Chordates (Chordata) – Page 10 – LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED

August 20, 2017October 5, 2023

The Dungeon

There’s something frightening going on down there. In the sand, beneath the plants on the shoreline, there’s a pile of soil next to a hole it’s been digging. Now, it’s dragging something toward the tunnel it made. What does it have? Is that alive?

We know how the system works, the food chain that is. The small stuff is eaten by the progressively bigger things, and there are fewer of the latter than there are of the former, thus the whole network keeps operating long-term. Some things chew plants, others devour animals whole or in part, and then there are those, like us, that do both. In the natural ecosystem, predators keep the numerous little critters from getting out of control and decimating certain other plant or animal populations and wrecking the whole business. When man brings an invasive and potentially destructive species to a new area, occasionally we’re fortunate enough to have a native species adapt and begin to keep the invader under control by eating it. It maintains the balance. It’s easy enough to understand.

Japanese Beetles (Popillia japonica) seen here on Halberd-leaved Rose Mallow. Without predation, exploding numbers of this invasive non-indigenous insect can defoliate and kill numerous species of plants in a given area.

The Song Sparrow (Melospiza melodia) is a generalist feeder, eating seeds and invertebrates including Japanese Beetles. This species is the omnipresent year-round occupant of shoreline vegetation along the lower Susquehanna River.

Late summer days are marked by a change in the sounds coming from the forests surrounding the falls. For birds, breeding season is ending, so the males cease their chorus of songs and insects take over the musical duties. The buzzing calls of male “Annual Cicadas” (Neotibicen species) are the most familiar. The female “Annual Cicada” lays her eggs in the twigs of trees. After hatching, the nymphs drop to the ground and burrow into the soil to live and feed along tree roots for the next two to five years. A dry exoskeleton clinging to a tree trunk is evidence that a nymph has emerged from its subterranean haunts and flown away as an adult to breed and soon thereafter die. Flights of adult “Annual Cicadas” occur every year, but never come anywhere close to reaching the enormous numbers of “Periodical Cicadas” (Magicicada species). The three species of “Periodical Cicadas” synchronize their life cycles throughout their combined regional populations to create broods that emerge as spectacular flights once every 13 or 17 years.

An “Annual Cicada” also known as a “Dog-day Cicada”, clings to the stem of a Halberd-leaved Rose Mallow at Conewago Falls.

For the adult cicada, there is danger, and that danger resembles an enormous bee. It’s an Eastern Cicada Killer (Specius speciosus) wasp, and it will latch onto a cicada and begin stinging while both are in flight. The stings soon paralyze the screeching, panicked cicada. The Cicada Killer then begins the task of airlifting and/or dragging its victim to the lair it has prepared. The cicada is placed in one of more than a dozen cells in the tunnel complex where it will serve as food for the wasp’s larvae. The wasp lays an egg on the cicada, then leaves and pushes the hole closed. The egg hatches in a several days and the larval grub is on its own to feast upon the hapless cicada.

An Eastern Cicada Killer *(Sphecius speciosus)* along the river shoreline. Despite their intimidating appearance, they do not sting humans and can be quite docile when approached.

Other species in the Solitary Wasp family (Sphecidae) have similar life cycles using specific prey which they incapacitate to serve as sustenance for their larvae.

A Solitary Wasp, *one of the Thread-waisted Wasps (Ammophila species)*, drags a paralyzed moth caterpillar to its breeding dungeon in the sandy soil at Conewago Falls. For the victim, there is no escape from the crypt.

The Solitary Wasps are an important control on the populations of their respective prey. Additionally, the wasp’s bizarre life cycle ensures a greater survival rate for its own offspring by providing sufficient food for each of its progeny before the egg beginning its life is ever put in place. It’s complete family planning.

The cicadas reproduce quickly and, as a species, seem to endure the assault by Cicada Killers, birds, and other predators. The Periodical Cicadas (Magicicada), with adult flights occurring as a massive swarm of an entire population every thirteen or seventeen years, survive as species by providing predators with so ample a supply of food that most of the adults go unmolested to complete reproduction. Stay tuned, 2021 is due to be the next Periodical Cicada year in the vicinity of Conewago Falls.

SOURCES

Eaton, Eric R., and Kenn Kaufman. 2007. Kaufman Field Guide to Insects of North America. Houghton Mifflin Company. New York.

August 14, 2017September 4, 2019

Summer Grasses

It has not been a good summer if you happen to be a submerged plant species in the lower Susquehanna River. Regularly occurring showers and thunderstorms have produced torrents of rain and higher than usual river stages. The high water alone wouldn’t prevent you from growing, colonizing a wider area, and floating several small flowers on the surface, however, the turbidity, the suspended sediment, would. The muddy current casts a dirty shadow on the benthic zone preventing bottom-rooted plants from getting much headway. There will be smaller floating mats of the uppermost leaves of these species. Fish and invertebrates which rely upon this habitat for food and shelter will find sparse accommodation…better luck next year.

Due to the dirty water, fish-eating birds are having a challenging season as they try to catch sufficient quantities of prey to feed themselves and their offspring. A family of Ospreys (Pandion haliaetus) at Conewago Falls, including recently fledged young, were observed throughout this morning and had no successful catches. Of the hundred or more individual piscivores of various species present, none were seen retrieving fish from the river. The visibility in the water column needs to improve before fishing is a viable enterprise again.

Ospreys competing for a suitable fishing perch. Improving water conditions in the coming week should increase their success as predators.

Versatile at finding food, adult Bald Eagles are experienced and know to be on the lookout for Ospreys with fish, a meal they can steal through intimidation.

While the submerged plant communities may be stunted by 2017’s extraordinary water levels, there is a very unique habitat in Conewago Falls which endures summer flooding and, in addition, requires the scouring effects of river ice to maintain its mosaic of unique plants. It is known as a Riverine Grassland or scour grassland.

The predominant plants of the Riverine Grasslands are perennial warm-season grasses. The deep root systems of these hardy species have evolved to survive events which prevent the grassland from reverting to woodland through succession. Fire, intense grazing by wild herd animals, poor soils, drought, and other hardships, including flooding and ice scour, will eliminate intolerant plant species and prevent an area from reforesting. In winter and early spring, scraping and grinding by flood-driven chunk ice mechanically removes large woody and poorly rooted herbaceous growth from susceptible portions of the falls. These adverse conditions clear the way for populations of species more often associated with North America’s tall grass prairies to take root. Let’s have a look at some of the common species found in the “Conewago Falls Pothole Rocks Prairie”.

Big Bluestem *(Andropogon* gerardi), seen here growing in the cracks of a pothole rock. High water nourishes the plant by filling the crevices with nutrient-loaded sediment. This species evolved with roots over three feet deep to survive fires, trampling by bison, and drought.

Freshwater Cordgrass *(Spartina pectinata)* does well with its roots in water. It creates exceptional bird habitat and grows in the falls and on ice-scoured small islands in free-flowing segments of the Susquehanna River downstream.

Switchgrass *(Panicum virgatum)*, like Big Bluestem, is one of the tall grass prairie species and, like Freshwater Cordgrass, grows in near pure stands on ice-scoured islands. It takes flooding well and its extensive root system prevents erosion.

Though not a grass, Water Willow *(Justicia americana)* is familiar as a flood-enduring emergent plant of river islands, gravel bars, and shorelines where its creeping rhizome root system spreads the plant into large masses. These stands are often known locally as “grass beds”. This member of the acanthus family provides habitat for fish and invertebrates among its flooded leaves and stems. Its presence is critical to aquatic life in a year such as this.

The Conewago Falls Riverine Grassland is home to numerous other very interesting plants. We’ll look at more of them next time.

SOURCES

Brown, Lauren. 1979. Grasses, An Identification Guide. Houghton Mifflin Company. New York, NY.

July 31, 2017November 29, 2019

Digging In

If you visit the shores of the Susquehanna River during the warmer months of the year, there’s a pretty good probability that you’ll be taking a visitor along home with you. Not to worry, it won’t raid the icebox or change the television channels when you leave the room to get a snack. It won’t put you in the doghouse with the landlord for having a forbidden pet. As a matter of fact, you may not even notice your new companion. Sure enough though, it’s there, crawling through the luxurious warm fabric of your clothing and seeking out a good place to dig in and chow down. O.K., so now you’re worried.

Ticks, particularly the American Dog Tick (Dermacentor variabilis), are widespread in the Lower Susquehanna River Watershed. Like spiders, they are arachnids. They have a four-stage life cycle (egg-larva-nymph-adult) which, in the case of D. variabilis, requires a minimum of two months to complete. Females lay up to 6,500 eggs on the ground. Then the fun begins as the larvae with any hope of survival must attach to a small mammal to feed. They can survive for almost a year before finding a host. After a successful hookup and subsequent blood feast of up to two weeks duration, the larva drops to the ground, molts into a nymph, and finds another small mammal, usually a bit bigger this time, to feed upon. A nymph can survive for up to six months before needing to feed. Finding the second host, the nymph feeds for 3 to 10 days, then drops to the ground to molt into an adult. Adult American Dog Ticks can endure up to two years without feeding on a host. The adults mate and feed on larger mammals such as deer and domestic animals including, of course, dogs. After a blood meal of five days to two weeks duration, the adult female tick drops to the ground to lay eggs and initiate a new generation.

The adult American Dog Tick attaches to a potential host by hanging from vegetation and grabbing the passing victim with its forward legs to hitch a ride. If undetected, a female will find a nice warm spot and “dig in” to begin feeding. This male is looking for love, and in all the wrong places.

The American Dog Tick is renowned as a carrier of the Rocky Mountain Spotted Fever bacteria (Rickettsia rickettsii). The bacteria is vectored by the ticks from rodents to dogs and humans. The adult tick must be attached to the victim for a minimum of six to eight hours to transmit the pathogen. A rash spreading from the wrists and the ankles to other portions of the body begins two to fourteen days after infection.

Tularemia, caused by the bacteria Francisella tularensis, can be passed by the American Dog Tick. Symptoms can appear in three to twenty-one days and include chills, fever, and inflammation of the lymph nodes.

American Dog Ticks which attach to dogs, particularly near the neck, and are left in place to feed and engorge themselves for longer than five days can cause Canine Tick Paralysis. Symptoms usually begin to subside only after a recovery period following removal of the arachnid.

The American Dog Tick is exposed to Borrelia burgdorferi, the bacteria responsible for Lyme Disease, however, transmittal of this pathogen is by the smaller Deer Tick (Ixodes scapularis), also known as the Black-legged Tick. The Deer Tick is not presently common at Conewago Falls. In the adjacent uplands, it is widespread and is carrying Lyme Disease where the White-tailed Deity (Odocoileus virginianus), the preferred host for the ticks, is found along with mice and other small rodents, the source of B. burgdorferi bacteria. The Deer Tick easily escapes notice and cases of Lyme Disease are frequent, so vigilance is necessary.

SOURCES

Chan, Wai-Han, and Kaufman, Phillip. 2008. American Dog Tick. University of Florida Featured Creatures website entnemdept.ufl.edu/creatures/urban/medical/american_dog_tick.htm as accessed July 30, 2017.

July 27, 2017October 13, 2019

The Antagonist

They can be a pesky nuisance. The annoying high-frequency buzzing is bad enough, but it’s the quiet ones that get you. While you were swatting at the noisy one, the silent gender sticks you and begins to feed. Maybe you know it, or maybe you don’t. She could make you itch and scratch. If she’s carrying a blood-borne pathogen, you could get sick and possibly die.

To humans, mosquitos are the most dangerous animal in the world (though not in the United States where man himself and the domestic dog are more of a threat). Globally, the Anopheles mosquitos that spread Malaria have been responsible for millions and millions of human deaths. Some areas of Africa are void of human habitation due to the prevalence of Malaria-spreading Anopheles mosquitos. In the northeastern United States, the Northern House Mosquito (Culex pipiens), as the carrier of West Nile Virus, is the species of greatest concern. Around human habitations, standing water in tires, gutters, and debris are favorite breeding areas. Dumping stagnant water helps prevent the rapid reproduction of this mosquito.

In recent years, the global distribution of these mosquito-borne illnesses has been one of man’s inadvertent accomplishments. An infected human is the source of pathogens which the feeding mosquito transmits to another unsuspecting victim. Infectious humans, traveling the globe, have spread some of these diseases to new areas or reintroduced them to sectors of the world where they were thought to have been eliminated. Additionally, where the specific mosquito carrier of a disease is absent, the mobility of man and his cargos has found a way to transport them there. Aedes aegypti, the “Yellow Fever Mosquito”, carrier of its namesake and the Zeka Virus, has found passage to much of the world including the southern United States. Unlike other species, Aedes aegypti dwells inside human habitations, thus transmitting disease rapidly from person to person. Another non-native species, the Asian Tiger Mosquito (Aedes albopictus), vector of Dengue Fever in the tropics, arrived in Houston in 1985 in shipments of used tires from Japan and in Los Angeles in 2001 in wet containers of “lucky bamboo” from Taiwan…some luck.

Asian Tiger Mosquito in action during the daylight hours, typical behavior of the genus. This species has been found in the area of Conewago Falls since at least 2013.

Poor mosquito, despite the death, suffering, and misery it has brought to Homo sapiens and other species around the planet, it will never be the most destructive animal on earth. You, my bloodthirsty friends, will place second at best. You see, mosquitos get no respect, even if they do create great wildlife sanctuaries by scaring people away.

The winner knows how to wipe out other species and environs not only to ensure its own survival, but, in many of its populations, to provide leisure, luxury, gluttony, and amusement. This species possesses the cognitive ability to think and reason. It can contemplate its own existence and the concepts of time. It is aware of its history, the present, and its future, though its optimism about the latter may be its greatest delusion. Despite possessing intellect and a capacity to empathize, it is devious, sinister, and selfish in its treatment of nearly every other living thing around it. Its numbers expand and its consumption increases. It travels the world carrying pest and disease to all its corners. It pollutes the water, land, and air. It has developed language, culture, and social hierarchies which create myths and superstitions to subdue the free will of its masses. Ignoring the gift of insight to evaluate the future, it continues to reproduce without regard for a means of sustenance. It is the ultimate organism, however, its numbers will overwhelm its resources. The crowning distinction will be the extinction.

Homo sapiens will be the first animal to cause a mass extinction of life on earth. The forces of nature and the cosmos need to wait their turn; man will take care of the species annihilation this time around. The plants, animals, and clean environment necessary for a prosperous healthy life will cease to exist. In the end, humans will degenerate, live in anguish, and leave no progeny. Fate will do to man what he has done to his co-inhabitants of the planet.

The Bald Eagle *(Haliaeetus leucocephalus)* is again a breeding species in the Susquehanna River watershed. It is generally believed that during the mid-twentieth century, Dichlorodiphenyltrichloroethane (DDT) pesticide residues accumulated in female top-of-the-food-chain birds including Bald Eagles. As a result, thinner egg shells were produced. These shells usually cracked during incubation, leading to failed reproduction in entire populations of birds, particularly those that fed upon fish or waterfowl. In much of the developed world, DDT was used liberally during the mid-twentieth century to combat Malaria by killing mosquitos. It was widely used throughout the United States as a general insecticide until it was banned here in 1972. (Editors Note: There is the possibility that polychlorinated biphenyls [P.C.B.s] and other industrial pollutants contributed to the reproductive failure of birds at the apex of aquatic food chains. Just prior to the recovery of these troubled species, passage of the Clean Water Act in 1972 initiated reductions in toxic discharges from point sources into streams, rivers, lakes, bays, and oceans. Production of P.C.B.s was banned in the United States in 1978. Today, P.C.B.s from former discharge and dumping sites continue to be found in water. Spills can still occur from sources including old electric transformers.)

To substitute any other beast would be folly. Man, the human, Homo sapiens, the winner and champion, will repeatedly avail himself as the antagonist during our examination of the wonders of wildlife. He is the villain. The tragedy of his self-proclaimed dominion over the living things of the world will wash across these pages like muddy water topping a dam. There’s nothing I can do about it, aside from fabricating a bad novel with a fictional characterization of man. So let’s get on with it and take a look at “A Natural History of Conewago Falls”. Let’s discover the protagonist, the heroic underdog of our story, “Life in the Lower Susquehanna River Watershed.”

SOURCES

Avery, Dennis T. 1995. Saving the Planet with Pesticides and Plastic: The Environmental Triumph of High-Yield Farming. Hudson Institute. Indianapolis, Indiana.

Eaton, Eric R., and Kenn Kaufman. 2007. Kaufman Field Guide to Insects of North America. Houghton Mifflin Co. New York.

Newman, L.H. 1965. Man and Insects. The Natural History Press. Garden City, New York.