Territoriality of Crayfish

Scott Baddeley

 

The crayfish is a very interesting creature. Being a complex crustacean that can live in fresh water creeks and streams, it can live all over the United States, not just in the sea. My study looked at the crayfish as an individual and how it is territorial and is on it's own in it's habitat. I conducted the study in my home in mid-April. I put two crayfish in a pre made habitat (fish bowl.) The study wasn't so much collecting hard data but more just watching interaction between individuals and how they react to direct confrontation. I would sit and watch them for thirty minutes to an hour at a time. I would also pick them up and put them next to each other for direct confrontation. I found that the individuals didn't take a liking and at times turned out hostile to each other. This showed how the crayfish is territorial and uses violent means to maintain protection of his territory. This implies that crayfish are independent and don't stay with mates and are released on their own at an early age.

Introduction

Small creeks and streams are common types of habitats for crayfish which I am proposing my study on. Crayfish also live in habitats in lakes and swamps. They are also known as crawfish by some scientists. Most crayfish measure from 2-6 inches (5 to 15 centimeters) long.

Crayfish belong to a group of animals called crustaceans. Crustaceans are a group of animals, mostly amphibians, who have a type of shell or skeleton on the outside of their body. Some examples include Sea Crabs, Hermit Crabs and Lobsters. Like other crustaceans, they are covered by a hard, protective structure know as the exoskeleton. As a crayfish grows, it molts (sheds) it's exoskeleton periodically and grows a new, larger one.

The body of the crayfish is divided into three main sections: (1) the head, (2) the thorax and (3) the abdomen. The head an thorax are rigid but the abdomen has flexible parts. Five pairs of legs extend from the sides of the thorax. The front pair are shaped into large claws. Several small reproductive structures called swimmerets hang from the abdomen.

Crayfish eat many kinds of plants, as well as snails, tadpoles, and fish. They are generally more active at night, returning to safety under a stone or inside their burrow during the day. When they are molting, crayfish lose the protection of their exoskeleton. As a result, they typically hide from their enemies for several days until a new exoskeleton hardens. In North America, crayfish are a favorite food of small mouth bass and other sport fish, and so they are often used as bait by fishing enthusiasts.

Crayfish are a popular food in some parts of the world, particularly the southern United States and the Scandinavian countries. In the United States, especially in southern Louisiana, crayfish are harvested from their natural habitats and raised on commercial "farms."

Crayfish vary in color from white through pink, orange, and brown, to greenish black and dark blue.

The body is divided into sections, or segments. The front part of the body is rigid, but the back part, or abdomen, has moveable segments. The crayfish has five legs on each side of the body. The two front legs are shaped into large, sharp claws, or pincers. They are similar to those of the lobster, and are used to capture and hold the prey. The four other pairs of legs are used for walking. There are also structures used in swimming, called swimmerets, under the abdomen of the crayfish. The crayfish also has two long feelers, or antennae, and two shorter ones.

The crayfish has burrowing habits which may destroy cropland or weaken levees and mill dams. One kind digs down to wade in damp meadows and throws up clay "chimneys" in the process. The crayfish is a fighter. If it loses and eye, or one of it's walking legs or one of its claws in battle, anew member soon grows in it's place.

Scientific classification- Crayfish belong to the order of decapoda. North American species belong to the families Astaciday and Cambaridae.

Materials and Methods

The object of the study will be to see exactly how the specimen will react with each other. I want to see behavioral differences and how they act independently. My hypothesis is that they won't take on to each other nicely. I think that when they come close to each other they might start to fight. My project will consist of temporarily catching two crayfish to participate in my study. The study site will be containers with the specimen in them most likely at my house. I will attempt to catch them from the creek in Nottingham Downs park or buy them from a local bait shop. To catch the crayfish I will use a meat bait of some sort to lure them and capture them in creek. The best place to hide bait is by rocks because they normally live under rocks during daytime. When the four are caught or purchased I will make an overall observation of them. I will measure the length of they're body, the length of their claws and legs. In the observation I will tell color and what ever I think is necessary. The main study will be taken in a pre made environment such as a fishbowl with rocks and dirt to try to simulate the normal habitat. The study will take place over three weeks with daily observations and weekly reports. The daily reports will consist of records of changes in habitat, shedding of the exoskeleton and any noticeable changes in appearance. The weekly reports will be a sum of the daily reports of the week and another measuring of all the things listed above. The specimens will be fed daily with vegetables and meat.

The study is basically trying to note the territoriality of the crayfish and how they relate to other individuals in a enclosed habitat and in the final article the results will be displayed.

Results

To start the project off, I called local bait shops and found on that sold crayfish. I did buy the crayfish and they turned out bigger than I expected. There were four of them. Three of them were regular sized and one was much smaller. I got them and put them in two separate containers. I named them and did an overall observation. The first specimen was the smallest. He was pretty much normal with no varying marks or missing limbs. He was the calmest and because of his small size he was attacked more than any other specimen. He used his ability to jet backwards for defense against another individual. The next specimen was of normal size. He had the most varying marks. First, he only had one pincher which made it harder for him to defend him self. He was in the same bowl as the small one so he had to fend off some attacks without much trouble. He also only had one antenna which didn't allow him to feel around as well but he did OK. The first two were in a Tupperware container. It was 10"x 10"x 6" and filled with tap water. There was also a rock in the middle for separation. Most of the time the two stayed separated not interacting at all. Sometimes one would crawl up next to the other one but it would be broken by fierce competition. When I tested direct confrontation, I would put them right next to each other or behind or on top of one another. When it was the small one on top, he would jet backwards and go crawl into the corner. When the big one was on top he would reach down and pinch at the small one until it jet away. To summarize that experiment, the crayfish would defend themselves against any confrontation they encountered in the time they were in the bowl.

The second experiment ran a bit differently. I had two crayfish in this one. But the container was bigger. It was an actual fish bowl 13 inches in diameter. The two specimen were of normal size with no varying marks or missing parts. The way to tell them apart is the color of them. One was red and the other was brown. In the last one both were brown but size would tell them apart. These two were very hostile towards each other. The extra space made more room for separation. But these two would go at it for no reason. The red one took an offensive toward everything including it's environment. When I used tongs to pick him up he would snap and pinch at it. This experiment really proved my hypothesis that adult crayfish really do take a hostile approach to any confrontation show how they defend there territory and themselves in the wild.

Conclusion

This experiment opened new doors in the understanding of freshwater amphibians. I choose the project because when I was younger I would catch crayfish in the creek behind my house. Since then the creature has interested me and I finally got to do a study on them. The study helps me understand the local creatures that are right in my back yard. I think it's neat how a whole world is living right behind me that I didn't have much idea about. As for the results, I thought they were interesting. The fact that they defend themselves in such a barbaric matter is fascinating. Also how they keep independent as I observed is a interesting fact. I didn't test this but I'm curious how they mate in the wild if they defend themselves like that.