Nov '02 [Home]
Justice Among Wolves, Disorderly Deer, Exploding Herons, and Hawk-Eye Butterflies
Wolf 40, the alpha female of the Druid Peak Pack in Yellowstone Park is found dead one morning, her injuries consistent with a combined peer attack, most likely by her sister, Wolf 42, and daughters, 103 and 105, who had been attending six pups in a den across the valley from her own. She was observed visiting the enclave the night before and the usual dominant-subordinate roles among the group had seemed intact. The year before, she had driven another sister, Wolf 41, her most contentious challenger, from the pack altogether.
Wolf 21, a big black male, had only recently arrived from elsewhere, offering himself at the risk of his life, to join with Wolf 40 and have a litter. After his mate's death, he continued to attend their pups in her den. Over several days, the sister and daughters carried all of their six charges four miles to Wolf 40's den.
Though the Park's trackers do not discount the possibility that Wolf 40 may have been killed by members of a different pack, circumstances suggest a much rarer occurrence, namely, that Wolf 40 threatened the pups of the subordinate contingent. Wolf 21's next mate will be Wolf 42. Her succession was apparent from the moment of his arrival and application, a six-hour ritual of howling approaches and retreats never before documented in the wild.
If preservationists succeed, the chance of documenting these and other rarely observed behaviors may be greatly enhanced. Founders of the Yellowstone to Yukon Project envisages an unbroken, 2000-mile swath of wild sanctuary, but the opposition is gunning for them.
What Meets the Eye
If physicality is destiny, it escapes no amateur zoologist's notice that the physical placement of the eye is a key characteristic distinguishing predator and prey. Predatory canines—the wolf, coyote, jackal, fox—and their feline counterparts—lynx, bob cat, mountain lion—have frontal placements which permit them to train on their target and stereoscopic 3-D vision to judge distance and speed. However, because their eyes reconcile to perceive the same scene (binocular), the scope of vision is narrower. The lateral orientation of their monocular prey—mice, rabbits, gophers, squirrels, weasels—helps them detect the approach of danger panoramically while remaining motionless.
Deer, the larger, fleeter game of these mammals and of man in-season, have sharp monocular vision, but, with their wide-set eyes, probably have an irreconcilable blind spot, as do horses. (The ability of horses to see different images simultaneously explains in part why they tend to spook.) Deer perceive the slightest movement, but will ignore a stationary object, say, an orange-vested hunter planted strategically along the herd's habitual trail. While the deer may not perceive the vest, she can perceive blues and yellows, even the detergent residue in his camouflage jacket. A doe locates her straying fawn (nearly invisible, thanks to its spotted coat, and almost odorless) by means of a yellow, waxy substance secreted from his hooves.
If November means hunting season to humans, it means breeding season to deer. The buck's antlers, in formation since spring, are hardened for battle with potential rivals. Unlike rams, bucks charge one another only once, lock horns and vie on strength alone until one prevails. If they cannot disentangle, as often happens, they starve together. In off-season, bucks are docile. A lead doe usually directs the feeding patterns, but these prey are not otherwise organized into a hierarchy like that of their lupine predators.
Bird and Worm
Ground nesting birds, such as grouse, expose their eggs and chicks to predation by other birds—hawks, crows, magpies, jays—as well as by rats, cats, weasels, and of course Reynard himself. The hen protects her young by a ruse of self-sacrifice: Feigning a broken wing, she scuttles out and away from the nest in an attempt to draw the predator to herself. Oftener than not, he takes the bait. [Photos]
Big water birds can't resist man-made fish hatcheries. The great blue heron, the commonest and most numerous species at northeastern aquaculture facilities, inflicts the most damage to the industry. It takes a while to grow a foot-long trout, and this fellow harvests three an hour. As many as seventy-five great blues have been recorded on a single day, consuming roughly $300 worth. Together with their kin—grackles, mallards, ospreys, and kingfishers—they cost large facilities about $500 thousand a year. Government recommended deterrents include: 'human effigies,' (vide: interns), canines ('results vary depending on temperament', i.e. Fido may crack up before Rover does), and 'pyrotechnic devices,' that is, firecrackers discharged from 12-gauge shotguns. (Note: "Because wads from the shell may stick in the gun, it is important to check the barrel after each shot.")
The most revered predators among birds: the owl and the eagle. Each has compound eye structures of course, the one frontally, the other laterally placed. Even without the flight advantage which evokes so much envy in would-be poets, birds are of another order entirely: The lowly pigeon sees many times the number of shades perceptible to the human eye.
The animal with the widest visual range is the butterfly, possessing a compound eye structure and spectral receptors for UV, violet, blue, red, and green. Champions of color constancy, they target the right nectar flowers rain or shine. Their tiny eyes are fitted with a pentachromatic system—five different types of cells sensitive to different bands of light. [Shown here, the Nabokov butterfly.]
Butterflies have little use for green—except to detect movement—until they are ready to lay their eggs: Caterpillars have voracious appetites; monarchs for milkweed. Ah, chrysalis! (Some moth catepillars feed exclusively on poison ivy.)
One Man's Foliage
In autumn, trees change their leaf color, not to inspire poets to life-cycle metaphors, but rather, to signal aphids in search of a host in which to lay eggs that they have self-inoculated. Scientific theory on the so-called 'handicap principle,' suggests that the brighter the color, especially red, the more costly the tree's investment of nutritive energy in producing anti-pest enzymes. [Source] Presumably, the tree would record its prior year experience and adjust its ambitions accordingly. Now then, ladybugs feed on aphids. So perhaps the poetry resumes.
The handicap principle is treated in the context of 'honest signaling' by prey to predator. Studies suggest that loud alarm calls, 'barking,' among birds known as 'babblers', may be intended, not to alert one's fellows to approaching danger, but rather, to advise the predator that he has been detected and will fail in his attack. If alarm calls deter the raptor's attack, wouldn't the prey gain by calling indiscriminately, just on the off chance that one is present? The answer: "A babbler who would cheat by going to the top of the canopy and barking before it saw a predator would expose itself to raptors it might not have noticed." [Source]
Oh. So it wouldn't risk the wrath of its peers for calling wolf just once too often?
Strength in Numbers, Maybe
First axiom: Wolves hunt in packs.
Second axiom: The best defense is a good offense.
Vervet monkeys have several different patterns of alarm calls. One call is for airborne predators. When this call is heard, they'll run down from the trees. There is a different alarm call for ground predators, which when heard they run into the trees. The last is for snakes, and they don't run anywhere but instead stand up on their hind legs and look around carefully. [Source]
A study performed with baboons concluded that they were most likely to assemble in groups when the risk of predation was high. Longtailed macaques grouped together in high-risk Borneo, but then, so did others on a low-risk offshore island. Chimps in a national park sometimes split their number into small units to slim the pickins, but then, sometimes reband to mob leopards and lions; rhesus monkeys mob tigers.
Empirical evidence: Humans are consistently observed doing any and all of the above.
Conclusion: We're all just monkeys in the trees.