Long-term monitoring of the relative density in the Eurasian otter (Lutra lutra) with track counts in Doñana National Park 2007-2022

Study Extent

The study area is located in southwest Spain in the Guadalquivir Basin and covers Doñana Protected Area (542.51 km2). Climate is Mediterranean sub-humid with Atlantic coast influence deriving in wet mild winters and dry warm summers. The rainy season occurs between October and April, with a peak in December–January (average rainfall is about 550 mm). Four main ecosystems are monitored in the area: freshwater marshes, mobile sand dunes, Mediterranean shrublands and woodlands and Doñana shoreline of 30 km. This monitoring protocol is carried out in 12 permanent and prefixed transects along Doñana National Park. Each transect was sampled three (3 consecutive days) times per year, after the first autumn rains.

Sampling

The long-term monitoring of carnivore tracks in Doñana started in 2008 by setting 12 permanent transects across the Doñana National Park. The transects have a length of 2 km and 1.5 m of width. Each transect is sampled three times during the sampling campaign in autumn (between October and November) always after the first rains of the hydrological year. Before each census the sand substrate was cleaned with a metal beam to facilitate the read of tracks and to ensure that the foot prints were from the previous day. Carnivores tracks, i.e. groups of carnivore foot prints, were identified and recorded in a Cybertracker sequence, that allows note coordinates information automatically. This census and his method enables esteem relative densities and also the calculation of Kilometric Abundance Indexes (KAI) of each species according to each transect of sampling period.

Quality Control

The protocol used has been supervised by ecological researchers and the data have been validated by the members who performed the transects.item-0

Method steps

1. The annual survey of each transect is composed by three different censuses on consecutive days. Furthermore, the day before of the first census day a metal beam of 1.5 m was passed along the transect of 2 km to eliminate previous old tracks, ensuring that the foot prints were from the previous day. During each census the metal beam was also passed cleaning the sand to the next day. That way, the detected tracks on each census belonged to the previous 24 hours, so each census is different to the ones made in the same period (3 consecutive days). An expert in mammals’ tracks identified all footprints in the transect area (2km x 1.5m), they were noted in Cybertracker that recorded the hour and the coordinates for each one. Data was download as Excel or csv files and then was validated, cleaned and prepared for the analysis. In order to clarify all carnivore datasets, the data was separated by species, this allows concrete analysis by species. In this dataset Eurasian otter´s (Lutra lutra) data is presented.

Tracks are identified to the species level.

1. Lutra lutra
   common name: Eurasian otter rank: species

The study area is located in southwest Spain in the Guadalquivir Basin and covers Doñana Protected Area (542.51 km2). Climate is Mediterranean sub-humid with Atlantic coast influence deriving in wet mild winters and dry warm summers. The rainy season occurs between October and April, with a peak in December–January (average rainfall is about 550 mm). Doñana Protected Area includes seven ecosystems types (coastal waters, beach, dunes, forest, shrubland, sandy lakes and marshes) and 21 habitat types, 11 of them of high conservation importance – such as the Bulrush and Glasswort marsh, floodplain lakes, sandy lakes, grassland ecotones, Cork-Oak forest, shrubland, coastal Juniper forest and dunes.