Peering into the Hidden World of Whales through Biopsies and Tagging!

These two techniques are considered invasive because they involve piercing the epidermis—the outermost layer of skin—and outer blubber. Biopsies remove a small sample from the animal, while satellite tags pierce the skin and part of the outer blubber to remain in place longer than if they were simply attached to the animal’s back with suction cups.

To understand the value of these techniques, we need to go back in time. About thirty years ago, scientific articles were being written about non-destructive research techniques (those that do not kill the animal being studied), which were still being employed at the time. This is an example of how science has evolved in sync with societal attitudes.

In addition to the ethical advantage, since the animal being studied was no longer killed, it became possible to observe changes in the same individual over the years.

This is an extremely important question to ensure that the research being carried out does not create more problems than it aims to solve!

Satellite tags

For tags, the behavioural effects are also generally short-lived. In the St. Lawrence, for example, tags attached to North Atlantic right whales indicate that the animals resume feeding within minutes of being tagged. In humpback whales, few behavioural reactions to tagging have been noted apart from the animals’ predictable tendency to accelerate in the presence of boats. Moreover, the individuals studied returned in subsequent years to the same sites 100% of the time and continued to reproduce. The types of satellite tags used on St. Lawrence cetaceans generally leave visible marks such as skin discolouring or a slight depression for a few months, though these are usually benign and superficial. In some cases, however, healing can take longer, albeit without compromising the animal’s survival. For example, all 27 North Atlantic right whales tagged between 2019 and 2022 were seen alive the following year. One of these individuals, which showed significant swelling where the tag was attached in the days following the intervention, was seen again the following year with some discolouring that will likely persist for a few years.

Certain data are simply not accessible from the living population using the most common research methods such as photo-identification and photogrammetry. Think hormonal or migratory analyses, for example.

Several hormones, including progesterone and testosterone, are lipophilic and easily detectable in cetaceans’ outer blubber layers. Studying progesterone levels is particularly useful for determining which female whales are pregnant. A 2025 study also reports on this method and the fact that the minke whales of the St. Lawrence are overwhelmingly female, and most of them are pregnant! Examining the ratio of certain stable isotopes in the skin allows for long-term diet monitoring, as has been done with belugas, fin whales and several other species. Additionally, scientists study fatty acids—energy-rich nutrients found in the lipids and external blubber of whales—to determine the age of individuals with an accuracy of ± 3 to 5 years in species like belugas.

By recording GPS data, tags provide particularly valuable information on population migrations or on the recurrence or persistence of animals in certain habitats, including blue whales and fin whales. By better understanding the animals’ movements, it is possible to develop targeted conservation techniques in important areas for these species. For cetaceans, the challenge is significant, as their range can extend across an entire ocean basin!

Lastly, we would be remiss not to mention DNA, social structure and population dynamics analyses. Indeed, intrusive technologies are an integral part of our ability to understand these marine species.

Non-invasive methods also exist! Depending on the objectives of the research project, non-invasive techniques may also be relevant in their own way, including DNA or skin microbiota sampling by skin swabbing or breath sampling using drones, collection of whale feces on the water surface, analysis of water samples containing whale DNA (e.g. the Code Béluga environmental DNA project), or even passive listening to whale vocalizations.