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Predator catches prey, predator eats prey. This scene alone looks pretty simple to anyone watching but among fish-eating resident killer whales in the Pacific Northwest, a successful hunt does not always end with the whale that caught the fish getting to consume it.

Salmon can and sometimes will be divided and passed between pod members. Mothers share with their offspring, while other relatives may receive portions of a catch. Adult sons can continue receiving food from their mothers long after they have reached adulthood. Food is about more than just feeding the individual whale; feeding is woven into the social lives of resident killer whales.

Much of what scientists know about these interactions has historically come from observations made at the surface. But a recent study published this year in Marine Mammal Science is showing that looking down from above may reveal details that you can’t see from the deck of a boat. This study used a decade of drone-derived imagery to examine prey sharing among Northern and Southern Resident killer whales. This research not only provided a closer look at who shares food with whom but also demonstrated how changing our perspective can reveal behaviors that have been happening beneath the surface all along.

Two Resident Populations

The Northern and Southern Resident killer whales are two distinct populations found along the Pacific coast of North America. Unlike their mammal-eating counterparts that hunt seals, sea lions, and other marine mammals, residents specialize primarily in fish. Their preferred prey are salmonids, especially Chinook Salmon (Hanson et al., 2021), which Free Willy taught us, is like chocolate to them.

Their lives are also deeply social.

Resident killer whales live within stable, matrilineal social groups. The matriline generally consists of a female and her descendants, with both male and female offspring maintaining strong associations with their mothers throughout their entire lives.

These relationships extend into feeding.

Previous research has shown that all ages and sexes can participate in prey sharing but much of the behavior occurs between maternal relatives. Adult females are particularly important sharers and frequently provide for their offspring. While prey sharing between the mother and daughter declines as the daughter matures, adult sons may continue receiving food from their mothers throughout adulthood (Wright et al., 2016).

Understanding that distribution may be particularly important for these whales because access to prey has consequences beyond a single feeding event. Both Northern and Southern Residents rely heavily on salmon, with previous research linking Chinook abundance with survival and reproductive success in both populations (Ward et al., 2009). Salish Sea Chinook salmon populations have declined by 60% since the Pacific Salmon Commission began tracking their abundance in 1984 (State of Salmon in Watersheds, 2024). With such an important food source under pressure, understanding how available prey is shared between individual whales may provide another piece of the conservation puzzle.

Northern and Southern Residents have also experienced very different population trajectories. These differences raise questions about whether variations in ecology, prey availability, and foraging behavior may also be reflected in the way food moves between individuals within each population.

Looking at Killer Whales from Above

Studying prey sharing in a wild killer whale is not easy.

A researcher observing from a boat only sees a fraction of what is happening around and immediately below the ocean surface. Salmon may disappear underwater, a whale may release a piece of prey that another individual retrieves, or several whales may be interacting around a fish while much of the exchange remains obscured

Technological advances in drones have changed the perspective.

From above, researchers can follow whales as they move through the water and observe interactions occurring at or near the surface that may be too difficult to detect from a boat. Individual whales can be identified, prey can sometimes be seen in their mouths or nearby, and researchers can examine how prey moves between members of the group.

Kay and colleagues analyzed aerial imagery collected during long-term studies of both resident populations; Northern Resident imagery spanned 2014–2024, while Southern Resident imagery was collected from 2018–2024. The researchers identified a predation event when imagery showed a whale handling prey. When a fish or portion of a fish moved from one whale to another, the interaction was classified as prey sharing.

The aerial perspective also allowed researchers to assign roles within those interactions. A whale handling and transferring prey could be identified as a sharer, the whale receiving it as a recipient, while nearby whales that did not handle the prey were classified as bystanders.

Even the way food changed hands could be observed.

Researchers described passive sharing as an interaction in which one whale released prey, and another retrieved it. During active sharing, the whales approached one another, and both interacted with the prey during the transfer.

Together, those details offered a much closer view of what a shared meal actually looks like.

What Did the Research Find?

Across the images analyzed, researchers identified 93 predation events: 41 involving Northern Residents and 52 involving Southern Residents. Prey sharing occurred in 24 of the 41 Northern Residents events (approximately 59%), compared with 22 of the 52 Southern Resident events (approximately 42%).

The researchers also found preliminary differences involving adult females. Northern Resident adult females shared prey more often than Southern Resident adult females and tended to share larger portions of prey.

Those findings are intriguing, but they require some caution.

A higher percentage of observed sharing does not mean that Northern Residents are simply more “generous” than Southern Residents. Human descriptions like generosity can easily impose motivations on animal behavior that the data cannot demonstrate. Instead, the differences raise questions.

Are the patterns related to differences in prey availability? Do ecological conditions affect how much of a captured fish can be shared? Could differences in social relationships or foraging strategies influence how food moves through a group?

The researchers describe the comparisons between the populations as preliminary, rather than providing a final explanation for why the patterns differ. The study generates new hypotheses that future research can investigate. Sometimes that is exactly what good science does: answering one question reveals several more waiting behind it.

A Salmon Is More Than a Salmon

Why should we care which whale receives part of a fish?

Because for an animal living within a tightly connected social system, access to food may not depend solely on its own ability to catch it.

Prey sharing creates another pathway through which energy can move through a killer whale population. A successful hunter may provide food to an offspring or another relative, meaning the consequences of one successful hunt can extend beyond the whale that made the capture.

That becomes especially important when the resource being shared is limited.

Chinook salmon availability has long been an important conservation concern for resident killer whales. If prey is scarce, understanding who catches food is only part of the picture. Scientists also need to understand what happens to that food after it is caught.

Who receives it? How much is shared? Does age or sex matter? Does relatedness matter? And do those relationships change when prey becomes more or less available?

The answers could help researchers better understand how changes in salmon abundance affect individuals differently within a population.

For Southern Residents in particular, these questions exist within a much larger conservation challenge. Vessel presence and noise can further complicate access to prey by reducing prey-capture effort (Holt et al., 2021). Understanding their foraging behavior at the level of individual whales adds another piece to an already complicated picture.

Seeing What We Couldn’t See Before

One of the most interesting parts of this study may not be a particular percentage or behavioral difference at all, it may be the view.

Resident killer whales are among the most intensively studied cetaceans in the world. Researchers have followed individuals across generations. Family relationships are documented. Individual whales can be recognized by their dorsal fins, saddle patches and other distinguishing features.

And yet there are still parts of their lives that are difficult for us to see.

Drone technology does not replace the decades of boat-based observations that created the foundation of what we know about these populations. Instead, it adds another perspective.

A behavior that might appear as little more than several whales surfacing together from the side can look very different from above. A salmon becomes visible. Its movement can be followed. The whale carrying it can be identified. Another approaches. The prey changes possession. And suddenly, what appeared to be a feeding event becomes a social interaction.

There are limitations. Weather, sea conditions, water clarity, battery life and image quality all affect what researchers can observe. The study also focused on prey sharing occurring at or near the surface, meaning interactions deeper underwater still remain unseen. But each improvement in how we observe wild animals gives us another opportunity to understand behavior that was previously hidden from us.

More Than a Meal

A salmon passing between two killer whales may last only moments but within that exchange are pieces of a much larger story: predator and prey, mother and offspring, individual and family, ecology and survival.

Kay and colleagues’ study gives us a new way to watch those relationships unfold. It also reminds us that even after decades of studying these whales, familiar behaviors can look different when we find a new way to see them.

There is still much we do not know about why Northern and Southern Residents may differ in how they share prey, or how those behaviors respond to changing ecological conditions. Future research and more observations from above may begin filling in those gaps. For now, the next time a resident killer whale surfaces with a salmon, the more interesting question may not simply be whether it caught dinner.

It may be who eats next.

Featured Research

Kay, S. W. C., Barrett-Lennard, L. G., Visona-Kelly, B. C., Mikus, M.-A., Weiss, M. N., Croft, D. P., Vergara, V., Fearnbach, H., Durban, J. W., & Darimont, C. T. (2026). Using drone-derived imagery to describe prey sharing behaviors in two piscivorous resident killer whale populations. Marine Mammal Science, 42(3), e70215. https://doi.org/10.1111/mms.70215

Additional References

Hanson, M. B., Emmons, C. K., Ford, M. J., et al. (2021). Endangered predators and endangered prey: Seasonal diet of Southern Resident killer whales. PLOS ONE, 16(3), e0247031. https://doi.org/10.1371/journal.pone.0247031

Holt, M. M., Tennessen, J. B., Hanson, M. B., et al. (2021). Vessels and their sounds reduce prey capture effort by endangered killer whales (Orcinus orca). Marine Environmental Research, 170, 105429. https://doi.org/10.1016/j.marenvres.2021.105429.

State of Salmon in Watersheds 2024. (2024). https://stateofsalmon.wa.gov/wp-content/uploads/2025/05/ExecSummary-2024.pdf

Ward, E. J., Holmes, E. E., & Balcomb, K. C. (2009). Quantifying the effects of prey abundance on killer whale reproduction. Journal of Applied Ecology, 46, 632–640. https://doi.org/10.1111/j.1365-2664.2009.01647.x

Wright, B. M., Stredulinsky, E. H., Ellis, G. M., Ford, J. K. B., & Ellis, G. M. (2016). Kin-directed food sharing promotes lifetime natal philopatry of both sexes in a population of fish-eating killer whales, Orcinus orca. Animal Behaviour, 115, 81–95.