My Stride is your Half Stride

Dennis Deck

Stride and straddle are fundamental measurements for diagonal strides in tracking but there is considerable variation in the definition of these terms among the authors of popular tracking guides. In preparation for various survey projects, The Tracking Club adopted definitions intended to coincide with those used by James Halfpenny in A Field Guide to Mammal Tracking in North America. Halfpenny measures stride from the heel of one footprint to the heel of the same foot in the next footprint. He measures trail width from the outer edge of the left footprint to the outer edge of the right footprint.

Unfortunately, other tracking field guides have adopted different standards. This can be confusing when you are trying to compare the measurements listed in different guides while puzzling over a trail in the field. At our standards meeting it became apparent that I was not the only one who had trouble remembering who uses what approach. How can something so basic be so complicated?

To help clarify it for myself, I set out to systematically compare six guides in common use. I ignored a sources like Stokes that do not include stride and straddle measurements. The table below summarizes my findings. I use "half stride" to refer to the measurement approach taken by most authors (right foot to left foot ).

Author

Stride measure

Straddle measure

Tom Brown

Half stride but intergroup distance for bounds and gallop

Calls outer width "trail width" and inner width "straddle"

James Halfpenny

Full stride

Outer width

Len McDougall

Half stride

Inner width

Olaus Murie

Half stride but only the inner distance between right toe and left heel

Outer width

Paul Rezendez

Half stride but appears to measure it diagonally from right toe to left toe rather than parallel to the direction of travel

Outer width

Ian Sheldon

Half stride from center

Outer width

I was surprised to note Halfpenny was the only author to measure the full stride. The other authors use what we are now calling half stride, from the toe of the left foot to the toe of the right foot, measured parallel with the direction of travel. In general, then, what we call stride should simply be about twice what most authors report in their guides. So far, so good!

Unfortunately, closer attention to detail shows that it isnít quite that easy since there are several variations. Murie appears to measure the inner distance between the left and right tracks. Rezendes measures diagonally between the right toe and the left toe, an approach that results in a deceptively long half stride measurement for animals with a wide straddle like cats, raccoons, or bears. Adding to the confusion, at least one author still uses the term stride when he switches to a different approach for bounds and gallops. Brown measures the distance between the forward toe of one group to the first heel of the next group, the measurement we call intergroup.

Although these authors disagreed about anchoring the measurement to toe, heel, or center of the track, our consensus was that each approach had merit in certain circumstances (e.g., foot drag blurring the heel print, foot prints enlarging in snow, etc). Choosing the anchor point that yields the most reliable measurement is the key.

I was relieved to find a little more consistency when I started comparing definitions of trail width. Five authors use the outer measurement that we adopted (outside of left track to outside of right track) and four of these call it straddle. McDougall and Brown, call the inner width (inside of left track to inside of right track) straddle.

All in all I came away from this task concluding that each author has more or less adopted his own conventions. This highlights the need to standardize our terminology. In the meantime, be sure to keep in mind how each author defines his measurements in any guidebooks that you reference in the field.