Long Term Ecological Data Series in cetaceans: essential but challenging!

Ecological systems usually operate at large temporal scales, which are not always considered in traditional data collection. For instance, some questions, such as climate change or anthropogenic pressure potential effects, require long-term datasets to understand how ecosystems may respond to any disturbances or impacts. In the short run, traditional studies often provide high quality data for a specific space and time. However, long temporal series are needed to identify natural variability and potential trends in the environment and its populations, such as changes in distribution or the ecology of the species. Collecting long-term wildlife occurrence data is challenging and has been often undervalued. Dedicated data collection is generally expensive and limited in space and time for cetaceans. However, opportunistic platforms provide a cost-effective method to obtain information over long periods and defined areas. Nevertheless, challenges are evident for both opportunistic and dedicated programs. Here we summarize critical aspects for long-term initiatives to survive. We account for considerations such as standardization of protocols, long-term planning, specific training, or even robust data validation to guarantee data quality. Additionally, making the data openly available, standardised, providing biases and limitations, or even dedicated consultancy and expertise to avoid misleading conclusions are highly desirable steps towards a FAIR and better-quality scientific output. Finally, long-term initiatives need a long-term engagement. This might be achieved through enthusiastic people or leaders who can keep involved over time with data collectors, third parties interested in data and also the general public. Nowadays, collaboration is vital for highly mobile species such as cetaceans to get information over large areas and long periods. Only by doing so we will obtain the data we require for the studies we need.