or a student) might have, something that you find curious or startling about the world. How you go about answering that question is the story for each chapter.
In the spirit of Connected Learning, one of the most important strategic things great searchers do is to rely on their personal set of connections to amplify the range and scope of what they can find. This message resonates throughout all of the stories and is an important lesson: One of the properties of great researchers is that they have a great set of connected people they can contact with questions.  

Serendipity amplification
As you know, serendipity can be amplified by social networking—just letting people know of your interests can open up connections you might not have known about. Networking casts a broad net on your behalf and suddenly you’ve got dozens of eyes and ears scanning the world around you for your research questions. It pays to have friends.
Mudejar Stars
Mudejar stars are a common design feature in Spain. Where do they come from?
For instance, I’d mentioned my interest in Mudejar stars (a kind of Moorish visual design element) to a couple of friends, and sure enough, just a few days later, one of them emailed me this link to a podcast on that very topic. (To be honest, I hadn’t thought of looking for a podcast about Mudejar stars—I’d assumed it was just too obscure a topic for someone to dedicate an entire podcast. How wrong I was!)
The point is, social media and social networks are big players when researching online content, if only for the powerful effect that recommendations have on people. When you’re doing online research, your social network (and implicitly, all of the social media systems and tools) can be an incredibly valuable ally in your research. Your Personal Learning Network is the golden circle of friends. The players and the platforms may change over time, but it’s worth cultivating your personal network of friends-who-know that you can ask for help. That network should transcend the particularities of whatever platform happens to be in fashion at the time. (Anyone remember the MySpace social media site? You still have those friends, right?) In my studies of really extraordinarily skilled researchers, one striking thing I noticed was that they all had (and used) deep and broad Rolodexes, or what would today be called “social contact lists.”

Writing a mini-essay is useful to organize your thoughts
A useful strategic trick to get to a deeper understanding of your research question is to write up a mini-essay that presents all of your information and frames what it is you’re trying to figure out. I’m 99% convinced that having to write something down (and have that writeup make sense) is a great method to making sure that all of your ducks are in a row. If you’re being honest with yourself, you’ll pick up all KINDS of mistakes in your reasoning and data.
Naturally, the simplest, fastest way I know to write a mini-essay is a social one: send an email to a friend who shares your interest—ideally, someone who doesn’t know TOO much about the topic so you’re forced to explain the idea in some detail. In my case, I bombard friends with emails that start out “I bet you didn’t know that…” and then I write on and on about. The key thing is that in order to write that mini-essay (or email), YOU have to make sense of what you’ve found. You won’t just write gibberish to a friend (at least, I don’t recommend that), but you’ll see any gaps or inconsistencies in what you’ve discovered.

Content continues to grow in quantity and kind
The Joy of Search is also about the future of online content and how to be future-proof in your online research skills.
There’s every reason to believe that content will continue to grow, both in the amount of online content and the different kinds of content. A perpetual challenge as new kinds of resources become available will be how well they can be indexed. Although it doesn’t make much sense to create a new kind of online content that can’t be found by search engines or online catalogs, it happens every day, leaving unhappy researchers having to manually track down the content without the aid of an online index. One side effect is that media literacy will be an ever-evolving concept. How media is used will continue to change, and as new kinds of media evolve, so too will the way they’re used.

Content continues to splinter 
It’s not much of a prediction to point out the obvious— new content providers will arise, new media types will continue to be invented, and walled-gardens of all kinds will continue to operate and flourish. The side effect of these forces is that searchable content will continue to be in unsearchable silos. The good news here is that there are also shifts towards increasingly open access publication. But as the publishing industry continues to search for an effective funding model, we, the researchers, should expect information to still be in repositories, some of which are open, some of which are not. Some will require payment to read their content, others will be free and open to the public. The more you know about these trends, the more you know about what you can find and what’s possible to research online.
For instance, local historical societies and libraries often have great historical information. For more than one piece of research, I’ve used the “look for a county historical society” trick to locate a nearby cache of archival photos and materials. Keep that in mind when you’re searching for this kind of information. Often, their archival content is splintered offline or is difficult to search. A phone call and a visit in real-life will often give you great results through the help of friendly librarians and archivists.

And yet..
But at the same time, one of the surprises (and delights) of my work has been learning about the vast quantities of information that’s available on an immense variety of topics. Want to learn about different diseases of abalone  (Viral? Bacterial?), it’s simple to do. How about dressage style of the 16th century? Sure. Not a problem. Want to see 19th century records from Ellis Island immigration? That’s simple too. There is just an amazing amount of content online.
In other words, the kinds of research that used to be a huge hassle is now fairly straightforward as more content becomes available. This stuff is either “born digital” content, or becomes available as older content is scanned and indexed. That’s how you can learn about 16th century Italian dressage; the Google Books project scanned and then indexed the original text. Sure, it’s in Renaissance Italian, but if you’re not up on that, at least you’ve got the pictures.
One of the consequences of this is that new content is popping up all the time—new web sites appear minute-by-minute (there were 1.3 million new website domain names registered in the first three months of 2017, up 3.7% from 2016). 
New online applications let us see content in new ways (such as the site, which specializes in this kind of seeing-in-new-ways of data, or Google Earth VR, which lets you fly through a 3D model of the Earth, including many city buildingscapes).
And the side effect of that is that you can’t really keep up-to-date on what’s newest and greatest in your field. Instead, you’ll have to keep your eyes open, and periodically search for new content in your area of interest. We have shifted into an age of information triage—separating out what’s useful and important from the stuff that isn’t.
These skills are something we should all command. Having the methods of online search, and understanding the range of what’s possible to search for—that’s a potent combination. That’s what these stories are all about. 
May you search bravely, with skill and alacrity in the future.
Search on.  

Wednesday, November 27, 2019

Answer: Where'd the river go? What's the logo?

I first noticed the river's end because it didn't make any sense to me...  

When I went on my run, I got to that point at the river's edge and noticed that it just sort of... stopped!  That's the part that didn't look right to me.  How can a big river like this just quit?   

Here's a closeup of that part.  River's just don't do this.  They fan out, or get narrower and smaller--but they don't just just squared off at one end.  At least they don't do that naturally.  Here's a closeup: 

So this is an engineered cutoff.  But why?

1.  What's the story here?  When was the dark green river cut off from the pale green river?  Can you figure out when this happened?  How about WHY it happened?  What was the city hoping to accomplish?  

Like SRS Regular Reader Arthur Weiss, I thought this was an old bit of engineering.  So I looked for old, archival maps to start--I was hoping to see the original course of the river.  And while I could find lots of OLD maps (like this one below from 1860), it was remarkably hard to find maps that showed the river just outside of the city.  Here's one from 1826 that shows a very different river (islands!).  

Map of Seville from 1860.  Wikimedia.

That's when I turned to the Wikipedia article about the Guadalquivir river. I read the article and, like Arthur, noticed the map showing the various construction projects on the river over the past century.  

Map by Álvaro C.E. From Wikipedia.  

Look at the very top of the map--the Tapón de San Jeronimo is that bit of geo-engineering that cut off the river at the north end.  But read this map carefully--you'll see there have been a number of significant re-routes of the river.  In particular note that the old canal, Antigua corte de Chapina, has been filled in.  That area, like the Tapón de San Jeronimo is now used for something else. 

And, again, like Arthur, searching for:
     [ Expo 92 Tapón de San Jeronimo ] 

led me to the Washington Post's 1992 article about the engineering projects in Seville, including the creation of the Tapón in 1987.  

I also found this great diagram that lays it all out for us (from a great article on all of the engineering work needed to create the Expo 92 grounds).   

Geo-engineering on the Gudalquiver River in Seville.  From the History of the Seville Fair site.

All of this work over the years has been to control the periodic and terribly damaging flooding, with subsequent changes to fix problems that each solution caused!  (Prediction: There will be more river-engineering in Seville over the next 100 years.)  If you're interested, another article goes into great detail about the various projects over the years.  This was not a simple task!  

The second Challenge was obscure, but actually easy to solve... 

2.  What is the story behind the NO8DO logo?  Why does it appear everywhere in Seville--from a tomb in the cathedral to lampposts downtown, on sewer covers, and even the tops of bollards?  

As you see, the "8" symbol isn't just a numeral 8.    But I was puzzled about what it was--sometimes it looks like an infinity symbol, sometimes it looks like a skein of yarn.  

Here's a beautiful version of the logo as it appears on Christopher Columbus's tomb in the Cathedral: 

Reverse image search works well here, but I initially did the obvious search for: 

     [ NO8DO ] 

and quickly learned that this is the city's logo.  

The story goes that this logo began with the 13th-century coat of arms awarded to Sevilla by King Alfonso X the Wise for the city's loyalty. 

He gave this odd mark in gratitude for Seville's support of his wartime efforts in his battles against his son, Sancho IV of Castile.  

Sancho IV wanted to usurp his father's throne during the Reconquest of Spain (an immensely long power struggle on the Iberian peninsula, of which this is just one part).    

As you can see, between the ´NO and ´DO´ is an 8-shaped bundle of wool (madeja in Spanish). 

When you put all three elements together it forms a kind of rebus. If you then read it quickly, it sounds like no-madeja-do which,  more correctly would be spelled out as 'no me ha dejado' which means  "it (the city) has not abandoned me."  

It's a small award for a dangerous task, but hey, it's royal recognition! 

Search Lessons: 

1.  Diagrams are great.  Be sure to read them as they often have clues that are useful in your quest.  Don't just gloss over them!  

2.  Google Translate rocks!  I read Spanish, but there were lots of vocabulary I'd never heard of in these texts.  (tapón, pasarela, etc.)  But with the autotranslate feature of Chrome turned on, I was able to navigate all of these pages fairly quickly. 

3.  The MOST OBVIOUS search queries sometimes work really well.  We now know that the symbol in the middle of the NO8DO logo is not an 8... doesn't matter.  So many people have written about the logo as though it were a number 8 that this search works well.  Remember that you're searching what other people have written about these things.  Go with what's right in front of you--go with what's obvious, and that will often turn out to be the right thing.  

Search on! 

Wednesday, November 20, 2019

SearchResearch Challenge (11/20/19): Where'd the river go? What's the logo?

Travel is always surprising.  

At least it is to me.  I go somewhere, and I usually find myself asking WHY questions.  I know I must sound like a 6-year oldwhy...why...why...why but those questions often lead to fun adventures, and I definitely get my curiosity scratched in the process.  

Last week I was in Seville, Spain to give a talk at an educational conference (ICERI, for the curious).  I did all of the usual tourist thingsa visit to the cathedral, walking through the narrow streets, a visit to the glorious Plaza de España and the Parque Maria-Luisa.  

But among all of the glories of Andalusian Spain, I noticed two things in particular that I had to go look up, and I thought you might find them interesting.  

As is my habit, I went for a run near the hotel.  As it turns out, the hotel I was at is right next to the Guadalquivir river.  Here's the path I took from the hotel...  

If you look carefully, you'll see that the river has two branches--a pale green one running straight, nearly due north/south, and another part that's dark green.  

It's pretty clear that the curvy part used to be the original path of the river, while the pale green section is a channel that was added.  

But what surprised me on my run was to see that the dark green river apparently used to connect to the pale green river.  When I got to the northern part of my run, it was pretty clear that the river was cut off at some time in the past.  If you go to this location on Google Maps you can easily see that this is a bit of geo-engineering.  Someone at sometime cut off the river.  Why?

And this leads me to our first Challenge of the week: 

1.  What's the story here?  When was the dark green river cut off from the pale green river?  Can you figure out when this happened?  How about WHY it happened?  What was the city hoping to accomplish?  

If you look carefully at the above image you'll see that I was running towards the "Huevo de Colon" statue.  If you remember, we actually talked about this moment in history in this blog, way back in 2012 when we were looking for a phrase that captured the idea of a problem that seems impossible, but actually has a simple answer.  The answer was "The Egg of Columbus."  This statue is Seville's monument to that story.  

But on the way there I also noticed something that I couldn't explain and HAD to look up when I got back to the hotel.  I kept seeing a particular logo on many of the city pieces of infrastructure.  It's looks like NO8DO, but not quite that.  Here's a collection of those logos: 

As you see, the "8" symbol isn't just a numeral 8.  

Here's a beautiful version of the logo as it appears on Christopher Columbus's tomb in the Cathedral: 

I saw this logo everywhere in Seville... but what was it trying to tell me?  

2.  What is the story behind the NO8DO logo?  Why does it appear everywhere in Seville--from a tomb in the cathedral to lampposts downtown, on sewer covers, and even the tops of bollards?  

Can you figure these two little Challenges out?  

As always, let us know what steps you took to come to an understanding.  

Search on!  

Wednesday, November 13, 2019

Answer: How many species aren't 1:1 in gender ratios?

You'd expect it to be a 50/50 split... 

... that is, the split of sexes in any particular animal population. 

But, as we've noticed before the majority of parrotfish on a reef are female (see our earlier blog post about parrotfish).  

The  Atlantic Monthly article that started off this Challenge points out that the majority of bats in museums are females, but other species (like bison or bears) tends to skew primarily male.  Really?  Is this due to the way animals are collected, or do the animals really have an intrinsic difference in their sex ratios?  

There are more female bats than males bats in museum collections, but more bison and bears are male in those collections.
Can that possibly be true in reality?

Thinking about this made me wonder about this topic more generally: 

1.  Do most animal populations consist of males and females split roughly 50% and 50%?  

2.  If that's not true (and it's clearly not for parrotfish), what causes a species to have a non-equal split between males and females?  What kinds of animals have very different splits?  

I started with a basic query: 

     [  sex ratios animals ] 

(I used "sex" rather than "gender" because the term gender typically implies some kind of social agreements, and for animals I just wanted the biology.) 

But even before I read the SERP, I realized as I was typing the query that I already know about the changing sex of parrotfish AND the fact that something like 90% of all honeybees are female.  So when I saw this set of results, I wasn't terribly surprised... 

There are scholarly articles about sex ratios, and 4 different results at the very top of the results (indicating that these are especially relevant to the topic of the query).  

To do a quick scan, I did a bit of parallel browsing (see our earlier discussion), opening the  top is 7 links, as well as all of the Scholarly articles, the Wikipedia article on sex ratio, and that LiveScience article about "Why some species have more females than males."  

My goal in opening all of these parallel tabs was to get a quick broad scan of the topic (rather than just trusting the first result I saw).  

Sure enough, I quickly learned that: 

- sex can be determined by environmental conditions; it's not always genetically determined!   Korpelainen, Helena. Sex ratios and conditions required for environmental sex determination in animals. Biological Reviews 65.2 (1990): 147-184.
- the sex ratios for sex-changing animals are different in female-first animals (vs. male-first) Allsop, D. J., & West, S. A. (2004). Sex‐ratio evolution in sex changing animals. Evolution, 58(5), 1019-1027.
- there's value in having more males in animal populations that are environmentally stressed McGinley, M. A. (1984). The adaptive value of male-biased sex ratios among stressed animals. The American Naturalist, 124(4), 597-599.

So my naive notion that animals come in roughly 50/50 male/female splits went out the window in a hurry!  

That was a great start to my Research Question, preparing me for reading the Wikipedia article on Sex Ratios among animals.  I read this article and clicked through to several of the articles that were linked there.  (It's got a pretty great set of links.)  

Here's what I found:  

Among many species of animals, in general, the ratio is 50/50.  Why?  

According to Fisher's Principle, i.e., with all other things being equal, it's most beneficial to produce a balanced sex ratio in the children because it leads to the maximum chances for reproduction in future generations.  (It's an interesting game theory article--worth a read.)  

But the catch phrase here is "all other things being equal."   I learned there are lots of special cases here.  

The other hits on that first SERP told me that 

* the Seychelles warblers are 90% female.  When females are in high quality territory, they primarily produce female chicks. They seem to have pre-ovulation control of offspring sex ratio. Likewise, when they move into low quality territory, the chicks become much more male.  
* likewise, Wood lemmings are 66% female.  They have two different types of X chromosomes, the normal X and a mutated X*. This leads to three genetic types of females: XX, X*X and X*Y and one genetic type of male: XY. The X*Y females are fertile, but only produce X* ova, which means they only produce female offspring.
* the wasp Nasonia vitripennis has few or no male offspring.  Ever.
This is pretty amazing stuff.  This tells me that while the majority of species have a 50/50 split, there are lots of animals that have REALLY variable sex ratios.

Of course, now I'm interested in bats.  What is their sex ratio?   

     [ sex ratio bats ] 

leads quickly to articles that tell us: 

* bats in the Thar desert (on the border of India and Pakistan) come in all three conditions depending on species:  there are several male-dominated species, several female-dominated species, and a few 50/50 splits. 
* hibernating bats (Pipstrellus subflavus) in the northeast United States are predominantly female
* meanwhile, the Big Brown Bats (Eptesicus fuscus) in Michigan are predominantly male (60/40 split), apparently because the males live longer.  
You see the point.  Bat sex ratios vary by species, by region, and by time of year.  If you collect hibernating bats (which is really easy--they don't fly around much), you'll get a very different result!  

Our other Research Question for this Challenge is WHY?  

We're starting to see some hints:  

- group organization:  parrotfish live in harems with 1 male and many females (with the largest female converting to male when the pod loses the male).  Likewise, ants and honeybees live in eusocial groups which have a single female (as a queen) and many others in sex-defined roles, often as females, 

- genetic mechanisms: such as the Wood lemmings which have 3 different sex chromosomes, or parthogenesis among other animals (primarily insects, fish, and lizards) where all members of the species are female (and therefore genetic clones),  

- environmental conditions:  temperature of the eggs plays a big part in determining the sex of American alligators and other reptiles (see: temperature-dependent sex determination)

- infection:  Infection by the Wolbachia bacteria causes skewed sex ratios in some arthropod species as the infection selectively kills males.  As a result, some isopod species start off at 50/50 male/female, but the males die off due to the infection before they're born.  

Other things found while researching... 

* among mallard ducks, males are around 60% of the total population, with lots of local variation (probably due to different predation patterns), 

* at the National Zoo in DC, they have an Asian Water Dragon (Physignathus cocincinus) that had a parthogenetic birth.  See the video below for mother and daughter... 

There is a significant shift in sex ratios among some animals by age.  The most interesting example is that of humans.  (These numbers are male/female.)  

     At birth:  1.05  (according to WHO, 2019
     At age 50:  1.00 
     At age 90:  0.50

Here's that data graphed out (ibid):  

Data from WHO. World health statistics, p. 4.  

This tells us that men die at a faster rate than women once they get beyond age 60 or so.   

Research Lessons 

1.  Use parallel browsing.  Parallel browsing is a great technique for getting a lot of different perspectives all at once.  Especially for this kind of topic, I was able to quickly see that my assumptions were NOT correct, and then able to drill down into the different leads that I had.  (This is a great way to avoid confirmation bias!)  

2. Search for mechanisms.  It's pretty simple to find the sex ratio differences, but looking into the causes underlying the differences opens up an entirely new set of issues.  I could have easily written a MUCH longer (and fascinating) blog post just about why these ratio differences occur.  In general, looking into the underlying mechanisms is a great strategy for understanding any topic.  

Hope you had fun with this! 

Search on!