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

The long-term monitoring of carnivore tracks in Doñana is part of a harmonised protocol for the Long-term Ecological Monitoring Program of Natural Resources and Processes targeting mammals' populations. The general aim of this protocol is to study the temporal evolution of the relative density of the main species of carnivores in the main habitats of the Doñana National Park. Tracks surveys were done annually after the first rains of the hydrological year, i.e. the first autumn rains, usually in October. Due to climate change, in recent years the rainy season has been delayed until the beginning of the year. This protocol has stablished in 2007 and it has done annually until the present (2022), except in 2021 when due to logistical problems no census was made. Censuses are carried out through 12 prefixed transects, with sand substrate, in Doñana National Park. Each transect consists of a 2 km of length and 1.5 m of width that is done by a car at a constant speed between 10 and 15 km/h. Transects are cleaned the day before of the census with a metal beam to facilitate the read of the tracks and to ensure that the foot prints were from the previous day. Each transect is repeated in three consecutive days, and during the transect the sand is cleaned for the next day. In the census an expert in mammals’ tracks identifies all the tracks, i.e. groups of carnivore foot prints, and he/she records them in Cybertracker. That way, tracks' information like coordinates, hour, species identification and observation was recorded; and also the information of each transect was recorded: surveyors, drivers, date, start and end (hour and coordinates). This method enables to calculate Kilometric Abundance Indexes (KAI) for each species and transect. 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.

对多纳尼亚地区食肉动物踪迹的长期监测构成了自然资源与过程长期生态监测计划中的一项统一协议的一部分，旨在针对哺乳动物种群进行监测。本协议的总体目标在于探究多纳尼亚国家公园主要栖息地中主要食肉动物物种相对密度的时空演变。踪迹调查通常在年度水文周期的首场秋雨后进行，即每年的秋季初，通常为10月。受气候变化影响，近年来雨季推迟至年初。该协议自2007年起建立，直至2022年，除2021年因物流问题未能进行普查外，每年均进行监测。普查通过12条预定的、以沙质土壤为基础的横断面进行，每条横断面长2公里，宽1.5米，由汽车以10至15公里/小时的速度进行巡查。在普查前一天，使用金属杆清理横断面，以便利踪迹的读取并确保脚印来自前一天。每条横断面连续三天重复进行，并在巡查过程中清理沙土以备次日之用。在普查过程中，由擅长识别哺乳动物踪迹的专家识别所有踪迹，即食肉动物的脚印群，并在Cybertracker中记录。以此方式，记录了踪迹的相关信息，如坐标、时间、物种识别和观察结果；同时，也记录了每条横断面的信息：调查员、驾驶员、日期、开始和结束时间（小时和坐标）。此方法使得能够为每个物种和横断面计算千米丰度指数（KAI）。为了明确区分所有食肉动物数据集，数据根据物种进行了分类，从而允许对特定物种进行具体分析。本数据集展示了欧洲水獭（Lutra lutra）的数据。