Personalized flowcharts: A technique for learning identification in a very effective manner

Happy Spring 2023 all readers of these blogs. Field season now really kicks off for another year and in the spring a young biologist’s fancy lightly turns to thoughts of… species identification (with apologies to Alfred, Lord Tennyson). Accurate and confident identification to species can be very challenging. I personally greatly struggle with tree identification despite decades of working on it; still not totally confident in my abilities. The common and easy ones, sure I can get those; but give me something unusual or new and I am thrown for a loop.

The most powerful technique that I know to learn species identification for a group is by creating your own flowchart, or you could make a dichotomous key if that is your preference. The value in developing your own pathways of identification is that you customize for your situation and, most importantly, you determine for yourself what is key to look for. The limitation to typical keys and flowcharts that you find are they include too great a geographic scope (your province rather than the region you live in) and often include features a field biologist will not see (labial grooves of a salamander; number of scales on head of a snake; gill raker count of a fish). In creating your own guide, you customize for your area and what you are likely to be able to observe.

Below is a flowchart I have created for frogs and toads of Vancouver Island, where I live. It is a pretty simple chart as we have a fairly depauperate amphibian fauna here (total five species frogs and toads – two of which are introduced).

The value of this graphic, over those developed by other, far more experienced, professionals (and with all respect to them), is that it focusses my observation on less than half of the total of twelve species in the province. Five species I can easily learn… a dozen is more challenging. It also forces me to decide what features I will use in the field to identify. I will not have a microscope, am unlikely to capture and handle the animal, and am very likely to be watching them through binoculars sitting on a muddy streambank. The features I use must be obvious and easily seen irrespective of angle of view or light level.

It was in the act of creating this diagram that I figured out, for myself, what the key features are to identify and a path to provide an order to look for these features. So, for the area that I live and do much of my work, I can identify my frogs and toads simply by:

1: Distinguishing frog from toad. For my island there is only one toad species so that path ends there. If animal is a frog, I then:

2: look for presence of mask. This gets me down to two species in each lower group. I can then use an assortment of features to confirm which of the two it is. These obvious features for me to look for are:

  • Dorsolateral folds
  • Size

There, now I have something manageable. All I need to do is be able to discriminate frogs from toads (which I have been able to do since an eight year old boy playing in ponds) and look for size, facial mask, and dorso-lateral folds. These I can remember to look for. I like to include a few extra tips (e.g., black flecking vs solid colour; red on legs for red-legged frog; fold of skin and sacral hump for bullfrog; sticky toe pads for treefrog). These are, to me, confirmatory features; they help me be confident in my identification… but they are not what I initially look for. I may get a chance to see them if I handle the animal or it sits still long enough for me to really get an excellent view (I certainly do not count on the patience of the animal though, they usually leap well before I am done observing).

This chart or key, however you develop it, should be personal. It does not have to follow standard rigid scientific conventions. Notice in the case shown here the lack of scientific names and absence of description of the anatomical features (sacral hump, dorso-lateral folds, tympanum, etc.). And likely particularly jarring, my use of imperial units in place of metric. This is because the diagram is for my personal use and so does not have to follow any conventions – I can make it anything I like. So, I don’t need scientific names because I know precisely what I mean. There are no diagrams of the morphological characteristics as I am familiar with them. And, yes, I use imperial units. I find it much easier to remember a treefrog is ¾” to 2” long, as opposed to 19-50 mm; same with bullfrog, 3-8” rather than 80-200 mm. 

Patient reader, I hope that you can see the value to this method; that the time spent researching and developing your own identification key allows you to truly learn what to look for. It is active learning by creation and engagement, not passive learning from someone else’s key. The tremendous value to an approach such as this is it formalizes and structures your observations. It gives you a map of what to look for. This is in contrast to simply carrying around isolated descriptions of each species. It becomes clear what separates one species from another.

Now to make my flowcharts for identifying local amphibian eggs and larvae to accompany the adult guide…

Photo credit : Mackenzie Anderson 

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