Climate warming and disease spread

The effects of climate change are being felt far and wide. We see headlines about ocean warming related to starvation of marine birds, die-offs of polar bears, invasions of green crabs, and year-round dangers of PSP.

On land, the warming climate brings other biological changes, including the northward spread of ticks, which has been well-documented in Eurasia and North America. Ticks are vectors of several diseases, such as Lyme disease, Rocky Mountain spotted fever, tularemia, encephalitis, and many other bad-news ailments. As the ticks spread northward, we can expect the tick-borne diseases to spread too.

One kind of tick is reported to be native to Alaska, occurring chiefly on hares, squirrels, and mice; it can carry tularemia bacteria. But non-native ticks arrive regularly, often on the bodies of dogs or humans or sometimes birds that acquired the tick elsewhere. For example, the American dog tick (genus Dermacentor) is already established in wild mammal populations here; this species (and the brown dog tick) can carry Rocky Mountain spotted fever, which is caused by a Rickettsia bacterium. So far, no humans have contracted this fever in Alaska; the bacterium can make dogs very sick and has been found in several small mammals, where the consequences are unreported.

The so-called rabbit tick (genus Haemohysalis) carries the tularemia bacterium (Francisella). The bacterium can be transmitted by a tick bite and by biting flies or by contact with an infected animal. If aquatic animals (beavers, muskrats) get tularemia, the bacterium can spread in the water from their decomposing carcasses and be transmitted by drinking contaminated water and by contact with lacerated skin of a swimmer. It can be lethal to hares, and it can make dogs, cats, humans, rodents, other mammals, and birds quite sick. Both the tick and the bacterium have been in Alaska for a long time. However, as the climate warms up, the tick and the bacterium will spread more widely.

The larvae of some Ixodes ticks feed on rodents and other small mammals, while the adults parasitize larger beasts, such as deer. These so-called deer ticks (or black-legged ticks, in the West) can carry several diseases; perhaps the best known is Lyme disease, caused by a spirochaete bacterium in the genus Borrelia. Ixodes ticks can also afflict birds, reptiles, and amphibians, which apparently don’t necessarily show clinical symptoms but can be vectors of the ticks to other animals. The life cycle of deer ticks goes through several stages, from larva to nymph to adult, in each case tending to move onto larger host animals; they can pick up the bacterium by biting an infected host. (Some infected mammals are not ‘reservoirs’ of the bacterium and–for some reason–do not transmit the bacterium to a feeding tick.) As each developmental stage grows and becomes ready to molt into the next stage, the young tick moves up onto vegetation and waits for another potential host to brush past. So far, Lyme disease is rare in Alaska, reported chiefly from people who picked it up in more southern areas. But a dog in Kenai apparently got it from a tick bite. Who is next?

The winter tick (Dermacentor albipictus) sucks the blood of its host mammal, maturing from larva to adult. Although deer, caribou, and elk can serve as hosts, they are not greatly affected. Moose, on the other hand, can be badly troubled; a heavily infested moose itches and scratches itself intensely, losing much of its insulating winter fur and becomes anemic from loss of blood. Moose calves are very vulnerable and can die—sometimes over half the calves in a population. In this tick, as many others, the larva climbs up on plants (in autumn) and hopes to hop onto a passing moose or deer. This tick species has not yet (!) been documented in Alaska, but it occurs in the Yukon and the Northwest Territories as far north as the Arctic Circle (and research has shown that it could reproduce in Alaskan conditions). It will surely cross the border into Alaska, perhaps not too long in the future.

Ticks are just one interesting link to the spread of diseases. Another kind of affliction may be waiting in the wings, so to speak. This one is a kind of fungus in the genus Monilinia, which includes many species that are commonly quite host-specific. Some of them cause brown rot of orchard fruits such as plums, cherries, apples, and pears; others attack blueberries and cranberries (and Labrador tea). Both types occur in the Pacific Northwest and British Columbia but apparently are not yet a major concern in Alaska.

The best-studied type of Monilinia attacks a blueberry species that is native to eastern North America but is also widely cultivated (e.g., in PNW and B.C.). When Monilinia vaccinii-corymbosi infests Vaccinium corymbosum, the vegetative parts are blighted and the fruits become hard, wizened ‘mummy berries’. The life cycle of this fungus neatly captures the interest of insects, which transfer spores. An infected leaf attracts insects by mimicking scent and UV patterns of flowers. Spores (asexual, called conidia) produced by this phase mimic pollen grains, so the insects (bees, wasps, flies) gather them; the spores can also just stick to the outside of the insect. Many of these insects are pollinators, so they transfer the spores to the stigma of a flower, where the spores germinate and send hyphal filaments to the ovary (using much the same pathway that a germinating pollen grain would use). Fungal tissue then turns the developing berry into a gray, shriveled, inedible ‘mummy’. In fall, the ‘mummy’ falls to the ground, overwinters, and produces sexual spores in the spring, which are wafted onto leaves and shoots, to begin the cycle again.

That type of Monilinia could reach Alaska via commercial sets of young cultivated blueberry plants (unless they are treated with fungicide?), potentially spreading to gardens here. Related species of Monilinia could attack wild Alaskan species, including bog or alpine blueberry (V. uliginosum), bog cranberry (V. oxycoccus), lingonberry (V. vitis-idaea), perhaps red huckleberry (V. parvifolium), and the cultivated cranberry (V. macrocarpon)–all of those plants occur in the Pacific Northwest and B.C. and at least some of them are known to be vulnerable to particular species of Monilinia. Naturalists in Sitka have already found Monilinia on some plants; the availability of fruits for many consumers will be reduced when it spreads.

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Field notes

Most of my recent trail walks have produced little sign of wildlife activity. But on a stroll in the Dredge Lake area, I saw a river otter in a bit of open water near the inlet of the Holding Pond. It soon dove under the ice and came up near the outlet, where the creek flows out to the river. I’ve seen otters here in other winters too and suspect they come up from the river to see if there are any fish to be had, not staying long. And at Point Louisa, there are sometimes scoters, goldeneyes, buffleheads, harlequins.

Over on north Douglas, a tight little bunch of sea lions surged past the boat ramp. A friend and I cruised the Outer Point/Rainforest loops while falling snow quickly covered lots of squirrel tracks. There were a few fresh tracks of a small bird, perhaps a junco, in the snow at the edge of the meadow. A big vole or a mouse had bounded across a gap between clumps of grass on the upper beach, making a leap of about seven inches. Goldeneyes nibbled along the rocks at the edge of the water and, a bit offshore, a little bunch of harlequins dove. Back in the woods, a wren darted out from under a foot bridge into a brushy tangle and then under a big log, not to be seen again.

That little wren is known as the Pacific wren, but it used to be called the winter wren, part of a species that nests widely across North America (and in Eurasia too). But taxonomists got busy and decided that these were really three different species, so they split the old classification and assigned new names. Now there’s the Eurasian wren (Troglodytes troglodytes), the Pacific wren (T. pacificus) that nests along the Pacific coast and in the Pacific Northwest, and the winter wren (T. hiemalis) that nests in the northern part of the eastern U.S. and adjacent Canada—but with a long westward extension of the breeding range out to northern British Columbia, where it overlaps with the Pacific wren.

Pacific wren. Photo by Bob Armstrong

Most of us could not tell these North American species apart by sight, although the Pacific wren is somewhat darker. But the vocalizations are known to be different. Where the ranges overlap in B. C., males of different song types held territories next to each other. Furthermore, singers of the different songs have different genetics, different enough to justify splitting them into separate species. Now we need information on what the females are doing…selecting males that match their own type?

And the taxonomists may have fun with another bird, known to us as Steller’s jay. Bird-watchers have noted the existence of plumage variation in various parts of the species’ range: Coastal jays have short black crests, blue forehead streaks, no eyebrow mark. Interior jays are similar but have a white eyebrow mark. Rocky Mountain jays have a long black crest and white marks on forehead and eyebrow. (In addition, jays in Guatemala and southern Mexico have blue, not black, crests.)

Coastal Steller’s jay. Photo by Kerry Howard

Geneticists got to work on comparing the Rocky Mountain jays with the Coastal/Interior jays and found significant genetic differences. That pair of populations is at least as different genetically as other pairs that are now accepted as different species: for instance, alder and Traill’s flycatchers, red-breasted and red-naped sapsuckers, white-crowned and white-throated sparrows. Furthermore, the Rocky Mountain jays occupy areas with different vegetation, a different climatic regime, and probably had a different history during glacial times.

So the researchers suggested some new names, perhaps officially becoming names of separate species. The Rocky Mountain forms might be called the long-crested jay (or perhaps the long-crested Steller’s jay), while the coastal/interior forms might be called the blue-fronted jay (or the blue-fronted Steller’s jay). More distinctions probably lurk down the taxonomic road!

Why bother with such distinctions?

From a scholarly perspective: sometimes, when we compare two very similar things (in this case, species), we discover that some tiny, subtle difference is actually not subtle at all but has significant ramifications for ecology and behavior. These discoveries expand our understanding. Furthermore, if two populations are sufficiently different to rank as separate species, they are capable of evolving in different, independent, directions, acquiring new, distinctive traits. Discovering those new directions increases our understanding of the ecological system.

In directly practical matters, distinguishing related but separate species is a useful tool for conservation: population trends can be monitored separately, not obscured by whatever is happening in the whole taxonomic complex. In this era of massive declines in many populations, it is useful to know how each population is faring.

Self-medication

Humans have self-medicated for ages, in various ways (not always healthy ones!), commonly using plant-derived materials applied externally or used internally. Although many of these uses remain in the realm of myth and wishful-thinking, some have been scientifically shown to be effective, at least in certain circumstances, although the sample sizes are usually small and the studies need replication.

I take a walk every day and find that this almost always improves my outlook on life. Walking can serve many functions, often overlapping and interacting, including exercise, observations and exploration, socializing (and, if I am lucky, a friendly canine greeting), contemplation and assessment… I find it useful in all those ways and typically feel better after a walk…so, in effect, this is a form of self-medication—one that is unlikely to be harmful.

Other animals may self-medicate too, although the evidence is largely suggestive and needs fundamental experimental documentation. The circumstantial evidence lies in observations that strongly, logically, indicate a medical function but, of itself, it is not proof. Examples come from many kinds of critters.

–European wood ants incorporate lots of solidified conifer resin in their nests. This reduces the growth of micro-organisms (as it does in the originating trees).

–Certain tiger moth caterpillars (sometimes called woolly bears, but not the same as the ones we call by that name) selectively eat particular kinds of plants containing alkaloids that increase survival of individuals parasitized by tachinid flies.

–Fruit flies, which can be parasitized by certain wasps, seek out foods that provide ethanol. Ingestion of this alcohol decreases oviposition by the wasps and increases the death of any wasp larvae already in the host fly. (Note: this only works with generalist wasp species, not with the species that specializes on fruit flies).

–Monarch butterfly caterpillars feed on milkweed plants but don’t favor any particular species. Mama does it for them: if she is infected by parasites, she oviposits preferentially on milkweeds that reduce parasite growth in the caterpillars.

–Chimpanzees and other great apes in Africa sometimes eat parts of plants that have little nutritional value (e.g., bark) as well as whole leaves and clay. These dietary choices may be useful against intestinal parasites.

–Starlings (and many other birds) often place bits of aromatic herbs (such as fleabane and wild carrot) into their nests during the nest-building process. Males begin the nest building in a cavity, later joined by a female; experienced, adult males are more selective of particular plants than are first-year males. Placement of the herbs continues until the eggs hatch. The volatile compounds in the aromatic herbs in one experiment reduced infestations of blood-sucking mites on nestlings, although nestling survival did not improve significantly. Another experiment found no difference in the numbers of mites on the nestlings, and no difference in nestling survival, but a significant difference in chick survival to age one year.

–Hummingbirds in Patagonia select a rare moss for nest material, constructing most of the nest with this moss. The preferred moss has effective antimicrobial activity, and it also has toxic compounds that might deter predation on eggs and chicks by small mammals.

Photo by RSA Kaler

–Some parrots in some parts of Amazonia gather at clay banks, eating the clay. Some researchers suggest that the clay may neutralize toxins in the seeds that parrots eat, but others claim that the birds are getting scarce minerals, such as sodium. Still another notion is that adult parrots feed the clay to their chicks, which do not have much resistance to toxins.

–Songbirds sometimes hold ants (or millipedes) in their bills and smear the ants over their feathers; or sometimes they just sit closely on ant nests and let the ants crawl over them. Anting may deposit some formic acid on the birds’ skins, which could deter ectoparasites or just feel good or something else.

–Great bustards are big ground-dwelling birds of Eurasia. Males gather on communal display grounds called leks in the mating season, displaying vigorously and trying to attract females. The energetic displays divert energy from the immune system, so it is less effective. These birds, especially the males, selectively eat blister beetles that contain toxic cantharidin, but because the toxin is lethal to the birds except at very low doses, only one or two at a time. This toxin is known, from in vitro experiments in the lab, to kill fungi, round worms, and bacteria (although its activity in bustards has not been tested directly). Males (more than females) also prefer to eat certain plants (a poppy and a bugloss) containing compounds that are effective against protozoan and round-worm parasites. Selective eating of beetles and these plants has only been documented for the Spanish population of bustards, which is geographically isolated from other populations.

The courtship display of male great bustards includes raising and exposing the rear end, where the digestive and genital tracts end in a common cavity (the cloaca). A courting male presents his rear end to a prospecting female, which inspects the cloaca very closely. The cloacal opening is surrounded by small white feathers, where parasites or traces of diarrhea would be visible to a female. Absence of parasites (and resistance to the toxin) would be good indicators of male health, which in combination with other traits, allows the female to make a good choice. Females are extremely choosy and most males don’t get a mate.

A lot remains to be learned about self-medication!

Small vertebrates in winter

On the last day of November, on the way to the end of the dike trail, I saw a warbler fossicking about on a mossy area near the spruce trees. It was probably finding small moribund insects and spiders. I got a good look at it: a male Wilson’s warbler. That was a surprise! I didn’t expect to see any warbler at that time of year, especially since we were having a series of cold night with temperatures in the teens. I could only hope that he would find enough food to fuel a flight to somewhat warmer places.

Photo by Gus Van Vliet

I began to wonder if this sighting was unusual. So I explored the information recorded in ebird.com a little and found that, over the years, this warbler has been spotted in northern Southeast Alaska uncommonly in November and December and even, but very rarely, in the depths of winter. Then I wanted to learn what other warblers (of those that commonly breed around here) are seen at this time of year. In particular, I thought of orange-crowned warblers and yellow-rumped warblers, which I often see in early spring (March-April), so they seemed like candidates for appearing in early winter too. Although yellow-rumps are recorded quite frequently in November-December and rarely in deep winter, orange-crowns are rare in northern Southeast in November-December. Then I found out that early arrival is not necessarily a good predictor of late fall sightings; Townsend’s warbler comes early but is seldom seen in late fall.

Do the warblers that sometimes stay into late fall have anything in common that might explain their presence? All our warblers feed chiefly on arthropods. Wilson’s, orange-crowns, and yellow-rumps are also known to eat berries and other small fruits at times, but so do some other warblers (but perhaps less often). And, in any case, our region does not offer many small fruits suitable for small birds. Maybe those three just strayed from a relatively nearby wintering ground? But that could not be the case for Wilson’s, which winters in Mexico and the Gulf coast. So neither what we know of diet nor proximity to wintering grounds goes very far to accounting for the three late-stayers. Perhaps they just misread a cue or get delayed by some unknown matter.

Other small birds characteristically spend the winter in Alaska: Pacific wrens, black-capped chickadees in the Interior and the closely related chestnut –backed species here, red-breasted nuthatches, and brown creepers. All of these species usually weigh about the same as the warblers discussed above: in the range of 8-12 g (YRWA at the top of the range). Being small means that they cannot store large quantities of fat to sustain themselves overnight or for several days— their metabolism is quite high and they are so small that there is no place to store a lot of fat on the body as large animals (such as bears and beavers) can do. And they don’t hibernate—they stay active all winter. Some of them (chickadees, nuthatches, occasionally creepers) include seeds in the diet, which are available in winter and which the warblers don’t eat. Chickadees, creepers, and nuthatches often cache their food—in effect, storing their energy outside the body, and black-capped chickadees (possibly also the others) have a temporary increase in brain size, with increased spatial memory during winter.

Red-breasted nuthatch. Photo by Bob Armstrong

In addition, chickadees (the black-capped species has been studied, but other species may do this also) can reduce their metabolism at night and let body temperature decrease; this saves energy, although in extremely cold conditions, it may be impractical, because body temperatures can’t drop too far (being ‘warm-blooded’). The over-wintering species have several tricks that are apparently not used by the warblers. Roosting in cavities, away from the winds, can increase the effective temperature by 25% or more, saving energy, and any sheltered site would be helpful to some degree. Moreover, roosting with companions would also help save energy. Both sheltering and companionship are used by these four species upon occasion. Wrens sometimes roost in cavities, sometimes communally. Chickadees sometimes roost in pairs, sometimes in cavities but more usually in dense foliage. Creepers sometimes roost in small groups, often in sheltered spots. Red-breasted nuthatches may sometimes use cavities, and if seed crops fail, they travel southward in search of better foraging. Apparently none of these methods (except for travelling south) is used by the late-staying warblers (as far as is known).

I can’t resist adding one more bird species: the common redpoll, which is slightly larger than those birds already mentioned, averaging about 13 to 14 g. They eat lots of seeds, especially in winter. And they have the intriguing habit of using snow blankets, dropping down to the snow and making a tunnel with a chamber at the end, 6-11 cm below the snow surface.

Shrews are very small, short-lived mammals that stay active during the winter. They can’t store sufficient body fat, so they have to keep eating every day—twice or three times their body weight in bugs, worms, and other inverts, to maintain their high metabolic rate. European common shrews (Sorex araneus) , weighing less than twelve grams, undergo a marked autumnal reduction in body size, including spine, internal organs, skull, and (!!) brain, as they enter their first winter. Home ranges are smaller and cognitive function related to spatial explorations seems to be diminished in winter. But they regain body mass and re-grow these parts in spring, almost to the original size, ready for the mating season. Researchers suggest that those winter reductions may be a way for saving energy. I have not found comparable information about Sorex species in Alaska, but similar seasonal changes might occur. I wonder what the Alaska tiny shrew does, living in the Interior and weighing less that two grams. Interestingly, the pygmy shrew (in a different genus) does not show these seasonal patterns, leaving open a number of intriguing questions.

European studies of least weasels and stoats (or ermine) have also revealed seasonal changes in depth of the braincase. (Both stoats and least weasels are considerably larger than shrews: stoats weigh up to about 330 g (esp. males), and the weasels weigh up to about 190g, esp. males. However, the long, narrow body shape means heat conservation is difficult, and the metabolic rates are high). Again, brain size reduction may be a way of saving energy. Juveniles decrease braincase depth during their first winter but regain it the next summer. Adults also lose braincase volume in winter and regain it the following summer, but males regain more than females (perhaps related to female’s energy expenditure on rearing offspring and less need to range widely).

Thanks to Gus van Vliet for helpful consultation.

Harlequins

On a cold, windy day in late November, I wandered out to Point Louisa. A strong, cold north wind had a mixed gang of scoters and goldeneyes clustered in the lee of the point. Right along the edge of the protected shore, some harlequin ducks were pottering about in the shoreline rocks. We often see such groups hanging out near rocky points.

The scientific name for harlequin ducks is Histrionicus histrionicus, from the Latin word ‘histrio’, meaning ‘actor’. In the Italian commedia dell’arte of the sixteen century, that word got expanded to mean specifically a certain kind of actor, who initially was something of a joker or trickster or mischief-maker, but became a high-spirited, clever servant, dressed in a patchwork of colorful fabrics. The bright patchwork of color on male harlequin ducks probably earned them that name.

Etymological note: Despite the similarities, the origin of that name is not to be confused with the old Greek word ‘hystrix’, meaning porcupine, nor with the Greek word ‘hystera’, meaning uterus (thus leading to words such as hysteria, originally used as a term for a supposed neurotic disease of females, imagining that it was caused by uterine troubles. Later, the term was expanded to refer to anyone’s excessive, uncontrolled emotions). Furthermore, the nickname for this duck is ‘harley’, but that’s not to be confused with a certain kind of motorcycle.

We most often see harlequins near salt water shores, where they commonly forage. They eat all sorts of intertidal and subtidal invertebrates—crabs, amphipods, periwinkles, mussels, chitons, barnacles, and so on. They commonly pick small prey items from rocks or gravel. The bill must have lots of touch sensors, so they can detect kinds of prey and precise locations for grabbing them. Sometimes they feed from a position on the surface, poking the head under the water or tipping the whole body with the head down. Sometimes they paddle their feet to disturb bottom sediments and grab prey from the resulting muddy plume. And they often make shallow dives, usually of less than half a minute in duration. Sometimes they feed on fish roe; herring spawn is a favorite in some places.

Photo by Bob Armstrong

Harlequins have a wide distribution, nesting in Iceland, southern Greenland, the east coast of Canada, eastern Siberia, and northwestern North America. Breeding is not restricted to coastal areas; inland mountains offer good nesting habitats along whitewater creeks and rivers (and in some cases, the birds then may migrate to salt water for the winter). They are very adept at swimming in rough water and strong currents.

These ducks commonly keep the same mate every year; long-term monogamy is the rule, if both members of the pair use the same wintering area. Established pairs don’t engage in elaborate courtship rituals; the association is one of mate-guarding usually by males but sometimes also by females. However, divorces and extra-pair copulations are said to be rare. New pairs are formed by mate-less individuals in winter, when the birds are on salt water.

Come spring, pairs move from salt water into fast-moving streams, where the females choose their nest sites. They walk along a stream bank and gravel bars, looking for something suitable. Nest sites are variable, but always on or near the ground (on cliff ledges, in rock crevices or tree cavities, on stumps, under logs, etc.), not far from the stream. Females do the incubating, often lining the nest with down, while the male goes back to sea to molt, temporarily loosening the pair bond. An egg is laid at one to three day intervals, usually in clutches of five to seven eggs. The females incubate for about four weeks, sometimes a bit more, and all the chicks hatch on approximately the same day. Hatchlings can feed themselves immediately; larval insects (e.g., of blackfly and midges) are often a favorite kind of item. They can dive when they are three or four weeks old, and fly not long after.

Photo by Bob Armstrong

Females sometimes abandon their broods, letting them find their own way down to the sea. But mothers often accompany their young ones downstream; that’s when we sometimes see them floating down a mountain creek. However, the offspring are on their own when they get to the sea.

Survival of the ducklings is highly variable, often depending on the food supply in the stream. On average, annually, usually less than fifty percent of females are successful in rearing a brood. The average brood size at fledging is two to four young ones. Mortality is due not only to starvation, but also to various predators, such as eagles, mink, and otters.

Although occasional females mature and breed at age one or two years, they usually form their first pair bond at age three or more. In any one year, some females do not breed at all. Males, too, seldom breed before age three or so. If we see males and females loafing about together at the shore in spring and summer, those females have failed to raise a breed or failed to breed at all. Harlequins are not globally threatened, but some populations have declined seriously.

Sexual dimorphism of this species is pronounced: males are far more colorful than females. In some studied cases, this kind of difference is related to sexual selection: competition among males for breeding rights, favoring distinctive displays, and choices by females about whom to have as a mate, favoring elaborate plumage of males. In harlequins, that kind of activity probably would be most intense among young birds (or widows and widowers) just starting to form long-term pairs, when they are congregated on salt water in winter. But I have not found detailed studies of mate choice and initial pair formation, so this hypothesis is untested, apparently. And perhaps there are other explanations???

The sense of touch

Touch is a mechanical sense, detecting physical stimuli such as pressure, texture, stretch, vibrations, and flow. Touch receptors come in a variety of forms—special cells, often housed in bumps or pits, or triggered by special hairs or feathers.

Human animals have touch receptors all over our bodies, but these receptors are especially concentrated in our hands, with which we continually experience and manipulate our immediate surroundings. Other animals often have touch receptors concentrated in particular parts of the body too, related (of course) to how those parts are used.

The emerald jewel wasp, native to Asia and Africa, has a long stinger that not only injects venom into its prey but also serves as an ovipositor for laying eggs. This parasitic wasp stings its cockroach prey in the body to slow it down, then stings it in the head to render it incapable of walking, and then lays its eggs near the zombie-victim’s legs; the larvae feed on the helpless victim. At the tip of that multi-purpose weapon are touch-receptors that register the feel of cockroach brain; if that brain is experimentally removed by researchers, the wasp can’t feel the texture of the brain and just keeps feeling around in vain. (Without that step of feeling and stinging the brain, the wasp presumably can’t proceed to oviposition.)

Fishes (and some amphibians) have lateral lines containing sensitive structures allowing the fish to ‘read’ water currents. As a fish swims, it displaces water that flows back along the body. The lateral line is a row of pits containing sensory cells that detect pressure and distortions of that flow, created by an obstacle or an approaching predator. The lateral line also allows schooling fish keep track of each other and to coordinate their movements.

Dolly Varden fish, showing lateral line. Photo by Bob Armstrong

We see shorebirds foraging out on the intertidal zone, poking their bills into the sand and mud. The tips of their stiff little bills are loaded with touch receptors that can sense the movement of water around pebbles, sand grains, and little clams or worms. As the birds probe down into the sediments, their bills set up tiny currents of water that flow around objects that distort the currents—distortions that can be detected by the bill-tip sensors. (Then the bird has to discriminate pebbles from food…).

Mice and rats (and opossums) sweep the spaces ahead of themselves with long, mobile whiskers, each whisker registering contacts in a different part of the brain, so the critter can form a sort of map of what’s in front of it. But cats and dogs don’t whisk their mobile whiskers back and forth like that (Why?).

Harbor seals have a face full of whiskers, which the seals use to follow hydrodynamic wakes left by prey fish; even a blind seal can track a fish this way, discriminating victims by size and shape and direction of movement. And here is the fascinating part of this story: As a seal swims, its whiskers create their own little turbulences, which might get in the way of detecting wakes produced by prey. But it turns out that seal whiskers have a special shape: they are elliptical (not round) in cross-section and variable in thickness and that somehow reduces the whisker’s own turbulence, allowing better reception of prey wakes. These modified whiskers are not found in walruses and seals that are bottom-feeders nor in sea lions that are reported to rely chiefly on vision for hunting.

Photo by Bob Armstrong

Crocodiles and alligators have little pressure-sensitive bumps along the edges of their jaws. These predators often lurk quietly in the water, with the snout at the water’s surface. Those bumps can detect surface vibrations created when an animal falls or walks into the water (and can even note the disturbance made by a drop of water falling onto the surface). Then the predator responds quickly! The sensitive bumps may be used in other ways too, such as registering water-surface disturbances made when males emit their deep bellows in mating season.

As a bird flies, tiny specialized feathers (called filoplumes) with sensors at their bases monitor the positions of adjacent bigger feathers. This lets the bird make the small adjustments of its wings that are needed to fly efficiently as conditions change. Similarly, the membranous wings of bats bear lots of touch-sensitive hairs that sense airflow, allowing bats to make quick adjustments of their flight path around obstacles.

Lots of arthropods have tiny, astonishingly sensitive hairs on their legs or elsewhere. In many cases, those hairs are tuned to particular frequencies of vibrations in the air. So a spider may detect extremely small pressure waves of a tiny insect flying close by, and pounce on it. And prey may detect an approaching predator: a cricket can detect the air waves of a spider moving in, unless that spider is moving extremely slowly and not setting up air waves. These hairs are more sensitive than any visual receptors can be; in fact, the energy needed to trigger these hairs is said to be almost as small as that of heat-activated, jiggling molecules.

Of course, this is just a sample of the marvellous array of ways that animals use touch-sensitiveness.

November

A good snowfall in early November drew us out to enjoy the brightened landscape and see what we could see. Before we got very far, we crossed the trail of a very small porcupine that had travelled for many yards as if it had a known destination despite its presumed lack of experience.

Our route of choice for this first wintry walk was the beach on the west side of Mendenhall Lake., which is walkable when the water level is low. Snow clung decoratively to alder twigs and cones (and built up huge cakes under my cleats). At the upper edge of the beach, we found two big ice-boulders, presumably rounded remnants of ice bergs cast up by the jokulhlaup a couple of weeks ago.

The creeks that come down to the west side of the lake were still open and flowing, although crossing them was easy. At one creek edge, a little plaza of ice had made a dining table for mink: There were scuffle marks, a few blood stains, and lots of mink tracks. Some small fish had made that mink happy.

Then the weather changed, temperatures rose, and the rains came, destroying the lovely snow. Fog settled down over the valleys and the channel, turning the visual world into shades of gray. From the east side of Mendenhall Lake, we could see lots of recent icebergs parked partway down the lake. The blue reflections from the denser ice were the only bright spots of color visible on the landscape. An eagle hunched down, just resting, on a high cliff not far from Nugget Falls. A great blue heron stood motionless in the shallows at the edge of the lake, presumably hoping a little fish would wander by. A gray bird on a gray lakeshore with a gray and white backdrop.

Photo by Katherine Hocker

On my home pond, the ice cover thinned but still supported several mallards that gobble up seeds that fall from the overhead feeder. They often rest in open water just below the dam—maybe watching that feeder for signs that the little birds are shaking out some seeds. Then they slide over the dam and hustle out to the place where seeds fall. When that is cleaned up, they march up and down the pond, to the open water at the inlet and back to the fallen-seed place. As the inflow of the stream slowly melts a channel through the ice, the ducks swim along the edges of the channel, nibbling at the edge of the ice (perhaps some edible bits are there??).

Beavers in the Dredge Lake area had been quiet, but their activity resumed with the warmer weather. A Beaver Patrol trail-cam captured an adult beaver hauling branches out to its winter cache, taking time to nibble a twig, while an observant youngster watched closely. A half-culvert that had been ignored for many weeks was suddenly packed full of brush and weeds. Almost as soon as the Beaver Patrol removed all that stuff, by the next day the beavers had crammed the culvert full again. Usually, by mid-November, beaver activity has shut down for the winter, but not this year.

The Beaver Patrol team had a treat at the Holding Pond one day; a dipper was foraging by the outflow and did not want to leave; eventually it moved across the pond to a small inflow area and foraged in the shallows. I had not seen a dipper here for a long time, although in some previous winters I could find them here fairly frequently, when the water was at least partly ice-free.

A few days later, the skies were blue, and all that sunshine required a walk that took advantage of it, so we went to Eagle Beach State Rec Area. The brilliant sun was so low in the sky that shadows were extra-long—a small hill across the broad river cast a long shadow over the wide river and across the big meadow near the parking lot. The river had done more serious erosion of the bank by the big meadow. All the gulls were parked out on the farthest edges of the sand flats, at the water’s edge. No importunate ravens came to our picnic lunch on the beach, but the frost patterns were gorgeous. And a touch of sun-warming was welcome on a frosty day.

Walking out on the tide flats, we found lots of goose tracks and eventually saw a dozen geese resting on a distant sand bar. A big muddy channel was littered with thousands of horse clam shells; there are probably some live ones buried in that mud somewhere. In a very small muddy channel, mixed with some goose prints, there were recent tiny tracks of a shorebird (with three front toes and no hind toe), but the track-maker was not to be seen.

Unusual breathing arrangements

For most of us, breathing comes naturally and we don’t have to think about it. Inhale and exhale, alternating. When humans breathe normally, air enters the nose or mouth, passes into the trachea (windpipe), and then goes to the two lungs. Gas exchange occurs in the lungs: oxygen is passed from air to the blood stream and carbon dioxide from metabolic processes is passed from the blood to air. Then the ‘used’ air is exhaled by the same passage ways, but in reverse; some residual air is left in the lungs. Movement of air is powered chiefly by the muscular diaphragm.

With training and lots of practice, humans can use other breathing patterns. One of these is called circular breathing. In this technique, air enters through the nose and goes to the lungs, but exhaled air is stored temporarily in the cheeks and pushed out (by the cheek muscles) through the mouth. So instead alternating intake and outflow, outbound air flow is maintained during inhalation by pushing out the air stored in the cheeks. Thus, circular breathing provides a continuous outward flow of air.

Circular breathing has been used for various purposes—including metal-smithing—but perhaps most notably for making music. Musical instruments that use circular breathing have arisen in many cultures in which production of a continuous tone is desired, and musicians have adopted the technique for various modern wind instruments. In some cases, continuous tones can last for half an hour or more. Perhaps the best known instrument requiring circular breathing is the Australian didgeridoo. This instrument is a hollow tube, cylindrical or tapered. Sounds are made when a player places the tube against the face and blows, vibrating the lips. The moving air resonates in the tube, acquiring harmonics (overtones). The pitch and resonance of the sound depend on the size of the tube. (Sometimes the output is modified by using the tongue or adding vocalizations.)

Birds have a very different breathing arrangement from that of mammals. Movement of air is powered by expanding and contracting the ribcage (birds do not have diaphragms). The lungs aren’t suspended in the thorax; instead, they are anchored to the dorsal body wall of the thorax. They are relatively small and dense: Instead of having thin-walled spaces that inflate and deflate with each breath, they consist of many narrow air channels intertwined with blood capillaries. The body contains air sacs (the number of them differs among species) that allow a continuous flow of air through the lungs. Inhaled air comes in through mouth or nostrils to the trachea; it bypasses the gas-exchange part of the lung and goes to a posterior pair of air sacs; exhalation then moves the air into the lungs for gas exchange. A second inhalation moves the ‘used’ air into anterior air sacs and a second exhalation moves it out through the trachea to the outside. In other words, it takes two breaths to move air through the full cycle. Thus, instead of the in/out cycle of mammals, the very efficient avian arrangement allows one-way flow through the gas-exchange part of the lung, and no residual air is left behind.

Illustration by Katherine Hocker

Air sacs have other functions too, including reducing the body weight, especially in birds that fly. But it seems that some of the (flightless) dinosaurs that were ancestors of birds may have had air sacs too. The origin of air sacs is still a matter of discussion.

Breath can also be used to make sounds. In mammals, vocalization typically occurs with exhaling, as the passage of air vibrates membranes in the larynx, which is located at the back of the throat where the trachea and esophagus separate. Birds use a different system: avian vocalizations are typically produced by the syrinx, which is located where the trachea bifurcates, sending branches to right and left lungs. Sound production is controlled by syringeal muscles, pressure from an adjacent air sac, and the diameter of the air passageway. Because the syrinx has two separately-controlled sides, one on each tracheal branch, birds can produce two notes at once.

Breath is also important to the sense of smell. Most non-human mammals have a much better sense of smell than we do, thanks largely to a larger number of olfactory receptors and more of the brain devoted to this function. In addition, although most inhaled air goes directly to the lungs, some is shunted to special areas in the nose that have concentrations of receptors (unlike in humans, in which incoming air passes over receptors on its way to the lungs). Some mammals also have modified nostrils that further increase the capacity to sense smells. Look at the nostrils of a dog, for example. There is small slit off to the side of the main opening. When a dog sniffs at something, it moves air in and out of the main opening. That outbound air is likely to push away the scented molecules. However, that little side slit diverts the exhaled air off to the side, so the scent intake is not interrupted by exhaling; furthermore, that diverted air stream may stir up more useful molecules and enhance the scents at the next inhalation.

That arrangement is best studied in dogs. But cats have a similar slit on the side of the nostril, and so do some other species, although I have not established a catalog of this feature. I would love to know how well developed this anatomical feature and its function are in other mammals.

October visit to Wisconsin

A mid-October trip to my old stomping ground in Wisconsin was full of quiet pleasures (plus a fine performance by the Madison symphony). Despite recent rains and high winds, the deciduous trees put on a grand show of color. Although there were pockets where all the leaves had turned to yellows and reds, the best color exhibits were the swathes of fall color set off by a hillside framework of green.

In certain fields outside my hometown, we often see cranes in the fall. So we went looking. No whooping cranes this year, but little groups of sandhill cranes were foraging in corn-stubble fields. We don’t usually see cranes in fields where soybeans had been harvested and stripped right down to the soil. But this time was an exception: six cranes were looking for things to eat in a now-barren soybean field. I had to wonder what they could be finding.

A visit to the International Crane Foundation offers not only some nice exhibits of cranes of the world but a chance to walk some easy trails in a variety of habitats. There’s mixed deciduous forest of oaks, maples, big-tooth aspen, cherry, and so on. This time I wanted to see the tall-grass prairie section with its rich mixture of grasses and late wildflowers—one of the most diverse ecosystems in the world. The tallest grass is called big bluestem or turkey foot (for the shape of the seed heads); it grows higher than my head. Thousands of small seed heads of little bluestem almost glowed when backlit by the sun. Here and there were a few yellow, white, or purple flowers persisting among the grasses. The tall-grass prairie once occupied thousands of square miles in the Midwest: centered in Illinois and Iowa, but extending from eastern Nebraska to western Indiana and from Minnesota and southern Wisconsin to eastern Kansas, with outliers in southern Manitoba and Oklahoma. But most of it has long since been plowed under, leaving only small patches and a few conservation areas.

Photo by Steve Willson

A string of bird-feeders and a water-bath outside a window offered continual entertainment, much more variety than at my Juneau house. A male cardinal sometimes claimed the water-bath for himself, but a female was never far away. There were red- bellied and downy woodpeckers, black-capped chickadees, house finches and goldfinches, a few house sparrows, bluejays (real ones, not our Steller’s jay), and white-breasted nuthatches. I always enjoy watching nuthatches scurry vertically up and down tree trunks. Walking down a tree trunk is made possible, it seems, by the large, strong hind toe on each foot, giving a good purchase on the bark. Best of all is watching a nuthatch fly to a trunk and instead of landing head-up, it turns in a flash and lands head-down. (Why don’t woodpeckers do that? They have two back toes on each foot, which would give a good grab on the bark.)

Gray squirrels were occasional visitors to the spilled seed below the feeders, but they spent most of their time collecting hickory nuts and acorns. Gray squirrels occupy the eastern deciduous forests and are often found in wooded suburban areas. Bigger than our local red squirrels, they scatter-hoard their harvest, burying each prize separately; if they fail to retrieve their stash, the nuts may germinate and contribute to the forest composition.

Mixed in with the normal gray-colored squirrels, we often see a few melanistic ones with black fur. The black fur results from a mutation in the DNA of a certain chromosome. If a black squirrel has two copies of the mutation, it is deep black, darker than one that has just one copy. If a blackish squirrel with one copy of the mutation mates with a normal gray squirrel, the litter generally has both blackish and gray pups.

Photo by Steve Willson

Is black-ness an adaptation to some environmental condition? At present, there are two suggestions: It might contribute to concealment, especially in northern forests where there are more dark conifer trees mixed with the deciduous ones. Another suggestion deals with thermoregulation. Black squirrels are said to be uncommon in areas with high air temperatures. Research has shown that black squirrels have more cold-tolerance than the grays: they have lower heat loss at very low temperatures, as well as a lower metabolic rate and a better ability to generate heat. But it is not clear what, if anything, black fur has to do with all that. Things to ponder, but there seem to be no conclusive data, and other possible explanations may exist.

Electric ecology

Most of us here live in a way that’s dependent on electricity, but we are generally unaware of electrical phenomena in natural environments (except for lightning). However, many kinds of animals are able to sense the small electrical fields that are associated with virtually every organism (and Earth itself). This sensory ability can be used in several ways.

Water is a better conductor of electrical signals than air, so even tiny inadvertent signals from individual electric fields can be transmitted better through water than through air. And many studies have explored electroreception in aquatic organisms.

Many fishes, both freshwater and marine, are known to have electroreception. The structure of electroreceptive organs varies among species and has evolved separately in different lineages, but these organs are generally located in the skin of fishes. The ability of electroreceptive fishes to locate prey has been well-studied, in some cases even locating prey that is buried in sediments. Some fishes extend their electrical ‘reach’ (beyond their individual electric field) by a special organ that generates a greater electrical discharge, which facilitates prey location. These ‘weakly electric’ fishes (e.g., knifefishes) also use their electric capacities in social interactions, including recognition of species, sex, individual identity and the organizing of group hunting; they can adjust their electrical discharge to avoid jamming each other’s signals. In a few species (e.g., electric eel), that electric organ generates such a great discharge that prey can be stunned, incapacitated, and even killed.

Some Australian mammals use their electrosensitivity to find food. The platypus closes its eyes and ears and nose when it dives, and swishes its bill back and forth in murky water and sediments, locating invertebrate prey with the many electroreceptors on its bill. At least some of the related echidnas (although not aquatic) have electroreceptors in their snouts, which appear to work when the animals root about in damp soil or water, locating worms and other prey.

Other vertebrates known to have electroreceptors include salamanders and at least one dolphin. The capacity may occur in other dolphins and has been suggested but not shown in a few other mammals (e.g., star-nosed mole). Even less is understood about aquatic invertebrates sensing electric signals.

The big surprise for many scientists was finding that electroreceptors also work well in air. Even though air is not a good conductor, aerial electrical signals can work over short distances. There are many examples, some well demonstrated, others still to be fully documented. For instance, geckos are famous for their ability to climb vertical walls and cling to ceilings, and electrical charges (in addition to other factors) in their feet assist this activity.

Bumblebees and hoverflies use electric signals from plants when they visit flowers, as discussed in a previous essay. Electrical signals may enhance the information transferred from one honeybee to another, when the waggle dance is communicating the location of foraging sites. Spider webs may be attracted to insects carrying the opposite charge, deforming a few millimeters toward a flying insect. Spiders and moth larvae often disperse by ballooning on long silk strands, which could interact with the atmospheric potential gradient from the earth in a way to increase the height of the airborne disperser and even affect the decision about when to start ballooning. Bacteria and their spores carry electrical charges that may contribute to their aerial dispersal by interacting with the atmospheric gradient. Tall trees can shield their surroundings from the atmospheric gradient, which would impact ballooning and possibly other aerial activities.

Now consider an additional marvel. When an animal moves through its environment, it accumulates electrical charge; insects or birds in flight experience friction with the air, so do walking or running animals, which also brush against various objects in their path. Even rain drops, falling through the air, develop a tiny charge. These effects of motion are typically very small but potentially wide-ranging. For instance, some experiments have shown that more bacteria and viruses are deposited on flying insects that carry a charge. In addition, and closer to direct human concerns, more bacteria adhere to the garments of hospital workers as they whisk down the halls from room to room, suggesting that there is more clinical transfer of pathogens than we imagined.

It is also possible that electrical fields influence olfaction (sense of smell) in animals, by increasing interactions between airborne molecules and the olfactory organs. And since plants also communicate with aerial chemical signals, perhaps electricity is involved with that too!

We’ve just begun to explore the world of electric ecology and many hidden boxes remain to be opened. Meanwhile, we’ve learned that electroreception is a fact of life for many organisms, with vastly more still to be discovered and explained. Given that fact, we need to recognize that there are undoubtedly many aspects of human activity that affect the electric ecology of other organisms on earth. We already know something about anthropogenic pollution of water and land, light pollution, and noise pollution; now consider what we might do to electric ecology. For instance, spraying pesticides and fertilizers changes the electrical field of flowers and changes visitation by insects. Strong electrical fields around cables, power lines, and various man-made structures tend to be avoided by many animals. No doubt, more ways that humans can interfere with the rest of global ecology will emerge from continuing research in electric ecology.