[en] A study was conducted to assess the behavioural response of southern right whales (Eubalaena australis) to human-induced disturbance in Bahía San Antonio, Province of Río Negro, Argentina. Behavioural observations were made from June to October in 2008, 2009, and 2010. Aerial observa-tions carried out in 2010 show that up to one third of the whale groups were mating groups, indicat-ing that the study area is an important reproduction area for the species. The study compares 65.8 h (on a total effort of 120.3 h and 24 groups of whales) of land-based “undisturbed” whale behaviour obser-vations to 43.6 h of boat-based whale behaviour in a “disturbed” state (total effort of 326.1 h and 34 groups of whales). Analysis of the behavioural data show that whales significantly altered their behaviour by cutting social interactions short (on average 13%) when confronted with human short-range presence. At the same time, travelling whales experienced a significant increasing tendency to continue travelling (+21%) instead of starting to rest (-21%). However, social behavioural patterns returned swiftly to normal levels after the approach had ended, with a relative increase in “resting” (+18%) as opposed to “travelling” (-30%) rates.These data show that whale behaviour is altered by human approaches, pointing out the need for effective conservation measures and mitigation of behavioural impacts in relation to whale-based tourism.