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Whales Desert Historic Feeding Grounds—Is Climate Change to Blame?

Climate
Whales Desert Historic Feeding Grounds—Is Climate Change to Blame?

By Kieran Cooke

A mystery is unfolding in the waters of the North Atlantic. Every summer and autumn, numbers of North Atlantic right whales gather in the waters between the eastern Canadian provinces of New Brunswick and Nova Scotia to feed on massive amounts of zooplankton.

But this year the right whales—one of the rarest and most endangered animals on earth—have not turned up in a stretch of water called the Bay of Fundy.

In winter right whales usually move 1,000 miles south to breeding grounds off the coasts of the states of Georgia and Florida, but with warming waters, their habitual migrations could be changing. Photo credit: Australian Animal Learning Zone

While no-one is sure what is causing the change in the whales’ behavior, a report in Yale Environment 360 says alterations in the whales' feeding patterns are taking place against a backdrop of major climate-related ecosystem shifts throughout the north-west Atlantic Ocean.

The right whale—Eubalaena glacialis—came by its name because it was considered by whalers as “the right whale” to hunt, due to its large concentrations of valuable blubber.  It was also easy prey: adult right whales average between 12 and 16 meters in length and can weigh up to 70 tons. They move relatively slowly through the water and float when killed, making them easy to handle.

Record Year

At one stage the North Atlantic right whale was hunted to the point of extinction: in recent years numbers have grown to more than 500 individuals.

Marine scientists are now investigating whether changes in water temperature are responsible for shifting the whales’ food supplies and so causing their migratory pattern to alter.

The main ingredient in the whales’ diet is the zooplankton Calanus finmarchicus. Researchers say there’s been a scarcity of the zooplankton in waters around the Bay of Fundy recently: marine scientists say warming waters in the Gulf of Maine, south of the Bay of Fundy, are one likely cause of the decline.

The Grand Manan Basin Conservation Area is an important nursery ground for mother and calf right whales. Map courtesy of
Canadian Whale Institute

In 2012 waters in the Gulf of Maine and elsewhere in the north-western Atlantic underwent a sharp rise in temperature due, say scientists, both to long-term climate change and to an unusually warm year in the area. In the continental U.S., 2012 was the hottest summer ever recorded.

Fleeing the Heat

Various marine species, including cod and red hake, have been moving more to the north in recent years. A study by the U.S. National Oceanic and Atmospheric Administration found that of 36 fish stocks examined, more than half were shifting northwards or to greater depths to compensate for warming water temperatures. Lobster and shrimp—vital to the Gulf of Maine’s fishing industry—are also believed to be moving to cooler waters further north.

Shifts in stocks of species at the base of the food chain—phytoplankton and zooplankton—are thought to be due both to warming waters in the north-west Atlantic and to changes in ocean currents. Scientists have shown that the melt of Arctic sea ice, together with more melting of ice sheets in Greenland and Canada, is likely to mean more freshwater being poured into the north-west Atlantic, leading to increased stratification of ocean waters and alterations in plankton stocks.

But the disappearance of right whales from their usual autumn feeding ground in the Bay of Fundy remains a mystery. Some have been reported in waters well to the north. In winter, large numbers have been sighted further south, in Cape Cod Bay, off the U.S. coast.

In winter right whales usually move more than 1,000 miles south to breeding grounds off the coasts of the states of Georgia and Florida. Now, with waters staying relatively warm further north, they might be changing their migratory behavior, deciding not to make the long journey south in the winter months.

Visit EcoWatch’s CLIMATE CHANGE page for more related news on this topic.

 

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Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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