FIGURE CAPTIONS Fig 1. Location of study site: Punta Banda Estuary (PBE), Baja California, Mexico. Basemap source: CONABIO (Comisión Nacional para el Conocimiento y Uso de la Biodiversidad, National Commission on Biodiversity Knowledge and Use), División política estatal 1:250,000 (State political division 1:250,000), http://www.conabio.gob.mx/informacion/metadata/gis/dest_2015gw.xml?_httpcache=yes&_xsl=/db/metadata/xsl/fgdc_html.xsl&_indent=no Fig 2. Bayesian linear regressions of disturbance rates (number of disturbance events/h) for the sampling periods undertaken in 2015, 2016, and 2017. Shaded areas correspond to 95% Bayesian credible intervals. Fig 3. Disturbance rates (number of disturbance events/h) at PBE over three breeding seasons (white - 2015, grey - 2016, and black - 2017). Disturbance sources: P=pedestrians; MV=motorized vessels; VWM=vessels without motor; TV=terrestrial vehicles; and, N=noise. Fig 4. Nursing duration (min) under different disturbance scenarios and the control (no disturbance). Boxplots depict mean (horizontal line), standard deviation (box), and maximum and minimum values (bars). Circles denote outliers. Numbers correspond to the number of observations for each scenario. Scenario 1 (S1) – although nursing is momentarily interrupted by a disturbance, the mother-pup pair does not flush and continues to nurse; Scenario 2 (S2) – nursing is interrupted by a disturbance and the pair flushes, but recovers in less than 10 min and continues to nurse; and, Scenario 3 (S3) – nursing is interrupted by a disturbance, the pair flushes, and nursing does not resume until the end of the low tide cycle occurring during the sampling effort conducted on that day. The control observations (C) comprised nursing events that were not interrupted because no disturbance source was present. Fig 5. Relationships between disturbance sources and mother-pup reaction scenarios, according to multidimensional scaling. Scenario 1 (S1) – although nursing is momentarily interrupted by a disturbance, the mother-pup pair does not flush and continues to nurse; Scenario 2 (S2) – nursing is interrupted by a disturbance and the pair flushes, but recovers in less than 10 min and continues to nurse; and, Scenario 3 (S3) – nursing is interrupted by a disturbance, the pair flushes, and nursing does not resum...