spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online March 16, 2007
Journal of Experimental Biology 210, 1148-1160 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.002493
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jayne, B. C.
Right arrow Articles by Riley, M. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Jayne, B. C.
Right arrow Articles by Riley, M. A.

Scaling of the axial morphology and gap-bridging ability of the brown tree snake, Boiga irregularis

Bruce C. Jayne1,* and Michael A. Riley2

1 Department of Biological Sciences, University of Cincinnati, PO Box 210006, Cincinnati, OH 45221-0006, USA
2 Department of Psychology, University of Cincinnati, PO Box 210376, Cincinnati, OH 45221-0376, USA


Figure 1
View larger version (16K):
[in this window]
[in a new window]

  		Fig. 1. The smallest (SVL=43 cm, mass=9.9 g) and second largest (SVL=184 cm, mass=1137 g) brown tree snakes used to determine the scaling of anatomy and gap-bridging performance. The smaller snake is near the size of a hatchling.

 

Figure 2
View larger version (5K):
[in this window]
[in a new window]

  		Fig. 2. Methods used to quantify the posture of the snake one frame before bridging a gap. The image is a tracing of a right lateral view of a video of a snake with SVL=57 cm crossing a 30 cm gap. The pegs in the large horizontal cylinder are inclined approximately 45° relative to the horizontal plane, and the tips of those in the foreground were oriented towards the camera. The origin of the coordinate system used for kinematic analysis was the top center end of the perch upon which the snake was initially placed. The longitudinal positions were measured or calculated for the most posterior location of the snake (Xposterior), mid-way between the end of the initial perch and Xposterior (Xmid-perch) and the most anterior location of the snake that was underneath part of the initial perch or one of its pegs (third right peg from the edge in this example) so that upward forces could be applied (Xanchor). The x and y coordinates were digitized for the lowest location of the mid-dorsal line and center of mass (COM) for the portion of the body suspended in the gap between the two perches.

 

Figure 3
View larger version (20K):
[in this window]
[in a new window]

  		Fig. 3. Schematic right lateral view of the major epaxial muscles of the brown tree snake at mid-body. SSP-SP, semispinalis-spinalis muscle; M, multifidus muscle; LD, longissimus dorsi muscle; IL iliocostalis muscle. The colored areas indicate contractile tissue, the tendons are white, and the skeletal structures are gray. Vertebrae are numbered beginning at the anterior attachment site of a single segment of the SSP-SP, and five vertebrae (3–7) are not shown. The thin horizontal line represents the shelf formed by the pre- and postzygapophyses.

 

Figure 4
View larger version (91K):
[in this window]
[in a new window]

  		Fig. 4. Cross-sections at mid-body of the smallest (SVL=43 cm) and largest (SVL=188 cm) snakes. On the large section the major epaxial muscles for which cross-sectional area were determined are tinted blue (semispinalis-spinalis), yellow (multifidus), red (longissimus dorsi) and green (iliocostalis).

 

Figure 5
View larger version (32K):
[in this window]
[in a new window]

  		Fig. 5. Tracings from videotapes showing lateral (left) and dorsal (right) views of different gap-bridging behaviors. (A) Crawling behavior of a snake with SVL=136 cm crossing a 67 cm gap. (B) Lunging and tail wrapping behaviors of a snake with SVL=106 cm crossing a 52 cm gap. The most anterior anchor points in A and B are the fifth right peg and the third left peg from the edge of the initial perch, respectively. The white marks indicate intervals approximately one-eighth SVL along the body of the snake. The times before contacting the destination perch are to the left of each figure. The portion of the snake spanning the gap was nearly straight during crawling, whereas early in the lunge the body had several lateral bends that were later straightened. Videos of these behaviors can be viewed at http://bioweb.ad.uc.edu/faculty/jayne/videos.htm.

 

Figure 6
View larger version (6K):
[in this window]
[in a new window]

  		Fig. 6. The scaling of maximal gap distance crossed versus snake size. The solid line is the least-squares regression for log10-transformed data, and the broken line indicates a 1:1 ratio of snake SVL and gap distance. Each symbol represents one snake. Circles indicate the crawling behavior (see Fig. 5A); triangles, lunging behavior; inverted triangles, tail-wrapping behavior. Squares indicate a lunge while the tail was wrapped around the initial perch (Fig. 5B). A solid symbol indicates that the snake had a conspicuous anchor point on the initial perch against which upward forces could be applied (Fig. 2), whereas a hollow symbol indicates the lack of such a point. See Table 1 for regression statistics.

 

Figure 7
View larger version (7K):
[in this window]
[in a new window]

  		Fig. 7. The kinematics of a snake using the crawling behavior to cross a gap. (A) Forward (B) vertical and (C) lateral displacement of the snout of the snake versus time. The time intervals between successive points are all 100 ms. The snake touched the perch on the far side of the gap at 0 s. After moving forward with a nearly constant speed (–4.5 to –2.5 s), the snake gradually slowed before reaching the destination perch. Gap distance, 38 cm; snake SVL, 65 cm.

 

Figure 8
View larger version (10K):
[in this window]
[in a new window]

  		Fig. 8. Variation in the paths traveled by the snout of snakes while crawling across a gap. (A,C,E) Lateral views and (B,D,F) overhead views. (A,B) Snake SVL=65 cm, gap distance=38 cm; (C,D) SVL=54 cm, gap distance=30 cm; (E,F) SVL=87 cm, gap distance=38 cm. The time intervals between successive points are all 100 ms. The end and top center of the initial perch are at the origin of the x, y and z axes.

 

Figure 9
View larger version (16K):
[in this window]
[in a new window]

  		Fig. 9. The kinematics and the path traveled by a snake using the lunging behavior to cross a gap. (A) Forward and (B) lateral displacement versus time, and (C) a lateral view of the path traveled by the snout of the snake (SVL=106 cm) while crossing a 52 cm gap. The times between the last thirteen successive points are 33 ms; all other time intervals between successive points are 200 ms. The snake touched the perch on the far side of the gap at 0 s. Different colored symbols indicate four attempts to bridge the gap, for which only the last was successful. The rapid forward and vertical velocities (slope) within the last 0.5 s indicate when the snake lunged. The end and top center of the initial perch are at the origin of the x, y and z axes.

 




© The Company of Biologists Ltd 2007