Response to chemical cues from conspecifics reflects male mating preference for large females and avoidance of large competitors in the European pond turtle, Emys orbicularis Jens R. Poschadel 1,2) , Yvonne Meyer-Lucht 1) & Martin Plath 3,4) ( 1 Biozentrum Grindel, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany; 3 Unit of Evolutionary Biology and Systematic Zoology, Department of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht Str. 24-25, 14476 Potsdam, Germany; 4 Department of Zoology, University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA) (Accepted: 3 February 2006) Summary We examined chemical communication in male and female European pond turtles (Emys orbicularis). In simultaneous binary choice tests, a focal animal was given a choice between pheromones from a conspecific and a choice chamber containing untreated water. Females did not show a preference, both when male and when female stimuli were presented. On the contrary, males preferred the odor of a female over untreated water, suggesting that males actively search for females. The strength of preference was positively correlated with the body size difference between the female and the focal male, indicating that males prefer to mate with larger females. Female fecundity is positively correlated with female size in E. orbicularis, which may account for male choosiness. No overall preference for the stimulus animal was observed when males were presented cues from another male. However, the strength of preference was negatively correlated with the difference in body size. Males avoided large males, but oriented towards smaller stimulus males. This reflects that males form dominance hierarchies, where large males aggressively attack smaller ones. Far-range chemical communication probably enables males to minimize the risk of costly aggressive interactions. This is, to our knowledge, the first study on the role of chemical cues for inter- and intrasexual communication in the European pond turtle. Keywords: Chelonia, chemical communication, male mate choice, pheromones, sexual selec- tion. 2) Corresponding author’s e-mail address: jposchadel@web.de © Koninklijke Brill NV, Leiden, 2006 Behaviour 143, 569-587 Also available online - www.brill.nl