Data from: River otter predation of nesting seabirds along the coasts of North America
Data files
Nov 11, 2025 version files 203.86 KB
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anecdotal_present_nopredation.csv
1.70 KB
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anecdotal_records.csv
1.09 KB
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island_risk_.R
7.50 KB
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nonpredated_island_counts.csv
3.26 KB
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paper_review.R
3.68 KB
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paper_scoring.csv
10.44 KB
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predated_island_counts.csv
23.12 KB
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predation_mapping.R
5.99 KB
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predation_record_linking.R
5.44 KB
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README.md
10.54 KB
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RIOTRange.zip
97.67 KB
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species_info.csv
5.14 KB
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targeted_islands.csv
5.12 KB
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taxa_selection.R
6.94 KB
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updated_geography.csv
14.33 KB
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white_papers.csv
1.89 KB
Abstract
River otter (Lontra canadensis) predation of seabirds has been periodically documented throughout North America, but most knowledge about this subject exists as anecdotal observations in the memories of experienced seabird biologists. Using surveys, interviews, white papers, and published literature, we collected detailed records of seabird predation by river otters at 73 islands on the coasts of North America. From this dataset, we were able to conclude the seabird species experiencing river otter predation, the geographic distribution of predation records, and factors associated with river otter occurrence at colony islands. River otters preferentially select for small-bodied burrow-nesting species, with predation of ground-nesting species occurring mostly opportunistically. Predation of nesting seabirds occurs across the entire Pacific range of the river otter and throughout the northern Atlantic, but we did not locate a single record of this behavior on the Atlantic coast south of Maine; we hypothesize that this is due to geographic differences in nesting seabird assemblages. The presence of burrow-nesting seabirds and proximity to the mainland are both strong predictors of river otter occurrence at colony islands. River otters will swim up to eight kilometers across open ocean to access seabird colonies, but predation is significantly more common at nearshore islands (median distance of 1.7km). Reports of seabird predation by river otters in published literature are rare, heavily biased towards an ornithological audience, and have decreased over time as “Field Notes” style publications have decreased in popularity. Despite being more widespread than previously reported, predation by river otters appears to be sustainable for most colony nesting seabird populations.
Dataset DOI: 10.5061/dryad.gxd2547zv
Description of the data and file structure
Anecdotal data on seabird predation by river otters at colony islands throughout the United States and Canada were collected through surveys of biologists, review of white papers, and scraping of published literature. These records are accompanied in this dataset by geographic information for seabird colony islands and biological information for nesting seabird species.
Files and variables
File: anecdotal_present_nopredation.csv
Description: This tabular dataset indicates anecdotal records of seabird islands where river otters have been observed, but predation of nesting seabirds has not been observed. Records in this dataset come from direct communication/interview of seabird biologists and from white papers.
Variables
- island_name: Common name of the island for the record.
- State: State or province where the predation record occurred.
- otter_presence: Binary indicating whether river otter activity was observed. Inherently, 1 for all records in this dataset.
- Predation: Binary indicating whether river otter predation of seabirds was observed. Inherently 0 for all records in this dataset.
- Notes: Additional notes about the anecdotal record.
File: anecdotal_records.csv
Description: This tabular dataset indicates anecdotal records of seabird predation by river otters that were supplied by seabird biologists via survey (Table S1) or direct communication/interview.
Variables
- location_name: Common name of location for predation record.
- Island: Binary indicating whether the location was a coastal seabird colony island.
- State: State or province where the predation record occurred.
- Species: IBP code for bird species experiencing predation.
- Notes: Additional relevant notes about the anecdotal records.
File: nonpredated_island_counts.csv
Description: This tabular dataset indicates species occurrence and abundance records for seabird colony islands included in our final modelling dataset where river otter predation did not occur. Data were sourced from a variety of peer-reviewed papers, databases, white papers, and internal agency documents.
Variables
- island_name: Common name of the island for the record.
- State: State or province where the island is located.
- Species: IBP code for bird species with nesting information.
- Pairs: Reported number of nesting pairs present on the island.
- Year: Year when the abundance survey occurred.
- Source: Lead author or agency for data source.
- Notes: Additional relevant notes about the abundance estimate.
File: species_info.csv
Description: This tabular dataset includes biological covariate data for all seabird species included in our model datasets. All information presented here was sourced from Birds of the World.
Variables
- ibp: IBP code for bird species.
- common_name: Full common name for bird species.
- sci_name: Latin binomial name for bird species.
- Genus: Genus of bird species.
- Subfamily: Subfamily of bird species (if relevant).
- taxagroup: Commonly used taxonomic group name, based on phylogenetic classification.
- Family: Family of bird species.
- Order: Order of bird species.
- Burrowing: Binary indicating whether the species is a burrow-nester.
- Nest: Categorical variable indicating whether the species is a surface-nester, burrow-nester, or crevice-nester.
- Mass: Mean mass(g) of adult birds, averaged across sex (if applicable).
- nocturnal_visits: Binary indicating whether the species primarily completes provisioning visits during the night.
File: targeted_islands.csv
Description: This tabular dataset includes data collected from targeted surveys (Table S2) of seabird biologists with experience working on identified islands with long-term monitoring programs. Data have been aggregated across multiple survey respondents (where applicable).
Variables
- island_name: Common name of the island for the record.
- Years: Number of cumulative years of monitoring activity reported by survey respondents.
- total_weeks: Number of cumulative weeks of monitoring activity reported by survey respondents. Often cumulative/extrapolated/estimated.
- nest_species: IBP codes of seabird species known to be nested on the island.
- otter_presence: Binary indicating whether river otters have ever been observed on the island.
- otter_residence: Categorical description of residence patterns for river otters occurring on the island.
- Predation: Binary indicating whether river otter predation of nesting seabirds has ever been observed.
- depredated_species: IBP codes of seabird species known to have been depredated by river otters on the island.
- Notes: Additional notes from biologist survey responses.
File: paper_scoring.csv
Description: This tabular dataset includes results from the systematic review of references from peer-reviewed journals on seabird predation by river otters.
Variables
- article: Full title of the published article.
- Authors: Full author list for the published article.
- Journal: The full title of the journal where the article was published.
- Year: The year of publication.
- journal_bg: Categorical classification of the journal focus.
- journal_bg2: Categorical classification of the journal focus, with all naturalist journals grouped into one category.
- author_institution: The affiliated institution for the lead author at the time of publication.
- author_bg: Categorical classification of the professional/academic background/expertise of the lead author.
- Mammalogist: Binary indicating whether a mammalogist was included in the author list.
- ref_type: Categorical classification of the type of reference made to seabird predation by river otters; e.g., primary focus of a targeted study, anecdotal mention in a river otter diet study, anecdotal mention in a seabird predation study.
- ref_type2: Coarse categorical classification of the type of reference made to seabird predation by river otters: anecdotal mention, natural history note, or primary study.
- words_otter: Total number of words in the article discussing river otter predation of seabirds. If river otters or their impacts were mentioned or alluded to in any degree in a sentence, the entirety of words in that sentence were included in this count.
- words_total: Total number of words in the published manuscript.
- location_name: Common name of location for predation record.
- Island: Binary indicating whether the location was a coastal seabird colony island.
- State: State or province where predation record occurred.
- Coordinates: Geographic coordinates for the location where predation occurred.
- Family: Family name of the seabird species experiencing predation.
- Species: IBP code for bird species experiencing predation.
- resident_transient: Categorical class describing whether the river otters engaging in predation were transient visitors to the location or permanent residents.
- Excavation: Binary indicating whether river otters were described as excavating the burrows of burrow-nesting seabirds in the article.
- Notes: Additional notes about the described predation record.
File: updated_geography.csv
Description: This tabular dataset provides geographic data for all seabird colony islands included in our modeling datasets. All island sizes and shore distances were measured from aerial imagery using Google Earth Pro.
Variables
- island_name: Common name of the island.
- State: State or province where the island is located.
- size_ha: Area of island in hectares, rounded to two significant digits.
- Lat: Latitude of island location, rounded to a hundredth of a degree north.
- Long: Longitude of island location, rounded to a hundredth of a degree west.
- dist_eXha: Minimum distance from the island to another landmass greater than 10X hectares in size. Measured in kilometers, rounded to two significant digits.
- Freshwater: Categorical variable describing the presence of standing freshwater on the island (no freshwater, rainfed pools, temporary seasonal pools, persistent freshwater).
- freshwater_notes: Notes about the information source for freshwater presence. If nothing is included in this column, information came from biologist survey respondents.
File: white_papers.csv
Description: This tabular dataset indicates anecdotal records of seabird predation by river otters that were sourced from white papers and internal agency documents.
Variables
- location_name: Common name of location for predation record.
- Island: Binary indicating whether the location was a coastal seabird colony island.
- State: State or province where the predation record occurred.
- Species: IBP code for bird species experiencing predation.
- Source: Author and year of publication.
- Notes: Additional relevant notes about the anecdotal records.
File: RIOTRange.zip
Description: This compressed shapefile indicates the approximated species range of the northern river otter, Lontra canadensis. This file was solely used for mapping purposes (Figure 1). The range map shown here was based on observation data from iNaturalist.
Code/software
All analysis was performed in R version 4.2.3. All packages required are listed at the top of each script.
File: predation_mapping.R
Description: This script generates maps of seabird predation records throughout North America.
File: predation_record_linking.R
Description: This script takes our many disparate sources of anecdotal data (anecdotal biologist surveys, targeted surveys, white papers, published literature) and combines them into unified datasets for further analysis. It must be run before the other scripts in this project.
File: taxa_selection.R
Description: This script uses anecdotal predation records and seabird assemblage data to evaluate prey selection by river otters via logistic modeling.
File: island_risk_.R
Description: This script uses both the targeted island survey and anecdotal records to perform logistic regression on island risk factors.
File: paper_review.R
Description: This script analyzes the results of the systematic literature review and paper scoring to analyze trends in publications about river otter seabird predation.