Picture yourself looking down at the North Atlantic Ocean from space — there are no forests, mountains or obvious boundaries marking where one habitat ends and another begins. Just an enormous blue surface stretching from the continental shelf into the open ocean. If you could see the ocean the way marine animals experience it… the map would look very different. But scientists are increasingly learning how to make that hidden map visible.

A new study has used satellite tracking of 82 individual animals, including 28 blue sharks, 26 leatherback turtles and 28 fin whales, to ask a rather simple question: do marine animals choose particular kinds of ocean habitat? The answer appears to be yes. The concept is called “pelagic Seascapes;” rather than treating the ocean as a collection of individual measurements (such as temperature or chlorophyll), Seascapes combine multiple physical and biological characteristics into recognizable environmental categories. These include sea-surface temperature, salinity, ocean height, sea ice, chlorophyll-a and measures of ocean color and fluorescence. The result? Maps produced globally by NOAA CoastWatch that are available for free, providing a standardized way to describe the constantly changing habitats of the open ocean! And boy, does it change. The ocean does not behave like a terrestrial landscape. While a forest can remain a forest for decades, an ocean habitat can shift, stretch, disappear or re-form as currents move, temperatures change and biological productivity rises and falls. Water masses have “diffuse boundaries” rather than neat borders. But those shifting properties can still create recognizable ecological conditions. Think of it as the difference between saying, “This part of the ocean is 22°C” and saying, “This is a warm, nutrient-rich system where several environmental conditions occur together.” The second description may be much closer to what an animal actually experiences.

To test this idea out, the researchers combined monthly Seascape maps with satellite tracking data from the Northwest Atlantic Ocean. The animals’ movements covered hundreds to thousands of kilometers and generated more than 117,000 original location points before the tracking data were standardized for analysis. The researchers then used resource selection functions (RSFs) to compare where animals actually traveled with the habitat available to them, revealing whether they selected or avoided particular habitat types based on how often they used them relative to their availability.

Blue sharks showed particularly strong selection for several coastal and productive Seascapes, including fresh-influenced subtropical coastal systems and warm nutrient-rich bloom systems. They also selected temperate subpolar transition waters while showing evidence of avoiding equatorial tropical transition systems. Leatherback turtles similarly selected several productive Seascapes, including fresh-influenced subtropical coastal waters, seasonal polar bloom systems and warm nutrient-rich bloom systems. Fin whales showed a strong preference for seasonal polar bloom and freshwater-influenced shelf environments, although the whale results carried greater uncertainty because their tracking data covered fewer months. Each of these animals has radically different ways of living. Blue sharks are ectothermic predators that eat fish and squid; leatherbacks are large reptiles that specialize on gelatinous zooplankton; fin whales are enormous warm-blooded filter feeders that target krill-like euphausiids and small fish. Yet all three responded to the broader environmental mosaics represented by Seascapes!

That suggests perhaps an animal is not simply following one environmental variable at a time. A shark may not be thinking, in biological terms, “the temperature is right.” Instead, its movements likely are due to a combination of temperature, productivity, ocean circulation and other conditions that together create a useful foraging environment. Seascapes revealed many patterns of habitat use that emerged from interacting biophysical conditions rather than from a single measurement. So when researchers examine environmental variables separately, they can miss relationships that only become apparent when those variables occur together.

This doesn’t mean the scientists are suggesting that managers could simply draw enormous protected areas around every preferred Seascape. Not even remotely possible because the preferred environments identified in this study can extend across hundreds of kilometres, while many management decisions need much finer-scale information. Instead, Seascapes could function more like a constantly updating environmental warning system. If we know that particular marine megafauna tend to concentrate in certain ocean conditions, those conditions can be monitored as they develop. That could help identify when and where animals are more likely to overlap with threats such as fishing activity. And because the Seascape product is automated, globally consistent and freely available, it could also be useful in places where detailed environmental data or expensive modelling are difficult to obtain. But what is more intriguing about Seascapes is what they could tell us about a changing ocean. If the Seascapes themselves shift in extent, frequency or persistence as the climate changes, those changes could potentially provide an early signal that marine animals’ preferred habitats are moving too. The researchers suggest that Seascapes could eventually be paired with forecasting systems and climate models to explore how important pelagic habitats might reorganize in the future.

There are still important caveats. For exampel, the three species were not tracked for identical periods and fin whale data were particularly limited seasonally. The researchers also emphasize that more species and longer tracking records will be needed to determine whether these patterns extend across entire marine megafauna communities. Still, the bigger idea is… compelling. We often talk about the ocean as though it were one enormous habitat but for the animals living there, it is anything but. It is a shifting mosaic of conditions, opportunities and constraints. If forests have habitats and landscapes, why shouldn’t the open ocean have them too?