Figure 1. Differences in claw clipping used in Bloch and Irschick (2005) and our study. (A) Bloch and Irschick (2005) clipped the entire claw after the distal end of the toe pad. (B) In our study, we partially clipped the distalmost portion of the claw.
Toe and claw clipping are common techniques used to identify individuals in mark and recapture studies, but their impacts on whole organism performance are unclear (Dunham et al., 1988). Anoles have not only developed subdigital adhesive toe pads to promote adhesion on relatively smooth substrates, but have also retained claws to enhance attachment to rough substrates (Irschick et al., 1996; Zani, 2000). Thus, clipping entire toes or claws may have drastic effects on the clinging ability of anoles or other adhesive pad-bearing lizards. In our recent article published in Acta Herpetologica, my co-authors and I investigated how partially removing the claws of brown anoles affects their adhesive performance.
Figure 2. Mean maximum clinging force of Anolis sagrei with intact and partially clipped claws. Overall, partial claw clipping had no significant effect on maximum clinging ability.
Bloch and Irschick (2005) removed entire claws from Anolis carolinensis (Fig. 1A) and measured its impact on their clinging ability. Not surprisingly, claw removal resulted in a significant decrease in the clinging ability of A. carolinensis, likely a consequence of the severing of flexor tendons that are critical in adhesive toe pad engagement. In an effort to test this hypothesis and preserve these tendons, we used a motorized force sensor (Niewiarowski et al., 2008) to measure the maximum clinging ability of 19 Anolis sagrei before and after their claws were partially clipped (Fig. 1B).
Overall, we found that partial claw clipping did not significantly impact maximum clinging ability (Figure 2). This suggests that clipping the entire claws of anoles may indeed sever the flexor tendons crucial to toe pad engagement. Furthermore, we expected clinging ability to increase after partial claw clipping because claws should theoretically interfere with the contact the subdigital adhesive pads are capable of producing. However, this did not appear to be the case, suggesting that claws may not inhibit the engagement of subdigital pads or that morphological features and/or behavioral traits reduce the effect of this interaction.
Anolis sagrei
Although permanent marking solutions would be most beneficial for mark and recapture studies, partial claw clipping may be a useful alternative for shorter-term studies because it does not appear to reduce adhesive performance on smooth substrates. Future work should further consider the interactions between subdigital adhesive toe pads and claws, and determine the possible ramifications for adhesion and adhesive locomotion, particularly on rough substrates. Be sure to check out our full article for more details!
References
Bloch, N., Irschick, D.J. (2005): Toe-clipping dramatically reduces clinging performance in a pad-bearing lizard (Anolis carolinensis). J. Herpetol. 39: 288-293.
Dunham, A.E., Morin, P.J., Wilbur, H.M. (1988): Methods for the study of reptile populations. In: Biology of the Reptilia, pp. 331-386. Gans, C. Huey, R.B., Eds, Alan R. Liss, Inc., New York.
Irschick, D.J., Austin, C.C., Petren, K., Fisher, R.N., Losos, J.B., Ellers, O. (1996): A comparative analysis of clinging ability among pad-bearing lizards. Biol. J. Linn. Soc. 59: 21-35.
Niewiarowski, P.H., Lopez, S., Ge, L., Hagan, E., Dhinojwala, A. (2008): Sticky gecko feet: the role of temperature and humidity. PLoS ONE 3: e2192.
Zani, P. (2000): The comparative evolution of lizard claw and toe morphology and clinging performance. J. Evol. Biol. 13: 316-325.
- Anoles as Models for Dry Fibrillar Adhesion - April 12, 2019
- Clipped Claws and Consequences for Anolis Adhesive Performance - January 13, 2018
Kevin de Queiroz
Block and Irschick (2005) seem to have removed considerably more than the claw. Cutting off everything distal to the pad means removing the terminal two phalanges–not just the claw-bearing (ultimate/ungual) phalanx. That’s like cutting off the distal two (out of three) segments of a human finger (other than the thumb)! I suspect that their method of claw removal was based on the common misconception that only a single phalanx is distal to the pad (i.e., that the distal part of the pad is under the second rather than the third phalanx, counting from distal to proximal).
Austin Garner
Yes, it seems they clipped more than just the claw. While they refer to their clipping method as toe clipping in their study, we discussed their method as complete claw clipping to highlight the differences in clipping methods with respect to the claw. In our study, we just partially clipped the claw with nail scissors, while Bloch and Irschick (2005) removed the entire claw (and, as you point out, much more than just the claw!).