Science of the Seasons: Bearing study

Photo courtesy of Dr. David Wartinbee. A polar bear rests on a gravel bar near Kaktovik during September 2010. Until sea ice reforms in the winter, bears are relegated to shore.
waiting for the sea ice to form.

Polar bears (Ursus maritimus) are an iconic creature that most of us have experienced as cuddly children’s toys or as friendly family groups interacting with penguins in Coca-Cola commercials.

Much of what we commonly see portrayed about polar bears is quite distant from reality. When viewing TV ads, I always want to point out that polar bears and penguins live worlds apart, penguins in the Antarctic and polar bears only in the Arctic. They only meet in fairy tales. I am also bothered by the anthropogenic portrayal of large family units of polar bears because in the real world they are mostly solitary predators who actively avoid contact with their relatives.

Polar bears are found throughout the northern hemisphere Arctic. There are populations in Norway, Russia, Canada, Alaska and Greenland. Most of their lives are spent as ice-pack hunters, looking for seals that have created breathing holes through the ice, or those basking on the ice. When the sea ice melts in the summer, the bears hang out along shore areas. Typically they fast during this onshore time, although they are happy to take carrion or feed on whale carcasses from Native subsistence hunts. They head back out on the pack ice to hunt seals again, as soon as the sea ice starts to reform.

In Alaska villages, like Kaktovik, polar bears are spending more and more time on land due to the earlier and more extensive summer sea ice melting. And the sea ice is reforming later in the fall than it used to, so bears are onshore longer these days. In these situations, they are not usually feeding, so social interactions are less intense.

Tusks on the cusp of climate change in Arctic

By Dr. David Wartinbee, for the Redoubt Reporter

Walruses (Odobenus rosmarus divergens) are unique within the animal world because of their characteristic tusks. Their scientific name indicates a “tooth-walking sea cow” and may refer to the “head-high” position large males must maintain as they move about because of the long tusks projecting downward. The tusks are actually elongated canines from the upper jaw and can be nearly 4 feet long on some 2,500-pound males.

The tusks are used as a mating display or a weapon when dominance is being challenged. As well, these same tusks are used to carve out breathing holes in the ice packs where they are usually found. Contrary to long held thoughts, these large tusks are not believed to be used when feeding in bottom sediments.

The most important food sources for Pacific walruses are various bivalves (clams) from the ocean sediments. Apparently, walruses are able to sense clams with their stiff whiskers, called facial vibrissae. These vibrissae are actually about as thick as coat-hanger wire. They swim along the bottom sediments with their muzzle in the sediments and occasionally they will sweep water across the sediments with their front flipper.

In addition, it is believed that walruses may squirt water at the bottom sediments to uncover clams and marine worms. When a whole clam is taken into the mouth, walruses are able to use a powerful suction-squirt action within the mouth to separate clams from their shells. Supposedly, walruses can take in and shuck about six clams a minute. While their molar teeth show some wear, it is not believed to come from crushing shells during feeding, but rather from inadvertent sand taken in while feeding. Walruses are known to occasionally feed on seals and even some birds, but it is not known how important these other food sources are in their overall dietary scheme.

Science of the Seasons: Bearded seals buoy the Arctic food chain

By Dr. David Wartinbee, for the Redoubt Reporter

Bearded seals are about four times the size of a ringed seal and can weigh up to 900 pounds. They are named for the abundant, thick, bristlelike whiskers on their muzzle. Like ringed seals, they are intimately tied to sea ice in the Arctic Ocean and are considered one of the ice seals.

During the winter months, bearded seals maintain numerous breathing holes in the Arctic Ocean ice. They also maintain larger openings where they can haul out to rest on the ice after foraging. This resting time is when they are most susceptible to hungry polar bears or hungry humans.

In April, the females give birth to a single pup on the ice. The young seal has the thick lanugo fur to keep it warm until it builds up a layer of blubber from its mother’s fat-rich milk. Unlike the ringed seal, bearded seals do not dig out a protective lair for their young; they just lie out there on the ice and snow.

Science of the Seasons: Arctic sea ice is nice for many mammals

By Dr. David Wartinbee, for the Redoubt Reporter

My first introduction to seals came on a grainy, black-and-white TV when trained seals performed on some variety show. They were a strange animal when first seen, since they didn’t look anything like the all familiar dogs, cats, horses or cows. They were awkward on land and I never got to see their graceful swimming motions until underwater cameras became popular. It took many trips to Alaska and several years as a volunteer at the Alaska SeaLife Center before I really had any understanding about these amazing creatures.

However, many Alaskans learn the ways of seals as they grow up because seals are a normal part of the rural subsistence lifestyle. Seals are hunted on a regular basis in many Native communities as a nutrient-rich food source. Seals are not only hunted for their meat. Seal oil, which is rendered from seal blubber, can be used as an additive to other traditional foods, for waterproofing skin boats or as a traditional fuel for oil lamps. Additionally, seal furs are treasured for garments like boots, hats, gloves and coats.

Along Alaska’s north and western coasts, two of the most commonly hunted seals are the bearded and ringed seals. These are commonly referred to as ice seals because they spend most of their time on or around ice. These seals mate, give birth, raise their young, and rest on or under Arctic sea ice. Only rarely do these seals actually come to shore.

Science of the Seasons: Frozen (just in) time — Lake ice takes variable durations to form, sink, rise again

By Dr. David Wartinbee, for the Redoubt Reporter

Photo by Jenny Neyman, Redoubt Reporter. Smaller and midsized lakes, like ARC, Sports, Scout and Headquarters, seen here, are frozen enough for skaters, but care should still be taken, especially with larger lakes and ones that have streams flowing into and out of them.

As we shivered through this past week’s zero degree (and less) temperatures, there was really a silver lining for some of us. That is, if you are interested in ice fishing or skating on some of our local lakes.

Several weeks back I flew over a number of local lakes and some were completely covered with ice, while others were completely open. This time of year reminds me of the changes taking place within the lakes, as well as the physical properties of water that put ice where it is.

In order for a lake to form ice, the entire lake must first reach 4 degrees Celsius, or 39 degrees Fahrenheit. The way this happens is quite interesting. As water cools and gets closer to the magical 4 degrees C, it becomes more dense and sinks to the bottom of the lake.

This way, warmer water is forced to the top of the lake and it gets exposed to the colder air. When that surface water cools, it then sinks and warmer water from a little bit lower takes its place. Eventually, the entire lake water is the same temperature. Since shallow waters around the edge of a lake, or shallow coves of a lake, can more quickly reach the critical temperature of 4 degrees C, ice usually forms there first.

Lakes like Tustumena and Skilak contain huge volumes of water at great depths, so it takes a long time for the entire lake to reach the 4-degree C level. Only then can ice formation begin.

When the surface water starts to get even colder than 4 degrees C, the density reverses itself. Water colder than 4 degrees C becomes a little bit less dense and stays on top. Now it can cool to zero degrees C. Once some of the surface water has reached freezing temperatures, the “heat of fusion” needs to be satisfied. This simply means that once the water has reached zero degrees C, it must now give up 80 calories of heat per gram of water in order for it to change into ice. After all that heat loss, the newly formed ice is still only zero degrees.

Science of the Seasons: Whoo goes there? Great horned owls often heard before seen

By Dr. David Wartinbee, for the Redoubt Reporter

Photo courtesy of Dr. David Wartinbee. A great horned owl is silhouetted in a tree. The birds have excellent camouflage. Often their hoots are heard before they are seen.

On a recent evening, as I was watching the end of a cold, beautiful sunset, I noticed a large bird land in a tree in front of the house. From its broad wings, short tail and large size, I was pretty certain it was a great horned owl. Sundown is when they are fairly active as they survey for their next meal. With binoculars I could make out some of its mottled coloration and the all-important feather tufts that give it the “horned” name.

Great horned owls are fairly common here on the Kenai Peninsula and can actually be found all over North and South America. So they are well-known throughout the country. They are one of the larger owls, with a wingspan of almost 5 feet, and they weigh 4 to 6 pounds. That may seem light because they have a barrel-shaped body and their feather fluff-up makes for an impressively large-sized bird.

These predators will take just about any animal they can capture, including grouse, crows, squirrels, marmots, hares, voles, weasels and even fish. In some parts of their range they are known to take bats, reptiles and amphibians. Great horned owls are also a major predator on young raptors, like osprey. They are able to take on more formidable prey because of their large and powerful talons. Some prey items are eaten on the ground, while smaller rodents or birds can be carried to a perch for a more leisurely repast. These owls are not above taking carrion or road kill, too. Because of the willingness to take animals off the roads, younger owls often become road kill themselves.

With the current high numbers of varying hares on the peninsula, great horned owls have probably been feeding well for the past couple years. Recently there have been reports of large local populations of redback voles, so their good food fortunes continue.

Great horned owl food choices remind me of a favorite children’s book called “Owls in the Family” by Farley Mowat. In the story, the two pet great horned owl return to an open porch window with their nightly prey until one flies in with a freshly killed skunk. The family was no longer amused! While that is just a story, great horned owl are actually the only known avian predator of skunks. One western owl nest was found to have remains of more than 50 different skunks. Apparently, owls are not put off by the powerful skunk odor.

Science of the Seasons: Depth of study — Stonefly nymphs an integral part of ecology of peninsula streams

By Dr. David Wartinbee, for the Redoubt Reporter

Photo courtesy of Dr. David Wartinbee. A Pteronarcella stonefly, common to the Kenai Peninsula, seen under magnification.

This spring I was waiting for the ice to melt and for the water levels to drop enough that I could get into some of the deeper sections of the Anchor River. A colleague from Utah had asked if I had ever found a particular genus of stonefly on the Kenai Peninsula, and the place where I had found them in greatest abundance was the North Fork of the Anchor River. So I headed just south of Anchor Point and collected a few Pteronarcella nymphs.

My friend had a graduate student who was interested in determining which species of Pteronarcella are found in our area and was using a new technique to determine the species. Instead of using the more common presence or absence of specific anatomical structures, the species would be determined by differences in DNA.

In the past 20 years, scientists have refined their abilities to determine DNA sequences, and it can now be done relatively rapidly. Using a series of known DNA sections, called “probes” for comparison, similarities and differences in organisms can be quickly examined. These techniques have identified different species when only one was previously recognized and synonymized (joined together) species that were previously thought to be different.

There are a couple different species of Pteronarcella that might be found here, but for most folks, the species delineation isn’t all that important. The Pteronarcella nymph, no matter what its real species name, is quite an interesting creature.

First, Pteronarcidae stoneflies are some of the largest stoneflies and some members of the family can get to 2 inches or more in length.

They often have a multiple-year life cycle and some may take four years to go from an egg to an adult. I found two distinct size classes when I was sampling and that suggests that they have a two-year life cycle in the Anchor River. Some nymphs had well-developed wing pads and were getting ready to emerge while others probably had another year to go.

Science of the Seasons: Evergreen, except when rusty red

By Dr. David Wartinbee, for the Redoubt Reporter

Photo by Joseph Robertia, Redoubt Reporter. Tree needles show the effect of “spruce rust,” a fungus that only affects the growth of the year. Needles are discolored, but the tree generally isn’t harmed overall.

Recently, I put my boat in at the upper launch of Skilak Lake. The water around the launch area, and all along the rocky shoreline, was covered with a bright, Creamsicle-orange layer. Immediately, I guessed that this was a layer created by spruce needle rust spores, remembering that similar orange-colored floating masses were reported in Kivalina and at Twin Lakes last year.

I photographed the large floating layer and collected samples to examine in the lab. Then I set about to see if many of the surrounding spruce trees showed the characteristic infection of yellowed needles at the tips of the branches. In the areas near the boat launch, I found no trees showing the infection. However, when I went to the far side of the lake, I found a large number of heavily infected trees. The winds had been from the southwest for a couple days and had apparently blown the spores to this northern shoreline.

The following day I was approached by two different individuals who asked about cream-colored or orange-colored layers they had seen on lakes near their particular homes. A day later, while fishing the Kenai River below Skilak Lake, I encountered thinner layers of the orange mass floating downriver. Because the brightly colored collections of spores have recently been seen on Skilak Lake, Arc Lake, the Kenai River and other lakes, I decided to revisit the topic of spruce needle rust.

Science of the Seasons: Feast your eyes on watermelon snow in alpine

By Dr. David Wartinbee, for the Redoubt Reporter

Photo courtesy of Dr. David Wartinbee. Chlamydomonas nivalis cells are shown at 400-times magnifications. These tiny alga cells, responsible for the phenomenon of “watermelon snow,” are only a couple times larger than human blood cells. While the alga cells are nontoxic, notice the amount of debris that has collected in areas where these cells are found in the snow, making ingesting watermelon snow inadvisable.

Years ago as a graduate student studying in the Beartooth Mountains of Wyoming, I first encountered what was called “watermelon snow.” Many of the snow piles above 10,000 feet had an unusual, reddish-pink color. When approaching them, there was an odor similar to a fresh watermelon, and when we tried tasting it, there was even a hint of watermelon taste. It wasn’t sweet like a flavored snow cone but, yet, a hint of watermelon was good enough to justify the name. Our professors told us there were algae in the snow, and since we were working on bugs, we considered it kind of an anomaly and let it go.

We are not the first to this occurrence. Supposedly there are reports of red-colored snow from the early Greeks. The red-colored algal cells causing the color were probably first seen in the early 1800s as microscopes were being refined.

Recently, while flying over the west side of Cook Inlet, I noticed snow piles with pink ridges and was reminded of the “watermelon snow” I had seen so many years ago. I decided it was time to look at the snow under a microscope and learn more about these algae. A friend mentioned that he has seen snow piles with distinct pink coloration in Hatcher Pass, so I made a special trip to gather some specimens.

Don’t spring to conclusions — Springtails not to blame for skin rashes

By Dr. David Wartinbee, for the Redoubt Reporter

Photos courtesy of Dr. David Wartinbee. Collembola specimens are shown next to millimeter markings. Below, a “springtail” is enlarged at over 50 times magnification. They usually are around 4 millimeters long, or the size of the letter “i.”

During the past few months I have been sorting through samples I collected last year from a number of streams and lakes. While I am mostly interested in dipteran insects, I frequently come across other aquatic creatures that pique my interest.

The midges I am looking for are very small, but recently I came across a number of the smallest known aquatic insects, called collembola or springtails.

Springtails are wingless creatures that rarely get larger than a few millimeters in length. They are often only as long as the letter “i” in this paper. The one in the picture is only 4 millimeters long and is magnified more than 40 times.
Within the taxonomic arena, collembola have recently become somewhat of a football.

Dozens of my invertebrate books clearly place them within the class Insecta, since they look like insects and have six legs. Up until recently, that is all I have ever known them to be.

Now, DNA analysis indicates that they are not closely related to other insects and should be classified differently.

Currently they are being described as hexapods (six-legged arthropods) that belong within the class Entognatha. This new class consists of arthropods with an internal jaw, which differs from insects since they have external jaws. No matter what their proper names, they are quite interesting creatures.

Science of the Seasons: Leeches eke a living on fish

By Dr. David Wartinbee, for the Redoubt Reporter

Photo courtesy of Dr. David Wartinbee

Over the past couple of months, I have enjoyed being out ice fishing on a number of local lakes. Though I’ve caught some trout, my catch in some cases — from Egumen, Duckling, Nest and Snag lakes — were often infested with worm ectoparasites.

The slender worms were easily dislodged from the fish as I removed the hook or as they lay on the ice beside the hole. They were between .5 and 1 inch in length and seemed to have a slight greenish banding pattern on their body. Even without the aid of a microscope, I could identify a small sucker at the posterior end, so I was pretty sure I was seeing a leech of some kind. With a little magnification, I could see that there was a small sucker disk at the mouth end to accompany the larger posterior disk.

After consulting a variety of literature sources, I believe that I have been seeing a fairly common fish leech in the genus Piscicola. The species may be geometra but I have not had time to send specimens to colleagues who specialize in these aquatic worms. They are related to some of the other, larger leeches that are found worldwide and are sometimes parasitic on human swimmers.

Like their larger, aggressive relatives, these small leeches are able swimmers and will actively search out a fish for their meal. Often, they attach their posterior end on submerged vegetation and reach out and attach to a fish as it swims past.

Science of the Seasons: Drivers take a shine to some animals’ tapetum lucidum

By Dr. David Wartinbee, for the Redoubt Reporter

Photos courtesy of Dr. David Wartinbee. A moose with a case of red eye browses at dusk.

At this time of the year in Alaska, a drive of more than a couple hundred miles will involve some time during darkness. While heading north to visit friends during the holidays, I spotted a small, bright spot in the roadway ahead.

As my lights got closer, a huge, brown ungulate appeared surrounding that tiny light spot. I slowed appropriately. A few miles farther down the road, a pair of bright spots appeared on one side of the road. A second later I was able to see the faintly lit image of a lynx crossing the road. I had first seen both of these animals because of their tapetum lucidum reflecting my headlight illumination.

While many are familiar with the phrase, “A deer-in-the-headlights look,” not as many may realize there is an interesting anatomical basis for this situation. Most nocturnal animals, like dogs, cats, deer, etc., will demonstrate “eye shine” when a bright light is shown on them at night. What happens is the light entering the animal’s eyeball is being reflected right back at us as if there were a mirror in there. The mirror analogy is actually pretty close to what is happening.

In order to understand how the tapetum lucidum works, we have to know a little about the layers inside the eyeball itself. First, the retina is the thin, innermost layer of the eye and it contains the light-sensitive cells called rods and cones, and lots of blood vessels. In very close proximity to the rods and cones is a black layer called the choroid.

The important choroid layer absorbs light that has just passed by the light-sensitive

Photo courtesy of Dr. David Wartinbee. Moose’s reflective eyes are typically less noticeable to drivers because the animals’ heads are usually above a driver’s headlights.

rods and cones. In humans that do not have a heavily pigmented choroids, like albinos, to absorb the passing rays, light gets reflected and scattered inside the eyeball. These individuals suffer with visual difficulties and even small amounts of light are blindingly bright.

In nocturnal animals with a tapetum lucidum, the choroid, or a special portion of the retina, will act as a slight reflector. The actual tapetum lucidum can vary in its composition depending on the specific animal. Since there are so many different animals that exhibit “eye shine,” it is easy to understand that there are many different kinds of reflective layers.

In some, it is composed of a special layer of iridescent crystals like guanine, or in others it might be a layer of cells with reflective fibers.