Mites and burying beetles (2 of 2)

passengers on the beetle

Last week I wrote about the remarkable burying beetles, which typically inter and prepare the carcasses of mice and small birds on which the beetle larvae feed. The individual beetle that prompted my interest was just crawling across the ground, but it looked very strange. It was covered, top and bottom, with at least two layers of tiny, squirming mites, hundreds of them.

So many mites could not, realistically, be feeding on the beetle, so what was going on? A cursory search of the literature revealed that certain kinds of mites regularly ride around on burying beetles, using the beetles for transportation to another carcass. In effect, the mites are hitch-hikers. There are several kinds of mites that hitch-hike on burying beetles, and at least some of them have strong preferences about which beetle species they ride on. The beetle we found had probably left its nest very recently and had not yet dumped off many of its riders on other carcasses.

beetle-2-with-mites-by-bob-armstrong
Photo by Bob Armstrong

Like their beetle transporters, the hitch-hiking mites reproduce on carcasses. Their effect on reproduction of the beetles varies from positive to neutral to negative: In some circumstances they benefit the beetle by killing the eggs and larvae of flies or other carrion-users such as nematode worms that colonize the same carcass and compete with the beetles for use of this food supply. Thus, they can enhance the reproductive success of the beetle. However, at very high densities, the mites may start to eat beetle eggs too, which sounds like a simple negative effect from the beetles’ perspective. But reducing the number of beetle eggs can leave more food for the remaining larvae, which then grow faster and bigger. And because large larvae turn into large adults that can lay more eggs (if female) and dominate other males (if male), a limited amount of egg-eating can ultimately benefit the beetles (provided that not too many of the beetles’ eggs get eaten).

Other kinds of organisms are also carried to new carcasses by burying beetles. For example nematode worms can be common in beetle nests, and they are competitors for the food supply in the carcass. They ride in the guts and genitalia of the beetles when the adults move to a new carcass. But this relationship is not as well-studied as the one with mites.

The official name for these hitch-hiking relationships is ‘phoresy’ or ‘phoresis’. Some phoretic mites latch onto bumblebees or honeybees and get carried from one flower to another, where they eat pollen and nectar. Similarly, tropical flower mites hop onto the bills and into the nostrils of nectar-seeking hummingbirds, and catch a ride to another flower. Because the flower mites eat nectar, they compete with the hummers for food. By reducing the amount of nectar in a flower, the mites may cause the hummers to move to more and more flowers, and thus become both better pollinators (from the plant’s perspective) and better transporters (from the mites’ perspective). The mites apparently do not harm their hummingbird carriers directly but may cost them a little energy if the hummers have to visit more flowers to get a full meal.

Insects that feed on wood often have phoretic fungi, whose spores are carried on the wood-boring or bark-eating insects. The fungi help weaken the tree and may also be food for the insects’ larvae. Cactus-loving fruit flies carry a yeast that detoxifies certain plant chemicals, allowing the fly larvae to grow faster and bigger as they eat the cactus.

One of the best-developed phoretic relationships involves blister beetles that lay their eggs in flowers. The larvae of certain beetle species mimic the appearance and the chemical sex-attractants of bees. Male bees visiting the flower, to feed on nectar, try to copulate with the mimics, which grab onto the bee’s legs for a free ride to the bee’s nest. There the beetle larvae act as parasites, eating bee eggs, larvae, and honey stores.

This is just a small sample of the diversity of phoretic relationships in nature, most of which have not been studied in detail.

Burying beetles and mites (1 of 2)

a beetle with many stories to tell

On a recent junket to watch bears catch salmon, we encountered a beast with a different story to tell. This was a beetle about an inch long, and its entire body, top and bottom, was covered with layers of tiny, squirming mites. Together, the beetle and the mites represent a remarkable and fascinating story—in two parts.

nicrophorus-with-mites-2-bergeson
Photo by Pam Bergeson

First, the beetle. This kind of beetle is called, variously, a carrion beetle, a sexton beetle, or a burying beetle. It belongs to a genus of beetles that is widespread in the world, especially the northern hemisphere, with about 68 species known so far, and three species in Southeast Alaska. The name of the genus is Nicrophorus, but formerly this was spelled Necrophorus, which give a clue to its behavior. ‘Necro’ (as in necropsy and necrophilia) refers to the dead, and ‘phor’ refers to carrying or bearing something –thus, a bearer of the dead. The beetles are typically black, with orange blotches on their wing covers.

These beetles are scavengers, eaters of vertebrate carrion (and one species has recently been found to use snake eggs). Adults can feed on any large or small carrion, but perhaps the most interesting relationship is generally with small mammals or birds.

The entire life history of burying beetles typically centers on finding a dead shrew, mouse, or small bird. There usually aren’t lots of these just lying around, up for grabs, and what few there are, are very attractive to other scavengers, be they ravens, blowflies, worms, or microbes. So it pays to find a carcass quickly; competition for dead mice or birds is intense. One study showed that the size of the population of burying beetles depended on the availability of suitable carcasses, which depended on the size of the populations of small mammals.

In addition to competition with other kinds of organisms, there is competition among the beetles themselves. When a male beetle locates a suitable carcass, he advertises for females, using airborne chemical scents or, in some cases, courtship songs produced by rubbing a rough part of the abdomen against the underside of the wing covers. Large males can outfight smaller males for possession of the carcass, but the subordinate males may hang around and sneak some copulations with arriving females. In addition, because female beetles can store sperm from a previous mating elsewhere, a male parent on a carcass may not be the father of all of her eggs. In at least one species of beetle, females also fight each other for rights to use the carcass, but subordinate females may add some eggs to the brood.

The beetles use the carcass to rear their young. When a burying beetle finds a relatively fresh carcass, it buries its find on the spot, by scratching out a hole under the body, or it moves the prize to a usable spot, by lying on its back under the body and pushing with its legs, and then buries it. These beetles are strong, and can move a carcass over and around obstacles.

Once the body is buried, the beetles chew off the fur or feathers, roll the body into a ball, and anoint it with chemicals that deter the growth of microbes that would decompose the carcass, competing for the flesh and reducing its nutritional value. Adult beetles carve a hole in the top of the ball, chewing some of the flesh into a soup that fills the hole.

Female beetles lay their eggs in a tunnel near the carcass. The eggs hatch in just a few days, and the larvae move to the carcass. There they may be fed by the parents from the soup of chewed up flesh, or they may feed for themselves. The larvae beg from the parent beetles, and larvae that hatch a day or so ahead of others are more successful at begging.

Usually both male and female parents tend the brood of larvae, although either one can also do it alone. The primary role of the male appears to be in defense of the carcass against flies and other beetles but, in addition, the female benefits, because she doesn’t have to work so hard and can save energy for a second brood on a different carcass.

The number of eggs laid by a female beetle depends largely on her body size, her body condition (which depends on how well fed she is), and the size of the carcass. However, if too many eggs are laid (for example, if a second and subordinate female has deposited her eggs in the same area), females may destroy some of the eggs or larvae.

The larvae go through several molts as they grow. In some species, they turn into adults in summer, overwintering as adults that come out the next spring. In other species, the larvae spend the winter as inactive pupae, and adults emerge from the pupae the next summer.

Some of the beetle species, including one of those in our area, may nest communally. That is, several pairs of beetles may share a large carcass (if they can get there before another scavenger gets it!). On the north Pacific coast, salmon carcasses offer a relatively predictable source of carcasses in late summer and fall. Bears and other foragers leave partially eaten carcasses on the floor of the forest, where they become available to burying beetles. A salmon carcass may harbor three or more pairs of beetles, all rearing their broods on different portions of the carcass. In this case, the carcass is not buried; instead, the beetles just move in underneath the body. The larvae are then reared on salmon flesh, instead of the more usual mammal or bird.

The story of the mites riding on the beetles will have to wait until next time.

Granite Basin denizens

visiting the world of marmots and spotted sandpipers

A long, lazy lunch, which we enjoyed while sprawled on a huge boulder in the noontime sun: we basked like lizards—or, more appropriately for our locale, like marmots.

Soon thereafter, we were whistled at—by a pair of baby marmots that had just recently begun to emerge from the den where they were born. These toddlers tried very hard to sound the alarm about the ‘monsters’ tramping along the creek, but their whistles sounded very raspy and feeble. That didn’t deter them, however, and they shrilled every few seconds until we were well past their rock.

It seems to take a while for youngsters to learn how often to ‘cry wolf’. Adult marmots would probably not have gotten quite so excited at the sight of two-footed monsters traipsing by. Interestingly, baby beavers behave much the same way, tail-slapping over and over again at something strange, often ignored by their parents, until they learn to tailor their alarms to the circumstances.

hoary-marmot-young-of-the-year-sept-5
A young hoary marmot

The scientific name of our hoary marmot is Marmota caligata. The second name refers to boots, because the marmots’ black feet reminded some taxonomist of that footgear. Farther south, hoary marmots typically inhabit high elevations, with other marmot species at lower altitudes, but in our area, these marmots range from sea level to the alpine zone.

These marmots have a very flexible mating system. Some mate in pairs, or social monogamy; a study in south-central Alaska suggested that this was the common arrangement there. Others are polygynous, two or more females socially bonded to a male. Sometimes an extra male resides on the periphery of a mated male’s territory. Regardless of the social arrangement, however, there is reportedly a lively scene of extracurricular activity. Males go gallivanting over the hillsides, looking for receptive females. And they find them: many litters have been shown to have multiple fathers. So perhaps the two we saw were just half sibs.

Gallivanting males are most common in big patches of suitable habitat, where several colonies of marmots are neighbors. Small habitat patches may only support one family group and opportunities for gallivanting are fewer. Males reportedly behave more parentally when gallivanting is not an option; they guard their offspring more assiduously and even play with them.

Hoary marmots typically mature disperse from their natal territory to find their own place in the world when two years old. Mature females, age 3 or more, can produce a litter every year if food is very abundant but often skip a year or two if food is scarce. Mating occurs in spring, soon after the adults emerge from hibernation. Gestation lasts about four weeks and the pups are weaned after roughly four more weeks. Litters usually consist of about three pups, but pup mortality can be high, especially during winter. Litter size and frequency of reproduction varies with the social mating arrangements: monogamously mated females produce larger litters more often than bigamously or trigamously mated females, which are more likely to skip a year—and whose males do more gallivanting in the females’ off-years!

I heard but failed to see a spotted sandpiper near the pool at the top of the falls at the basin entrance. Spotties are found there virtually every year. They usually nest on gravel bars and upper beach fringes, and the basin provides several gravel bars.

Spotted sandpiper females arrive first on the breeding ground and claim a territory. Males arrive later and set up their own territories inside those of females. Some females mate monogamously, and both parents may care for the eggs; this mating arrangement is more common among younger females. Older females are commonly polyandrous: a female often mates with two or even three males in succession. She lays a clutch of four eggs for Number 1 and leaves him to do all the incubation and chick-tending, while she goes on to Number 2. If there is no Number 3, a female may help Number 2 care for the brood.

spotted-sandpiper-by-bob-armstrong
Photo by Bob Armstrong

Some polyandrous females bond with males within her original territory. Others search widely for a second mate. It turns out these females keep track of their neighbors and they know which territories previously have been successful in producing chicks. And to the males on those territories go the females to find a sire for their second broods. In this case, it seems to pay to be a nosy neighbor!

The plot thickens still further! Those second males may indeed perform all their parental duties and also may be helped by the female if it is her last brood of the season. But second males are not necessarily the fathers of the chicks. In some cases the female stores sperm of Number 1, which becomes the father of at least some chicks in the second brood. In effect, Number 2 has been cuckolded by the first male and ends up caring for another male’s chicks.

 

Fritz Cove

wildlife spotting and speculation along a quiet stretch of highway

It was murky sort of day, low overcast, occasional rain squalls, and sloppy snow underfoot. Our schedules didn’t offer many breaks either, so we opted for an easy walk along the North Douglas Highway.

The beach by the North Douglas boat ramp could well be called our very own ‘Skeleton Coast’ (with apologies to southwestern Africa), for the number of picked-over, disassembled deer carcasses reposing on the cobbles. Two eagles each claimed a deer head, while ravens, crows, and gulls squabbled over the few remaining scraps.

A couple of humpbacks cruised and dove, attended by a small gang of sea lions. Either the whales weren’t stirring up much tasty fare for the sea lions, or they had already provided very well for the ‘lions, which spent a good deal of time lolling about, floating belly-up or side-up, poking out a fin or two occasionally.

We counted nineteen kinds of birds (and there may have been more). All the usual suspects were there. We watched a red-throated loon with a long, wriggly fish, which was finally subdued and swallowed. There were a few Pacific loons and what we thought was an immature yellow-billed loon. A duo of common murres was a nice surprise. The only songbird was a song sparrow, which—around here—could well be called a beach sparrow.

A mixed flock of numerous scoters included mostly surf scoters, some white-winged scoters, and a probable black scoter. The scoters were diving, apparently for mussels. Most of the birds were diving independently of each other, with only a few of their famous chain-dives (in which a whole line of birds all comes up a spot where, one by one, they go down; a little later they all come up, one by one, at another spot a short distance away. I’ve never been able to find out why they do that.)

Several glaucous-winged gulls were hanging out with the scoters, mostly behaving very casually and innocently, floating around together. But every so often, a gull pounced on a scoter that was just coming up with food in its bill. At least some of those pounces made the scoter release its catch, to the benefit of the piratic gull. But many attempts at piracy seemed to fail. More puzzling was the observation that a gull would jump on the back of a floating scoter, forcing the scoter under the surface. Are the gulls trying to make the scoters dive for food or are they just having fun?

A few days later, it was still raining, and blowing, and I stopped at the North Douglas boat ramp. I was attracted by dozens of crows in the parking lot and on the cobbly beach. I pulled up near the far end of the lot, away from the crows, and just sat there to watch what was happening. It soon became clear: the crows were collecting small mussels from the beach, flying up and dropping them on the hard blacktop surface (and on the beach cobbles). By careful watching, I determined that sometimes a mussel shell cracked after one drop, but sometimes it took four drops of the same mussel before the crow could gain access to the soft interior.

crow-with-mussel-by-bob-armstrong
Photo by Bob Armstrong

The height of the drops varied greatly, from about five feet to maybe twenty feet or so, and longer drops seemed to be more effective. But a high-flying crow took longer to descend to its prey, which gave other crows time to sneak in and appropriate it. There were many attempts at stealing food from each other, so theft was a real risk. There was a trade-off between effective cracking and protecting the prey from competing crows.

I would love to know more about the energetics of this behavior. Flying up and then zooming down to protect the food takes energy. If a crow has to fly up three or four times, does the energy in one mussel fully repay that effort? Once a mussel shell cracked, the crows would poke and pry to extract the insides, often holding down the shell with a foot. Can crows wrench out the strong muscle that bivalves use to shut the shell—that muscle is very tightly attached to the shell, or can they only feed on the other organs?

This was also a bathing place for the crows. A pothole in the blacktop had collected rainwater. It was big enough for two crows to fit in at the same time, with much exuberant flapping and splashing. Occasionally several crows would line up politely to have a turn at their public bath. Bathing was not as competitive as feeding!

Kingfishers

divers and burrowers

I’ve been thinking about kingfishers lately, although I don’t know what brought them to mind. I certainly haven’t seen any recently—their freshwater fishing spots are mostly iced-over, so they are out along the saltwater shores where I seldom go. Our species is formally called the Belted Kingfisher; males have a blue belt and females have both a blue and a rusty-orange belt across the belly.

With kingfishers on my mind, I found I was recalling a nest I once found. Several years ago, while we were deeply involved in a study of American dippers, I was watching a pair of dippers that had a nest in an old broken-down wooden dam. I sat on a brushy cliff above the nest site, watching the dippers go about their business of raising a family. The dippers paid me no heed, coming and going up- and downstream unperturbed.

Not so the kingfishers, who—I soon discovered—had a nest across the creek. Kingfishers nest in burrows dug one or two yards deep (but sometime more than four yards deep!) in earthen banks, and this one was beautifully inaccessible to almost any predator. The dirt bank was vertical, and the nest entrance was well below the top of the bank and several yards above the stream. No way was I a threat, nor was anything else. But every time they arrived and discovered me on my perch, those parent birds sat in trees just upstream and glared at me for long minutes. Eventually, if I stayed very still indeed, they would go to the nest.

I don’t know if they raised their chicks successfully, because my dippers finished raising their young ones before the long chick-rearing period of the kingfishers was done. However, it is likely that they were successful, because they nested in this same bank for several years. The steep dirt bank eroded a bit almost every fall and winter, but the birds just dug a little deeper, extending the burrow, and carried on.

At the end of a nesting burrow, kingfishers excavate a nesting chamber, big enough for five or six eggs and an incubating adult and, later, for those chicks to grow to full size. The chicks stay in their chamber for about four weeks. The parents, but especially the male, feed them diligently, first on partly digested fish and then on small but whole fish. These parents typically had to fly at least half a mile downstream to find good fishing, because small fish are not abundant in the upper reaches of this creek. Long foraging flights are not unusual for these birds.

Unlike songbirds, kingfisher parents do no nest sanitation. Instead, the chicks squirt the walls of the chamber with their liquid excrement and then pound the walls above the wet spot, putting a thin layer of dirt over it. I have to wonder how that habit got started!

Most of us have seen kingfishers perched on a branch over the water or even hovering over the water surface, looking, looking, looking. And if they spot something good, then down they plunge. Most dives are shallow, not much below the surface of the water. Usually they capture fish, but they can also eat frogs, large insects, crayfish and so on.

An interesting thing happens as the diver enters the water. Think about this: if you reach down into water to grab something, you often find that the object of your reach isn’t quite where you thought it was, and you miss it by several inches. That’s because water bends the light rays more than air does and your eyes don’t compensate for the change of direction. This problem occurs when light crosses a surface between two media at an angle.

k-hocker-kingfisher
Photo by Kathy Hocker

Kingfishers face the same problem. Sighting the prey from the air only gives them an approximate locations to aim for. But their eyes (and those of other birds that pursue active prey) have a feature we don’t have. In the back of a human eye, on the retina, is a little pit (the fovea) where there is a high density of visual cells, so this is an area of very acute vision in one medium (usually air). However, these birds have not one but two foveas, separated by a little distance, and their vision shifts smoothly from one to the other as they enter the water. One fovea works primarily for lateral, monocular vision, with the line of sight directed mostly to the side, but the second one is located where the line of sight converges with that of the other eye, producing very sharp binocular vision over a wide field of view. So when the diver enters the water, the second fovea is engaged, and that gives the diving bird high visual acuity at the all-important last moment before the prey is grabbed in the bill.

I have not found much published information on the success of kingfishers in capturing prey. A study of the Amazon kingfisher (which lives in Latin America) showed that capture success ranged from eighteen to sixty-two percent of attempts, depending on circumstances. A study of our Belted Kingfisher in California found that over half of attempts were successful if the bird was hunting from a perch but only twenty percent if the bird was hovering.

Mermaids’ purses

…and their cartilaginous currency

alaska-skate-egg-case-by-gerald-hoff-afsc
Photo by Gerald Hoff, Alaska Fisheries Science Center

This is a fanciful name for the egg cases of skates, which are cartilaginous fishes related to rays and, more distantly, to sharks. When some friends found a few of these egg cases on North Douglas beaches, I got interested in learning more about them. Not being a marine biologist, I had to do a bit of digging, but I got a start with the help of a genial skate biologist at NOAA. Here are some of the things I think I have learned.

Skates put their eggs into tough, leathery cases. The cases are deposited in traditional nursery sites that are used year after year. According to the skate biologist, there are two skate species in our area that use relatively shallow-water nurseries and are the most likely ones whose egg cases occasionally appear on our beaches. These two are the big skate and the longnose skate. Beachcombers should be able to distinguish the egg cases of these two species quite easily: Egg cases of big skates are typically more than eight inches long with short stubby horns at the four corners; those of the longnose skate are about four inches long, with slender horns. When the cases are laid, they often bear tufts of sticky threads that help stick the case to the seafloor; these threads may get worn off on cases that wash up on beaches. Most egg cases that show up on beaches are empty; the young skates are gone.

Most skates, including the longnose, put only one egg in each case, but the big skate may have as many as seven or so in each case. There is little available information on how many egg cases a female skate produces each year, but it is only a few hundred at most or, in some instances, much less. The growing embryos are well endowed with abundant yolk and the cases require considerable material and energy to make; this large parental investment per embryo means that the number of embryos must be fairly small. The case stays closed for several weeks, and then slits open in the horns, letting in sea water and oxygen; the embryo develops a temporary filament on the tail, and this undulates in one of the horns to facilitate the movement of water in and out. The eggs incubate in their cases for a long time, averaging about nine months for the big skate (but some other skates living in very cold water, such as the Bering Sea, may have incubation periods of several years!).

Predatory snails can bore into the cases and eat the contents; in some situations, over 40% of egg cases have been depredated by snails. In the Bering Sea, the intensity of predation was lower in nurseries with high densities of egg cases, suggesting that there is some safety in numbers—(this is referred to as predator satiation, or predator swamping, or the selfish herd effect). After the lengthy incubation, when the eggs finally hatch, the ‘pups’ are miniature versions of their parents. They have many predators, and juvenile survival is undoubtedly very low.

Both big skates and longnose skates can, but apparently seldom do, live for more than about twenty years. Big skates in the Gulf of Alaska were estimated to mature at about five to nine years of age, longnose skate at age nine to twelve years. Females mature somewhat later in life than males, particularly in big skates.

Skates eat a variety of fishes and invertebrates, including crabs, octopus and squid, and worms.

alaska-skate-by-alaska-fisheries-science-center
Photo by Alaska Fisheries Science Center

Around the world, some skate populations have crashed dramatically, due to overharvesting plus numerous by-catch captures in fisheries directed at other species; by-catch captures are just discarded. Both big skates and longnose skates in Alaska are increasingly subject to both directed harvest and by-catch mortality, and fisheries biologists report declining numbers of these species. Therefore there is both management and conservation concern for these species.

The North Pacific Fishery Management Council recently identified six skate nursery areas in the Bering Sea as Habitat Areas of Particular Concern. These areas are not closed to fishing but will be monitored for changes in skate egg density and other factors. Consultation will be needed for proposed activities that might modify habitat or otherwise impair skate reproduction, such as drilling or laying of cable in these areas. There was no report of any quasi-protective measures for the Gulf of Alaska.

All you beach-walkers, take note: if you find a skate egg case in your peregrinations, please send a good digital photograph of it, with precise location information, to jerry.hoff@noaa.gov. He is keeping records in a database and will identify the egg cases you find.

An early autumn

Leaves and flowers, fish, mammals, and birds in transition

Fall came to Juneau in mid August. Cottonwood trees began dropping yellow leaves and alder leaves browned and shriveled. The air felt different, and it smelled different, too. On fine, sunny days, clouds of fireweed seeds, floating on their white parachutes, filled the air and collected in windrows on the shores. Mushrooms appeared all over the forest, as if from nowhere.

The grasses and sedges in the coastal meadows slowly changed from green to yellow and gold. Although the splendid pink flowers of fireweed were gone, the stems, leaves, and pods still filled fields with pink and red.

At mid elevations, a few fireweed stalks still bore flowers and some had, in fact, just started to bloom. But the deer cabbage leaves already showed yellow and orange and russet. As the rains increased, the once-fluffy heads of cottongrass drooped dismally, like small mop-heads. But there seems to be a bumper crop of highbush cranberries, glowing brilliant, translucent red (slightly less ‘bumper’ now, after my visit…).

Flocks of robins scoured the roadsides for grubs and worms. In Sheep Creek valley, robins, varied thrushes, and whole families of fox sparrows foraged on elderberries. Near Steep Creek, dozens of warblers flitted from bush to bush. Most were yellow-rumped warblers in immature plumage, but the flocks included several ruby-crowned kinglets and occasional Townsend’s warblers and orange-crowned warblers. I was interested to observe the reactions of the crowds of visitors who waited, mostly impatiently, for a bear to appear. Almost none appeared to notice the many warblers that flew back and forth across the creek and gleaned bugs from the shrubs.

If the bears were occupied elsewhere, many folks enjoyed watching porcupines—studies in slow motion. There were several small ones (known as porcupettes), born last spring, that frequented the Steep Creek area. They were now largely independent of their mothers, foraging on their own and growing perceptibly from week to week. Sometimes one would spend several days in a single cottonwood, taking long naps in between sessions of shredding and skeletonized the leaves. We watched one chomping on willow leaves for a while and then wandering to the creekside, where it avidly consumed dwarf fireweed and then drank from the creek.

The sockeye run in Steep Creek dwindled dramatically during the last two weeks of August. The few remaining pairs of salmon were attended by lots of Dolly Varden, which eagerly line up behind a spawning pair. Dollies, young coho, and sculpin all love to gobble up loose salmon eggs.

Foraging bears left partly eaten salmon carcasses on the streambanks, and it wasn’t long before the flies found them. Soon some carcasses were squirming with hundreds, maybe thousands, of fly larvae (maggots). I was initially surprised to see a bear lick up a pile of maggots and then show one of her cubs the tasty little morsels remaining from her snack. On second thought, however, there should have been no surprise, because bears eat grubs and ants and bee larva when they can. But this was the first time I observed bears eating maggots instead of salmon.

A family of well-grown mallards, still accompanied by mama, foraged regularly in the creek. They scarfed up unburied salmon eggs, enjoyed a snack of maggots on old carcasses, and enthusiastically ate fresh salmon meat when a bear abandoned its catch.