Open letter regarding killer whale behaviour around boats

Lance Barrett-Lennard signed a public letter following interactions between killer whales and boats in Spain and Portugal.

Although our work as Raincoasters is focused on coastal BC, many of us are members of broader communities, and our expertise and research often have wider ramifications. Our duties as scientists and conservationists, likewise, are not constrained by where we happen to live and work. Thus, when I was asked to co-author a letter contextualizing the behaviour of the Iberian killer whales, whose interactions with boats have generated so much public interest of late, I quickly agreed. 

In the way of background, I’ve spent my career studying the foraging behaviour, genetics, echolocation capabilities, and health of killer whales. The thing that drew me to the species as a young scientist is that it lives in small, discrete populations, each of which has its own culturally-maintained traditions and behaviours, and each of which actively avoids mixing with other such populations. This kind of population structure is not known in any other species–except, in some cases, humans. Some killer whale populations have learned to slide onto gravel beaches or tip ice floes to catch seals, others to herd and stun herring, still others to share salmon with pod-mates and/or use unique stereotyped calls to maintain the coherence of family groups. These behaviours clearly benefit the whales, but as with humans they are also prone to developing fads, behaviours that have little obvious survival value.  Beach rubbing by Northern Resident killer whales is a notable local example.  

To those of us who study killer whales in the wild, the propensity of Iberian killer whales to interact with boats by pushing them around, breaking their rudders, and thumping their hulls,  is a classic play-like fad. The interactions are not attacks (unmistakable in killer whales)  regardless of the damage they may cause. The letter by my colleagues and me urges caution in interpreting the causes and nature of the whales’ behaviours. Our concern is that wrongly characterizing killer whales as fearsome animals that deliberately set out to attack mariners could wind back progress made in recent decades to appreciate, value, and protect these intelligent, complicated, magnificent ocean creatures. 

Open letter

September 2023

The undersigned are experts in the biology and behaviour of cetaceans, with several specialising in orcas (also known as killer whales). 

There has been intense public interest in the interactions between orcas (referred to hereafter as the Iberian orcas) and marine vessels along the coast of the Iberian Peninsula (Spain and Portugal) and in neighbouring waters. We are concerned that factual errors related to these interactions are being repeated in the media, along with a narrative—lacking a basis in science or reality—that the animals are aggressively attacking vessels or seeking revenge against mariners. We believe this narrative inappropriately projects human motivations onto these whales and we are concerned that perpetuating it will lead to punitive responses by mariners or managers. The whales have shown a wide range of behaviours during the interactions, many of them consistent with playful social behaviour.

We therefore seek to clarify the facts on the basis of available scientific evidence. Much of this information comes from a peer-reviewed article published in Marine Mammal Science in 2022 by several signatories to this letter. 

The Iberian orcas are categorised on the International Union for Conservation of Nature’s Red List as Critically Endangered. There may be fewer than 40 individuals in this population. They represent a geographically isolated, genetically distinct subpopulation, which feeds primarily on bluefin tuna.

These disruptive interactions with vessels began in earnest in July 2020. To date, at least 11 juveniles and four adult females have been identified as participating in or observing the interactions. There is no evidence of an identifiable ‘leader’ of these interactions. Researchers have given these 15 whales the Latin identifier Gladis and an individual name; for example, Gladis Blanca or Gladis Negra (White Gladis and Black Gladis, respectively, in English). Gladis Negra, a juvenile female—and one of the initially reported interacting animals—was observed with a head laceration in spring 2020 and a wound behind the dorsal fin later in 2021. Both injuries were of unknown origin. 

The interactions have ranged from no contact with the vessel, through mild or moderate contact with no or minor damage to the vessel, to significant contact with severe damage (preventing navigation). Starting in spring 2021, at least five damaged vessels have sunk. Severe damage has occurred in only 20% of the interactions.

Despite the damage to vessels, we believe characterising the interactions as ‘attacks’ is misleading. While some parts of the vessels infrequently have teeth marks on them, the predominant damage to rudders and keels are due to strikes or rams with the head or body. The whales are not ripping the rudders apart, as they might if this were hunting behaviour. While the behaviour may be frightening (and costly) from a human perspective, from the whales’ perspective, it seems to be somehow gratifying.

Orcas (and other dolphin species) elsewhere have been known to develop cultural ‘fads’ (novel behaviour that briefly persists and expands within a population—an analogy might be fashion trends in people), such as carrying dead fish on their heads. While these vessel interactions may be a similar phenomenon, they are persisting longer than typical fad behaviour, expanding within the population and escalating in impact. Nevertheless, it is possible the behaviour, as previous fads have, will disappear as suddenly as it appeared.

We urge the media and public to avoid projecting narratives onto these animals. In the absence of further evidence, people should not assume they understand the animals’ motivations. The orca is an intelligent, socially complex species, and each population has its own culture—different vocalisations (known as dialects), prey preferences, hunting techniques, even different social structures and migratory behaviours. The Iberian orcas are exhibiting a behaviour never before seen with this consistency among cetaceans—even in the days of industrial whaling from wooden ships and boats, when far larger whales were known to smash or otherwise damage vessels, such incidents were relatively uncommon. Science cannot yet explain why the Iberian orcas are doing this, although we repeat that it is more likely related to play/socialising than aggression. However, it is unfounded and potentially harmful to the animals to claim it is for revenge for past wrongs or to promote some other melodramatic storyline. 

When we are at sea, we are in the realm of marine life. We should not punish wildlife for being wild. We need to keep cool heads when wild animals exhibit novel behaviour and we must put greater effort into adapting our own actions and behaviour to the presence of wildlife. The survival of the species with which we share this planet depends on it.


Naomi A. Rose, PhD
Senior Scientist, Marine Mammal Biology
Animal Welfare Institute

Artur Andriolo, PhD
Profesor Titular, Universidade Federal Juiz de Fora
Presidente, la Sociedad Latinoamericana de Especialistas en Mamíferos Acuáticos 

Lucy Babey
Director of Programmes
United Kingdom

Robin W. Baird, PhD
Hawai‘i Program Director
Cascadia Research Collective

Lance Barrett-Lennard, PhD
Senior Research Scientist and Co-Director
Raincoast Conservation Foundation

Giovanni Bearzi, PhD
Dolphin Biology and Conservation

Maddalena Bearzi, PhD
Ocean Conservation Society

Alessandro Bocconcelli, MSc
Emeritus Research Scholar
Woods Hole Oceanographic Institution

Jaime Bolaños, PhD
Caribbean-Wide Orca Project (CWOP), Coordinator
Sea Vida (Venezuela), Executive Director

Philippa Brakes, PhD
Honorary Lecturer, University of Exeter
Research Fellow, Whale and Dolphin Conservation
New Zealand

Inês Carvalho, PhD
Population and Conservation Genetics Group
Instituto Gulbenkian Ciência

César Castro-Azofeifa
Investigador sobre mamíferos marinos
Escuela de Biología, Universidad de Costa Rica
Centro Nacional de Alta Tecnología de Costa Rica
Costa Rica

Phillip J. Clapham, PhD
Senior Scientist
Seastar Scientific Inc.

Mel Cosentino, PhD
Marine mammal researcher
Aarhus University

Volker Deecke, PhD
Professor of Wildlife Conservation
University of Cumbria
United Kingdom

Judith Denkinger, PhD
Universidad San Francisco de Quito, Galapagos Science Center

Manuel E. dos Santos, PhD

Cindy Elliser, PhD
Research Director
Pacific Mammal Research

Rocío Espada-Ruiz
University of Sevilla, Ecolocaliza
GTOA (Grupo de Trabajo Orca Atlántica/Atlantic Orca Working Group)

Ruth Esteban, PhD
Madeira Whale Museum

Lilián Flórez-González, MSc
Founder, President
Fundación Yubarta

Andrew Foote, PhD
Centre for Ecological and Evolutionary Synthesis, University of Oslo

John K. B. Ford, PhD
Research scientist (emeritus), Pacific Biological Station, Fisheries and Oceans
Co-chair, COSEWIC Marine Mammals Species Specialist Subcommittee

Claire Garrigue, PhD
French National Research Institute for Sustainable Development, UMR ENTROPIE
New Caledonia (France)

Tilen Genov, PhD
Morigenos – Slovenian Marine Mammal Society
IUCN Cetacean Specialist Group

Deborah Giles, PhD
Science and Research Director
Wild Orca

Christophe Guinet, PhD
Senior Scientist, CNRS
Centre d’Etudes Biologiques de Chizé

Patricia Holm, PhD
Universität Basel

Erich Hoyt
Research Fellow, Whale and Dolphin Conservation
Co-chair, IUCN SSC-WCPA Marine Mammal Protected Areas Task Force
United Kingdom

Rodrigo Hucke-Gaete, PhD
Director, Marine Mammal Laboratory, Universidad Austral de Chile 
Centro Ballena Azul

Miguel Iñíguez Bessega, MSc
Fundación Cethus

Dan Jarvis
Director of Welfare and Conservation
British Divers Marine Life Rescue
United Kingdom

Maria Clara Jimenez A. 
Alianzas para la Conservación 
Fundación Conservaré

Eve Jourdain, PhD
Director and Researcher
Norwegian Orca Survey

Ulrich Karlowski, Biologist (Univ.)
Board of Directors
Deutsche Stiftung Meeresschutz

Sven Koschinski, MSc
Consultant, Marine Nature Conservation

Giancarlo Lauriano, PhD
Senior researcher
ISPRA – Institute for Environmental Protection and Research (ISPRA)

Alfredo López Fernández, PhD
University of Aveiro, CESAM

Paula Méndez Fernandez, PhD
Marine Mammal Researcher
Pelagis Observatory, La Rochelle University

Olaf Meynecke, PhD
CEO, Humpbacks & High-rises Inc
Marine Scientist, Whales and Climate Program

Eduardo Morteo Ortiz, PhD
Laboratorio de Mamíferos Marinos de la Universidad Veracruzana (LabMMar-IIB-ICIMAP-UV)

Giuseppe Notarbartolo di Sciara, PhD
Honorary President
Tethys Research Institute 

Laetitia Nunny, MSc
Science Officer

Liliana Olaya-Ponzone
University of Sevilla

Christian D. Ortega Ortiz, PhD
Universidad de Colima

Daniel M. Palacios, PhD
Endowed Associate Professor in Whale Habitats
Marine Mammal Institute, Oregon State University

Mario A. Pardo, PhD
Research Associate

E. C. M. Parsons, PhD
Associate Professor
Centre for Conservation and Ecology, University of Exeter
United Kingdom

Héctor Pérez Puig, MSc
Coordinador Programa de Mamíferos Marinos
Centro de Estudios Culturales y Ecológicos Prescott, A.C.

M. Rafael Ramírez-León, PhD
Postdoctoral researcher 
Departamento de Oceanografía Biológica, CICESE

Marianne H. Rasmussen, PhD
Research Professor
University of Iceland

Randall Reeves, PhD
IUCN SSC Cetacean Specialist Group

Fabian Ritter, Dipl-Biol 
President, Director of Research
M.E.E.R. e.V.

Lorenzo Rojas-Bracho, PhD
Senior Expert, Whales
Ocean Wise

Hiram Rosales Nanduca, PhD
Professor, Universidad Autónoma de Baja California Sur
Coordinator, Marine Megafauna and Fisheries Research Group

Filipa Samarra, PhD
Research specialist
University of Iceland

Eduardo R. Secchi, PhD
Marine Megafauna Ecology and Conservation Laboratory, Federal University of Rio Grande-FURG

Jörn Selling

Maritza Sepúlveda, PhD
Laboratorio de Ecología de Mamíferos Marinos (LECMMAR), Universidad de Valparaíso

Marina Sequeira
Institute for Nature Conservation and Forests

Salvatore Siciliano, PhD
Pesquisador Titular
Grupo de Estudos de Mamíferos Marinhos da Região dos Lagos

Tiu Similä, PhD
Head of Science

Mark Peter Simmonds, OBE
Director of Science
United Kingdom 

Courtney E. Smith, PhD
Affiliate Faculty
Department of Environmental Science and Policy, George Mason University

Jennifer B. Tennessen, PhD
Senior Research Scientist
Center for Ecosystem Sentinels, University of Washington

Paul Tixier, PhD
Researcher, marine mammal ecology and their interactions with human activities 
French National Research Institute for Sustainable Development, IRD MARBEC

Jared Towers
Executive Director
Bay Cetology

Fernando Trujillo, PhD
Founder, Scientific Director
Fundación Omacha

Jorge Urbán R., PhD
Universidad Autónoma de Baja California Sur

Ingrid N. Visser, PhD 
Orca Research Trust
New Zealand

Lindy Weilgart, PhD
Senior Ocean Noise Expert and Policy Consultant, OceanCare
Adjunct, Department of Biology, Dalhousie University

Hal Whitehead, PhD
Dalhousie University

Alex Zerbini, PhD
Senior Scientist
Cooperative Institute for Climate, Ocean and Ecosystem Studies, University of Washington 

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