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Nature Note: Shrews

Posted by: Tony Mills

Tagged in: nature notes , mammals

The Biting of the Shrew

I felt a sting on the tip of my finger and at first I could not figure out what had poked, bitten or stung me. Closer inspection revealed a small silvery mammal racing around the bottom of the  drift fence bucket ( a pitfall trap used for animal surveys). I quickly realized that a shrew had latched on to me, presumably to protect itself. It took a minute to sink in; I had actually been bitten by one of only a couple of venomous mammals in the whole world. My finger turned red on the end and ached mildly for a few days but it was totally worth it!

Many people don’t realize that our yards and woods are home to miniscule venomous mammals called shrews. Shrews belong to a family of small mammals called insectivores. This large family also includes moles and hedgehogs. One member of the shrew family, the Etruscan shrew, has the distinction of being the world’s smallest mammal. It weighs only about two grams (less than a penny). The much larger short-tailed shrew (about half the size of a mouse) is a common resident of vacant lots and wooded areas in the lowcountry. There is a good chance that your cat or dog has excavated a shrew tunnel and left the carcass on your doorstep. Shrews secrete a musky odor and apparently have a foul taste so they are often killed but rarely eaten by domestic pets.

Don’t let the short-tailed shrew’s small size fool you. These tiny insectivores are voracious predators, attacking animals much larger than themselves and subduing them with toxic saliva. Venom is the shrew’s meal ticket, allowing it to immobilize insects, worms, frogs, salamanders and small mammals for eating. Shrews often find food using echolocation, a similar system to that used by bats. They send out a series of clicks and chirps through underground tunnels and listen for returning echoes that allow them to differentiate between food and non-edible material. Some shrews will capture and ingest two to three times their body weight in a single day. Shrews owe their insatiable appetites to their spectacular metabolisms. A short-tailed shrew’s resting heart rate can be 800 beats per minute and a relaxing shrew may breathe 168 times in 60 seconds. Shrews often prepare for lean times by caching a selection of snails, worms and beetles and even small snakes to insure ample food supplies for the winter.

Short-tailed shrews mate in any season and females often have three or more litters of 5-7 pups per year. The young shrews are weaned and leave the nest within a month of birth. They may live as long as three years but usually don’t survive past the first. Shrews are intolerant of each other, except during breeding, and will fight and even kill each other in territorial disputes.

Because shrews are very abundant and eat large quantities of invertebrates they are considered beneficial. They feed on a variety of harmful insect species like mole crickets and other pests. It is very unlikely that a person would be harmed by a shrew unless they tried to pick it up. So, while it was pretty silly for me to put my hand in a pitfall trap before looking inside, I feel kind of lucky to have been bitten by the only venomous mammal in this hemisphere.


Nature Note: Bats

Posted by: Tony Mills

Tagged in: nature notes , mammals

I never claimed to be a bat expert, but when I was called one afternoon to check out a large colony from a nearby residence, I jumped at the opportunity.  I mean, how often does one get to go play with a bunch of bats?  My oldest son (nine at that time) begrudgingly agreed to accompany me on yet another escapade. Marshall was well aware that I was a "snake guy" not a "bat guy" and expressed some misgivings about our involvement in the project. The homeowner didn't want to hurt the bats, but they were making a bit of a mess on the eaves of her house and in the attic.  After assessing the situation (40-50 bats lining a small section of the attic wall), we formulated our plan and raced back to the house for supplies.  It was easy: pluck the bats off the wall of the attic and place them in a large "tupperware" container for relocation.  My trusty sidekick, Marshall, would be standing behind me armed with a butterfly net to catch any animals that took flight.

I put on a hefty glove and began carefully removing the somewhat torpid bats off the wall, placing them in the container.  As I removed about the fourth bat, the inevitable happened.  A flock of bats fluttered up into the crawlspace like a covey of quail.  After a moment of indecision, I yelled for Marshall to start the netting process.  Upon receiving no response, I turned to find Marshall gone and the net lying limply on the floor of the attic.

Bats are extremely beneficial to human beings.  According to the book "Bats of the United States" by Michael J. Harvey et. al., a single bat can consume 4500 small flying insects in a single night.  Imagine what a colony of a thousand bats individuals could accomplish.  If bats were not present, we would have to spray far more insecticide into our skies to control mosquitoes and other pesky bugs.

Bats are the only true flying mammals. Similar to those of a human arm and hand, the extremely elongated finger bones are covered with membranous skin forming a wing.  Bats are spectacular aerialists, swooping and maneuvering to catch insects on the wing.  They use echolocation (sonar) to navigate and locate their prey.  They emit pulses of high frequency sound and listen to the echoes that bounce off various objects sensing what is in their paths.  Although bats are primarily nocturnal, they can often be seen at dusk, preparing for night flight. They spend days in attics of houses, barns, or hollow trees. Common predators of bats include snakes, owls and raccoons.

Because of past misconceptions, bats are still regarded as unwanted pests by some people.  Bats are beneficial because they play important roles in pest control, seed dispersal, and pollination.  Many people have even warmed-up to the idea of having bats in their attics, barns and yards .  Numerous plans for artificial bat dwellings (bat houses) are available on the internet and in outdoor magazines.

Marshall and I did manage to catch many of the bats in that attic. After a bit of research, I determined they were big brown bats Eptesicus fuscus, a harmless and beneficial species common in the the lowcountry.  In fact, this group turned out to be a maternity colony with lots of bat "pups."  I relocated the bats many miles away, in an old, dilapidated farmhouse where I had seen many bats in the past. I asked my neighbor to place hardware cloth over the gaps in the eaves of her house so no additional bats could get back inside and as far as I know that solved the problem.


Nature Note: Rat Snakes

Posted by: Tony Mills

Tagged in: nature notes , herps

I realize a few of you guys have heard this before but...I just love this story!


What could be taking Marshall so long, I thought? It had been a good twenty minutes since I had sent my son to gather eggs from the chicken house. As Ben (my younger son) and I set out across the yard to see what the holdup was, we noticed Marshall come out of the coop wrestling a very large snake. Now I realize some parents might have needed therapy after such a traumatic event, but I was positively thrilled.

My boys and I had removed many non-venomous snakes from the chicken pen together and spent hours  capturing  snakes in the field, but this was Marshall's first solo capture. He knew the rat snake he extracted from the shed was a non venomous species but he also knew it was capable of biting pretty hard.  I don't want to get all sentimental or anything, but it looked as though my baby was really growing up. Marshall's snake had the telltale signs of ingested chicken eggs running the length of its swollen body. As Marshall struggled with his catch, we watched in fascination as the large snake regurgitated chicken eggs one-by-one on to the ground in front of us. Some of the eggs were intact and others broken and runny. I guess some people might have been repulsed at the scene but to us this was quality father son bonding.

The rat snake is one of the biggest snakes in Southeast with some individuals exceeding seven feet in length. Although they reach impressive sizes, these snakes pose no serious threat to people. They vary in color and pattern throughout their range. Adults maybe dark grey or black with only traces of a lighter pattern (inland) or yellowish and heavily striped (like we have on the coast).

Rat snakes are powerful constrictors, suffocating rats, birds, squirrels, and even young rabbits and swallowing them whole. They are also particularly fond of bird eggs. Since they are adept climbers they often venture up the sides of barns and houses and into the tree canopy. Rat snakes are at home in wetlands and can be occasionally be seen swimming on ponds, rivers and even in the salt marsh.

Baby rat snakes are about 10 inches long and boldly patterned at hatching, but they lose those markings over the next  several years as they mature.  Individuals have been known to live more than 25 years in captivity. Although they are large, look a bit foreboding and steal an occasional egg from the Mills chicken coop, rat snakes are important members of the ecosystem. They help control populations of mice, rats, and squirrels and on a slow summer day in the country, what could be better than watching a rat snake throw up chicken eggs on the front lawn :)

Nature Note: Blue Crabs

Posted by: Tony Mills

Tagged in: nature notes , marine life

I sure remember the first time I got really "tagged" by a blue crab.  I was conducting field work in coastal South Carolina, netting diamondback terrapins for a population study with a group of graduate students. We positioned two jon boats along the edge of a trammel net so everyone could see any turtles caught in the mesh.  As I reeled the 50 foot net into the jon boat, I rested a swath of bundled net across my legs so I could collect another section into my hands. Feeling a jolt of searing pain, I looked down to see a blue crab pinching the inner portion of my thigh with one of his claws. I squirmed around on the boat seat and wiggled my body in an awkward attempt to remove the net and (more importantly) the crab from my lap. This seemed to irritate the feisty crustacean, causing him to sink the other claw into my leg. I stood up on the boat bench and shook my legs and hips violently performing an impromptu "crab dance" until the little guy fell off. Although I escaped the ordeal with very little physical damage and provided unplanned entertainment for the students, this event probably left some significant scars on my psyche.

The scientific name of the blue crab (Callinectes sapidus) loosely translates into "beautiful savory swimmer".  Adult blue crabs are adorned with a pleasing complement of blue and red hues on a light gray background. They are excellent examples of form following function because every body part is designed for mate acquisition, feeding or protection. The first pair of legs (claws) is important for feeding, fighting and holding a female during mating. These appendages possess great power allowing a crab to crush small mollusks and to rip apart fish and other marine animals into bite-sized pieces. The middle legs are for traditional walking but the last pair of legs are flattened paddles giving the crab great swimming ability.

Crabs are formidable predators feeding on just about any type of marine life small enough to capture and overpower. They often rest beneath the sand or "pluff" mud with just their eye-stalks exposed. Since they have excellent vision, they wait for an unwary victim to venture too close and blast out from under cover and grab it. Blue crabs are cannibals feeding on their own kind especially "softshell" crabs that have recently molted. They may also venture up into the high salt marsh and pluck periwinkles and other snails off the spartina grass for eating.

Blue crabs are extremely important to the economy of the lowcountry. They are harvested in local waters and shipped all over the world as food. Many of our crabs are shipped up the coast and marketed as Maryland blue crabs. During certain periods of the year when the crabs are about to molt they are collected for the seafood industry. Experienced crabbers are very adept at identifying animals that are about to shed their exoskeletons. Crabs in this condition ("peelers") are placed in tanks until they molt and marketed as "softshells".

Blue crabs mate throughout the warmer months of the year with peaks in the Spring and Fall in lower salinity waters. Although males likely mate many times, females mate only after their final molt and must be in a softshell condition. The adult females called ‘sooks" give off chemical signals (pheromones) to announce their reproductive condition. The larger males or "Jimmies" will stay with the female until she molts and mating is accomplished. He will continue to "cradle" her to keep other males away and let her shell harden before releasing her.

Two to nine months later, females will develop a mass of about two million eggs under the apron of the shell. This "sponge" of eggs bulges out on all sides and remains attached to her abdomen until the eggs are ready to hatch. After hatching, the larvae are "wisked" away by the tides to fend for themselves. If they are not eaten by a variety of marine predators, they will molt frequently and go through a series of larval stages reaching maturity a year and a half later. At this point these guys can mate themselves and produce the next generation of tasty crustaceans.


Nature Note: Soft Shell Turtles

Posted by: Tony Mills

Tagged in: nature notes , herps

I sat on the edge of the jon boat balancing myself as I donned fins and a mask preparing to snorkel after my elusive quarry.  The setting was in a slow deep bend of the Savannah River on a sunny April Saturday. The plan was to capture a couple of softshell turtles that were basking on a log downriver. I would float with the current with just my head exposed and at the last moment, porpoise out of the water onto the unwary individuals. Since this technique had not been particularly effective in the past, I disguised my head and face with branches and Spanish moss to make my approach even more "stealthy."  It took some time to convince my buddy William that this idea had merit but he eventually agreed to drop me off and then bring the boat down to pick me up after I snagged the turtles. I slipped quietly out of the boat and floated toward the turtles being especially careful not to disrupt the smooth water around me or dislodge my camouflage headgear.

Some of our state's wildlife species are pretty good at staying hidden, so you could easily spend your entire life here hunting, fishing or otherwise engaged in outdoor activities and never encounter certain creatures. The unusual-looking softshell turtle is one such beast. Although they are common residents of local streams and rivers and they get as big as trash can lids, they are rarely seen. Their flattened, streamlined bodies and flexible shells prompt the names "pancake" or "flapjack" turtles. Their huge oval, soft shells are masterfully camouflaged to match the bottoms of rivers, streams or lakes. A long neck and odd-looking snorkel nose allows them to breathe without surfacing.

Softshell turtles can also absorb oxygen from the water through vessels in the lining of their throats and other body parts, allowing them to remain under water for hours. The habit of burrowing under the sand or mud on the bottom of the wetland with just the head or snout exposed allows them to stay hidden. This technique facilitates the capture of crayfish, fish and other small animals by firing their long necks out from under the sand and grabbing prey.  Softshells are powerful swimmers and are difficult for most predators to capture.

During the summer, softshells lay 10-30 eggs in neatly excavated holes in sandy areas near the water. They may even lay their eggs in a nearby alligator nest.  Raccoons, foxes, skunks and other predators commonly prey on softshell nests so many eggs never have a chance to incubate. If the eggs survive, brightly patterned hatchlings emerge two to three months later. These little guys must remain hidden as much as possible because newly hatched turtles are an ideal size for predators. It may take ten years or more for softshells to reach adult size. Even as adults they fall prey to alligators, otters or other predators. A surprising number are killed on highways presumably as they cross roads to find suitable nesting sites. People occasionally catch snapping turtles, softshells and other species for the dinner table. I have even heard a couple of guys remark that a softshell turtle has seven kinds of meat. Now I am no culinary expert but try as I might, I cannot think of seven different kinds of meat, much less that many contained in one animal. I have never actually eaten a softshell turtle or plan to, so I won't say for sure but maybe they taste like pancakes.

Seven kinds of meat didn't cross my mind even once as I floated toward the turtles basking downstream. And to be sure, the turtles resting on a log in front of me did not whet my appetite in the least. By the time I got to within a hundred feet of the reptiles, three out of four had slipped off the logs and into the murky depths. As I drew closer the last animal cocked its head slightly and blasted off the perch and into the water leaving me empty handed and looking really silly in my cryptic attire (turtles 4, Tony 0).