Zoo Biology 26:187–199 (2007) Research Article Seminal and Endocrine Characteristics of Male Pallas’ Cats (Otocolobus manul) Maintained Under Artificial Lighting With Simulated Natural Photoperiods Annie Newell-Fugate, 1 Suzanne Kennedy-Stoskopf, 2Ã Janine L. Brown, 3 Jay F. Levine, 2 and William F. Swanson 4 1 Veterinary Wildlife Unit, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa 2 Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina 3 Conservation and Research Center, National Zoological Park, Smithsonian Institution, Front Royal, Virginia 4 Center for Conservation and Research of Endangered Wildlife, Cincinnati Zoo and Botanical Garden, Cincinnati, Ohio Pallas’ cats (Otocolobus manul) have a pronounced reproductive seasonality controlled by photoperiod. Previous studies of reproduction in captive Pallas’ cats exposed to natural light showed a breeding season of December–April. This study evaluated the impact of artificial lighting timed to simulate natural photoperiods on male reproductive seasonality of four Pallas’ cats housed indoors. Semen evaluation, blood collection, and body weight measurements were conducted every 1–2 months from November 2000–June 2001. Fecal samples were collected from each male twice weekly to assess testosterone and corticoid concentrations. Mean values for reproductive traits (sperm attributes, testicular volume) were highest from February–April, the defined breeding season. Fecal testosterone concentrations were highest from mid-January to mid-March. Male Pallas’ cats managed indoors under simulated photoperiods experienced a delayed onset of the breeding season by 1–2 months and a decreased length of the breeding season. Published online 27 April 2007 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/zoo.20127 Received 4 April 2006; Revised 20 November 2006; Accepted 29 December 2006 Grant sponsors: IAMS Company; Disney’s Animal Kingdom; Cincinnati Zoo Center for Conservation and Research of Endangered Wildlife; North Carolina Zoological Society. Ã Correspondence to: Dr. Suzanne Kennedy-Stoskopf, North Carolina State University, College of Veterinary Medicine, 4700 Hillsborough Street, Raleigh, NC 27606. E-mail: suzanne_stoskopf@ncsu.edu r r 2007 Wiley-Liss, Inc.