Tag: Carl Gans

Snake on a wire

February 16, 2018 • 7:45 am

[JAC: In lieu of “readers’ wildlife” today, we have “Mayer’s wildlife”: His disquisition on snake locomotion. Be sure to keep those photos coming in, and don’t worry if you haven’t seen yours yet, as I have them all.]

by Greg Mayer

Matthew sends the following tweet of a tiger snake making its way along a wire fence.

At first glance, two things struck me at about this, aside from its generalized coolness. The form of locomotion is a typical one for snakes called lateral undulation, in which waves of muscular contraction alternate down the sides of the body. You can see the snake is pushing first on one side of the wire, then the other, in waves down the body. This is not unusual for snakes. And there are many arboreal snakes (vine snakes, parrot snakes, etc.) that habitually move along very narrow surfaces, such as vines and branches. The novelty here to me is the length of the narrow surface– most vine snakes frequently encounter crosswise vines and branches, so they don’t move for any great distance in a perfectly straight line along a narrow surface, as this snake is doing.

But its movements are not unprecedented. While checking into this particular mode of locomotion, I found the following in Carl Gans’ Biomechanics: An Approach to Vertebrate Biology (p. 93):

Other climbers show a fabulous ability to throw their trunk into multiple, regular, and controlled bends of very short radius. The African file snakes (Mehelya) apparently can travel along telephone wires with alternate half-loops hanging respectively over the left and right sides of the wire.

The second thing that struck me was that a tiger snake is not a vine snake of any sort– they’re terrestrial. So, climbing along wires is not where I would expect to see them. But that’s book knowledge, and perhaps Australian readers can enlighten us from experience.

On reflection, I was also struck by this being an example of what Gans called “excessive construction”– the ability of structures (and in this case also behaviors) to be successfully used in circumstances that were not part of the historical evolutionary development of the structure. Gans thought, and I agree, that such circumstances can be the basis for adaptation (i.e. heritable changes in the structure/behavior) to the new circumstances.  Again from Biomechanics (p. 14-15):

Gans provides a much more insightful view here of how functions change, and how new adaptations arise, than did Gould and Vrba in their largely unnecessary coining of the word and concept “exaptation“.

Gans, C. 1974 (1980). Biomechanics: An Approach to Vertebrate Biology. University of Michigan Press, Ann Arbor.

Gans, C.  1979.  Momentarily excessive construction as the basis for protoadaptation.  Evolution 33:227-233.

Gould, S.J. and E.S. Vrba. 1982. Exaptation- a missing term in the science of form. Paleobiology 8:4-15. pdf

Biology of the Reptilia— online

December 29, 2014 • 8:32 am

by Greg Mayer

Biology of the Reptilia, the 22 volume, 13,800 page, 150+ contributor, magnum opus of the late Carl Gans is now online, thanks to the efforts of the Gans Collections and Charitable Fund, a private foundation run by Carl’s family and colleagues. Carl inaugurated the series in 1969, with the last in 2010, the year after Carl’s death. In the tradition of the great German-language compendia, the series sought to compile all of the scientific knowledge about reptiles. The 22 volumes consist of 9 on morphology, 5 on physiology (including much on physiological ecology), 3 on neurology, 2 on ecology, 2 on development, and a final volume of bibliography. Carl had wanted even more to be included, but the series is a tremendous achievement, a monument to his editorial skill and sagacity, and to the breadth of his knowledge, interests, and influences. It is fabulous to have the full text available online.

Biology of the Reptilia Gans 1 (2)
The title page of my copy of volume 4 of the Biology of the Reptilia, signed by Carl.

An appreciation of Gans and the series is given in the foreword to the final volume by Harry Greene, and the preface by Kraig Adler is also invaluable as an appreciation of the series and its accomplishments. I knew Carl through our association with the Museum of Comparative Zoology, where we both did our doctoral work (Carl completing his in the year I was born!). Volumes in the series were fairly expensive, and I have only 4: one of my favorite volumes in the series, the one above (signed by Carl himself); another favorite, volume 16 on ecology; and two others. I have not been able to get a copy of one of my other favorite volumes, volume 7, on ecology.

The online version provides a convenient table of contents to the full series, and a very useful comprehensive index. Each volume is rendered as a series of single-page-per-pdf files. You can advance or go back a page at a time, or jump to a particular page by entering its number in a box. Searches can be done within pages using control-f. On my computer, the number typed into the box cannot actually be seen (the box is too small– the text of the numerals extends out the upper margin, so only a tiny part of the foot of the number can be seen). I’m not sure if this is browser or computer specific, or something they can fix at the site. The page-by-page pdfs means that it is not possible to download a pdf of an entire article (except by doing it one page at a time). With five different publishers over the years, three of them for-profit, this was probably a necessary compromise to get the full text online. So, the online version will most conveniently be used for onscreen reading.

When Matthew emailed me that the complete text was online, I emailed him back

I didn’t know– this is fabulous! Just last night I was thinking, “Man I wish I had the volume on the squamate skull.”

Well, now I can read the volume on the squamate skull, and it really is fabulous.

h/t Matthew Cobb