Sunday, June 03, 2007

Blakeman Comes Through With a Falconer's Take on Why Bunny Tails Are White

Tristan hunts. Photo: Donegal Browne
How would Manhattan's Red-tails fare against the evolutionary adaptation of the flashing white tail of a bunny?
I'd looked around for the answer to my question about what advantage the bright white tail of prey animals had when it comes to eluding predators without finding many explanations taken from the field, but a good bit of theorizing. As I'd hoped John Blakeman comes through and shares his hands on or should I say talons on experiences below with an excellent answer that sounds spot on.

The marked visibility of the white tail of the Eastern Cottontail Rabbit (and several other closely related species) is noted by everyone who sees these fleet animals run off.

Field biologists have certainly pondered the selective advantages given to a rabbit possessed of such an attention-drawing feature. It would certainly seem that a rabbit without any bright-colored body feature, a purely brown animal, would have a far better chance of avoiding a predator’s detection, especially as it runs to escape a pursuit.

As a falconer who has hunted cottontails extensively with my trained red-tailed hawks I've watched the dynamics of all of this first hand. I believe my thoughts on the matter are descriptive. For most others, the explanation of the white bunny tail phenomenon is primarily conjecture. For me, I've seen exactly how it works (or fails) in very wild conditions.

Here’s my explanation.

The white tail, which is exposed only when running at speed, when attempting to escape a predator, certainly causes the pursuing animal to visually concentrate on the rapidly bobbing white spot shooting across the landscape. For mammals in pursuit, the white tail probably has little effect because the fleeing rabbit can easily out run any fox, coyote, or other mammal. Yes, if chased over completely open ground, across a large mowed turf area, a fox or coyote might be able to keep up with the rabbit, even perhaps grab it.

But it must be understood that resident rabbits occupy rather small areas, usually no more than 5 or 10 acres at most. Within this small area, they create many “runways,” trampled or eaten narrow tunnels in the existing vegetation. Every falconer (and rabbit hunter) has seen these. While the falconer is stumbling through thick brush and high grasses and forbs, a sitting rabbit instantly bolts away. Upon examination, it’s clear that the bunny ran at full, unhindered speed through a rabbit-created freeway down in the vegetation. It’s too small for any running mammal to occupy. A fox or coyote (as with a human) gets tripped up with the high grass and brush. The bunny knows exactly where the runway ends, which is usually in a deep pile of rocks, brush, or a woodchuck hole. In every case, the pursuing mammal is left without a capture.

In its pursuit, it may have seen the bobbing white tail ahead, but realized soon that it couldn't be closed upon.

The advantageous function of the white tail works when the bunny is pursued by a hawk. As described, a bunny can usually run easily away from a mammalian predator that chooses to pursue it in a hunting chase. In that case, the color of the tail makes no difference, white or brown. Either way, the rabbit will get away.

Parenthetically, it must be noted here that the real issue of survival involves wild habitat, with sufficient brush, weeds, and other vegetation through which the rabbit can easily run and leave the mammalian predators behind. Without the habitat, the rabbit’s dead. Central Park doesn't likely have much good “rabit-tat,” rabbit habitat.

It’s different, however, when the bunny is being pursued by a big, powerful red-tailed hawk. In this case, the bird can keep up or close in on the fleeing rabbit. The hawk flies through thin air, not through the slowing brush or weeds. And the hawk is aloft. It can see exactly where the rabbit is running.

Even if the bunny were all camouflage brown or gray, it’s a big animal and the hawk would easily see it scooting through the vegetation below. There is no way it can avoid being seen when it moves. And to eat it must move. A red-tail sitting high in a distant tree can easily spot a rabbit slowly coursing through a meadow. That’s why rabbits have eyes on the sides of their heads, to detect a closing raptor as soon as it can, allowing it to run off to safety before the hawk approaches.

But as it runs, it throws up its pure-white tail, which bobs back and forth with every stride. As a falconer standing in a field where my red-tail has discovered a fleeing rabbit, I've seen numerous times how this works. Here’s the pivotal matter of the issue.

Yes, the hawk’s eye is drawn to the bunny’s white tail, and it becomes the hawk’s target. We see this particularly with young, inexperienced red-tails. The young bird flies right at the tail, and when possible it tries to grab it. Quite frequently, however, the hawk is unable to gain a grip on the fleeing bunny. Falconers have seen this time and again, where the hawk is left standing in the field with a fist-full of bunny tail fur. The victorious rabbit is watched running off to some place of safety.

Here’s how this works. Rabbit fur is waxy, and on the rabbit’s posterior a bit thicker than in the anterior regions. If the hawk grabs right for the bright target, the tail, it will be absolutely impossible hold on to. There’s nothing in the cotton tail more than the “cotton” itself, no flesh, no fat, nothing into which the sharp talons can pierce.

So, the bright tail lures the naive hawk into trying to grab the least vulnerable part of the rabbit’s anatomy. Even when the hawk grabs the rabbit’s adjacent rump, the talons have a tendency to slip through the waxy fur without piercing the skin. Falconers have seen this time and time again, realizing that their birds must have needle-sharp talons to make a kill.

A young wild red-tail probably tries a few cottontail pursuits, but is likely to end up with nothing for its efforts. After just a few of these worthless pursuits, it will then turn its attentions to other prey, leaving cottontail rabbits un-hunted, except in deep-snow periods in winter when nothing else presents itself.

But we falconers (and our hawks) quickly learn how to take cottontails. After just a few of these tail-fur failures, the hawk finally learns to sink its talons into the rear flesh of the rabbit. Now, the advantage has shifted to the hawk.

When grabbed, the hawk and rabbit roll as a now-connected ball of fur and feathers across the landscape. Finally, the rabbit is brought to a stop and the hawk instinctively tries to sink its talons ever deeper into the bunny, to make the kill. But there are no vulnerable organs in the rear flanks of the rabbit, which kicks the attached hawk with near-lethal kicks. This, too, can cause the hawk to retreat, allowing the rabbit to escape with a few thin talon piercings.

In all of this, the white tail has directed the hawk’s attention to the rabbit’s rear end. To make the kill, the hawk must re-direct its attention to the rabbit’s head, where a piercing talon punctures the cranium. A quick death then ensues.

Falconers who hunt cottontail rabbits, with red-tailed hawks, goshawks, or Harris’ hawks, have seen all of this. After the second or third thumping with the rabbit’s hind legs, the hawk learns to sink a second set of talons into the rabbit’s head. The episode is over.

As the hawks become ever more experienced in the pursuit of rabbits, they learn to forgo the deceptive white tail altogether. They go right to the head and make the quickest of kills. Old, experienced wild red-tails, such as Pale Male himself, have learned a multitude of such survival tricks, most of which involve learning how to effectively capture and kill available animals, which in Central Park are mostly pigeons and rats.

I must add very strongly and forcefully that no falconer delights in any way in the natural, albeit painful death the hawk has brought upon the captured rabbit. We strive to allow our hawks to make a quick and instant kill, which they quickly learn to do. Personally, I verbally applaud the many (the majority) of rabbits that avoid my hawk’s pursuit. More often than not, they make my hawk look to be inadequate to survive with only rabbit prey. Most often, the rabbits escape to live another day in the wild.

In summary, the white cottontail diverts a naive hawk’s attention to the rabbit’s least vulnerable body region, where it has the best chance of avoiding capture or escaping a non-lethal talon piercing. To fully understand this, it has to be repeatedly witnessed, as falconers have for millennia.

–John Blakeman

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