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Defense Mechanisms

Blister Beetles’ Defense Mechanism

10-5 short-winged blister beetle 064Blister beetles are aptly named, for when they are disturbed they emit a yellow, oily, defensive secretion (cantharidin) from their joints which usually causes blisters when it comes in contact with skin. This toxin deters many potential predators and is especially effective against ants. According to naturalist/forester/writer Ginny Barlow, as little as 100 milligrams is reported to be fatal to humans if ingested, and this amount can be extracted from just a few beetles. Humans used to crush and dry blister beetles and use the resulting concoction for gout and arthritis. It was also used as a popular aphrodisiac known as Spanish fly. Because of its toxicity, it is no longer widely used in medicine.

Cantharidin is, however, indirectly used by tree-nesting nuthatches. With a limited number of tree cavities, there is competition among animals using them to raise their young, especially between squirrels and nuthatches. Nuthatches have been seen with Short-winged Blister Beetles (Meloe angusticollis, see photo) in their beaks, “sweeping” them on the bark around tree cavity entrances. The nuthatches don’t eat the beetles, they strictly use them as tools. It is assumed that the birds do this in order to repel squirrels with the cantharidin that is smeared on the tree. (Thanks to Ginny Barlow for photo opportunity.)

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Two-month-old Striped Skunks Can Spray!

7-15-15 striped skunk2 058The answer to yesterday’s mystery photo is a lot less original than many of your guesses, all of which could have been true, given my natural curiosity. I am embarrassed to admit that it was the oily, yellow spray of a young striped skunk that covered my spectacles (and my entire head, arms and camera) – even with ample warning, I chose to persevere in order to get the perfect picture. Unfortunately, the skunk was a lot more successful at his mission than I was at mine.

There is a reason why coyotes, foxes and most predators (one exception is the great horned owl), including most sane photographers, keep their distance from striped skunks. Whether newborn or several years old, skunks are capable of using their musk-filled anal glands to ward off anything that threatens them. Skunks are generally reluctant to spray, however, as they only have a few teaspoons (half an ounce) of musk in their glands, and once their supply is depleted (five or six sprays), they are defenseless for about 10 days, while it builds up again. Hence, plenty of warning is given in the form of stomping front feet, erect hair, raised tail, and chattering before a skunk contracts the muscles surrounding its anal glands and shoots a pungent, yellowish spray as far as ten feet away. Only a fool would not heed the warning given…and be forewarned – a skunk’s aim is surprisingly accurate.

The organic compounds that make the smell of skunk spray so offensive are called thiols (mercaptans). Thiols are also found in garlic and onions, and form parts of the keratin in hair. If your dog or you happen to be at the wrong end of a skunk’s partially everted anus, the best combination to neutralize the musk smell is 1 quart of 3% hydrogen peroxide, ¼ cup of baking soda, and 1 teaspoon of liquid dish soap. (Thanks (?) to Tom Ripley for photo op.)

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Tortoise Beetle Larvae Making Fecal Shields

8-1-14  tortoise beetle larva with fecal shield 049Instead of discarding feces, or frass, some insects save their waste matter for defensive purposes such as “fecal shields.” These are coverings over the back of the larvae that are made largely of feces and provide either physical or chemical barriers to predation. Adult Tortoise Beetles have a type of shield (hence, their name), but it is formed from expanded, hardened forewings, and is not a fecal shield. The larvae of these beetles have fecal shields which serve as chemical deterrents, preventing most predators from even touching them. The deterrent in the feces comes from the beetles’ food source — plants in the order Solanales. Tortoise Beetle larvae have what is known as a “fecal fork” on their last abdominal segment, which they hold over their body. The larvae maneuvers its muscular, telescopic anus, or “anal turret” in such a manner as to excrete its feces and bits of shed exoskeleton onto the fecal fork, forming an umbrella-like fecal shield.

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Beaver-Porcupine Encounter

beaver with quills2  376A Porcupine’s 30,000 quills effectively defend it against two and four-legged enemies, and occasionally against its own species. Rarely, however, do we see evidence of this mode of defense outside of our family dogs, most of whom are challenged when it comes to learning from the experience. From the size of the quills in this Beaver, one can assume it came in contact with either the Porcupine’s upper back or neck, where the quills are longest (up to 4”). How and where this encounter took place is a mystery. Porcupines can and do swim – their quills are filled with a spongy material which may enhance their buoyancy. So it’s within the realm of possibility that these two rodents met in the water, but that seems unlikely. While some quill injuries result in death, a surprising number of victims recover. One researcher observed that the quills he saw in a raccoon’s muzzle were worn down to a stubble within a week. Due to tiny barbs on the end of the quill that contacts another animal, it can work itself into an animal’s body, but those in this Beaver will hopefully come to rest against its jawbones. As long as the Beaver can eat, its chances of survival are good. It is unlikely to get an infection from the quills, as they’re coated with fatty acids that inhibit the growth of bacteria (in case the Porcupine stabs itself?)

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Snowshoe Hares

1-21-14 snowshoe hare by Patsy Fortney IMG_4140 (3)You’re most likely to see Snowshoe Hares at dawn or dusk, when they are most active. That is, if you can detect them before they detect you. Snowshoe Hares depend upon camouflage as their first line of defense, with seasonal coats to match their environment. They sometimes freeze where they are, making no movement, or take shelter in a protected spot or “form” and sit quietly, with their feet tucked out of sight and their ears pressed tightly against their back, making them all but invisible. If threatened, they can break into a full run leaping up to 12 feet at a time, reaching 30 or more miles per hour thanks to their powerful hind legs. (Photo by Patsy Fortney)

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Eastern Chipmunks “Clucking”

10-2-13 eastern chipmunkIMG_3035Especially in the fall, and sometimes in the spring, the woods are full of “clucking” Eastern Chipmunks. It’s unusual to hear this call during the summer, but once leaves have started to fall off the trees, giving chipmunks a clearer view of the sky, the chorus begins. One chipmunk starts calling, and the message is passed on to other relatives, who join in. These vocal little rodents are warning each other of the presence of an aerial predator, perhaps a hawk or day-hunting owl. The next time you hear this distinctive alarm call, look skyward. You may well be rewarded with the sight of a raptor flying overhead.

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Green Lacewing Larvae Use Corpses as Camouflage

9-19-13 lacewing larva  232Green lacewings are aptly named for the prominent venation of the adults’ wings. Some species in this insect family even have “ears” in the larger veins that allow them to detect the ultrasonic sounds made by hunting bats. Lacewing larvae and adults are both predators of soft-bodied insects such as aphids. Larval lacewings have long, hollow mandibles with which they puncture prey and suck out the liquefied contents, leaving the woolly husks. Some species of lacewing larvae have hairy backs, and camouflage themselves when in the presence of woolly aphids by sticking aphid husks on these hairs. These “trash packets” camouflage the lacewing larvae from predators, including ants that would otherwise attack the larvae if they recognized that they were lacewings and not woolly aphids.

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