International Journal of Comparative Psychology

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three present experiments examined the relationship between calcium gland size, fecundity, and dominance/social behavior in the unisexual geckos, Lepidodactylus lugubris and Hemidactylus garnotii. Study 1 examined the above variables while the geckos were housed communally and solitarily. L.lugubris established stable dominance hierarchies through aggressive interactions, whereas H. garnotii neither established a dominance hierarchy nor displayed signs of aggression while housed communally. Eggs were developed by 4 of 4 dominant L lugubris but by only 1 of 4 subordinate L lugubris and 1 of 6 H. garnotii. Calcium glands decreased in size in the subordinate L lugubris and H. garnotii during communal housing, then recovered when the geckos were housed solitarily. Study 2 examined the relationship between reproductive state and calcium gland size in L lugubris. Calcium glands were found to be smallest prior to and immediately after oviposition and largest when  eggs were yolking follicles. Study 3 examined the effect of sociality on fecundity in H. garnotii.Egg development was not related to whether geckos were housed solitarily or as dyads. Calcium gland size in geckos appears to be related to both stress and to the reproductive state of the gecko. We hypothesize that stress decreases the size of geckos' calcium glands resulting in decreased egg production in stressed animals.