Constructing Fiddler Range Maps, part 1: History

This is the first of four planned posts about how I constructed the range maps for fiddler crabs. This first part (likely the longest) will give the history and background of how these maps were drawn in the first place. The second part will discuss where the maps become problematic when we want to use them as input data for analysis. The third  part will present a possible solution to the problem detailed in the second part. The fourth and final part will step back and ask if we’re actually thinking about range maps the wrong way entirely.

1. The Original Maps

In mid-2002 I decided to add maps depicting the distributions of each fiddler crab species to the website. I don’t recall why; possibly I just wanted updated information, possibly there was another motivation. This might be around when I expanded the site beyond its original collection of photos, videos, and references to be a bit more species-information-centric. The maps that ended up on the site were constructed in the roughest way possible.

The base data that went into each map started with the maps from Crane’s 1975 monograph.

Map 9 from Crane (1975) depicting the range of four fiddler crab taxa.

Using this as the starting range, I pored through the literature post-1975 (more or less) to look for publications that might have information altering the ranges presented by Crane. Once I’d established an updated range for a species, a background map of the coastline was drawn for the appropriate area using the first version of my spatial software PASSaGEThis map was imported into a graphics program (Photoshop? MS Paint?) and the range was hand drawn with a transparent brush and saved as a raster image (GIF of all things) for display on the site. Not precisely high-tech, but it got the job done.

Original hand drawn range map of Uca maracoani.

One obvious problem with this approach was updating a map often required redrawing it from scratch, particularly if the range needed to be reduced rather than expanded. Not the most efficient approach and not the best quality.

2. The Interactive Maps

At some point between 2011 and 2013, the entire website was rebuilt from the ground up; this is when the site was transitioned from hand-coded to dynamically created from a data back-end. How to handle the range maps was an interesting question, and after some exploration Google Maps seemed to be a good solution. By creating a custom KML layer for each species, I could use the Google Maps API to insert an interactive map into the webpages.

The challenge was how best to create the KML layers with the species ranges. The solution I came up with had a couple of different parts. One key element was to take advantage of the fact that (adult) fiddler crabs are essentially restricted to marine coastlines (they go a little bit inland into river mouths and estuaries and the like, but on the  global scale this is still within the margin of error of the “coast”). Juveniles presumably get a bit more into the ocean, but even there the limited data suggests most of them seem to stick close to the shore.

Thus, a set of coastline data can provide the entire framework on which to build a fiddler crab range: basically, any given piece of coastline can either be in the range or out of the range, and you don’t have to particularly worry about any space in between coastlines (whether land or open ocean). To create these, I imported a full set of world country borders from within Google Earth (Google Earth made it easy to quickly display, check, and update distributions without fighting with the vagaries of the online Google Maps API). For each country whose coastline had fiddler crabs, I exported the individual country to a KML file, then manually removed the parts of the boundaries that represented interior land borders, leaving only coastlines. Countries with borders that included multiple major oceanic regions were split into their constituent parts (e.g., an Atlantic Panama coast and a Pacific Panama coast). All of these coast outlines were re-imported into Google Earth. For each species it was then just a matter of copying the appropriate country borders into a new folder to represent that species; when only part of a country was in the species range, a copy of that country’s coastline was again exported, manually trimmed to the correct range, then re-imported. While seemingly a lot of up front work, for most species it became a fairly quick and easy method to produce the ranges. Each species had its own folder within Google Earth and the whole set was exported as a single KML file. I then wrote a program to extract all of the individual maps from this file, standardizing certain style elements, and exporting each one to its own individual file for integrating with the Google Maps API on the website. This also allowed the creation of the map which overlaps all of the species ranges with high transparency to get a worldwide view of species density.

Uca maracoani range displayed on Google Map embedded in website.

Updating or editing the maps, while still a bit of work, was substantially easier than with the original ones since it only required changing a subset of the coastline data, rather than redrawing an entire map by hand.

Interestingly, a few people complained about the new maps. As rough as they were, the old ones displayed the ranges in a fairly simple cartoon form which is lost with the more complicated Google Map backdrop; also, the new images are not easily exportable for use in another format (beyond doing a screen grab, as I had to do to display the above figure).

3. The New Static Maps

Recently, as part of some potential and planned updates to the site, I came to the realization that the inability to automatically export the maps to an image for use outside a webpage had become somewhat problematic. After a lot of time spent trying (and failing) to come up with ways to automatically export the layered Google Map, it finally occurred to me that the obvious solution was to back away from the Google Map approach entirely for non-web-based use. In fact, part of the solution was to go back to the beginning. As mentioned above, I’ve written code in the past that can draw a background map given a set of lines or polygons describing coastal outlines (data readily available from a number of online sources). And although it was never part of the original plan, the KML file that is being used to add the Google Map layers has all of the boundary data for the ranges in an already parsable format. Combining these into the site creation code with a drawing module that could export directly to a file suddenly allows us to automatically draw higher quality cartoon maps, much like the site originally had, but automated from the code rather than hand painted. (1) Use the world map data to draw a nice representation of key coastlines. (2) Draw the range data from the KML file on top of this in a different color and with a slightly thicker line to help make it stand out. (3) Export as a vector file format (SVG) rather than raster file to allow scalability for high quality figures. I still use the Google Maps and KML layers on the website for interactivity, but these new maps can be seen and downloaded by clicking on the link directly below the corresponding Google map (the link can be seen in the previous figure).

New range map for Uca maracoani.

On these new maps I decided to use a background map with country boundaries to help make the ranges more obvious, and filled in the land areas to make the maps clearer for species with more limited ranges, but unlike with the original maps, these decisions can be quickly changed and the maps redrawn with minimal effort since they are created programmatically. The range data itself is identical to that from the Google Maps.

For display purposes outside of webpages, these newer maps are quite nice. But all is not perfect if we actually start thinking about using these ranges as data rather than just visual guides. To be continued in part two…

The Indus Fiddler Crab, Uca sindensis (Fiddler Crab of the Week)

For our very first Fiddler Crab of the Week post, our random generator choose the Indus Fiddler Crab, Uca sindensis. Not the easiest species to start with.

The Indus Fiddler crab is a relatively unknown species found on the coasts of Pakistan, Iran, Iraq, and Kuwait. It has also been reported from the United Arab Emirates, near the Oman border (Ismail & Achmed, 1993), so it is feasible that it could be found on the southern shores of the Persian Gulf as well. It is arguably the most abundant species in Pakistan and most of what is known about its biology comes from the recent work and lab of Dr. Noor Us Saher at the Center of Excellence for Marine Biology at the University of Karachi.

It is a smallish fiddler crab (adult male carapace between 9 and 17mm wide, females a little smaller), lacking some of the more conspicuous colors of other species. It is generally grey in color; the carapace has grey and white bands, with the legs a bit darker grey-brown. The large claw of the male is described as generally pink, with a bit darker-purple toward the arm, shifting toward white toward the top and along the dactyl (the upper/movable finger), and more red toward the pollex (the lower/fixed finger). Unfortunately, I cannot find a photo of a living specimen, but some of the basic color can still be seen in this collected specimen.

A specimen of Uca sindensis from Pakistan. Photograph by Sahir Odhano.

This crab is usually found on open mudflats or muddy-sand in the upper intertidal zone, away from the waterline during low tide. In Pakistan it is often found intermixed with another species, Uca iranica; other fiddler crab species found on the same beaches are less likely to directly intermix.

Very little has been reported in the literature about its behavior, although like many species its waving display appears to involve much more than just the large claw. From minimal observations, Jocelyn Crane (1975, p. 108) stated:

“Wave obliquely vertical to lateral straight, the major cheliped not fully unflexed. Minor makes corresponding motion. Several ambulatories on minor side raised in turn during display.”

Phylogenetically, the Indus Fiddler Crab falls into the general category of “broad-front” species from the Indo-West Pacific (IWP) region. It was originally thought to be closely related to (and a subspecies of) Uca inversa, but now not only is recognized as a separate species, but thought to belong to an entirely different group of broad-front crabs (the subgenus Austruca).

So that’s the first Fiddler Crab of the Week entry. It would figure that my first one would involve one of the least-well known species on the planet (although not the very least).

Fiddler Crab of the Week

Starting next week, I’m going to pick one fiddler crab species at random every week to write a post about (no duplicates). With more than 100 species, it’ll take a bit more than two years to do them all, which if nothing else should give me some motivation to keep posting. It’ll be interesting to see which ones are easy to write about and which ones take a little more effort to find interesting tidbits.

Visual Chronologies of Names

One of the things to realize about the site is that it is now as much a research project as it is an information portal (it didn’t start this way…maybe I’ll write up the history of the site at some point). The research project end is a bit poorly defined, but could roughly be viewed as “what types of things can I say, infer, or visualize about fiddler crabs if I collect a whole lot of data on the back end.” Yeah…not very specific.

One idea that had been floating in the back of my mind for quite awhile was how to to visualize changes in taxonomic name usage over time. If one name replace another, how do we show that visually? Not surprisingly, others have thought about this and come up with some solutions. In late December I was sitting in an airport preparing to leave the country for the holidays when I stumbled across a blog post by Rod Page, Taxonomic name timelines for BHL, about just such a question. He mentioned an earlier project called Synonyms that would produce nice looking name chronology charts by mining data from the Biodiversity Heritage Library; unfortunately, Synonyms had gone defunct and Rod had hacked together a rough replacement (as is his wont to do). The Synonyms graphs were exactly what I had been trying to come up with so immediately made note to try to do this with my own data when I got back.

It only took me a few hours in early January to extract the data I needed and get some basic-Synonymy style charts plotted. It took quite a bit longer to fiddle with their formatting to get them “just right.” Let’s look at an example.

For a simple case, let’s compare the names of the genera. For most of their history, fiddler crabs have been placed in one of two genera: for most of the 19th century they were considered to be Gelasimus; since the start of the 20th century they have mostly been placed in Uca. Most of the other genera which have included fiddlers (23 in total) make up a tiny proportion of references relative to these two. Here are their chronology plots (I’m still struggling to come up with a good name for these):



These charts represent the number of publications per year that used each genus as an accepted name (whether a publication named one species or ten, it only counted as one valid use of the name).

Caveat: the database is still largely incomplete after about 1977, so the parts of the figure from the last 40 years are not representative of the full pattern.

A few things stand out from looking at these charts  (some of which I knew already):

  1. Generally, references to fiddler crabs skyrocketed starting in the 1950’s (this is when fiddlers really started being  used as model organisms to study certain aspects of behavior and physiology).
  2. It took about 15 years for the transition to Gelasimus to Uca to really take hold; from the late 1890’s through the late 1910’s, both genera were used in roughly equal numbers.
  3. Although Gelasimus was technically abandoned by taxonomists at the start of the 20th century, the genus continued to be used at a small, but steady pace at least through the 1970’s. It’s hard to see on the graph, but there has been at least one use of the genus as valid as recently as 2006.

Something not obvious from this chart: most of the uses of Uca prior to 1897 are actually references to a different type of crab. For most of the 19th century, Uca was used for crabs in the genus we now call Ucides (the somewhat tortured history of these names has been discussed by others and is summarized in the Systematics section of the main website).

To some extent, these figures aren’t quite as exciting as I’d hoped they’d be, but they still visually illustrate the name usage in a direct and attractive way. These charts are not live on the website yet, but the capability to add them is now built-in to the code and graphs depicting name usage for binomials and specific names, as well as directly comparing synonyms will all be made available at some point in the future, once a few more kinks are worked out.

Once again, into the breach…

On occasion in the past I’ve attempted to start a blog and each attempt has ended rather abruptly with rather few posts. We’re going to try this again and see what happens.

This particular blog is attached to my fiddler crab website ( and will mostly be focused on thoughts about these little critters and their biology and evolution, the website, the science, or related issues such as biodiversity informatics and cyber taxonomy. Or maybe just other stuff as it occurs to me if I find I have nowhere else to vent.

The look of the blog is amazingly bare bones right now, but we’ll see about sprucing it up into something slightly more visually appealing as I get into the hang of this (or not).

I’ll probably tackle the first real posts in the next day or so. I’ve got a couple of topics already in mind…