I would like to make a morpho-metric analysis on Indian spiny tailed lizard without capturing and disturbing the animal in its habitat. It is very much necessary for me to find out the age structure of the population.
Laser lights mounted onto camera/video apparatus are widely used in underwater fish length estimations. The lights are projected onto the body of the animal and as they are a known length apart, the length of the target species can be estimated. See the attached paper for the methodology used - this could easily be adapted for use in your study of lizards.
If there is an age length key it could be estimated from a picture/photograph without disturbing the animal. Image processing and use of video is used extensively in sonar/video camera in fisheries and I am sure a similar approach can be developed for lizards.
As long as you can include an object of known length at the same distance as your lizard in a photograph (or measure the length of an object directly adjacent to the lizard after you have taken the picture), you should be able to photograph your lizards and use basic photo analysis and photoediting software like Jdraw to measure them after the fact. You would need to ensure you have a clear picture of the entire lizard, based on your morphometric needs.
I know Romulus Whitaker was fond of photographs and then superimposing images of animals with known lengths over the top? Obviously only provides an estimation but you can probably get it to be reasonably accurate. Also, I know with Crocs, there is a good correlation between skull size and size of the animal. If you found parts of a skull, then you could potentially estimate the body length from that, if the correlation is similarly found in spiny-tailed Lizards?
Laser lights mounted onto camera/video apparatus are widely used in underwater fish length estimations. The lights are projected onto the body of the animal and as they are a known length apart, the length of the target species can be estimated. See the attached paper for the methodology used - this could easily be adapted for use in your study of lizards.
I think that with two parallel lasers you could analyze images or video simply. you could measure not only specimen length, but many things.
Best solution that comes to my mind is phototrap pointed straight down on a ruler (or something of known lenght) put on the ground on known reptile trail or bite. Best (and more important - free) way to measure lenght from picture is image J.
Somanath, this paper may be useful to you: "EVALUATION OF A PHOTOGRAPHIC TECHNIQUE FOR ESTIMATING BODY SIZE IN LIZARDS FROM A DISTANCE" (http://herpconbio.org/Volume_7/Issue_1/Lambert_etal_2012.pdf)
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