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Predator-Prey

A True Mystery Photo

11-2-18 flying squirrel tails_U1A1190A discovery recently brought to my attention has stumped this naturalist.   What you are looking at is a collection of Flying Squirrel tails lying within a 30-square-foot patch of ground adjacent to a stand of Eastern Hemlocks. For several days in succession, additional tails appeared each morning, eventually totaling 20 or more.

Flying Squirrels, both Northern and Southern, are part of many animals’ diet.  Among the documented predators are Great Horned Owls, Barred Owls, Screech Owls, Northern Goshawks, Red-tailed Hawks, Martens, River Otters, Weasels, Fishers, Red Foxes and Bobcat.  Many of these animals can gain access to the trees where the Flying Squirrels reside.  Others take advantage of squirrels foraging on the ground.

The puzzling part of this mystery is the large number of tails.  In cold weather (usually in winter, but we’ve had below-freezing nights recently), Flying Squirrels huddle together in tree cavities in an attempt to provide themselves with added warmth.  Did a foraging Fisher discover a communal den?  How did it manage to capture so many squirrels?  Did the survivors remain in the same cavity, only to be captured in subsequent nights?  So many questions that this naturalist cannot answer. Perhaps a reader can! (Thanks to John Quimby and Michael O’Donnell, who kindly shared their fascinating discovery with me.)

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Some Spiders Still Active

10-29-18 march fly and spider_U1A1162Spiders are ectotherms – warmed and cooled by their environment. In the fall, those outdoor species that remain alive through the winter begin preparing themselves by producing antifreeze proteins that allow their tissues to experience below-freezing temperatures. When a small particle of ice first starts to form, the antifreeze proteins bind to it and prevent the water around it from freezing, thus preventing the growth of an ice crystal. Some species survive in temperatures as low as -5 degrees Celsius.

The pictured hammock spider, still active in late October, is nourishing itself by drinking the dissolved innards of a fall-flying March fly, whose name comes from the predominantly springtime flight period of most March Flies (of the 32 species in the genus Bibio in North America, only three fly in fall).

A common belief is that once cold weather appears, outdoor spiders seek shelter inside houses.  In fact, only about 5% of the spiders you find in your house lived outside before coming into your house, according to Seattle’s Burk Museum.  The reason people tend to notice them more inside may be because sexually mature male spiders become more active in the fall, wandering far and wide in search of mates.

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Vulnerable Ducklings

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There is a reason why ducklings remain with their mother for their first month or two of life. It takes 50-70 days before most ducklings can fly, and survival during this period is highly variable, ranging from less than 10 percent to as high as 70 percent. They are at their most vulnerable during this stage. The most common causes of duckling mortality include predation, adverse weather conditions, starvation, disease, and parasites. The mother offers her young a degree of protection from some of these factors while they are under her care.

Predation is arguably the greatest threat to young waterfowl. Ducklings are sought after by nearly every type of predator, including other birds (eagles, hawks, owls, herons, crows), fish (largemouth bass and northern pike), amphibians (bullfrogs), reptiles (snakes and snapping turtles), and mammals (foxes, raccoons, and mink).  Their odds for survival increase dramatically when the ducklings obtain the ability to fly.  (Photo: female Wood Duck and ducklings)

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Snow Stories Begin

1-5-18 owl print in snow - Rob Foote IMG_4571 (002)

With snow on the ground, the season of stories in the snow has begun. Many of the animals that remain active in New England during the winter are nocturnal so we rarely get a glimpse of them. But, more than at any other time of year, we are privilege to their activities due to the tracks and traces they leave in and on the snow during the night.

Much information can be gathered from these signs. Often at a kill site, the identity of the predator as well as the prey can be determined by shape, form or measurement. One can see from this photograph that a bird of prey (measurements indicate a barred owl) swooped down on a small rodent (judging from tracks, probably a meadow vole) and was successful in capturing it.

Even though a kill scene such as this, or any other wildlife activity recorded in the snow, may reveal the probable identity of the characters in the story, there are always more questions than answers, which is what gets us out in this frigid weather, day after day. The main question I’m left with after viewing this scene is why do voles and mice risk their lives by travelling on the surface of the snow at times, when they just as well could have covered the same ground in the maze of tunnels they’ve created deep in the subnivean layer between the ground and the snow (where they would be out of sight of hungry predators)? (Thanks to Rob Foote for photo.)

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Blue Mud Dauber Wasps Building Nests

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Yesterday’s Mystery Photo showed evidence of a Blue Mud Dauber Wasp (Chalybion californicum) scraping the mud with its mandibles as well as the resulting ball of mud it had formed to use as building material for its nest.  You can get a hint in this photograph of the iridescent blue wings that give this wasp its common name.

Mud dauber is a common name for solitary wasps that make individual nests for their eggs/brood with mud. There are many species of mud daubers, but most are between one and one-and-a-half inches long, black or metallic blue, and typically have a narrowing, or “thread-waist,” between their thorax and abdomen.

Most species of mud daubers, after making a small (1/4” diameter) tube nest out of mud or refurbishing an old nest, leave to forage for spiders. Once a spider has been located, the wasp stings and paralyzes it, but does not kill it (so as to prolong decomposition), carries it back to its nest, and repeats this process over and over until the nest is stuffed with living prey. The wasp then lays an egg in this mass of spiders and seals the nest with mud. The egg hatches and the wasp larva consumes the spiders as it grows. After pupating in the fall, the adult wasp emerges in the spring, mates and the cycle continues.

The reason that the ball of mud that the Blue Mud Dauber had formed was not taken back to the nest site as building material appears to be a small rootlet which anchors the ball to the ground, preventing the wasp from removing it.


Thread-waisted Wasps Provisioning Nests

8-21-17 thread-waisted wasp by Mardie FullSizeRender (002)

There are over 1,000 North American species of solitary hunting wasps. All of them prey on arthropods, which the female stings and paralyzes (but doesn’t kill so that they don’t begin to decompose immediately). Most solitary wasps specialize on a single type of prey, and many build highly characteristic burrow nests. Once the prey is stung, the wasp carries it back to her nest where she then lays a single egg and closes up the nest. The developing wasp larva feeds on the paralyzed prey, pupates and emerges as an adult wasp.

One group of solitary hunting wasps is referred to as thread-waisted wasps (family Sphecidae), due to their long, stalk-like waists. While most close up their nests (by kicking sand over the entrance) after stocking it with prey and laying an egg, some species close their nest with a pebble and return, remove the pebble, and periodically restock the nest with fresh caterpillars for the growing larva. (Photo by Mardie Holland: thread-waisted sphecid wasp with caterpillar prey)


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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