American Journal of Primatology 69:255–266 (2007) RESEARCH ARTICLE Do Cavity-Nesting Primates Reduce Scent Marking Before Retirement to Avoid Attracting Predators to Sleeping Sites? SAMUEL P. FRANKLIN 1Ã , KIMRAN E. MILLER 2 , ANDREW J. BAKER 3 , AND JAMES M. DIETZ 1,2 1 Program in Behavior, Ecology, Evolution and Systematics, University of Maryland, College Park, Maryland 2 Department of Biology, University of Maryland, College Park, Maryland 3 Philadelphia Zoo, Philadelphia, Pennsylvania The largest population of endangered golden lion tamarins (Leontopithecus rosalia, GLTs) decreased from approximately 330 to 220 individuals between 1995 and 2000 due to a dramatic increase in predation at sleeping sites. We used behavioral data from eight social groups in this population to test two hypotheses: First, if GLTs attempt to mitigate the risk of predation at sleeping sites, they should reduce their rates of scent marking just prior to retirement. Second, if the benefits of scent marking prior to entering the sleeping site merit an increase in the rate of marking, then tamarins should increase their rate of pre-retirement scent marking during the breeding season, when such behavior would have its greatest impact on reproductive fitness. We used a generalized linear model (GLM) repeated-measures analysis to compare rates of daytime scent marking with rates of marking just prior to retirement for males and females. In addition, we compared scent marking prior to retiring in the nonbreeding season to marking rates before retirement in the breeding season for males and both sexes considered concurrently. Contrary to our expectations, GLTs significantly increased their rates of scent marking during the 30 min prior to entering their sleeping site–an observation driven by an increase in male (but not female) rates of marking. Rates of marking before entering the sleeping site were greater in the nonbreeding season compared to the breeding season, when both sexes were considered concomitantly and when males were evaluated alone. We conclude that GLTs do not attempt to minimize predation risk by decreasing scent marking in the period before they enter their sleeping site, and that tamarins do not scent mark at this time of day in order to transmit information about reproductive status or to control reproduc- tion of subordinates. We speculate that scent marking in the 30 min prior Published online 4 December 2006 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ajp.20339 Received 18 September 2005; revised 6 April 2006; revision accepted 10 April 2006 Contract grant sponsor: NSF. Ã Correspondence to: S.P. Franklin, Department of Microbiology, Immunology, and Pathology, 1619 Campus Delivery, Colorado State University, Fort Collins, CO 80523. E-mail: sam17franklin@hotmail.com r r 2006 Wiley-Liss, Inc.