Utah State University From the SelectedWorks of Julie Young March , 2011 Human Disturbance Influences Reproductive Success and Growth Rate in California Sea Lions ( Zalophus californianus )

The environment is currently undergoing changes at both global (e.g., climate change) and local (e.g., tourism, pollution, habitat modification) scales that have the capacity to affect the viability of animal and plant populations. Many of these changes, such as human disturbance, have an anthropogenic origin and therefore may be mitigated by management action. To do so requires an understanding of the impact of human activities and changing environmental conditions on population dynamics. We investigated the influence of human activity on important life history parameters (reproductive rate, and body condition, and growth rate of neonate pups) for California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Increased human presence was associated with lower reproductive rates, which translated into reduced long-term population growth rates and suggested that human activities are a disturbance that could lead to population declines. We also observed higher body growth rates in pups with increased exposure to humans. Increased growth rates in pups may reflect a density dependent response to declining reproductive rates (e.g., decreased competition for resources). Our results highlight the potentially complex changes in life history parameters that may result from human disturbance, and their implication for population dynamics. We recommend careful monitoring of human activities in the Gulf of California and emphasize the importance of management strategies that explicitly consider the potential impact of human activities such as ecotourism on vertebrate populations. Citation: French SS, González-Suárez M, Young JK, Durham S, Ge ber LR (2011) Human Disturbance Influences Reproductive Success and Growth Rate in California Sea Lions (Zalophus californianus). PLoS ONE 6(3): e17686. doi:10.1371/journal.pone. 0017686 Editor: Sharon Gursky-Doyen, Texas A&M University, United States of America Received November 12, 2010; Accepted February 8, 2011; Published March 16, 2011 Copyright: 2011 French et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was supported by a grant to LRG from the National Science Foundation (Animal Behavior, Biological Oceanography, and International Programs; Award # 0347960; www.nsf.gov) and a grant to MGS by the European Community’s Seventh Framework Programme (FP7/2007-2013; http://cordis. europa.eu/fp7) under grant agreement nu 235897, and the Spanish Ministry of Science and Innovation (Project: CGL2009-07301/BOS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: sfrench@biology.usu. edu ¤a Current address: Department of Conservation Biology, Estación Biológica de Doñana-CSIC, Sevilla, Spain ¤b Current address: United States Department of Agriculture-Animal and Plant Health Inspection Service-Wildlife Services-National Wildlife Research Center, Logan, Utah, United States of America