Species of the Month

Halloween is just around the corner. Traditionally, we examine a spooky critter with a connection to Halloween for the Species of the Month. This year let’s try something different. There’s nothing scary about a ghost crab, but its name fits the season. 

Ghost crab (Science Magazine)

Scientific name: Ocypode quadrata 

Kingdom: Animalia (animals)

Class: Malacostraca (soft-shelled crustaceans)

Order: Decapoda (ten-footed crustaceans)

Range: Rhode Island to Brazil 

Habitat: Ocean or estuary beaches, from the tide line to the dunes 

Lifespan: 3 years 

Diet: Bean clams, mole crabs, sea turtle eggs and hatchlings, organic detritus 

Predators: Shore birds, gulls, raccoons 

Conservation status: No special protection

Other info: Ghost crabs are small, nocturnal crustaceans. They grow to about a two inch carapace (back shell) with long legs and eye stalks, and their claws are uneven sizes. Ghost crabs hatch from an egg in the ocean and go through six larval stages before developing into adult crabs. Unlike other crabs that can only mate when the female is molting, ghost crabs can and do mate at anytime after reaching maturity which is usually after a year old.  

Juvenile ghost crab (NPS)

Ghost crabs live in burrows in the sand. They plug the holes during the day and emerge at night for feeding and mating. Mating occurs near the male’s burrow. They travel several feet per night and may not return to the same burrow. Occasionally they will go into the water to wet their gills; they are also capable of absorbing water from the sand into their gills. 

Ghost crabs can be used as an indicator species to monitor the health of their habitat. Populations can be easily estimated by counting burrows. Knowing the status of the crab population can tell what kind of impact human activities are having on the ecosystem overall. Off road vehicles and coastal development are the biggest challenges we give them. 

A pair of ghost crabs (NPS)

Once again this week's information comes from the Animal Diversity Web at University of Michigan. Next week is a rerun. We'll have fresh content after Halloween. Stay tuned!

Live Streaming

After so many stories from the road, this little story about one of my last events in Washington got shoved aside. I spent some time in Percival Creek with the Thurston County Stream Team conducting a stream bug survey, also known as a biological index of benthic invertebrates (BIBI). File this under “Things I wasn’t allowed to do 30 years ago”.

Stream bug monitoring is an important way to gauge the health of a stream. Some thrive in polluted water, some thrive in pristine water. To know how many of which kinds of insects are in the stream is a good indicator of water quality. Just what is a stream bug? The ones we looked for are actually the larvae of insects such as mayflies and caddisflies. The larvae are aquatic, living in freshwater, making a living in a variety of ways such as scrapers and shredders.

The method used by my group was to sample three areas within a riffle of the stream. A riffle is an area of faster moving water. Our leader, Debbie Smith, is the coordinator for Tumwater Stream Team. She supplied us with all the necessary equipment, minus our own boots. To collect samples, we used a funnel-shaped net that had a metal square at the front which marked the boundary of the sampling area. A weed fork is a great tool for the stream to, scaring up bugs on the rocks and in the substrate by rapidly mixing it around inside the metal square. Debbie also brought a stop watch, buckets, insect field guides, and lab equipment including magnifying glasses, headlamps, forceps, and sealed containers. While we began collecting samples, Debbie stayed behind with one other from our group to set up the lab. 

Net similar to the one we used for sampling. The front section defines the sampling area.

Weed fork

After washing our boots in a mild chemical solution, we took turns mixing up both the surface and substrate of the stream bed for a minute, loosening the bugs which then flowed into the net with the current. Large rocks in the square went into a bucket for analysis. Stream width and depth at the sample sites, as well as the length of the sampled riffle, were recorded for each sample. Distilled water (to prevent outside bugs from being counted in the sample) was used to rinse any bugs on the net into the collection bag at the bottom. 

Example of stream bugs clinging to a rock

Processing samples in the lab (Debbie Smith photo).

Our samples were taken to the lab for analysis. Our lab was a simple setup on a bridge that day. Small rocks in the collection bag were removed and inspected. Any bugs were removed with forceps and placed in alcohol for later analysis by entomologists that can ID them by genus and species. The same was true for the large rocks in the bucket. The collection bag was emptied and scoured for bugs. Rocks were not sent to the entomologists, but any organic matter in the net, such as leaves and woody debris, did go along with the insect samples. We did this at three different riffles, for a grand total of nine minutes of churning up creek bed.

We did our survey in because stream levels are low. If the water is too high, the bottom is unreachable and the current can be dangerous. There were always at least four of us in the water: one holding the net, one using the weed fork, one running the stopwatch, and one holding the bucket of rocks. If anything happened to one of us, there was always someone available to help. Always think safety in the lab and in the field. 

Stream Team following a successful morning of splashing around
Percival Creek. I am 4th from the left in the green shirt.
(Debbie Smith photo)

Keep Bugging Me

Plants are important to life on Earth. They put oxygen in the atmosphere as a byproduct of photosynthesis. Everyone has to eat, and plants for the base of the food chain. Just as important, and either overlooked or swatted aside, are insects. I consider insects to be the second lowest man on the food chain totem pole as they are super abundant and are the prey of choice for many of the first order predators. In addition, many of them support plant life by serving as pollinators. Others are beneficial because they eat other insects that are crop pests. 

Hoverfly working hard to pollinate

Fritillary butterfly pollinating

I never saw this little pollinator before today

Insect larvae, such as fly maggots or aquatic larva such as mayfly and caddisfly larva, play an important role in the nutrient cycle, breaking down dead plant and animal matter and cycling it into the soil for plants or cycle it even higher in the food chain by being eaten by something bigger than a plant.

Aquatic insect larvae are important indicators of ecosystem health. The absence or presence of certain bugs in the water can tell researchers a lot about water quality. Data collected from stream bug surveys can be used in habitat restoration and conservation projects. 

Caddisfly larvae, an important salmon food

Water strider- fish food

Insects are a great teaching tool. When my daughter was little, insects were her introduction to nature. They are lightweight, portable, easy to catch, and almost everywhere so there was always an opportunity to teach her something new. 

A ladybug, one of my daughter's favorites when she was little

Many of the birds we enjoy seeing or hearing eat insects. Salmon are commercially important fish species that depend on insects and/or insect larva in their early stages of life. The flowers in your garden, not to mention many crops, are there because of insects. Next time you eat an apple, smell a rose, or hear your favorite bird hug a bug! 

Unknown tiny insect that landed on my shirt one day

Bee on its 10 minute break

Praying mantis or preying mantis?

Amphibian Egg Mass Surveys

One of the things I do in my spare time (for self-serving fun and career development as well as stewarding my planet) is volunteer with Northwest Trek and Washington Department of Fish and Wildlife conducting amphibian egg mass surveys. No, I don’t go door to door asking questions about egg masses. I go to a pond and look for the eggs that several species of amphibians left behind following breeding.

            First, what is an amphibian? It’s a critter that leads a double life as both a terrestrial and aquatic animal. Unlike a reptile like an alligator that must surface to breathe, amphibians can breathe above or below water. The word amphibian comes from the Latin amphi bios meaning two lives.

            There are 27 species of amphibians in Washington, but WDFW only has us looking for the eggs of 8. They are Oregon spotted frog (state endangered, federally threatened), red-legged frog, American bullfrog (invasive to the Northwest), Pacific tree frog, western toad (candidate for listing as federally threatened or endangered), Northwestern salamander, long-toed salamander, and rough skinned newt.

            The pond I survey is in Eatonville. In and around, I have found eggs, tadpoles, or adults of four of those species. There were Northwestern salamander, Pacific tree frog, and red-legged frog egg masses; adult Pacific tree frogs, a red-legged frog, and American bullfrogs; and some tadpoles that were too fast to be able to identify.

American bullfrog

Red-legged frog

Pacific tree frogs

            To conduct a survey, I go into the pond with my partner Roger and slowly walk around looking for eggs. It seems like a challenge at first, but the egg masses are very obvious in most cases. Northwestern salamander egg masses are a huge solid ball of jelly, about the size of a grapefruit. They are likely to be attached to a pond lily stem. Pacific tree frog masses are smaller balls of jelly attached to smaller aquatic plants in most cases.

Northwestern salamander egg mass

Pacific tree frog egg mass

            When we find egg masses, we mark the location on a GPS and take a picture. It also gets logged on a tracking sheet. Last March the batteries in either the GPS or camera died and the spare batteries in our pack were also dead. It was a little frustrating switching batteries from one device to the other, especially because that was the day a river otter was helping us. It would’ve been great to get a shot of that little guy! As a consolation, we found a pile of his poo.

River otter scat

            Gently cleaning our waders before and after conducting a survey is a thoughtful way to help prevent the spread of invasives from one pond to another. It can also help reduce the spread of chytrid fungus, which causes disease in amphibians.

            The data we collect gets sent to the state to help biologists determine habitat conditions and species trends. Amphibians are an indicator species (species that can indicate trouble in an ecosystem by absence or presence) because their thin skin makes them very sensitive to environmental changes. By identifying trouble early on, biologists can analyze and correct the situation.

            Now you have a glimpse inside the working world of a nature guy. I’ll be back in the pond for a third season of egg mass surveying, starting this week. Weather permitting, of course. Don't forget to like Nature Minute on Facebook!