Determining Sexual Maturity of Crotaphytus collaris hatchings and yearlings as compared to body size, sex, and season.

Abstract

            In a few animal species, sexual mature is linked to body size.  These species will be sexually mature once they hit a certain size regardless of their age. This type of sexual maturity is what I am setting out to test in Crotaphytus collaris, eastern collared lizards. Collared lizards are interesting in that they display sexual dimorphism.  Even as hatchlings, males have bright, horizontal orange bars that reach across their backs while females’ coloring remains drab.  The purpose of the hatchling orange bars is still up for debate but the questions the orange bars raise are vital in understanding their purpose. Collared lizards also practice the act of pair bonding. Pair bonding is where males of the species spend time with females to create a bond so that when mating season comes, the females will be more likely to join a particular male’s mating harem. A harem is a group of females who mate with a particular male collared lizard and stay in that male’s territory.  Collared lizard hatchlings also practice pair bonding and territorial instincts although they are not thought to be sexually mature.  This raises the question of why would the hatchlings exhibit these behaviors if they are not yet sexually mature.  To test this question, I will be collecting a cloaca smear from yearlings in the spring and hatchlings in the spring.  This involves expressing the cloaca of the specimen onto a microscope slide and letting the slide dry.  If mature spermatozoa are present from a male specimen, the specimen lizard is sexually mature.  If mature spermatozoa are found, this means that she has been engaged in copulation.  The field steps of the project are as follows: capture specimen, record the area the specimen was found, identify specimen, take body measurements, and perform a cloaca smear.  Each lizard, apart from newborn hatchlings, has a set of toe clippings and paint drops on the back to identify it.  Body size measurements are taken to compare to sexual maturity.  The measurement is taken from nose to vent on the collared lizard as well as mass in grams.  The cloaca smears will be compared to body size, sex, and season to produce the results of the project