McGill University
Ph.D. candidate

Supervisor: Melissa McKinney
Robert J. Letcher
Start: 2019-01-01
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The role of feeding ecology in persistent organic pollutant exposures of killer whales (Orcinus orca) across the North Atlantic Ocean
Our world relies on a delicate balance between its systems, and billions of people depend on the oceans to live and thrive. According to the United Nations, the sustainability of our oceans is under severe threat. As sentinel species, marine mammals allow us to understand how humans impact the oceans and their ecosystems. They are also essential for the ecological balance of the oceans because their predation affects entire food chains. Yet, chemical pollution and reduced available prey due to climate change are serious threats to their survival. Therefore, understanding the threats to marine mammals is crucial to improve their conservation and allow human populations who rely on the same ecosystems to prosper. As the oceans' top marine mammal predators, killer whales are threatened by man-made pollutants like industrial chemicals, flame retardants, and pesticides. These pollutants bind to fat and concentrate through the food chains to reach high concentrations in killer whales. A high concentration of these chemicals can cause immune and reproductive problems. A recent study even suggested that half of killer whales populations could disappear by 2100 because of these pollutants. But not all killer whales are equally threatened. The ones that feed on marine mammals, like seals and toothed whales, are far more likely to accumulate toxic concentrations of these chemicals. Killer whales that rely on fish solely usually have pollutant levels within safe limits. Yet, these dietary differences sometimes occur inside the same population, with individuals specializing in different prey. We are only just realizing how important this phenomenon is for the health of these animals. We must consider individual ecology to understand the population-level threats posed by pollutants to this sensitive species. Unfortunately, studying killer whales' feeding ecology is challenging because observation alone cannot reflect long-term habits. Nevertheless, we can use chemical tools to understand killer whales' diets. To do so, we will extract, measure, and compare different elements (lipids and stable isotopes) in whale skin biopsies (skin and fat) and their prey. Using statistical models, we will then reconstruct their diets. My thesis aims to measure and compare killer whale diets across the North Atlantic Ocean and assess how these diets influence the accumulation of harmful pollutants in their bodies. It will use the biggest number of killer whales ever sampled in the North Atlantic, from Pond Inlet in Canada, to Skjervøy, Norway. Depending on what the whales eat, they will face different risks: health risks due to pollutants, food availability due to climate change, etc. Therefore, it is essential to study their feeding ecology to improve their conservation efforts and help our decision-makers reduce pollution. The tools we develop in my thesis will also help investigate their future dietary shifts caused by climate change. We know some killer whales are starting to invade the ice-free Arctic, and they likely started feeding on local prey. Our results may also explain how killer whales impact prey availability for other charismatic and threatened predators like polar bears and indigenous communities relying on subsistence harvesting.


ecotoxicology, killer whales


1- Humpback whales (Megaptera novaeangliae) breeding off Mozambique and Ecuador show geographic variation of persistent organic pollutants and isotopic niches
Remili, Anaïs, Pierre Gallego, Marianna Pinzone, Cristina Castro, Thierry Jauniaux, Mutien-Marie Garigliany, Govindan Malarvannan, Adrian Covaci, Krishna Das
2020 Environmental Pollution

2- Individual Prey Specialization Drives PCBs in Icelandic Killer Whales
Remili, Anaïs, Robert J. Letcher, Filipa I.P. Samarra, Rune Dietz, Christian Sonne, Jean-Pierre Desforges, Gislí Víkingsson, David Blair, Melissa A. McKinney
2021 Environmental Science & Technology