What You Otter Know About Sea Otters

Hello again, wonderful readers! As you may have guessed from the title, this entire blog post is going to be about awesome otter facts that I read about this week. I did do some work this week other than otter research, especially with the HFSS program, but I'll talk about that and more about antennas next week. This week is devoted to otters!

- Probably the most useful information that I found for my project is that an otter's neck is wider than its head, so it would be extremely difficult to put a comfortable collar on the otter. Also, observers have seen that an otter will frequently chew off most objects placed on their limbs, such as RF trackers, so we may have to get creative with where and how the tracking device will stay on the otter.

- There are several different kinds of otters. There are actually a lot of differences between the two different otters that I've read about, the sea otter (Enhydra lutris) and the European river otter (Lutra lutra). River otters can be found around Europe and Asia, and they live mostly on land and by fresh water, whereas sea otters are found primarily on the Western coasts of North America and Southern Alaska.

- Sea otters can live their entire lives in the sea! They can even give birth in the water; in fact, they prefer it to giving birth on land.

- A common nickname for the sea otter is "the old man of the sea," because of their bristly face and prominent whiskers that make them look like they have an old man's beard. Additionally, the sea otter has a long history of exploitation and hunting for their pelts, especially in the Alaskan and Californian regions, where it got so bad near the end of the nineteenth century that it was referred to as the "Soft Gold Rush."

Sea otters don't mind using their belly as a table

- There is a reason why sea otter pelts were valued so much. Their pelts have the thickest fur of any mammal at 110,000 hairs per cm². Also, their skin is very loose-fitting on their bodies and stretchy. This is all because of how important it is for them to groom themselves. Because of their extremely thick fur, they can keep air-bubbles trapped in the fur to help keep them afloat. However, over time they lose the air-bubbles to water soiling, so they have to frequently groom themselves to make sure they can stay afloat with relative ease.

- As many of you already know, sea otters will often wrap themselves in kelp and even hold hands with other otters so as not to float away while they sleep.

- Sea otters eat a ton! To keep up their body temperature and metabolism they will often eat 30% of their body weight every day. In order to obtain enough food, most sea otters will spend anywhere between 25% and 50% of their days foraging for food. If you weren't convinced that otters are awesome by now, please know that sea otters are the only mammals other than primates that use tools! They use rocks in a variety of ways in the pursuit and consumption of food, such as bashing clams against rocks held on their stomachs.

- Most otters aren't very happy about pollution, but some otters have taken to tearing open aluminum cans found on the bottom of the sea because more often than not they are the homes of small octopuses!

A mother and her pup

- I did promise to talk about why sea otters are especially sensitive to their environment and pollution. Sea otters are vulnerable to biomagnification, which many of you may remember from AP Bio. Biomagnification occurs when certain toxins that are present in small concentrations in the tissues of organisms low on the food chain become more present in higher trophic levels of the food-chain. Therefore, organisms higher on the food chain are more vulnerable and harmed by this effect. A toxin in boat paint called Tributyl tin has been of particular concern to otter conservation efforts because it is commonly found in the tissues of the invertebrates the sea otters eat.

- I am sorry if this ruins anybody's perceptions about sea otters, but sea otters are far from monogamous. A single pair of sea otters will almost always only mate one time. Female otters are polyestrous, which means that they can have cubs multiple times throughout the year, and many times they will do so. Also contributing to the lack of monogamy is the tendency of males to travel much greater distances than females, who are more likely to stay in the same area their entire lives.

I think that's enough about sea otters for the day. I have enough additional cool facts about otters to fill an entire other blog post (all sea otters that have been observed are right-handed!), but I don't want to be a crazy otter guy. If you're not a biology or ecology person, look forward to next week, where I will probably talk a lot about different antennas, how they work, and how they may or may not apply to my project.

In the meantime, if you want to know anything else about otters or have any questions, please let me know in the comments. I'd love to hear from you guys! See y'all next week.

Don't you want a pet otter now?

Sources:
Love, J. A., Sea Otters (Whittet Books, London, 1990)
Mason, C. F., and S. M. Macdonald, Otters: ecology and conservation (Cambridge University Press, Cambridge, 1986)

Pictures:
http://scienceillustrated.com.au/blog/wp-content/uploads/2012/03/sea-otter.gif
http://i.telegraph.co.uk/multimedia/archive/01923/otter_1923262i.jpg
http://25.media.tumblr.com/da9cd1da9aedd72e359d8b403946cbe5/tumblr_mqnucyG4DS1s15skfo1_400.gif

AOs and HFSS

Welcome back to my blog! As promised, I do have a picture of an otter, in case anybody needed some therapeutic cuteness (the AO in the title is obviously the acronym for Adorable Otters). After meeting with Dr. Melde, my advisor, I have begun to shift gears from learning about antennas and earlier designs for tracking collars to learning as much as I can about California otters and their environment. Surprisingly enough, there is a lot of information out there about California sea otters. I recently read an interesting but sad journal article about the bycatching of sea otters, where otters swim into crab and lobster traps but cannot get out and subsequently drown. The study uses statistics from past drownings and an experiment where otters of varying waist sizes and lengths are placed near traps full of food are observed in order to study the likeliness of certain otters becoming trapped (no otters were harmed in the structured experiment).

Hey Steve! There's a bunch of kelp over here!

Otters are very much a beloved species by humans. If you are like me at all, the thought of otters dying as a result of preventable events such as oil spills or fishing traps evokes a very emotional reaction. This is a large part of why I am looking at improving the existing tracking system for sea otters, because as Dr. Melde says, with modern technology, there must be a better way than surgically implanting tracking devices into the otters' abdomens. The device below is what is currently being used in otters, and this is essentially what my research project is all about, because most of my research is being done with the goal of figuring out if there is a viable option for sea otter tracking collars that is non-invasive, but still provides the luxury of a long lifetime.

Yes, this device goes into the abdomen of an otter.

Besides the fact that otters are adorable, there are very practical reasons for devoting resources towards the tracking of sea otters. As many of my peers will remember from the ecology section of biology, otters are an excellent example of a "keystone species," or a species that is so important to its ecosystem that if it is not present, the ecosystem will almost certainly collapse. Sea otters are big consumers of sea urchins, and sea urchins eat kelp. Sea urchin numbers are kept in check enough by otters so that they do not significantly damage the kelp forests, but if sea urchin populations were allowed to grow unchecked by otters, the sea urchin populations would grow exponentially due to the vast resources of the giant kelp forests. Eventually the urchins would eat all of the kelp, and the bottom of the underwater food chain would be eliminated, effectively destroying the ecosystem.
Additionally, I have noticed that many of my readings on otters mention that significant changes in the water environment become apparent in sea otters before they become apparent in other species, giving ecologists warnings about potentially negative changes in the water composition. Further information on that will have to come in a later blog post.

If any tech guys were bored by the last few paragraphs, then I have good news! I have spent a bit of this last week becoming familiar with this amazing computer program called High Frequency Structure Simulator, HFSS for short. Fortunately, trying to say that acronym as an english word is not the most fun part of the program. It allows users to virtually build structures out of myriad materials, and by changing the environment and conditions around the virtual model, the program uses Maxwell's equations to solve for results in order to give the user a ton of information about how their structure will theoretically function. Since I am very new to the physics of antennas and the HFSS program, I certainly do not have a great understanding of the capabilities and nuances of the vast program, but I did manage to "build" a PIFA in the program with the exact same dimensions as the ones that I physically built in order to see what would happen. One of the many features of the program is that it can analyze an antenna much like a network analyzer would, only it's all theoretical. Therefore, the graph of resonance of different frequencies on the right not only looks much prettier and neat than the measurement taken by the actual network analyzer, but the program predicts that the peak resonance of my PIFA will occur at 1.65 GHz instead of the 1.575 GHz that my physical PIFAs did.

My digital PIFA

The virtual network analyzer ( y-axis is in decibels)

The first question that comes to mind is why the program predicts that my PIFA would have its peak resonance at a frequency other than the one it actually had. The answer is obvious: no simulation can completely capture reality, and no device made by my hands will be as perfect as the one in the simulation. However, there are some specific aspects that I believe significantly affected the results. In the program, the plates of the PIFA are planes without any height, but the planes that I used in the physical antennas were over a millimeter in height. Also, my model did not include a coax stem, and there was dielectric inside the top plate of the physical PIFA that may have introduced enough capacitance to affect the frequency resonances. These are all things that I will be further exploring in the HFSS program, and along with researching even more about otters, I will be spending some time next week trying to more accurately replicate my physical PIFA in HFSS.
Have a great week!

Pictures:
http://seaotters.com/wp-content/uploads/2012/03/628x353-otter-cu-yawn.jpg
https://seagrant.uaf.edu/research/projects/10/otter/images/transmitter.jpg

PIFAs are Everywhere!

Hello again, and welcome back to my SRP blog! I have to say, it's really enjoyable to work in a university lab. As I've already mentioned, there are a lot of neat tools around, and there is an absurd amount of books about antennas. So if you have any questions about antennas, I can get back to you in a couple of business days with an answer (most likely). Also, the lab is the one place I know where my work habits are safe from my recent and extensive obsession with Parks and Recreation. Oops.

For the last week or so I have been working on building my own antennas. It was a ton of fun, even if it took me a couple of days to properly solder anything, and it took a whole day to tweak them after they were built. The type of antenna I was working with is called a PIFA antenna, and below is a picture of the two that I built. They don't look fantastically different from the model PIFA that I took a picture of last week, but that's a good thing I suppose.

My two 1.575 GHz PIFAs

This may be a gross oversimplification of antennas, but the reason why antennas are so helpful for us with modern technology is that they allow different devices to communicate with each other and transmit data, so long as the components that are communicating with each other are operating at the same frequency. The physical properties and dimensions of each antenna determine what frequency the antenna will operate at. Take a look at the data that the network analyzer took from one of the PIFAs that I built.

The peak resonance for this PIFA is practically exactly 1.575 GHz

The horizontal axis of this graph is a range of frequencies that the antenna is tested for, and the vertical axis is the return loss of the antenna. The lower, or more negative, the return loss is, the better the antenna is able to pick up and transmit signals at a certain frequency. The return loss is in decibels, which is 10*log( [% of signal returned] / [% of original signal] ). Therefore, according to this graph, less than 1% of the original signal at 1.575 GHz is returned, and more than 99% is transmitted. This is great! Ideally, this graph would just be a flat line at zero across all frequencies and an infinitely negative value at 1.575 GHz, but, alas, my PIFA-making skills are not that great yet. Just kidding, that would be impossible because there will always be human error and noise.
For those really interested in the workings of the PIFA, the length of the top plane plus the length of the distance between the two plates is supposed to be equal two a quarter-wavelength of the radiowave, but the antenna will also pick up the frequency that corresponds to a half-wavelength of another radiowave, which is why there is another return loss peak at about 3 GHz.

This tidbit probably relates to more of you out there: PIFAs are actually in use in many smartphones! Obviously they don't look too much like the clunky things that I've been making out of copper, but they are there, and oftentimes the ground plane (the larger of the two planes) is actually the back of the phone, and the top plate is concealed inside the phones and integrated very efficiently with the help of remarkable electronics packaging. If you don't believe me, check out the picture below of a Samsung Galaxy S. The six individual plates on the diagram on the right each serve as the top plate for a PIFA at different frequencies, and they all share the same ground plate. If you're anything like me, you've always wondered how the heck smartphones don't have antennas sticking out of them, and this is pretty fascinating and exciting.

Samsung Galaxy S and its fabulous PIFAs

I'll stop raving about antennas for now. Now that my PIFA mission has been completed, I will be reading all about the last three years of Golden Lion Tamarin collar research in order to get a 30,000 feet view of the entire problem so that I can start researching solutions and applications for otters. Plus, I have an entire 200-page book about otters, which I'm very excited to read. Because otters are adorable. I promise I'll find good pictures of otters for the next blog post, because frankly I don't think the otters would feel comfortable among a bunch of technology pictures. Until next week!

Source: http://www.antenna-theory.com/antennas/patches/samsungantennas.jpg

Cal-ing the Coax with SOLs, and Other Awesome Jargon

Welcome to my Senior Research Project blog! My name is Luke Wohlford, and I throughout the course of my project I will be working with Dr. Melde of the University of Arizona, some of her graduate students, and an Engineering Senior Design team to learn about the new innovations in tracking-collar technology for small mammals. For three years Engineering Senior Design teams at the University of Arizona have been working on tracking collars for the Golden Lion Tamarin, but much of my own project will be concerned with how the new technology can be applied towards tracking collars for the Monterrey Bay Otters.

I finally got to meet Dr. Melde and her team of graduate students on Monday, and I have a lot of reading to do on previous projects. Fortunately I already have the chance to get my hands dirty this week, since I have been asked to build several PIFAs. PIFA stands for Planar-Inverted-F Antenna, the F resulting from the F-shape. Today, one of the graduate students taught some Computer Engineering seniors and me how to calibrate a network analyzer using a short circuit, and open circuit, and a 50 Ohm load (SOL for short) so that we can test to make sure that our antennas resonate at the correct frequencies. It was like using a TI-83 on steroids, which, needless to say, was awesome.

The magnificent network analyzer, in all of its calibrated glory

After the demonstration, I got to use a caliper, one of the coolest things ever, to measure the already-built PIFAs so that I could get the dimensions for my new antennas. I got a little zealous and ended up measuring three different old PIFAs with different frequencies so that I could figure out the exact proportions of the different planes, the coaxial copper wire, and the distance between the planes and how they were all proportional to the wavelength or frequency. I'm a numbers guy, so it was a ton more fun than I'm probably making it sound, and now I'm ready to learn how to solder and build these PIFAs!

A PIFA and some of my calculations

The caliper (bottom), which electronically measures lengths

One more thing. There's a LOT of jargon that the electrical engineers and microwave engineers are throwing around. I mean, I definitely expected that from working with engineers, but it's pretty fun to talk in jargon and try to figure out what my parents would think if they heard what I'm saying. Everything that can be made an acronym already has one, and if an item is only two words long, most of the time it's cut down to two syllables. Need a coaxial cable? Just ask for a coax. Need a purple pen? Just ask for a pup (kidding). Also, having a larger bandwidth apparently isn't always a bad thing, because it can also mean that you have more free time. Clever, no? Overall, I'm really enjoying my project so far, and I'm really looking forward to the rest of what I will be doing over these next few months.