Hearing in Marine Mammals

Today was the annual Marine Naturalists' Gear-Down, an end-of-season lecture series hosted by The Whale Museum. While there was a lot of great information shared, I thought I would focus this post on one interesting fact I learned and have since been pondering (and reading about further in a marine mammal biology textbook).

Our first speaker was talking about the adaptations required by marine animals to deal with the conditions of oceanic life. He made an interesting point when talking about hearing underwater. Evolutionarily speaking, animals originally had ears designed for hearing in the water, but as animals moved to land there had to be changes in the structure of the ear to deal with hearing in air. Humans, like all terrestrial mammals, have air in the middle ear, which makes us great at hearing sounds transmitted through the air. If, however, we have our heads underwater, our hearing is impaired due to impedance mismatch, which basically happens when sound switches from one medium to another. When sound going through the water encounters the air in our middle ear, it impairs our ability to hear it clearly or determine which direction its coming from.

Marine mammals evolved from terrestrial mammals, so their ears still have the basic structure designed for hearing in the air. How, then, have they adapted to hear so well underwater? They've had to find a way to overcome the impedance mismatch caused by the air/fluid barrier.

Toothed whales spend all their time underwater and have "solved" this problem by receiving sounds directly to their inner ear not through their external ear canal but through the fatty tissue of their lower jaw, which conducts sound in a similar manner to water. But what about pinnipeds, which need to hear both in the air and underwater?

This harbor seal pup is adept at hearing in the air and underwater, due to a very interesting adapation

It's theorized that most pinnipeds primarily receive underwater sound through bone conduction, which means that sound reaches the inner ear by resonating through the bones in the skull. Some human hearing aids actually make use of bone conduction. This process isn't very well understood in pinnipeds, since orienting the direction of the sound must still be difficult. These pinnipeds then hear sound in air via the typical pathway through their external ear canal.

Different pinniped species have different hearing abilities in air/water depending on their life history. Elephant seals have sharper underwater hearing, whereas sea lions have better hearing in the air. Harbor seals, however, get the best of both worlds. As our speaker shared today, harbor seals actually have a mechanism to fill part of their middle ear with blood (a fluid which transmits sound more like water than air) when they are underwater to better receive sound. When they are at the surface, this blood drains, restoring the air to the middle ear and allowing them to hear better in the air. Since harbor seals use the external ear canal to hear underwater instead of bone conduction, they have better underwater directional sensitivity than other pinnipeds.

The biologist in me is fascinated by this kind of thing....

2010 Photo Calendars

It's amazing that 2010 is just around the corner, isn't it? Every year I put together a wildlife photo calendar, but this year I decided to do three with different themes: wildflowers, orcas, and birds. Since many of these photos have been featured on my blog, I thought I would link to them here. Click on a calendar to see all the photos for every month. The holiday gift-giving season is just coming up quickly, or get one to enjoy yourself! At checkout use the coupon code 10CALENDARS9 to get 10% off your order.

Orcas of the San Juan Islands ~ 2010 Calendar by OrcaWatcher
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San Juan Island Wildflowers by OrcaWatcher
Create your own personalized calendars using zazzle.com

Pacific Northwest Birds by OrcaWatcher
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Insect IDs

I've had some time to sit down with my new field guide (Insects of the Pacific Northwest by Peter and Judy Haggard) and have been successful in identifying some insects from my photos. There are some cool looking critters to share with you today!

This first one is one of my favorites for its interesting shape and unique coloration. (It was also relatively small at about 10-15 mm long, which made it more pleasant to approach than some of the larger specimens below. I'm not exactly an entomophobe, but I do believe in giving insects their space and hoping they give me mine!) From the shield-like shape I was immediately able to narrow it down to a stink bug (Family Pentatomidae), but the colors looked nothing like any of the photos in my guide. By referencing The Bug Guide, I was able to learn that its actually a stink bug nymph (Chlorochroa spp.):

Some insects, like butterflies, go through complete metamorphosis, progressing from an egg to a larva, then a pupa, then an adult. Others, like stink bugs, go through incomplete metamorphosis, hatching from an egg to become a nymph, then becoming an adult after one or several molts (instars). The fact that you can encounter a wide variety of nymphal stages in addition to the adult stage of an insect will make identification much more difficult, I can tell....

Aside from the charismatic butterflies and moths, the other large, common, distinctive insect group we often encounter is the order Coleoptera - the beetles. My field guide has a nice introduction at the beginning of the beetle section:

Coleoptera is the largest order in the animal kingdom and, with approximately 290,000 species described, contains an estimated 37 percent of all known insect species. More than 23,700 species have been recorded in the United States and Canada. Approximately one-third of the total number of insect species found in the Pacific Northwest are beetles.

This first beetle, pictured above, is a golden buprestid (Buprestis aurulenta) of the metallic wood-boring beetle family. In addition to its remarkable iridescent coloration, notice the four longitudinal grooves that run down each wing, another identifying mark.

The next one, pictured below, is a tiger beetle (Cincindela spp.). There are several similar species that vary in how green/brown the body are as well as the particular yellow markings on the wings, so I'm not sure which particular species this is. The field guide notes that they can be difficult to approach, and indeed this one was running when I saw it. This is the only photo I was able to get of it - I'm lucky it turned out as well as it did!

This next beetle I at first thought was either a ground beetle (big and black) or stag beetle (large jaws), so I was surprised to figure out that it was also in the tiger beetle family, although in a different genus. This is the flightless tiger beetle (Omus audouini). The mouth parts are what I immediately noticed, but upon closer examination I also looked at the shallow pits on the wing covers.

Moving on from beetles, here is a common fall critter that I've always heard referred to as a woollybear caterpillar. Turns out this is accurate - its a larval banded woollybear (Pyrrharctia isabella), that will eventually metamorphose into a tiger moth. According to an old wives' tale, the width of the orange band in the middle will tell you how cold the upcoming winter will be. Hmm, this band doesn't seem to be too wide - are we in store for a milder winter than last year?

Here is another closely related species - the larva of a rangeland tiger moth (Platyprepia virginalis). It's funny that I recognize many of the tiger moth larva, but not the boldy patterned adult moths.

There's nothing quite like picking up a new field guide and, while flipping through it, finding something that I haven't been able to identify anywhere else. As I've expanded my horizons over the last year and a half from birds and marine mammals to also encompass wildflowers, mushrooms, and insects, I've experienced this joy of identifying a new species several times - they are very much "Ah-ha!" moments. This last photo was one of those moments, the very first thing I identified using my new book - and I didn't have it down as being insectoid at all!

I thought this was some kind of fungal parasite when I found it growing on these plant leaves this summer. Take a look:

It's actually a gall formed by a gall wasp (Family Cynipidae). They're tiny wasps that are hard to find or identify, but each species lay their eggs on a particular host plant, and as a result a distinctive looking growth (the gall) develops in which the larva feed. The galls are the easiest way to detect and identify the species. The one pictured above is the rose leaf gall (Diplolepis polita). So THAT'S what that thing is! Amazing.

Happy Halloween!!

In honor of the date, I thought I would share my attempt at pumpkin carving this year.

Yesterday was my birthday, and my parents gave me a great field guide of insects of the Pacific Northwest, so my next post should feature some neat insect photos I've been saving up in the hopes of being able to ID them when I share the photos.

Happy Halloween everyone!

Albatross/Killer Whale Interaction At Sea

A recent study examining images retrieved from a digital camera attached to the back of an albatross made a remarkable find: albatrosses may follow killer whales in the open ocean in hopes of scavenging scraps of food. In addition to photographs, the camera also records temperature, so sharp drops in temperature often indicate the albatross is in the water feeding. Such temperature dips are associated with the whale photographs, which leads the researchers to speculate that whale-following may be an effective foraging tactic.

You can read more details and see a remarkable image showing albatrosses soaring behind a surfacing orca at this Wired Science article. Also, here's the link to the peer-reviewed journal article about this finding.

How cool!!

A Nudibranch and A Crow

During this, our last week of running trips on the boat, some of my coolest sightings have been on the dock to and from the boat.

There is one particular dock piling that seems to be a favorite of nudibranchs. Earlier this month I shared a photo of a golden dirona I saw there, but this week I found a clown dorid (Triopha catalinae):

I usually don't take much notice of the crows that hang out on the dock, but this one caught my eye. I had to do a double-take and and compare it to another nearby crow to confirm, but it was definitely missing the tip of its beak! Take a look:

It's hard to tell without taking a closer look, so here's a comparison with a normal crow's beak:

This makes the third blog post featuring an animal missing a body part. If you missed the other two, they were a fox without a tail and a Dall's porpoise without a dorsal fin. It's amazing to me how they're able to adapt and survive after such an injury, especially in the case of the crow. You've also got to wonder what kind of bind they got themselves into to end up this way! Any theories?

Western Sandpiper

I went out to Fourth of July Beach this afternoon to conduct a COASST survey for stranded birds. There have been several seabird wrecks (an event where lots of live or dead seabirds strand) along the Oregon and Washington coasts recently as a result of a particular algal bloom. The species of algae that has been involved is Akashiwa sanguinea, which when tossed in the waves creates a soap-like foam that takes the waterproofing right off the birds' feathers much like oil does. In some areas they've found as many as 40 stranded birds per kilometer.

Luckily, it doesn't look like the San Juans are affected as I haven't seen any foamy looking water and there were no dead birds on my beach. There were lots of cool live birds though, and unlike last time where I left my camera in the car only to have a close encounter with some semipalmated plovers, I put it in my backback today.

Out in the bay, there were both horned grebes and red-necked grebes diving in and among the flocks of bufflehead. All three are species are fairly common winter birds here. I also counted about six common loons, who looked very stocky compared to the grebes. The surf scoters weren't a surprise, but the 20+ white-winged scoters were. White-winged scoters are a more unusual sight than surf scoters, although looking back at my notes in addition to seeing them here last January I saw them last October, as well.

The highlight today was the very cooperative pair of western sandpipers foraging along the beach.

I couldn't pick just one favorite shot, so here are my top six photos. Normally I think of peeps as being pretty skittish, but this one let me approach it to within about 8-10 feet.

It was high tide at the beach, and all of the exposed beach was covered in a thick layer of wrack (mats of seaweed). It made for difficult walking because in most places it was six inches or more deep and slippery. It was, however, covered with little hopping insects, which is what the sandpipers feed on. Yum!

I always have a hard time differentiating the western and least sandpipers. It's a lot easier when you can get this close to them. Note that it has dark rather than yellowish legs, and that the winter plumage is entirely gray with no brown. The black bill also has a slight droop at the end.

Here's one in the process of ruffling its feathers. The sun also peaked out for a moment too, making the white a little bit too bright in this shot.

Remember how a group of shearwaters is called an improbability? Well, apparently a group of sandpipers can be called a contradiction, a bind, or a fling. Who comes up with this stuff? A fling of sandpipers is a nice description of a huge flock of them. The two pairs I saw today probably don't qualify, though.

It was pretty special to observe these birds up close, and I like looking at the photos where you can make out every detail of the individual feathers. When I got back to the parking lot, one final bonus was a flock of golden-crowned sparrows.