Spider webs

diverse in design and function

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spider-in-orb-web-Kerry

One fine, cold day in late January, I took a stroll on crunchy snow. In a couple of places, I ventured off-trail a little way, to check out some tracks or a lichen garden. As I did so, I ran into occasional dangling silk strands, decorated with frost. In warmer seasons, when spiders are busily making webs, I often find it convenient to follow a taller person, who conveniently clears the webs from the trail.

The single silk strands I saw on that wintery day may be been used, last fall or summer, by spiderlings (baby spiders) to ‘balloon’ away from their birthplace to a place of their own—a risky but common means of dispersal for some species. Most adult spiders are thought to be too heavy for this mode of transportation, but small adults of some species do it. When spiders are ready to balloon, they stand on tiptoe with their rear ends elevated. Then they spin a thread of silk that—as it elongates—catches a breeze that wafts the little spider away, maybe only a few feet or maybe many miles.

Those single silk strands might also have been an adult spider’s attempt to start a new web. The first step in web-building (for a spider that builds the familiar orb web) is to cast a line of silk across a gap between two twigs, in hopes of it catching on to an anchor point across the gap; it may take several tries. Once that basic line is established, the rest of the web is built below it. The ‘mis-fires’ are left to dangle. Or perhaps an adult spider dropped down its safety line to escape some perceived danger.

insects-in-spider-web-Kerry
Photo by Kerry Howard

 

Those elegant orb webs take some hours and a lot of silk to build. After the anchor line is firm, construction starts with the radiating ‘spokes’ of the orb, followed by the spiral across all the spokes.

Much of the spiral is sticky, so flying insects get trapped. Their struggles alert the patient spider lurking nearby. The waiting spider then darts out and immobilizes the prey in a silk wrap, to be hauled off and eaten or temporarily stored nearby. Webs can accumulate lots of small fragments of debris or little tears, but rather than repairing dirty or slightly damaged webs, some orb weavers eat their old webs after a day or two, thus recycling all the proteins of the silk.

Some orb weavers add a patch of thick, conspicuous strands to part of the web. This has been thought to make the delicate web visible to birds, which can then avoid flying into the web and destroying it. Or maybe it just makes the rest of the web less readily visible to potential insect victims.

Some decades ago, a researcher accidentally discovered that orb-weaving spiders that consumed various psycho-active drugs (caffeine, amphetamine, etc.) could no longer build normal webs. Instead, their webs were incomplete or seriously distorted, in some cases no longer functional at all.

Another kind of spider deliberately makes tangled webs of various forms; this group includes the common household spiders making cobwebs in secluded corners. Those spiders are mildly venomous but seldom bite humans; they could be considered to be helpful to us, because they consume insect pests in our houses. It’s another story with the black widow spiders, the females of which are highly venomous. Tangle-web spiders generally hang out somewhere in their messy webs, waiting for some hapless insect to stumble in.

Way Down Under, the Australian funnel-web spiders build their silk-lined burrows in the ground or in tree-holes. The mouth of the burrow is typically a funnel made of silk; from the top of the funnel, silken trip-lines radiate outward. The spider sits just inside the burrow, with its legs touching the trip lines. When an insect or a small lizard or other crawling critter touches a trip-line, the waiting spider dashes out to nab its prey. Females generally stay in their burrows, but males wander around more, as they look for females. Some of these spiders reach a body size of about two inches, and they are renowned for their venom.

A group of other spiders, known as funnel weavers, occurs worldwide. They are not related to the notorious funnel-web spiders and they are not nearly as venomous. They make a sheet-like web in front of their funnel-shaped retreat; this web is not sticky but its fibers snag the body parts of passing insects, holding them for the lurking predator. Some African species build communal webs, hunt cooperatively, and even raise their young communally.

A variety of spiders build sheet webs, flat mats of entangling fibers that trap the legs and bodies of unwary insects. One species in New Zealand builds enormous (compared to its small body size) sheets up to a meter across. A common one in parts of the U.S. is called the bowl-and-doily spider. Its web is complex, consisting of a silken bowl above a skimpy flat sheet, with a tangle of trip-lines above the bowl. The spider hangs upside down under the bowl, ready to reach through it to grab an insect that falls in. The ‘doily’ is thought to protect the waiting spider from predators. Females and sometimes young males build these webs; fully-grown males are too busy looking for females.

Among the most intriguing web-making spiders are the net-casters, found mostly in the tropics and subtropics. They have enormous eyes that are very sensitive in dim light. They hang from a silken framework, waiting for prey, holding a small web between the front legs. When the spider spies a passing prey insect, or the unwary insect happens to touch a strand of silk, the predator stretches out the web and pounces, entangling the prey in the expanded net, which folds up around the prey.

There are many thousands of species of spider, and all can make silk. But not all spiders make webs. Jumping spiders and wolf spiders hunt using their excellent vision for 3-D precision in locating prey. Jumping spiders often spin a safety line when they jump, so they can retreat to their perch if they miss their strike. One jumping spider species claims the spider record for high elevation—living on Mount Everest at twenty thousand feet and more. Wolf spiders often wander around, when hunting, but some prefer to sit near burrow and wait in ambush. Trapdoor spiders live in silk-lined burrows, behind a slightly open door disguised by various available materials; passing prey insects are ambushed as the door is flung open and the spider lunges out. Crab spiders don’t make webs, either. Some sit in flowers, mimicking the flower’s coloration, in hopes of ambushing some flower-visiting insect, while others perch on leaves or bark.

That’s just a sampling of what spiders can do!

Snow buntings

far northern nesters

snow-bunting-Jos
Photo by Jos Bakker

As a few green shoots popped up in intertidal meadows and along the beach fringes in the middle of March, a welcome avian harbinger of spring arrived: a small flock of snow buntings foraged among the dead grasses in the Lemon Creek wetlands. They were probably finding fallen seeds as well as some marine arthropods, such as amphipods.

Snow buntings nest in Arctic regions all around the world, as well as in alpine areas somewhat farther south. In western North America, for example, they have been recorded to nest in the high mountains of extreme northwestern British Columbia and parts of the Yukon. In Alaska, there are alpine nesting records from (for example) Katmai, Kenai, the Alaska Range, and even near the Muir Glacier in Glacier Bay.

Most snow buntings migrate south for the winter, spending several months in southern Canada and the northern tier of the contiguous U. S. However, in our part of the world, they sometimes winter at various places in the Interior of Alaska and the Seward Peninsula. And in the Aleutians and Pribilofs, most of the buntings are reported to be resident all year round, foraging in snow-free alpine areas and in the beach rye near the coasts.

The timing of arrival for northward migrants no doubt varies from year to year, depending on weather and snow cover and who knows what other factors. Sometimes these birds arrive quite early in the season: On the Seward Peninsula, the first migrants might be seen in early March; at Anatuvuk, it might be early April.

Male buntings migrate northward earlier than females, sometimes arriving on their nesting grounds perilously early and becoming victims of late snowstorms that cover the ground where food might be found. However, there are advantages to arriving early and staking out the best nest sites and territories. So if all goes well, the males set up their territories in open country and defend their borders against other males. Females generally arrive a few weeks later. Well before then, the males have lost the brownish edges of their feathers and now sport a resplendent white and black plumage.

Snow buntings like to nest in rock crevices; sometimes the nest is a foot or more deep in a crack, well-concealed and protected from wind (but not from cold). Sometimes a niche under a boulder suffices. If cracks in a cliff or a pile of boulders are not available, buntings may resort to heaps of driftwood or human debris (such as junked cars) or even niches in buildings. Suitable nest sites are thought to be quite limited, which would make it advantageous for males to claim them early in the season. At least in some regions, the territories function chiefly to claim nest sites, and the adults may forage much more widely.

When the females arrive, they no doubt look around at several males and possible nest sites. Eventually, they pair up with their chosen males; buntings are typically socially monogamous—one male with one female, although a rare male might get two mates. Females are said to be very aggressive toward other females, which may reflect the limited availability of nest sites and which may tend to enforce the social monogamy. However, if buntings are like most other birds that have been studied closely, they too sometimes make extra-curricular excursions, so some of the chicks in a nest may have different fathers.

A mated pair checks out possible nest sites together. Then females do the nest-building, generally accompanied by their mates as they gather material. That may reinforce the pair bond and reduce the chances of copulations outside of the pair bond. The number of eggs in a nest varies a lot but apparently is often four to six eggs, the average clutch size increasing slightly with latitude. Females do all the incubating, although at least in some part of the species’ geographic range, males feed their mates while they are sitting on their eggs. Incubation commonly begins before all the eggs have been laid, so some chicks hatch later than others in the same nest. Both male and female feed chicks in the nest, but fledglings are divided into two groups, each one tended by one parent. Males typically take charge of the early fledglings while females stay with the chicks still in the nest.

The role of males in determining the number of chicks produced from a nest can be important, depending on circumstances. For instance, one set of studies showed that when a male fed his mate during incubation, hatching success was improved, compared to nests at which males that did not feed their mates. And in years of poor food supply, widowed females raised fewer chicks, and those chicks were thinner, than the chicks in nests tended by both parents. Some studies have shown that even if chick-feeding rates increase at very low temperatures, that is not enough for the chicks to survive. But still other studies have not found some of these results, indicating that the reproductive success of buntings depends on a variety of factors that vary with place and time.

The nesting biology of snow buntings has been studied is some detail in a variety of places such as Svalbard, Spitzbergen, Greenland, and Nunavut (Canada), but apparently not in Alaska. Given that researchers in the various places at differing times have not always observed the same patterns, it seems that some detailed studies of Alaska populations would be very useful in determining what is happening here.

That is particularly so because the numbers of snow buntings may be declining, at least in North America, although more research is needed to confirm this. On-going climate change and decreasing snow cover in the Arctic may change this apparent trend, provided there are no major ecological problems (such as pesticides) in the wintering range.

Signs of spring

…in the air, on the trees, in the water…

The days get longer and longer, and folks in Juneau begin to wish that spring would hurry up and get here. The spring equinox occurred this week, so now Spring is officially here.

The real world was ever-so-slightly ahead of officialdom. In the days of March before the equinox, there were clear signs that spring might really happen, even though snow still covered the ground and hung in clumps on tree branches, and creeks were mostly ice-covered. Redpolls still thronged to our seed feeders, and the magpies were still in town too, not yet ready to head over the mountains to their nesting places.

But the plants knew that the times were changing. Cottonwood buds swelled with the developing leaves inside them. The catkins of feltleaf willow, always the earliest willow to flower, began to emerge from their bud covers but were not yet sexually mature. The still-immature male catkins of red alders along the roads began to blush with a rusty-red hue. Blueberry twigs took on a brighter red and their buds began to peep open. Young willow shoots shone with a yellow hue.

Near several streams, adult stoneflies began to emerge from the creeks, crawling over the snow. Some observers have suggested that female stoneflies stay closer to the streams than males do, because they lay their eggs in the water, where the larvae develop. That leads me to wonder why the males don’t hang out where the girls are, since their main goal is to find mates.

The early birds were singing: Juncos trilled from the tops of trees and shrubs. I heard a few song sparrows and had reports of varied thrushes and a wren in song—still rather sporadically. A few robins foraged for skimpy foods. At least some sapsuckers are back, drumming their rhythms on metal roofs and drainpipes. There is a report of black oystercatchers, early returnees to our rocky shores from points south. Groups of gulls were checking out their nesting areas near Mendenhall Lake one day, but apparently they decided that the visit was premature and it would be better to wait a while. Then, just before the equinox, they tried again; I heard their calls as they flew up the valley and over the lake toward the glacier.

Pairs of ravens canoodled on lamp posts, and a raven on Sandy Beach was diligently filling its bill with clumps of dog fur, a sign that a nest was being lined with those cozy materials. At least some of the Canada geese near the Boy Scout camp were consorting in pairs. A few days later, in the same broad meadow, hundreds of Canadas grazed, joined by a lone snow goose. Steller’s jays expanded their vocabulary: their spring repertoire includes a variety of more musical sounds than the familiar year-round squawk.

snow-goos-with-canadas-Jos
Photo by Jos Bakker

One of the beaches on Douglas Island is a place I like to check, about this time of year, because I often find ‘mermaids’ purses’ washed up at the high tide line. These are the egg cases of long-nose skates (relatives of rays and, more distantly, sharks). There is one egg, and thus one embryo, in each egg case of this species. Eggs are fertilized inside the female skates and the cases of protein fibers are constructed around the eggs. The cases are yellowish-brown before they dry out and turn black on the shore. Most of those that I found had been hacked open, perhaps by a raven or gull, but some appeared to be intact. Maybe the embryo had already emerged through the seam in the side of the case, ready to go as a fully formed young skate. Or maybe a predatory snail had drilled a very small hole (less than five millimeters or so) in the case and slurped up the young embryo. Or there is also a possibility that no embryo had been there—that the case was produced with no egg.

When someone says ‘spring is in the air’, it really is! As Parks and Rec hikers waded through flooded meadows to the beach just beyond the Cowee Meadow cabin, little zephyrs brought the welcome smell of spring to our noses. I don’t know what makes that aroma so distinct, but there is nothing quite like it.

Wordplay with beastly epithets

there’s very little natural history in animal-based slurs and slights!

We often use the names of beasts to label a person’s look or behavior. We take a real or imagined trait of some critter and transfer that description to a person. Most of these labels are derogatory, to both the person and the critter, and some are usually gender-specific. Even the adjective ‘beastly’ implies something negative, perhaps rough or cruel or otherwise unpleasant to us. Here are some examples.

We might call a dirty, messy person a ‘pig’. Pigs in pens are indeed messy, but the operative word is ‘pens’. Penned pigs have no choice but to void their body wastes underfoot. But pigs don’t have sweat glands, so in order to stay cool, they normally roll in mud. In a pen, that mud is fouled with wastes. Not the pig’s fault! And in any case, people are known to pay good money for a cosmetic mud bath.

Somewhat similarly, a young person might (rudely) call an older woman a ‘silly old cow’, implying that she is slow in thought and movement (and thus somehow interfering with the youth’s activity). Or we use the term ‘bovine’ (cow-like) to describe a person who appears to be somewhat dim-witted, standing around staring blankly, not responding (outwardly, at least) to surrounding activities. I don’t know much about real cows, except they are not usually fast runners; if they are slow of thought, it is probably because they have been domesticated for so long that their thought processes have been dulled.

A weasely person (usually male) is sneaky, sly, evasive, somewhat treacherous. Although real weasels are predators that are slim enough to run down vole tunnels, that does not make them sneaky and sly and so on. A shrewish person (usually female) is hypercritical, constantly directing complaints to another person.

But real shrews are just small predators with high metabolisms and are not known to nag each other.

Two persons (usually female) gossiping snidely about an acquaintance may be said to be ‘catty’, but cats are not known to be nasty gossips.

A mousey person (usually but not always female) is habitually weak and timid. But it pays a real mouse to be ultra-cautious in their world of many predators. Mousey may characterize a personality, but anyone can be a ‘chicken’ upon occasion. We chickens may not run squawking away from every perceived threat, but we may nonetheless avoid certain places or activities. However, it is not clear that real chickens are any more flighty than lots of other critters.

An old person may be called an old coot or a buzzard, with no relation to those real birds at all. An ‘old bat’ is typically a female, given that libelous label when she has irritated or frustrated a younger person. However, no true bat interacts in that way. A person that is seen as ‘owly’ may be somewhat grumpy, but quietly so. However, there is no indication that real owls are grumpy (except perhaps when mobbed by other birds). If one ‘rats’ on a friend, that is a betrayal at some level, so a ratty person may be very unreliable as a friend—or just a messy dresser. In either case, real rats are not known to be that way; we just don’t like them in our houses.

A foolish person is a goose; a devious cheat is a ‘snake in the grass’. We may ‘quail’ at the sight of something scary or be ‘gulled’ by a slick salesperson. A total loser is a ‘turkey’. None of those terms has much to do with the real animals. A human ‘skunk’ has no relation to the beautiful mustelids of that name.

Not all of these epithets are totally pejorative, though. Someone with an ‘eagle eye’ is good at spotting a tiny bird in a thicket or small errors in a text. A foxy lady is seen as sexually attractive (although how foxes got into that mix is not clear; the word fox has many meanings), and an ‘old fox’ is known to be a clever person. A roomful of small children may get ‘squirrely’, restless and fidgety and running around in circles, like a squirrel confined in a cage (with a running wheel). This I understand!—even if it is hard to deal with.

‘Slippery as a fish’ is fair enough (their protective mucus coating makes them so), and when a deal ‘smells fishy’, the dealer may be trying to slide something (perhaps smelly as a long-dead fish) past us.

Here’s an interesting and complex example. A female dog is called a bitch. Both men and women may ‘bitch’ (grouse (!), complain, grumble) about something, but only women are called ‘bitches’ by those who object to their complaints. I doubt very much, however, that female dogs do more whining than male dogs. In an odd twist in language, something (a concert, a trip, etc.) that was a wonderful experience may be referred to as really ‘bitchin’!

So the language becomes more colorful. But at the same time, the overwhelming frequency of derogatory uses of animal names reflects an unfair and arrogant attitude toward the beasts whose names we bandy about. Most of those pejoratives bear no relation to the real beasts.

The many uses of urine

courtship and defense, signposts and bragging rights… and a few human uses too

Reading about porcupine courtship made me think about how other animals use this metabolic waste product. Urine is an excellent vector for delivering scents and hormones that are signals involved with courtship (as in porcupines) and territorial defense. Many mammals, as well as some fishes and invertebrates, makes use of this convenient and readily available delivery system for olfactory communication.

We are all familiar with domestic dogs lifting a leg to urinate on a tree or fencepost. Such scent marks are sniffed by other dogs, who can learn the identity of the mark maker from the unique mix of scents, and often leave their own marks atop the original one. We sorry humans, with our relatively poor sense of smell, sometimes have a hard time imagining the scented world of dogs and many other animals, but these other beasts can identify individuals, as well as sexual and social status, from scent marks.

Both members of the dominant pair in a pack of wolves use urine to scent-mark the borders of their territory; newly formed pairs superimpose urine-borne scent marks on each other’s previous marks, probably as a part of courtship. Territorial borders marked with urine deposits are a regular feature of behavior in a variety of mammals, including coyotes and tigers. Beaver families make small, black piles of debris marked with urine and anal gland secretions to establish claims to particular waterways; other beavers are thus given notice that the place is occupied.

Males of many ungulates (such as moose, bison) either urinate over their own legs or wallow in urine-soaked dirt as a way of chemically signaling their status. Stallions urinate on established dung piles to advertise their dominant status. Male elephants and giraffes actually taste a few drops of female urine to detect hormones that signal readiness (or not) to mate. Female crayfish and swordfish send out a chemical signal via urine to attract willing males. Urine is used for certain forms of chemical communication among individuals of some species of primates (the taxonomic group to which humans belong).

Human campers sometimes urinate all around a camp site in hopes of deterring unwelcome four-footed visitors (although I don’t think the efficacy of this boundary marking has been fully determined), but human uses of urine go way beyond simple boundary marks. In the course of history, urine has been used in several inventive ways. Perhaps best known are the roles of urine in tanning hides and as a mordant to bind dyes to cloth. In sixteenth century England, whole casks of urine were shipped across the country for use in the dye industry.

The ammonia in urine can cut dirt and grease, and so it has been used as a cleaner. Even after soap became available, urine from chamber pots was used as a household stain-remover. In ancient Rome, urine collected from public urinals was hauled to laundries, diluted with water, and poured over dirty clothes in a tub; a person then stood in the tub and stomped on the wet pile to thoroughly mix the cleaner with the dirty clothes. Commercial persons who made a business of collecting and selling vats of urine were even subject to Roman taxes.

A traditional Scottish way to treat woven wool was to soak a length of the cloth in household urine to clean it and set the dye, and then pound it on a board. The process is called ‘waulking’ and still continues in the Hebrides (and in Nova Scotia by descendants of Scottish emigrants) as a cultural celebration.

Urine has been used as a tooth-whitener and for making gun-powder. Hormones extracted from pregnant mare’s urine are one way of treating fertility and menopausal problems. More recently, stem cells extracted from urine have been re-programmed to grow new nerves and other tissues. Many other medical applications are part of folklore, and indeed may be efficacious, but they could use verification by scientific study.

Very versatile stuff!

Three vignettes

a portrait of the naturalist in her own element

— Worming my way through the throngs of tourists, who were jabbering in at least four languages, I finally could peer over shoulders and outstretched arms with attached cameras. And there they were, the objects of all this attention: a female black bear with three tiny cubs of the year. Both tourists and bears were well-behaved. The bears lolled about between the platform and Steep Creek, occasionally nibbling on a leftover bit of sockeye.

After a while, Mom got up and sauntered a few feet away, where she munched on some greens. Her salad. A bit later, she walked slowly into the creek and, in one quick rush, caught a salmon. Crunch, crunch, crunch. She took it back to the cubs, and that was the main course.

Then they all ambled off through the brush, appearing a few minutes later under the next viewing platform. There they all snuffled around in the low vegetation, picking nagoon berries. Even the cubs know what to look for. Dessert!

— Between the north end of Fifth Street in Douglas and the gravelly part of the Crow Hill Road lies a short trail. Access into and out or a steep little ravine is assisted by knotted ropes, providing a new experience and a small thrill for the youngsters with us.

A small distance along is an old concrete dam on Bear Creek. Thanks to the works of Earl Redman and Bob DeArmond, I found a little information about the dam and the creek in the State Historical Library. Bear Creek was once known as Mission Creek, because of a nearby Quaker mission (the missionaries sometimes had a hard time with the miners…but that is another story). The first record of activity on the creek was an 1882 water claim for mining use. In 1888, a short-lived mining claim saw some sluicing and tunneling action at the very end of the Treadwell orebody.

The concrete dam was built in 1934, to supply water to the town of Douglas. It no long backs up water and the little creek flows unimpeded through the base, but I failed to find out when it ceased to impound water. Judging from the vegetation in the valley, it was many years ago. The trail goes right along the top of the dam, with concrete railings on both sides. I’m sure there are folks in town who remember the history of this little dam, and I’d love to know more about it.

— The top of Thunder Mountain on a warm, sunny day in mid August was a floral paradise: Splendid arrays of the intensely blue broad-petaled gentian, whose flowers open and wait for visiting bees only in the sun; patches of the low-growing, single-flowered harebell, with its up-turned blue cup; tall monkshood with deep purple flowers; pink subalpine daisies; tall groundsels presenting their crowns of yellow sunbursts.

The ground-hugging dwarf willows were sending white tufts into the breeze, dispersing their seeds to parts unknown. Bog blueberries grew in mats over the thin soil, and some patches of them were loaded with ripe fruit.

There are spectacular views down to the glacier, the Valley, and the islands, to the bridge and on southward, and up to Heinzleman Ridge (and a possible mountain goat). The only birds were two ravens overhead, in leisurely conversation, and a few savanna sparrows (probably), dodging around in the low vegetation.

An interesting find was a single plate from the back of a chiton. A little more searching revealed a total of seven plates, weathering out of a pellet cast by some bird, perhaps a raven. So that’s one way the remains of intertidal creatures can end up in the alpine.

Lunchtime on top of Thunder has a lot to offer! Well worth the steep climb up and the long trek down through a string of pretty meadows, a scattered stand of yellow cedars, and through the woods and mud along an old pipeline to the East Glacier trail.

Tidepooling

an invertebrate extravaganza (with some vertebrates too)

When the tide goes out, it’s time for a natural history treasure hunt. This year, both May and June brought really low tides (more than minus-four feet) at more or less reasonable hours of the day. Of course, we had to go looking for weird and wonderful creatures that might be visible. We went to two likely spots, one in May and the other in June. At one of them, we were supervised closely by a pair of watchful black oystercatchers.

Here are a few of our ‘treasures’. All of them were viewed in place and sometimes photographed, or they were carefully replaced where they were found.

Numerous tiny sculpins scuttled for cover as soon as their pools were disturbed or even at the approach of the terrestrial monsters that cast long shadows. Hiding under small boulders were cockscomb pricklebacks, crescent gunnels, and a pale, thin fish called a gravel-diver. These little fishes are sometimes called eels, which they are not, or blennies, although they are not even very closely related to true blennies. They are reported to eat a variety of small invertebrates.

Sunflower sea stars, with their soft surfaces and multiple arms, were plentiful at one site; they came in all sizes from about four inches to perhaps twenty inches in diameter. They usually feed by swallowing their prey whole, and they eat almost anything, including sea urchins, clams, snails, other sea stars, and mussels. The common five-armed sea stars displayed an astounding array of colors: gray, olive, bright and dull orange, brilliant purple, turquoise, and tan. There were lots of little ones of this species, about half an inch across, and these didn’t seem to show such a wide variety of color. These sea stars can use their tube feet to pry molluscs open or lift them off the rocks. They typically feed by everting part of the stomach over the prey and digesting it in place. Despite their very crunchy nature, they are preyed upon by large gulls, big sunflower sea stars, and large crabs. A special treat was finding a few brittle stars, mottled in maroon and green. They are detritus feeders, preyed upon by some fishes and diving ducks.

There were at least five kinds of sea cucumbers, a big purple one, medium orange ones, small white ones, smaller translucent ones, and thousands of the very small black ‘tar spot’ cucumbers. Sea cucumbers typically breathe through their hind ends—pulling sea water through the anus into a set of branched respiratory tubules connected to the hind gut. They feed on organic detritus mopped up from the substrate or captured in the water column. I presume there is a mechanism for keeping digestive products out of the respiratory system! Their predators include several kinds of sea stars, some fishes, and sea otters.

Worms came in several guises. My favorite, one I’d never seen before, was an intertidal gillworm, buried in mud under a rock: bright red, with feeding tentacles at the front end and many thin filaments along the side that serve as gills for breathing. Of course, there also were other polychaete (meaning ‘many-bristled’) worms of several types, with their numerous body extensions containing various kinds of stiff bristles that may help in locomotion, and the extensions also assist in respiration. Many polychaetes feed by extending a tubular, muscular proboscis, usually armed with teeth, to grab their invertebrate prey. Polychaetes are the favored prey of ribbon worms, which can change their shape from elongate, skinny ribbons to stubby slug-like forms. Ribbon worms subdue their prey by stabbing with a sharp stylet and injecting a neurotoxin, then pulling it in to digest.

The common ‘black katy’ chitons came in all sizes, and so did the more colorful lined chiton. We found one hairy chiton, with its frill of ‘hairs’ all around the edge. Chitons are basically grazers, eating algae and little invertebrates that are stuck to the rocks (baby barnacles, sponges, and so on). Chitons are prey of sea urchins, some sea stars, black oystercatchers, harlequin ducks, and river otters, among others. I once found a pile of plates from a chiton on top of one of the mountain ridges, perhaps indicating that a raven had pilfered one from another predator.

1-lined-chiton-on-coraline-alage-pam-1
Lined chiton. Photo by Pam Bergeson

There were hermit crabs of all sizes, hundreds of urchins, the usual big green and red anemones, and the smaller green burrowing anemones that somehow squeezed themselves into impossibly small crevices. Small periwinkle snails abounded in some places; they are grazers. And there were a few larger, carnivorous snails known as whelks, which can drill into other shelled creatures and slurp out the innards. Just imagine being a blue mussel and feeling that big snail rasping through your shell! Ah, but sometimes even those sedentary mussels can fight back, by ensnaring the attacking whelk in byssal threads, which are usually used to attach mussels to the rocks but can be diverted to repel invaders.

A nice find was an alga that turned out, upon investigation, to be two algae. A dark, filamentous alga bore odd, warty, oval bubbles or sacs on its fronds. Those sacs didn’t belong to that alga; they were another alga altogether, one that lives epiphytically, attached to other kinds of algae. It is called ‘studded sea balloons.’ A new one for me!

A treasure hunt, indeed. I’m basically a terrestrial ecologist, so a visit to the intertidal zone is always both fun and educational.