Vocalization and predation

Four baby juncos, in a nest tucked under a dropping clump of grass, lie low and are very quiet. Only when their parents come with food do they raise their heads and beg. When the parents leave, the chicks again are still. There’s a good reason for this: a nestful of lively, loud chicks would probably attract predators, who are always on the watch for succulent little morsels. Even the repeated back-and-forth trips of attentive parents are often enough to alert watchful predators to the location of a nest.

The nestlings of many other songbirds (robins, sparrows, warblers, etc.) behave in the same way, for the same reasons. They nest in open-cup nests, which are vulnerable to all comers. Cavity-nesters, such as woodpeckers, can be a little more brash in their protective holes. Predators may come, but only some of them can enter or reach into a deep cavity, and if they do, they may face a barrage of sharp beaks. Predations rates on cavity-nesters are much lower than on open-cup nesters. As the chicks get bigger, they sometimes perch right next to their front door, poking their heads out and yelling for food (that’s how I easily found the nest of a black-backed woodpecker, some years ago).

Ducks and shorebirds do it differently. Wherever they nest, the chicks leave the nest soon after hatching, typically following a parent around but feeding themselves. When incubation is done, there are no back-and-forth parental feeding trips to lure a predator to a particular place. The family is now a moving target, not a stationary one.

Among mammals that are subject to predation, we find a similar dichotomy. The young of some species follow their mothers, but in other species the babies cuddle in a nest. Humpback whale calves stay close to their mothers, and recent research shows that they talk to them in ‘whispers’—soft vocalizations that cannot be heard at any distance. This may reduce the risk of killer whale attacks. The young of deer, moose, zebras, elephants and other large herbivores are also able to accompany their mothers soon after birth; I wonder if they whisper too!

Young marmots stay near the den, which offers a quick retreat when danger threatens, and young beavers gain some protection from the pond outside the lodge, a haven, when the alarm sounds. Smaller mammals have a variety of arrangements, mostly depending on being cryptic and hard to find.

But some small rodents add another feature that improves safety: They can produce ultrasound: too high-pitched for human ears (hence, “ultra”), these sounds have a very short wavelength along with the very high frequency. Such sounds attenuate rapidly with distance, so they do not carry very far; they are more directional than low-frequency sounds, but they get scattered by reflecting off twigs and leaves. Young lemmings, mice, and rats emit ultrasounds to call their mothers, if they have become separated too long; the calls prompt the mother to retrieve the wandering pups. Although many predators of small rodents cannot hear ultrasound, some can (e.g., dogs and cats and their relatives), and a short-range call of distress might reduce the risk of predation from such carnivores.

Adult small rodents also use ultrasound as a form of social communication within a group, quiet talk among companions. Certain ground squirrels emit ultrasounds that alert others to the presence of a distant threat, the rapid attenuation ensuring that the sound does not carry as far as the potential threat.

On the other hand, some predators have evolved the ability to use ultrasound in hunting—as an aid to predation (rather than a way to avoid it). The toothed whales use echolocation (sonar), much of it in the ultrasonic range, to navigate in turbid waters and to detect their prey. Our resident killer whales, for instance, use ultrasound to locate and capture their fish; the transient killer whales, however, seldom use it while hunting their prey of marine mammals. Not only are the prey mammals much larger and easier to see than the prey fish, typically, they are also more likely to be able to hear the sonar calls of the hunting killer whales. So the transients usually hunt silently.

Bats are perhaps the best-studied predators that hunt using ultrasound. The short wavelengths permit the sounds to bounce off small prey, such as insects, and bats emit very high intensity (‘loud’) ultrasounds as they close in on a hapless bug. Not all insects are hapless, however! Some toxic tiger moths make ultrasonic clicks to warn off approaching bats, which then often abort their attack. Other, nontoxic, tiger moths use their ultrasound to jam the sonar of an attacking bat, making the attack less likely to be successful.

Echolocating calls sometimes also allow the bats to communicate with each other, as they are looking for roosts or food. Because the calls can be individually recognizable, young bats can communicate with their mothers, and friends can talk to each other (although others may eavesdrop). There remains much to be learned about the social uses of sound in bats.

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Animals at play

Any observant dog owners can recognize the invitation-to-play posture of their dogs, sometimes addressed to persons, and sometimes to other dogs. Surely none of us doubts that dogs love to play, with balls or sticks or each other. And cat owners watch their feline friends toss and chase toy mice, frolic with rumpled scatter rugs, and push pingpong balls under the couch only to fish them back out again. A favorite trick of some cats is ‘ambush’…running ahead of a person or another cat, hiding behind a door, and pouncing out as the victim passes by. Some cats and dogs even know how to make jokes, sometimes deliberately and mischievously misleading their humans or each other in frivolous ways. Of course, dogs and cats are domestic critters, which often have lots of time for frolicking, because they usually don’t have the need to find food or escape from enemies or find mates; the same is true for animals in captivity, which often need sources of amusement.

What about animals in the wild? Do they play too? Sure; especially younger ones, but adults too. Wolves and coyotes tussle and chase. They use the same play-invitation postures among themselves as dogs do; our late-lamented black wolf, Romeo, used to invite passing dogs to play. On-line sources offer plenty of examples: young elephants mud-sliding and mud-wrestling or macaques repeatedly leaping from a tower into a pool of water or….you name it.

Play behavior often has some utilitarian physiological functions, such as muscle toning or sharpening reflexes or improving coordination. It can also have useful social functions, such as learning the rules of interaction among members of a group (e.g., don’t play too roughly!) or establishing a dominance order. But play behavior would not be so common among critters if it weren’t simply FUN.

It took a long time for humans to recognize that animals, both domestic and wild ones, like to have fun. Having fun requires a degree of intelligence that humans have been slow to admit is found in animals—irrationally and wrongly preferring to think ourselves superior to everybody else.

Here are a few examples of animals that play, mostly from animals that we often see around here.

Young marmots box and wrestle on the threshold of their den. Bear cubs tumble and tussle with each other, sometimes engaging mama as well; so do beaver kits and young ones of many other species. Mountain goat kids sometimes bounce from ledge to ledge, apparently just because they can and it is fun.

Young humpback whales sometimes cavort, fluke slapping, pectoral slapping, and breaching, as if saying Hey mom, look at me! A local photographer watched one breach seventeen times in quick succession!

Photo by Doug Jones

We can see ravens having fun. They might fly up with a feather or some other object, and then drop it, only to swoop down and catch it again; or maybe a friend would dart in to snatch it away. Sometimes there is a game of keep-away: I’ve got a toy, you try to get it from me. We’ve watched ravens roll down a snowy slope, or slide like a toboggan, only to trot back up to the top and do it over again.

Crows play, too. There is an on-line video of a European crow sliding down a snowy roof while standing on a plastic lid; then it picked up the lid, went back to the top of the roof, and slid down again. What a hoot! (I couldn’t leave that one out, even though it is not local). Our northwestern crows sometimes dangle upside down from a branch, not reaching for anything nor avoiding something, just showing off. The biggest showoffs dangle on one foot: see what I can do! Then they may swing back upright with a wing-flap or two, or let go and try it again on a different branch.

Otters slide down muddy or snowy slopes. Some slide tracks are many yards long, and the otter then continued onward to wherever it was going. This is an energy-efficient mode of transportation—just push off and let gravity do the rest. But sometimes they are not really going anywhere, just down a small slope and back up again, to do it all over once more. Sometimes a whole slope will be covered with their slide marks. It must be fun!

Dall’s porpoises sometimes come to ride the bow wave of a fast-moving boat. A little group of them seems to appear from nowhere and together they ride that wave, sometimes for a considerable distance. Then they are gone, as suddenly as they came.

One day at Eaglecrest I found a place where ptarmigan had pranced around, leaving lots of footprints. These were interspersed with a number of slide marks, about three feet long, going down a little slope. We know that ptarmigan often glide to a stop when they come in for a snow-landing, leaving a short slide mark, but the marks I saw did not look like landing marks. They made me think of the otter slides, so I wondered if ptarmigan can play too. I turned up only one report, which says that flocks or family groups of willow ptarmigan frolic together, crouching low with head extended, jumping around, and flapping one or both wings. I would love to see that!

Outdoor therapy

One day recently, I was feeling quite grumpy, disgusted, annoyed, and getting down-hearted, so I decided to cheer myself up by thinking about ‘a few of my favorite things’ that happened in the past couple of weeks.

On Hearthside’s annual author’s cruise, a humpback whale put on a fabulous show. She swam along a shore, pec-slapping vigorously, and then turned around and did the same coming back—sometimes flailing both pectoral fins at once. Then we saw that she had a calf alongside, and the two of them breached repeatedly. They were attended by several sea lions, who jumped and cavorted in and out of the waves created by the breaching. The show had everyone on board in a state of happy fascination.

A trip up Gold Ridge above the tram was a good one, despite the heat that had me just creeping along. The marmots were, sensibly, dozing in their cool burrows (unlike Alice falling down a rabbit hole, I did not fit the burrow entrances—too many cookies, perhaps?). Bumblebees were busy, attending to the tiny blossoms of alpine blueberry growing close to the ground in a tight mat. The alpine zone was a sea of flowers (I counted over twenty kinds, including one that was a complete mystery to me). An American pipit perched on a hot rock, overseeing his nesting territory of alpine tundra and rocky outcrops. Two male rock ptarmigan showed off their brilliant white plumage in soaring flight displays from one rocky tower to another, cackling all the way—still looking for ready females. As the afternoon breezes picked up, ravens began to play in the air currents, sharing air space with hang gliders.

One day I sauntered around some muskegs with a friend, just seeing what we could see (a most enjoyable occupation!). Even though the ponds were mostly dried up, a few held some stubborn water striders, and the mud held evidence of the passage of jays, squirrels, mice, and other small beasts. We noticed a fly bearing an irregular yellow patch on its back, perhaps pollen from a floral visit. It found another fly, which obligingly spread its wings and allowed the first fly—now clearly a male—access to her rear end. They copulated for several minutes; through his beautiful, translucent blue abdomen, we could see his internal organs moving. Together they moved around in the low vegetation; eventually she brushed him off under a twig.

The beavers seem to have returned to Steep Creek, after an absence of several years. We had seen beavers visiting the lower ponds, but this time it looks more serious. The broken dams have been rebuilt and a friend watched a beaver collect a huge mouthful of grass and carry it toward the old lodge. This made me wonder if the grass might be bedding for a young family. There is hope, then, that the beavers may restore the upper dams as well, creating ponds that trap sediment, provide fine rearing habitat for juvenile coho and Dolly Varden, and good foraging habitat for birds. In the past, the sockeye and coho salmon that spawn in this stream proved themselves quite able to surmount the previous dams, and there were good populations of both species in the creek.

The rains came! Not, this time, a source of gloom but of gladness! May was a drought month in Juneau, with very high temperatures on several days. Muskeg ponds dried up, lichens and mosses got crispy, and streams turned into trickles. But the soft rains in early June brought lower temperatures and turned Juneau into its usual lush, verdant self; the creeks flowed again. (And now we are ready for some more sun!)

There, that’s a list of good things observed. Thinking about all that, I found that I was still grumpy, disgusted, and annoyed—oh yes—but it no longer got me down-hearted. Good stuff!—simple things for a simple mind, maybe, but equanimity was restored!

Cruisin’ to Berners Bay

Every year, Juneau Audubon offers several spring cruises to Berners Bay, not far north of town. There is always a hope that the cruise might happen to arrive in the bay during the time when the hooligan (=eulachon=candlefish=salvation fish) are running. this is hard to do, because the hooligan spawning run is short, only a week or two, and the timing varies from year to year—and it may be getting earlier than it was a few years ago.

When the hooligan come in, they mill about in the bay for a while, and that’s when the marine mammals enjoy a feast. Whales pass through, and seals hang out on a reef near Slate Cove. Steller’s sea lions stock up on the fatty little fish before heading out to their outer-coast rookeries for pupping and mating. On the rookeries, males don’t feed for several weeks, being busy defending harems and mating; females give birth and nurse the newborns, which costs them a lot of energy—so putting on some fat ahead of all that activity is essential. Years ago, when we studied the predators at hooligan runs, we counted over two hundred sea lions in the bay on some days, making a racket and leaving hooligan-grease slicks on the water.

Hooligan spawn in the lower reaches of the glacial rivers that enter the bay, and sometimes the seals and sea lions follow their prey up-river. It was quite a sight to watch a big bull sea lion humping hastily over the sand bars to reach deeper river waters and the up-running spawners.

A Thayer’s Gull with eulachon. Photo by Bob Armstrong

Birds come to the spawning run in droves. White clouds of over forty thousand gulls would be calling, chasing, pirating fish from each other, loafing on the sands. Eagles lined the river banks—we estimated that there could be a thousand or so. Local ravens and crows scavenged hooligan that were stranded by out-going tides and stashed their prey in the grass or fed them to chicks in the nest. Even dabbling ducks, such as mallards, chowed down moribund hooligan.

In some years, herring also spawn in the bay about the same time as the hooligan run. Herring spawn on the seaweeds along the rocky shores and attract hordes of egg-eating scoters and gulls, along with eagles interested in the fish themselves.

It was all very exciting! But, as a naturalist aboard the cruises this year, I had to tell folks to imagine all that predatory excitement. It seemed as if the hooligan run was over, although gulls still hung out along the edges of the river mouths. We heard rumors that the herring were in, and getting ready to spawn, but it didn’t seem to be happening just yet.

While it was a bit disappointing, perhaps, to miss the big show, I suspect that the folks on board were not unhappy at all. We saw a fine display of “pec-slapping” by humpback whales: whacking the water with powerful slaps of their long pectoral fins. The pectoral fins of humpbacks are longer, relative to body size, than those of other whales. Those mighty pecs are reportedly used to herd small fish, in fighting off attacks by orcas, and in making a swimming whale very maneuverable. They may also be used as some kind of display (still to be studied), and male humpbacks sometimes use them as props for their headstand posture while they sing during the mating season in winter.

Near Tee Harbor we chanced upon several orcas (=killer whales), splashing about and moving along the shores. There were several orcas, including one quite small one, mostly foraging independently, not in a close bunch. I guessed that these were likely to be the fish-eating ‘resident’ sort of orcas, probably after spring king salmon. Orcas had recently been seen near downtown in Gastineau Channel too, and we wondered what had lured them there.

We were treated to the delightful presence of several Dall’s porpoises, rushing hither and thither, sometimes riding our bow waves. A picturesque little flight of swans headed north, against a backdrop of the Chilkats. And I have not even mentioned the pigeon guillemots, marbled murrelets, loons, Arctic terns, scoters of two species, and clusters of Bonaparte’s gulls dipping down to the water surface to snatch some tiny prey.

Altogether, very satisfactory wildlife viewing, and fine days on the water!

Out and about

I try to get out for a walk every day, whatever the weather, although the weather may determine the length and location of the outing. How much I see of natural history interest varies greatly, depending on many factors, including a perceived need to watch the footing in sloppy mud or on slippery ice or wet rocks, sometimes a wish to be a bit sociable, or even do some serious (or not-so-serious) thinking. But most of the time, I like to keep my eyes and ears open to what is around me. So here are some bits and pieces from December.

As a cold snap settled in, Mendenhall Lake grumbled and growled and muttered in a long-winded soliloquy—the ice, talking to itself as the water froze and expanded. Smaller ponds were less loquacious but still murmured and popped at a lower decibel level. Meanwhile, overhead, large flocks of pine siskins flitted from spruce to spruce, sometimes swooping high over the canopy before disappearing in the crown of another cone-laden spruce.

In between short periods of deep cold, however, we had spells of surprisingly warm temperatures, turning our little bit of snow to slush and sending meltwater down over the existing ice on streams and ponds. Open water formed at inlets and outlets of ponds and along the fringes of Mendenhall Lake. A reliable observer reported seeing a beaver swimming in Mendenhall River in late December, when local beavers are normally snug in their lodges, sleeping or nibbling from their winter cache of twigs. That beaver was not the only one escaping cabin fever: in several locations, I saw very recent tree-cutting and branch-gnawing that had not been there a few days earlier.

On the ground near Moose Lake I found several small wind-broken cottonwood branches, with the upper sides nicely de-barked. Some lucky gnawer had capitalized on this bonanza. But who was it? Not a beaver, although beavers had debarked a cottonwood tree trunk near the lake, leaving the marks of wide incisor teeth. Not a porcupine—the tooth marks were too small. But the marks were too big for a mouse. My best guess was probably a snowshoe hare; hares are generally fairly numerous in the area and the incisor marks were similar in size to the teeth in a hare skull in my collection.

Photo by Pam Bergeson

Along the Treadwell Ditch are many trees, usually hemlocks, that show the marks of porcupine gnawing—tooth-marked, barkless patches, low on the trunk. This is a common sight around here, of course. I was particularly interested to find at least two trees that seemed to have been completely girdled sometime in the past. The bark had been removed all the way around the tree, which would interrupt the flow of water and nutrients between roots and crown, starving the roots of food and the crown of water. Yet these trees sported full crowns of needles and looked healthy. How could that be? The porcupines had removed all the outer bark and eaten most of the nutritious inner bark, but a meager, sketchy, brown network of inner bark was still visible. Could it be that enough strands of inner bark remained to connect the roots and the crowns? Hard to believe that would be enough to support a good-sized tree!

There are other little mysteries about porcupines and hemlocks. Some trees have obviously been visited repeatedly, in different years. Old chewings have partially healed, but new ones are there too. Are these trees particularly tasty? Also, I get an impression (untested, so far) that porcupine gnawing is more common on the uphill side of a hemlock trunk. Is that really so, and if so, why?

A special pleasure was seeing two humpback whales spouting as they cruised near Lena Point. They may have been late-departers for winter in Hawaii or they may have been among the few that overwinter here, feeding on herring (and any other luckless little forage fishes). Not on this day, but sometimes one can see a few sea lions swimming near the corners of a foraging whale’s mouth, trying to catch the fish that slipped away from the whale. The herring equivalent of ‘out of the frying pan, into the fire’!