Many studies of natural selection, behavioral ecology, and population biology in anoles focus on one to several populations over the course of days, weeks, or months. These studies require reliable identification of individual lizards over time. I describe several ID’ing methods in this post. Read on!
Felt-tip Permanent Markers (or paint pens) are great for marking lizards for fast identification in the field. A number or blotch on either side is quickly applied and easily visible from afar, especially with binoculars, so this method is great for behavioral observations. The major drawback of the permanent marker, however, is its impermanence (ironic, I know). A mark lasts only until the lizard sheds its skin. Thus, the ID could last a month, or it could be gone tomorrow.
Colored Beads, sewn into the tail musculature in different combinations using a thin wire, also allow for long range identification and behavioral study (see photo above). Akin to bird banding, beading is more permanent than marker. This method is more stressful to the animal, and quick and effective application takes some practice. It has been successful in lizards down to about 40 mm snout-vent length (Michele Johnson, personal communication).
Visible Implant Elastomers, made by Northwest Marine Technologies, are biologically inert solids that can be injected just beneath the surface of translucent tissues where they remain externally visible. By injecting any of the 10 available colors (6 colors will fluoresce under UV light) into different positions on the body, researchers have an inexhaustible number of unique combinations available for marking animals. Properly injected, these tags are permanent as the skin heals over the entry site. Because the tags aren’t visible from afar, the animal has to be in hand to determine its identity. Thus, for behavioral studies, combining permanent marker or colored beads with the VI elastomer allows for long range identification with the assurance that the animal is also permanently marked.
Visible Implant Alpha Tags, also made by Northwest Marine Technologies, are perfect for those of us who struggle with combinatorics or just don’t want to deal with multiple marks and locations per animal. Like the elastomers, these are biologically inert, implantable tags with the difference that they have a black letter-number combo (i.e. A00, A01, … Z98, Z99) printed on one of four fluorescent background colors. These tags carry the same advantages and drawbacks of the elastomer tags. A unique drawback to this method is that a poorly implanted tag can be difficult to read, even under UV fluorescence.
Toe clipping is a classic method for marking small vertebrates. By clipping toes in different combinations on different limbs, a large number of lizards can be marked uniquely. Toe clipping, like the elastomer and alpha tags described above, is permanent, but the lizard has to be in hand for identification. For studies in the wild, clipping toes may negatively affect performance and survival. The evidence for this negative impact is mixed, however, and many wild lizards lose toes naturally so perhaps this isn’t a big issue. That said, the high prevalence of lost toes in the wild can introduce error to the marking system and lead to misidentification.
Spray paint is a great tool for mark-recapture studies estimating population size. A researcher visits the population on three different days, each day painting the lizard with a different color using a pump sprayer. The non-toxic, water-based paint is applied as minimally as possible while still allowing for color detection from all angles. The researcher uses a statistical model that uses the number of lizards painted with one, two, or three colors at the end of the survey to estimate population size.