Aarhus University Seal

Marine Mammal Research

We focus on the biology and prevalence of marine mammals and other marine vertebrates as well as the factors that affect the animals’ survival and population development. We study this by means of aerial surveys, telemetry data and data on the animals' health status, which enable us to quantify the effects of anthropogenic disturbances at both the individual and population level.

We are responsible for the national monitoring of marine mammals and underwater noise and contribute to the development of new management initiatives, both nationally and internationally. In addition, we conduct research to understand how the factors that affect the behaviour and health of individual animals interact and influence the distribution and dynamics of different populations. This becomes increasingly important as the marine environment becomes more affected by human activities such as fishing, noise from construction activities and ships, emissions of chemicals and climate change.

Research topics in brief


Signe Sveegaard

Head of Section/Senior Advisor

Ecotoxicology, climate and health

Through international projects, we uncover the relationship between climate change and the up-concentration of environmental contaminants including their impact on the health of fish, birds, mammals and humans. We particularly focus on predatory animals and birds in the Arctic and the Baltic Sea, where, among other things, we study diseases that can be transmitted from wild animals to humans (zoonoses). In addition, we specifically focus on understanding ecosystem dynamics, and in this context, we study food chains and climate change and how they affect the composition and exposure of environmental contaminants and diseases. Some of our core activities are to incorporate temporal and geographical trends into risk assessments in the circumpolar AMAP and BONUS programs.


Disturbance and underwater noise

Ever since diesel engines became common in ships about 100 years ago, there has been an increase in the human contribution to ambient noise in marine waters. However, ships are not the only source of the problem. Offshore activities, such as construction of offshore wind farms, oil and gas exploration and military activities, such as disposing of old ammunition and antisubmarine sonars also contribute to the noise. For these reasons, we monitor underwater noise in Danish marine areas for the Ministry of Environment and Food of Denmark and conduct research to quantify the effects of underwater noise on marine mammals and fish. As underwater noise knows no borders, we also participate in international research projects and expert groups that coordinate monitoring and regulation of underwater noise in the Baltic and the North Seas (within the framework of the regional seas conventions HELCOM and OSPAR, respectively).


Monitoring populations

The section for Marine Mammal Research is responsible for coordinating and conducting the national monitoring of the Danish marine mammals. We have many years of experience in tracking the population dynamics and prevalence of our three most common species: The harbour seal, the grey seal and the harbour porpoise. Seals are monitored throughout Denmark by plane at their haul-outs on land. Harbour porpoises are monitored by plane, from ship and by passive acoustic listening stations that detect their echolocation clicks under water. The surveillance of marine mammals is part of the NOVANA program (the national surveillance program of the aquatic environment and nature).


Collecting of dead marine mammals

We collect dead, stranded marine mammals, regulated seals and bycaught porpoises and seals in order to measure their blubber thickness in connection with a project for the Danish Environmental Protection Agency. The f blubber layer is a measure of the animal's health and nutritional state: When the animal is healthy and receives the quality and quantity of food it needs, energy is stored in a subcutaneous layer around the animal. The thickness of the blubber layer varies over the year to regulate heat loss from the animal to the water. In addition, blubber thickness varies with gender, age and reproductive status, as well as there are differences between populations. Therefore, a large number of animals must be collected to describe the blubber thickness of Danish marine mammals quantitatively.

If you find a dead marine mammal

Take a picture of the animal and note the position/address. Please send information to:


Modelling population effects

Marine mammals are influenced by anthropogenic disturbances, but it is usually not possible to observe these effects directly – both because the animals are difficult to observe and because we wish to understand the effects of the potential impacts before they actually happen. For this reason, we use different types of models to examine population effects. Among other things, we use spatial models to predict animal abundances in different areas at different times of the year and agent-based models that simulate the behavioral reaction of individual animals to disturbances. The population dynamics emerge through the interaction between the individual animals in the model.

DEPONS is an example of an agent-based model for harbour porpoises: https://depons.eu/



From Sveegaard, S., Nabe-Nielsen, J., & Teilmann, J. (2018). The prevalence and status of porpoises in marine habitats in Danish waters.

Telemetry and tagging

The study of animal movement patterns enables us to monitor survival rates and reproduction of species and populations and to gain a solid understanding of the distribution and interactions among individuals, populations and species. By looking into these patterns and interactions, we can learn more about the animals' ecology, including foraging, reactions to disturbances, mating, distribution and migration. A broader and deeper understanding of movement patterns, behaviour and disturbances plays a key role in our research and has fundamental value for our work with managing and protecting each species.

We focus on tagging porpoises and seals in Danish waters. Among other things, we use the research results for consultancy tasks with public as well as private sector clients.



Marine mammals need energy for growth, survival and reproduction. The energy required to support this comes from the prey they consume. When marine mammals are disturbed by human activities (e.g. noise), it may lead to an increase in energetic costs and/or a decrease in energy gains. In the long term, repeated disturbances may lead to a reduction in body fat reserves (body condition), which marine mammals need to survive and reproduce. We study the relationship between marine mammals' behaviour and bioenergetics, as well as the relationship between body condition and individual survival and reproduction, in order to better understand the consequences of human disturbance on marine mammal populations. We carry out and collaborate on a wide range of bioenergetic projects around the world, from the polar regions to the tropics, where we use new drone photogrammetry methods to measure the size and body condition of whales.