In Venezuela, common dolphin (Delphinus sp.) is considered the cetacean with the highest incidence. Studies in the region indicate a possible isolated coastal population so called Venezuelan stock settled mainly in the northeast of the country. . The objective of this study is to describe the habitat use of common dolphin in the Mochima National Park (MNP), a protected area with a high and growing anthropic pressure. Seventy surveys were carried out, with predefined survey route, from September 2009 to August 2010. Each group sighted was monitored while possible to a maximum of 30min.. During this time we registered location (Latitude-longitude), behaviour, group size and composition every 5min. Additionally, environmental variables were assessed from the sight location in a nautical chart. The study area was divided into a grid (cell: 500 x 500m) and the Coefficient of Area Use (CAU) was calculated for each cell. The proportion of the total observation time where the common dolphin displayed behaviours into the areas being used was estimated. A logistic regression model was applied to identify the variables that better explained usage pattern. In 55h of observation, 111 groups were recorded. The common dolphin used the habitat differentially, showing preferences for shallow areas near to the coast. Areas of greatest intensity of use were Tigrillo inlet and the northeast of the Caracas Islands. The probability of presence of dolphins decreased with depth and distance to the coast. Common dolphin invested more time in feeding and socializing activities. Behaviours were significantly dependent of season, group size, composition, depth and distance to the coast. Finally, these data on habitat use and behaviour allow the identification of priority habitats. Throughout the year, the MNP provided areas for refuge, feeding and resting. , It is therefore imperative to promote management and conservation policies that prevent the negative impacts of the increasing tourism and fishing activities we observed in this Park.
Factors influencing guanaco habitat use and group size in Torres del Paine National Park, Chile
