Why marine creatures swim in circles

Animals might swim in circles to collect navigational information. Movement patterns may represent an intuitive connection to Earth’s geomagnetic field.

Pixabay / Public Domain
Ecology & Science

Thanks for advancements in tracking technologies, scientists have discovered an intriguing behavioural trait amongst some marine species: They sometimes swim in circles.

When studying the navigational abilities of sea turtles, Tomoko Narazaki, a marine researcher at the University of Tokyo, observed that the turtles in her study would swim in circles so constantly “just like a machine.”

Whales and dolphins naturally muffle loud sounds

Adjustable sensitivity protection from sonar

Ecology & Science

Instead of wearing earplugs at a rock concert, imagine you could simply tune a dial inside your ears to lower the volume and protect your hearing. In a new report published in Integrative Zoology, researchers have discovered four whale species and dolphins can do just that. This could potentially shield the animals from navy sonar and oil drilling, linked to at least 500 marine mammal deaths since 1963.

Seals may use Earth's magnetic field to navigate

How are seals able find their way back to their dive holes with such amazing precision? Researchers believe they are using the Earth's magnetic field as a natural GPS

Ecology & Science

If the hypothesis turns out to be true, it would represent the first evidence of such a trait in a marine mammal.

Randall Davis of the Department of Marine Biology at Texas A&M University, Terrie Williams, a professor of ecology and evolutionary biology at the University of California, Santa Cruz and another colleague, Lee Fuiman, associate director of the University of Texas' Marine Science Institute in Port Aransas, have been studying the behaviour of Weddell's for decades.

X-RAY MAGAZINE FEATURE

Navigation in Fish

Coral reef fishes have a life cycle that is divided in two. They begin their life after hatching with a pelagic larval phase, lasting from a week up to two months depending on the species, and ends with a benthic phase, when the fish larvae settles to the coral reef one night. For decades the pelagic phase has been a black box to researchers. Only recently has the lid to this black box been opened.

Words:
Michael Arvedlund
Peter Symes
Images:
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Ecology & Science

In a recent article in X-RAY MAG, we looked at the astonishing swimming ability reef fish larvae have.

However, long-distance swimming is of little use without navigation. Orientation is necessary if a pelagic reef fish larva is to find a reef by other than chance, and orientation requires not only cues and the sensory means to detect a coral reef, but also the ability to determine the direction from which the cues originate.

Vertical distribution

Vertical distributions can also differ between locations. For example, fish larvae may swim deeper in the ocean than in an atoll lagoon, or they may swim deeper off the windward than off the leeward side of a reef. We can expect that behaviour differs between night and day and probably at different stages in larvae development.

Owing to Odours

Olfaction has the potential to operate over larger scales, as has been known with salmons for many years. If odors are carried by currents and structured by fronts between water masses, olfaction operating at a small scale could result in orientation over larger scales. This may also be the case with temperature differences. Damselfishes, among them the popular anemonefishes, have been shown to use chemical cues to locate settlement sites over relatively small distances, i.e. a few meters.

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