Data from: Effects of recreational boats on harbour porpoise swimming speed and surfacing interval investigated by two synchronised UAVs
Data files
Mar 25, 2026 version files 272.56 KB
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Exemplary_Code_Extraction.Rmd
11.37 KB
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Follow_1_Boat.csv
9.08 KB
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Follow_1_Porpoise.csv
885 B
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Follow_14_15_Boat.csv
10.24 KB
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Follow_14_15_Porpoise.csv
5.52 KB
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Follow_16_Boat.csv
6.53 KB
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Follow_16_Porpoise.csv
4.42 KB
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Follow_17_18_Boat.csv
6.34 KB
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Follow_17_18_Porpoise.csv
7.15 KB
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Follow_19_20_21_22_Boat.csv
9.19 KB
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Follow_19_20_21_22_Porpoise.csv
10.22 KB
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Follow_2_Boat.csv
16.64 KB
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Follow_2_Porpoise.csv
6.04 KB
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Follow_23_Boat.csv
14.36 KB
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Follow_23_Porpoise.csv
3.25 KB
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Follow_24_Boat.csv
4.52 KB
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Follow_24_Porpoise.csv
4.96 KB
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Follow_25_26_Boat.csv
1.24 KB
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Follow_25_26_Porpoise.csv
2.44 KB
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Follow_27_Boat.csv
1.11 KB
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Follow_27_Porpoise.csv
1.77 KB
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Follow_28_Boat.csv
2.56 KB
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Follow_28_Porpoise.csv
1.97 KB
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Follow_29_Boat.csv
8.54 KB
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Follow_29_Porpoise.csv
3.22 KB
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Follow_3_Boat.csv
11.85 KB
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Follow_3_Porpoise.csv
2.13 KB
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Follow_4_5_Boat.csv
26.98 KB
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Follow_4_5_Porpoise.csv
5.33 KB
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Follow_6_7_Boat.csv
2.78 KB
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Follow_6_7_Porpoise.csv
2.60 KB
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Follow_8_Boat.csv
25.26 KB
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Follow_8_Porpoise.csv
930 B
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Follow_9_10_11_12_13__Porpoise.csv
8.21 KB
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Follow_9_10_11_12_13_Boat.csv
24.88 KB
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Porpoise_Boat_Interaction.csv
2.55 KB
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README.md
5.48 KB
Abstract
Cetaceans are negatively affected by anthropogenic activities, including acoustic and physical disturbance from boat traffic. Behavioural responses to such disturbances are context-dependent, and site-specific insights are needed for effective local management plans. In this study, the impact of speed and proximity of recreational boats on the swimming speed and surfacing interval of one of the most common coastal cetacean species, the harbour porpoise (Phocoena phocoena), is investigated using data collected by unmanned aerial vehicles (UAVs) within a key habitat for the endangered Belt Sea population (HELCOM, 2024). In August 2024, two UAVs were flown simultaneously on predefined routes within the area. One UAV searched for and followed detected porpoises, while the other monitored recreational boats. All data was captured as UAV video and used to determine surfacing intervals of individual porpoises, measure the speed of porpoises and boats, and calculate the closest distance between porpoises and boats for each simultaneous sighting. A total of 91 synchronous flights were conducted, resulting in 28 porpoise observational events. GLM analyses showed that an interaction between mean boat speed and distance to the boat influenced the mean speed of the porpoises. In the presence of boats with high mean speeds, porpoises at close range reduced their swimming speed, while porpoises at greater distances instead increased their swimming speed. Also, porpoise surfacing intervals decreased (i.e., porpoises surfaced more frequently) with decreasing distance to boats. This study demonstrates that recreational boats influence the behaviour of porpoises, which could lead to potential negative individual- and population-level effects.
Dataset DOI: 10.5061/dryad.j0zpc86v7
Description of the data and file structure
This is a compilation of data collected to study the behavioural responses of harbour porpoises (belonging to the endangered Belt Sea population) to recreational boats. The data was collected in August 2024 using a field method involving the simultaneous use of two UAVs. Position data for the harbour porpoises and boats was extracted from the video recordings made by the UAVs, which was used to calculate the distances between them, their swimming and travelling speeds, and their accelerations. NA values within columns indicate ‘not available’. These entries occur due to missing data in the flight logs.
HELCOM, 2024. 2024 Red List II of Marine Mammals – HELCOM [WWW Document]. URL https://helcom.fi/baltic-sea-trends/biodiversity/2024-red-list-of-species/2024-red-list-of-marine-mammals/ (accessed 3.18.26).
Files and variables
File: Follow_1_Boat.csv
Description: This is an example description of the files named Follow_XX_XXXX.csv. The word ‘Boat’ or ‘Porpoise’ in the title indicates which object the annotations originate from. The number in the title links the annotations about harbour porpoises and boats that originate from the same time. These files contain annotations extracted from the recorded video footage using Drone Video Measure. The annotations were later used to calculate the distances between harbour porpoises and boats, as well as the corresponding speeds and accelerations, as shown in Exemplary_Code_Extraction.RMD. Coordinates of porpoises were geomasked by applying a random spatial offset of 100–200 km in a projected coordinate system, preserving all movement distances and speeds while obscuring true geographic locations.
Variables
- name: Name of the annotations as given in Drone Video Measure. The same name indicates the same object.
- time: Timestamp of the annotation (mm:ss).
- time.2: Timestamp of the annotation (mm:ss.s).
- height: Altitude of the UAV (meters).
- yaw: Yaw of the UAV (degrees).
- pitch: Pitch of the UAV (degrees).
- roll: Roll of the UAV (degrees).
- lat: Latitudinal position of the annotation (decimal degrees).
- lon: Longitudinal position of the annotation (decimal degrees).
- east: Eastward position of the annotation (meters).
- north: Northward position of the annotation (meters).
File: The description and explanation of the variables in Follow_1_Boat.csv apply to the following list of files:
- Follow_1_Porpoise.csv
- Follow_14_15_Boat.csv
- Follow_14_15_Porpoise.csv
- Follow_16_Boat.csv
- Follow_16_Porpoise.csv
- Follow_17_18_Boat.csv
- Follow_17_18_Porpoise.csv
- Follow_19_20_21_22_Boat.csv
- Follow_19_20_21_22_Porpoise.csv
- Follow_2_Boat.csv
- Follow_2_Porpoise.csv
- Follow_23_Boat.csv
- Follow_23_Porpoise.csv
- Follow_24_Boat.csv
- Follow_24_Porpoise.csv
- Follow_25_26_Boat.csv
- Follow_25_26_Porpoise.csv
- Follow_27_Boat.csv
- Follow_27_Porpoise.csv
- Follow_28_Boat.csv
- Follow_28_Porpoise.csv
- Follow_29_Boat.csv
- Follow_29_Porpoise.csv
- Follow_3_Boat.csv
- Follow_3_Porpoise.csv
- Follow_4_5_Boat.csv
- Follow_4_5_Porpoise.csv
- Follow_6_7_Boat.csv
- Follow_6_7_Porpoise.csv
- Follow_8_Boat.csv
- Follow_8_Porpoise.csv
- Follow_9_10_11_12_13__Porpoise.csv
- Follow_9_10_11_12_13_Boat.csv
File: Porpoise_Boat_Interaction.csv
Description: This file contains the compiled data extracted from the raw annotations using the script illustrated in Exemplary_Code_Extraction.Rmd. NA indicates 'not available' and occurred due to methodological constraints (see corresponding paper https://doi.org/10.1002/ece3.73165).
Variables
- Follow_nr: ID number of the focal follow.
- date: Date the focal follow was recorded (dd/mm/yyyy).
- starting_time: Starting time of the focal follow (hh:mm:ss).
- boat_distance: Closest distance between recreational boat and harbour porpoise (m).
- boat_type: The type of the closest recreational boat (motor: motorboat; sail: sailing boat; SUP: stand-up paddle board).
- max_boat_speed: Maximum speed of the closest boat (m/s).
- mean_boat_speed: Mean speed of the closest boat (m/s).
- max_boat_acceleration: Maximum acceleration of the closest boat (m/s^2).
- mean_porpoise_speed: Mean swimming speed of the harbour porpoise (m/s).
- mean_surfacing: Mean surfacing interval of the harbour porpoise (s).
- max_porpoise_speed: Maximum swimming speed of the harbour porpoise (m/s).
- type: The social status of the harbour porpoise (mother: mother with calf; normal: adult harbour porpoise).
File: Exemplary_Code_Extraction.Rmd
Description: Example of the code used to calculate the distances between harbour porpoises and boats, mean and maximum speeds, and maximum accelerations from the raw annotations. The paths to directories and files need to be personalised within the setwd() function before use (Lines 17, 21, 23).
Code/software
The RMD file provided require readers to use R to open and run the script. The author used R version 4.4.1 with the sf, zoo, dplyr, tidyverse, and lubridate packages.