An online resource based on the award-winning nature guide

Predators

Great Horned Owls & Striped Skunks

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Striped Skunks do have predators other than Great Horned Owls (bobcats, foxes and coyotes-fishers have been known to prey on skunks, but very infrequently), but these predators have to be pretty desperate before they will prey on a skunk.  Automobiles and disease kill more skunks than all of their predators put together, but Great Horned Owls have the distinction of being the primary predator of Striped Skunks.

Being a nocturnal hunter, a Great Horned Owl necessarily consumes prey which are nocturnal. Striped Skunks are active at night and are consumed by Great Horned Owls with regularity, even though a skunk can weigh up to three times as much as a Great Horned Owl (average GHO weighs a little over 3 pounds) and has a potent way of defending itself.

For many years scientists assumed that birds had a poor sense of smell because the area of a bird’s brain involved in smell is relatively small compared with the area found in mammals.  However, recent research reveals that birds have a high number of active genes that are associated with smell, and many species may have an excellent sense of smell.  It’s fairly safe to assume, however, from its consumption of skunks, that the Great Horned Owl’s sense of smell is not very well developed. In addition, if a skunk sprays, much of the odor is absorbed by the Great Horned Owl’s leg feathers, which extend down to its talons.

A favorite memory of mine is walking through a field at dusk and suddenly noticing a strong skunk-like smell coming from above, not below, me. A Great Horned Owl silently flew overhead, with only the tell-tale smell of a recently-captured skunk announcing its presence.

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Small Birds Beware of Sharp-shinned Hawks

coopers-and-blue-jay-by-jeannieShort, powerful, rounded wings and a relatively long tail enable Sharp-shinned Hawks to maneuver in dense cover in pursuit of small birds, which compose 90% of their diet. Small mammals and insects are consumed, but not nearly as frequently as birds. The size of the birds eaten range from hummingbirds to Ruffed Grouse. Long legs and toes (especially middle toes) enable individuals to reach into vegetation and large eyes enhance its ability to catch fast-moving prey.

Sharp-shinned Hawks are familiar sights to those of us with bird feeders – this species is responsible for 35% of 1,138 predation incidents reported at feeders in continent-wide survey. In this photograph, a Blue Jay is successfully warding off an attack by a juvenile Sharp-shinned Hawk. (Photo by Jeannie Killam.)

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Barn Spiders Spinning

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If there is a fairly large spider spinning orb webs in a corner of your shed or barn and it has striped gray, brown and white legs, chances are great that it is a Barn Spider, Araneus cavaticus. These spiders are nocturnal, so it’s often the early-rising/late-to-bed folks that observe these arachnids. During the day, Barn Spiders hide in a nearby crevice where birds and other predators cannot easily find them.  Webs are freshly constructed every night (or every few nights) and the remains of the old web are eaten in order to conserve the valuable silk. During the night Barn Spiders can be found hanging in the center of their web, awaiting prey.

Male Barn Spiders reach between ¼” and ½” in size and adult females typically are around ¾”. Most males spin webs less frequently and spend much of their lives wandering, attempting to find a female to mate with. Thus, most Barns Spiders you see in webs tend to be females.

The spider in E. B. White’s Charlotte’s Web was based on a Barn Spider. In his inimitable way, White named her Charlotte A. Cavatica, a reference to the Barn Spider’s scientific name. One of Charlotte’s daughters, after asking what her mother’s middle initial was, names herself Aranea.

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Praying Mantises Mating & Laying Eggs

9-18-16-praying-mantis-laying-eggs-by-ba-reaIn the fall, after mating, the female praying mantis lays up to 400 eggs in a frothy foam; together the eggs and the foam they are encased in are called an ootheca. This one to two-inch long mass is attached to vegetation, usually about a foot or two off the ground. Eventually the frothy structure hardens, providing a protective case for the eggs.

In the spring, miniature (wingless) mantises, called nymphs, will hatch from this egg case. When hatching, the nymphs appear all at once, crawling from between tiny flaps in the case and then hanging from silk threads about two inches below the case. They are identical to adult mantises, except that they lack wings. Within an hour or two, after drying out, they disappear into nearby vegetation.

A  video of a praying mantis laying her eggs and of the young mantises hatching can be seen at https://www.youtube.com/watch?v=1K2BPg7iNZA .

Thanks to Ba Rea, of Bas Relief Publishing (http://basrelief.org/ ) for the use of her West Virginian egg-laying mantis photograph.

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Forest Floor Mystery: Pellets? Old Scat? Cache?

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Lying at the base of a large Eastern Hemlock I recently found two piles of bleached bones.  One pile consisted of mostly vertebrae; the other pile had numerous tibias, humeri and ribs.  All were the appropriate size and shape to have come from several Eastern Chipmunk skeletons – at least four or five.   How did they end up in two distinct piles?

The lack of any fur indicated that regardless of how these bones came to be here, they were deposited quite a while ago.  The lack of any partial skulls or jaw bones and the large number of bones in each pile led me to believe that these were not the remains of two pellets that had been regurgitated by resident Barred Owls. No wild owl pellet I’ve ever dissected, including the large pellets cast by Snowy and Great Gray Owls, has contained even half this many bones, and most contained at least part of a jaw bone.

If not pellets, then scat?  How likely is it that a predator could catch and consume multiple chipmunks rapidly enough so that they would end up in the same pile of scat?  One feasible explanation could be that a fox, coyote or fisher preyed on young, inexperienced chipmunks, but the bones were adult-size bones.

Perhaps these two piles are the remains of a predator’s cache – perhaps a bobcat?

The possibilities are endless as to how this chipmunk graveyard came to be.  However, none of the theories proposed here can explain the dissimilarity between the types of bones in each pile.  If any naturally curious readers have insight into this phenomenon, your thoughts are welcome!

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Twelve-spotted Tiger Beetles Mating

twelve-spotted tiger beetles  137 As their name implies, all species of tiger beetles are ferocious predators.  They are equipped with huge eyes, large three-toothed mandibles that crisscross at their tips and the ability to move very fast . Twelve-spotted Tiger Beetles (Cicindela duodecimguttata) are usually found in open, sandy spots, where their larvae can dig and live in burrows.  Adult tiger beetles use their formidable mandibles to masticate their prey and then squeeze the bits and drink the resulting liquid.

In May and June, whenever they are not ambushing prey, Twelve-spotted Tiger Beetles are concentrating on reproducing, as the “menage a trois” photo illustrates.

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A Gardener’s Favorite Beetle

bronze carabid 161Ground beetles (family Carabidae) are fast moving beetles, many of which are predators with specialized diets.  One ground beetle (Cychrus caraboides) eats only snails (its head and thorax are very slender, allowing access to the inside of a snail’s shell).  Another, Harpalus rufipes, limits its diet to strawberry seeds.  Loricera pilicornis uses bristles on its antennae to trap springtails and mites.

The Bronze Carabid, Carabus nemoralis, (pictured) uses its large curved mandibles to crush and slice through prey – it will eat or try to eat just about any invertebrate, but specializes in capturing and eating slugs. Its hardened forewings, or elytra, have a coppery sheen to them, and parts of its thorax and the edges of its elytra are iridescent purple. This nocturnal, introduced, flightless, one-inch-long beetle resides throughout the Northeast and is already actively pursuing slugs.

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