Behaviour

Lemon sharks doing ... erh... something. A cobia is joining the merry-go-round
Lemon sharks doing ... erh... something. A cobia is joining the merry-go-round

What do sharks do all day?

What do sharks do when we’re not looking?

To answer this question, Murdoch University fish biologist Lauran Brewster attached accelerometers to the fins of 24 lemon sharks in the Bimini Islands, Bahamas to find out.

Similar to our wearable Fitbits, the accelerometer collects data about the sharks’ movements, which are then analysed using a statistical approach called machine learning. “Very basically, machine learning is a model that learns patterns in data and can be used to identify similar patterns in new data and make predictions from it,” said Brewster.

Shark diving.
On a shark dive

On Shark "Feeding" Dives

Shark dives provide an excellent way to meet a lot of sharks, and represent a unique situation in which sharks are treated well by humanity.

Shark dive clubs usually bring some fishy scraps—in most cases the remains left over after big fish have been cut up for sale. The scent attracts the sharks into view, and provides a bit of excitement as the animals investigate and try to get a piece.

Masked spinefoots (S. puellus)
Masked spinefoots (S. puellus)

Fishes look out for their buddies

In pairs of coral reef rabbitfishes (f. Siganidae), one fish frequently assumes an upright vigilance position in the water column, while the partner forages in small crevices in the reef substratum. Both behaviours are strongly coordinated and partners regularly alternate their positions, resulting in a balanced distribution of foraging activity.

Many species of sharks, including the lemon shark, are known to actively prefer to be social and live in groups or loose aggregations. Social interaction is thought to be important for the survival and success of juvenile lemon sharks.

Sharks can form social bonds

Sand tiger sharks, top predators that live in coastal waters off the Eastern United States, have experienced drastic population declines over the past several decades. Understanding how these sharks move and interact could help biologists better conserve this species and determine how vulnerable they are to human activities. During summer, the sharks congregate in the shallow waters of Delaware Bay but are highly migratory, travelling as far south as the Carolinas and Florida during the winter and early spring.

Sperm whales form clans with diverse cultures

After studying more than 23,000 sperm whale vocalisations recorded from 1978 to 2017 in the Pacific Ocean, researchers have concluded that sperm whales use distinctive vocalisations to identify themselves with specific whale clans.

Called “identity codas,” these vocalisations comprise sequences of clicking sounds that distinguish different social groups. They are different from non-identity vocalisations used across all the different whale clans.

Sailfish hunting sardines in the open ocean off the coast of Mexico. Image courtesy of Rodrigo Friscione
Sailfish hunting sardines in the open ocean off the coast of Mexico

How marine predators find food hot spots in open ocean

Ocean eddies are coherent, rotating features which are ubiquitous at mid-latitudes and rotate clockwise In the Northern Hemisphere.

As these anticyclonic eddies move throughout the open ocean, a recent study suggests that the predators are also moving with them, foraging on the high deep-ocean biomass which tends to accumulate within.

Got an itch that needs scratching?

Scientists have observed instances in which tuna rub themselves against the side of sharks. Apparently, they do this to dislodge painful parasites that cling to their head, eyes and gills.

“Shark skin is really smooth in one direction and it’s like sandpaper in the other,” said Chris Thompson, a Research Fellow at the University of Western Australia.

Thompson and his colleagues observed this behaviour after studying the footage of floating, baited underwater cameras which they had deployed in 36 regions in the Pacific, Indian and Atlantic Oceans in 2012 to 2019.

Orcas and humpbacks brawl

Whale watchers were making their way toward the U.S.-Canadian border in the Strait of Juan de Fuca when the captain spotted the group of whales. At first, whale watchers observed what they thought was a pod of roughly 15 Bigg’s orcas swimming and "being unusually active at the surface." Before long, it became apparent that two humpback whales were in their midst.

Intense

According to observers who came and went throughout the day, the intense encounter that unfolded included an astonishing three hours of breaching, tail-slapping and loud vocalizations.

Dolphin BFFs?
Dolphin BFFs?

Male dolphins form lifelong bonds

Researchers have discovered that male bottleneck dolphins form long-term social groups to help one another find mates and fight off competitors.

It was the first time such behaviour was observed in the animal world.

Their conclusions were based on data collected of 202 Indo-Pacific bottlenose dolphins between 2001 and 2006 in Shark Bay, Australia, using visual and auditory data. In the lab, the researchers then focused on studying the interactions of 121 of individuals for the next decade.

Seeking Eye Contact: Fish Gaze Reveals Self-Awareness

For many years, I held a weekly feeding session for the resident reef sharks and their visitors in the study area where I observed their behaviour. If I had enough shark food, I would scatter crumbs into the water for the fish after the sharks had left. The fish knew this, so they had to wait, and while they were waiting, they were excited.