Harbour Seal Feeding Behavior: Uncovered and Explained

One of the predators missing from the documented literature is the harbour seal”, says Austen Thomas, a PhD candidate at the University of British Columbia.

In 2008, Austen led an exciting research project examining the feeding behaviour of harbour seals in the Strait of Juan de Fuca, off the coast of Washington state. Austen was interested in finding out whether harbour seals have different feeding patterns during the winter spawning season of Pacific herring — a species which comes into close proximity with the seals when they move inshore to lay their eggs. Austen wanted to know whether the seals made use of the increased herring numbers when they occurred conveniently nearby. Surprisingly, he found that the seals did not catch more spawning herring during winter spawning season in general, choosing instead to catch young, small fish. This behaviour allows for the successful laying and hatching of a new generation of herring.

We set out to find out more about how Austen carried out his research; how he used equipment and analysis to track seals and uncover their feeding habits and diet; and what the “bigger picture” implications of his work are. The below video tells the story of Austen’s research.


Austen and his team use glue to attach the TDR-GPS combo to a seal. Austen Thomas photo.

As mentioned in the video, Austen used Global Positioning Systems (GPS) and time depth recorders (TDR) to understand where and when harbour seals most frequently feed. Both the GPS and TDR use satellites to pinpoint the seals location and monitor their diving behaviour at their feeding grounds. While the GPS revealed movement of the seals around their home, Protection Island, the TDR showed the diving depth patterns of seals. The tracking devices showed Austen how the seals movements matched up with the movement of the Pacific herring population.

A seal makes a break for home after getting outfitted with the tracking devices. The devices are designed to come off when the seal molts. Whether they floated as planned is another story. Austen Thomas photo.

seal scat. Austen Thomas photo.

In addition to tracking seal movement through space and time, Austen also collected and analyzed harbour seal feces, or scats. This portion of his research allowed him to identify the species and age of fish consumed.

 

Collecting seal scat for diet analysis. Austen Thomas photo.

Scat analysis was done by examining the bone remains under a microscope. Specifically, looking at the otoliths (the inner ear bone of the fish) that remained in seal fecal samples enabled Austen to identify age, size, and species of the fish consumed. This research revealed how much of different-aged Pacific herring was being eaten during different times of the year.

Besides learning about Austen’s research, we wanted to find out about the broader impacts of his work. For example, his work has potential implications for both local fisheries and the Species at Risk Act (SARA), which is used to guide resource management efforts. In the following podcast, we discuss the “bigger picture” context that Austen’s research fits into.

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Austen’s research sheds light on unexpected feeding behaviour of the seals residing on Washington’s Protection Island. These findings are not only interesting; we will likely see that Austen’s discovery of surprising seal feeding patterns contributes to shaking up common understanding of this marine ecosystem.

-This multimedia project was a Group A production.

Protected: The Unsustainable Truth behind Small-scale Fisheries

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Beetle feet inspire extra sticky glue

Source: robault.co.uk

Like many insects, beetles can walk upside down without falling due to the extremely sticky structures of their foot pads.  Scientists James Bullock and Walter Federle from the University of Cambridge recently published a study in the journal Naturwissenschaften (The Nature of Science) that found different hair structures have different levels of stickiness.  Their study is the first to measure the adhesive strength of a single seta, the adhesive hairs that are responsible for the “stickiness” of the beetle’s feet.

The researchers found there were three different structures of setae on the foot pads: pointed, flat (spatula-tipped) and disk-like.  The three structures have different functions depending on the specific pattern they are arranged in.  Each of these structures is made up of thousands of microscopic hairs and prior to this study there was no way to determine the adhesiveness of one individual hair due simply to their microscopic size.

By using an extremely fine glass cantilever and measuring the deflection of the cantilever with a microscope, the exact force needed to detach each hair was calculated.  By use of this novel technique the researchers were able to calculate the exact stickiness of each hair, which are only 5 micrometers across.

Source: sophiewasadog.wordpress.com

Of the three different seta structures the disk like hairs had the greatest level of stickiness, followed by the spatula shaped hairs, with the pointed hairs coming in least sticky.  The most sticky hairs were also the most stiff, most likely providing stability to the foot-pad.  The researchers hypothesize it is these disk-like hairs that are particularly responsible for the strong adhesion the beetles have to smooth surfaces, such as the underside of a leaf.

This adhesion is also important during mating so that males can attach themselves to a female’s back.  The other hair structures which aren’t as sticky are probably used for adhesion while running because they are quicker and easier to unstick.

This new understanding of the beetle’s sticky feet may one day lead to the creation of bio-inspired synthetic adhesives, such as extra sticky super glue.

Cyborgs of Tomorrow

Remember that movie ‘I, Robot’ (2004) with Will Smith? He plays a cop in the near future who loses one of his arms in an accident and gets it replaced with a fully integrated robotic arm. By “fully integrated” I mean it has full range of motion of a normal arm and Will Smith can operate just by thought.

While this certainly is the work of science fiction, you may be surprised to know how close science is to actually achieving this kind of technology.

Back in 2008, a team of scientists from the University of Pittsburgh implanted micro-electrodes into a monkey’s brain that enabled it to move a rudimentary robotic arm. Two years later, the same group of scientists improved the technology as they were able to get the monkey to operate a more complex robotic arm just using its thoughts. Watch the video below.

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These scientists are not the only ones to pioneer this sort of technology. In 2009, Toyota had developed a wheelchair that could operate based on the user’s “thoughts”. This technology did not require any implants, but instead worked by picking up brain signals from the user (they had to wear a special cap) and transmitting those to a computer which controlled the wheelchair. This technology seemed to be limited to the most basic commands; left, right, forward and back. The emergency stop command was actually puffing out one of your cheeks in case the wheelchair went out of control.

So where does the technology sit today? Interestingly enough, the Defense Advanced Research Projects Agency (DARPA) had been funding scientists to develop a super complex prosthetic limb for a few years now. It’s one of the most complex ones to date capable of all kinds of fine motor control.

Much like the research from University of Pittsburgh, this arm relies upon implants in the brain to be fully integrated. The latest news is that the technology is about to begin its first round of human trials!

Considering the implications of this technology, there’s good and bad sides to it. For example; on the good side we may be able to turn Stephen Hawking into a cyborg. That side of the technology is both cool and good news for people who have suffered accidents or were born with the inability to use their bodies fully.

On the scarier side, this technology could be used to “replace” healthy limbs with stronger, more durable ones. Why else would the military be funding the research? Cyborgs may be just around the corner. Universal Soldier anyone?

Interested in reading more?

The monkey: http://www.switched.com/2010/06 /04/monkey-mind-control-evolves-with-elaborate-new-robotic-arm/

The Toyota wheelchair: http://www.switched.com/2009/06 /29/toyota-developing-a-mind-controlled-wheelchair/)

The DARPA arm: http://www.wired.com/dangerroom/ 2010/07/human-trials-ahead-for-darpas-mind-controlled-artificial-arm/