Invasive Species Archives - Following Deer Creek

Young crayfish on Deer Creek, August 2019

Crayfish are freshwater crustaceans related to shrimp, lobster, and crabs. They’re all decapods—having ten legs.

Fossil records show crayfish have been in North America for millions of years.

According to the U.S. Geological Survey, the native range for the Signal crayfish (Pacifastacus leniusculus) is the Columbia River’s lower estuary. The range goes northwest and through tributaries that reach into British Columbia, Washington, Idaho, and Oregon.

Historical records say crayfish were first introduced to the Truckee River and Lake Tahoe sometime between 1895 and 1909. They were placed there for fish food, bait, and human consumption. Crayfish are currently planted in ponds and on fish farms to control aquatic weeds.

Habitat:

Crayfish live in a variety of freshwater environments from backwater pools to large rivers, streams. and subalpine lakes. Favorite places include hiding among rocks and in stands of partially submerged plants. They are temperature and pH-sensitive.

Diet:

Anything and everything…

rotting leaves and twigs
animals and insects (younger crayfish are most attracted to these)
dead fish
live plants and algae (older crayfish are most attracted to these)
other crayfish (large crayfish are most likely to cannibalize other crayfish)

Behavior:

Crayfish breathe through gills. They can survive on land as long as gills remain moist. In water, gills also collect small food particles.

Most activity and feeding occurs at night.

Crayfish have two sets of antennae, one set for touch and the other for smell.

Defense:

Body armor—or the exoskeleton—is a crayfish’s main defense, though pincers are also used for battle.

The exoskeleton is made up of calcium carbonate (limestone), taken from the water. It builds up in layers. When the animal grows, it sheds its exoskeleton. At this time, it is at its most vulnerable until the new exoskeleton hardens.

Molting occurs most often as young grow to adulthood. Once crayfish are fully grown molting only happens a few times per year.

Crayfish have the ability to regrow claws if they are lost. Claws are also used for eating and mating.

Breeding:

Depending on food availability and water temperature, breeding can begin between three to six months of age. Mating usually occurs in the spring and summer months.

Mothers can hold sperm until conditions for egg-laying are right, usually in fall.

Females lay somewhere between 200 – 400 eggs. These are attached to her swimmerets under her tail. Young remain with their mother through several molts. As they grow, they separate somewhat, staying attached by thread-like tethers. Once fully separated, the mother secretes a pheromone that keeps the young close for protection.

Lifespan:

Average is about 3 years. In captivity, some have lived up to twenty years.

Predators:

Anything living in or near the water.

fish
birds
turtles
otters
raccoons
bullfrogs
coyote
humans

Crayfish Consumption in the West:

Washington, Oregon, and the Sacramento Delta are the main crayfish food consuming areas on the west coast. According to the California Department of Fish and Wildlife, over ten-thousand pounds of Signal Crayfish were taken out of the Sacramento Delta in 2018.

Dangers to Crayfish:

pollution
fertilizers
pesticides
oil or fuel
dams
changing land use activities that alter water flows
silt loads

Crayfish Species Where They Don’t Belong (Shipping Crayfish to Classrooms):

Carriers of a Plague Organism:

According to the U.S. Fish and Wildlife Service, “crayfish plague, caused by the fungus-like organism Aphanomyces astaci Schikora, is listed in the top 100 of the “World’s Worst” invaders by the International Union for Conservation of Nature.”

Like the Asian Ladybug, Signal crayfish can live in a balanced host-parasitic relationship. If they are brought into places where that balance hasn’t been established, ecosystem havoc can result.

California Department of Fish and Wildlife Recommends Eating Some Invasive Species

To catch crayfish you’ll need;

a valid fishing license,
a homemade trap,
or fishing line and bait.

Invasive Eats (California Specific)| Eat the Invaders | Invasivore

click on image to purchase or view more Life on the Creek art

If you enjoyed this post, check out Invasive Species Choke Natives & California’s Floristic Provence.

Resources:

California Department of Fish and Wildlife – California Invasive Species Action Week

National Park Service – The impact of introduced crayfish on a unique population of salamander in Crater Lake, Oregon

USGS – Pacifastacus leniusculus (Signal Crayfish) fact sheet

Wikipedia – Pacifastacus fortis. California’s only native crayfish.

Origin & Name

Raccoons evolved around water sources. People observing them gave them names describing their ‘washing’ behavior.

Scientific name – Procyon lotor means “before-dog washer” in Latin
Aztecs – Mapachitli – “one who takes everything in its hands”
Chinese – Orsetto lavatore “little-bear washing”
Garman – Waschbär – “wash-bear”
Italian – Araiguma – “washing-bear”
Algonquian / Powhatan Indian – Arocoun – “he scratches with his hands”
English speaking North American colonists changed Arocoun to raccoon

Hands & Masks

Raccoons explore with touch. It’s long been thought that ‘food washing’ was for cleanliness. Dipping ‘hands’ in water is called dousing; it stimulates nerve endings in the forepaws, giving the animal an improved ability to detect changes in pressure.

Raccoons don’t have thumbs but use both forepaws to manipulate objects, like hands. Their forepaws have concentrations of mechanoreceptor cells similar to primates and humans.

Since the animal is nocturnal and thought to be colorblind, it makes sense that it interprets the world through touch.

The mask, a stripe of dark fur surrounding the eyes, maximizes night vision by blocking glare.

Intelligence

Raccoons are omnivores; they’ll eat anything. Scientists believe that this characteristic, as with humans, contributes to their extraordinary intelligence.

A raccoon is a relentless problem solver, passing learning along to their young. As people attempt to keep them out, raccoons adapt, becoming smarter in the process.

In 1907, H.B. Davis published a raccoon intelligence study in The American Journal of Psychology. Twelve raccoons were given a series of locks to crack. He presented the test subjects with 13 puzzles to solve. Their success rate was nearly 85%.

“The learning curves for the raccoons and Kinnaman’s monkeys… seem to show a nearly equal facility in learning to undo fasten-ings.”

“Test of the raccoon’s powers of retention show that skill in undoing simple fastenings once learned remains practically undiminished…”

Breeding & Raising Young

Mating Season – January and June
Females mature and can reproduce at about one year
Two – five kits are common per litter, born in spring
Females separate from others to raise young.
Mothers teach kits by example
Kits remain with mother between 13-14 months
Raccoons in tree cavities & burroughs – keeping up to 20 den sites at one time

Factoids

Full grown = up to 23 pounds
Adult male = boar
Adult female = sow
Young = kits
Lifespan = wild – 2 – 3 years, captivity 20 years

Predators

In the wild bobcats, coyotes, mountain lions, great horned owls, and red-tailed hawks pose threats.

In urban environments, infection, disease, and cars are the major causes of death

Differing Interactions with Humans

Raccoons in the wild are shy around humans, avoiding them when possible.

Urban raccoons will approach them looking for handouts.

Highly adaptable, raccoons are able to easily navigate living in urban environments. Food sources (pet and bird feeding stations and garbage day) are plentiful and they’ll den in attics and abandoned buildings. Raccoons understand traffic patterns and travel on roofs and fence tops.

The trapper in the above video is from Florida, but his topics and the other animals he talks about are applicable to Nevada County.

Becoming Invasive

Germany
In 1934 a forester released a pair of raccoons to “enrich the fauna” for hunting. In 1945, twenty-five raccoons escaped from a fur farm after an air strike. Since then, the raccoon population in Germany has grown tremendously.

Raccoons are now considered an invasive species. A zero-tolerance policy is in place. Over 10,000 raccoons are trapped and killed in Germany per year.

Japan
Rascal the Raccoon anime show appeared in the 1970s. As a result, children wanted pet raccoons. At one time, over 1,500 raccoons were imported per month. When keeping them became difficult, many were released in the forest.

Today, raccoons cause hundreds of thousands of dollars of damage to ancient, irreplaceable buildings and temples. Raccoons have spread to most regions in the country. Japan prohibits raccoon imports.

Problem Prevention

To discourage denning on or near the property;

• Securely close trash containers
• Don’t leave pet food outside
• Remove bird feeders
• Eliminate water sources and ornamental fish
• Cover outdoor sandboxes when not in use
• Keep brush cleared
• Eliminate access to attics, basements, and barns

Raccoon Voiding Spots and Latrines

Wilderness raccoons prefer to poo at the base of trees, on horizontal surfaces, on large rocks or in raised tree forks. Undigested seeds are often visible.

In urban areas, they’ll go on rooftops, decks, woodpiles, and in attics, haylofts, and in garages.

A raccoon latrine is a communal defecation area used by multiple raccoons.

Feces Spread Disease

Fungal Spores
Parasitic raccoon roundworm- causes neurologic damage and possible death: eggs are temperature resistant and can become airborne when dry
Giardia
Leptospirosis – contact with open wounds

Above is a list of some of the infectious diseases carried by raccoon feces. They can also be spread through contact with urine, saliva, bites and scratches.

Communal Food

Because food sources attract a variety of animals, disease can spread. Infectious raccoons may appear healthy. When a disease moves from a raccoon to a cat, dog, or human, it can be more challenging to combat.

Feces Clean-Up

Prepare for cleaning by protecting your airways (mucous membranes) and skin.

• Wear disposable gloves and rubber boots (or disposable booties that cover shoes)
• Wear an N95-rated respirator (hardware store)
• Plan to burn or sterilize gear when finished

Outdoor Latrine Cleaning

• Use a shovel (or inverted bag) to collect feces and contaminated material. Bury or burn. If placing in the trash, double bag and secure to protect landfill workers
• Roundworm eggs are chemical resistant. High heat will kill them. Cover feces with boiling water or blast with a propane torch
• Use boiling water to disinfect shovel blades and deck surfaces
• Burn or boil and disinfect protective gear
• Wash hands thoroughly with hot, soapy water. Launder clothing with hot water and detergent

Indoor Latrine Cleaning

Lightly mist area with soapy water in a spray bottle to avoid stirring up dust
Collect and dispose of feces as listed above
Use a bucket of hot, soapy water and a damp sponge to wipe down the area
Rinse sponge frequently
Flush contaminated water down the toilet
Disinfect the bucket with boiling water
Burn or boil and disinfect protective gear
Wash hands thoroughly with hot, soapy water
Launder clothing with hot water and detergent

Editor’s Note:

Apart from post titles, I endeavor to present Deer Creek topics objectively from multiple angles, using reliable sources. While the Center for Disease Control says, “human infections are rare,” I think a cautionary note is valuable.

As more people spread into wild areas, animals with the ability to live in urban areas join us. Our structures, pets, feeding stations and trash fulfill their hierarchy of needs. As a result, species whose paths would rarely cross are ‘meeting at the grocery store,’ creating opportunities for infectious organisms.