Hermit Crabs as Pets

By now, reading all about hermit crabs and seeing where they live may have you pretty interested in getting a hermit crab as a pet. I can tell you that hermit crabs make wonderful pets! They are very cute and busy animals, always on the move climbing, eating, and interacting with each other. They are also disease-free (they don't carry bacteria like reptiles do), very clean, and low-maintenance pets. They are also widely available through pet stores and other outlets. Here are a few things to consider before getting your pet.

Hermit crabs have needs, just like other pets. Hermits evolved in a specific environment and therefore need specific things found in their original environment to stay healthy and happy. Here are a list of some of the things you will need to buy for your hermit:

• A Place to live - Hermits need some kind of enclosure that is big enough for them to have a little space to move. Don't skimp for your new pet, get one that is nice and large. Fish tanks work well, as well as reptile terrariums, but don't feel like you need to buy something. If you are good at making things, you can build one out of plexiglass or whatever else is handy.
  
• Something to dig in - Hermit crabs love to dig! And it is very important for their biology as well. They will dig burrows at night or during the day to keep cool and as a safe place to molt their exoskeleton when it is time for them to grow (very important!). Hermits live on beaches and slightly inland, so get the appropriate dirt: sand mixed with coconut mulch or the like which also serves to absorb moisture to keep their home humid. This stuff is sold in pet stores, and T-Rex (carried at Petsmart) has several soil types that are perfect for your crabs. Give them plenty, too. They should be able to bury and cover themselves with at least 3/4" of dirt! You should also change this occasionally to keep it healthy and clean (every 6-8 months).
  
• Stuff to climb on - Hermits are pretty busy animals and the more you give them to climb on, the busier they will be! There are all sort of stuff available for this purpose.
  
• Food - Get them good crab food at the petstore, but also you can give them other fruits and veggies as treats. Crabs love tropical fruits like coconut, banana, mango and papaya, but they also really like apples, cashews, and carrots.
  
• Temperature and Humidity - Hermits evolved in tropical environments, so we need to keep their home as close to those environments as possible so they stay healthy. A thermometer and a hygrometer (measures humidity) are absolute musts to make sure you know what kind of conditions they are in. Hermit crabs hate the cold but can also overheat easily, so keep them between 75°F and 85°F. You can use a heating rock or a lamp to warm them up if your house or classroom is too cold. Humidity is also extremely important because hermit crabs breathe through very thin parts of their exoskeleton which lose water very quickly to try air! Humidity should stay between 60% and 80%. Long-term exposure to low humidity will cause your hermit to die. :(
  
• Fresh and sea water - Hermit crabs may live on land, but they never stray too far away from a water source. They carry water in their shells to prevent dehydration from breathing. Make sure your hermit crab has fresh water everyday, but they can't drink tap water. There are dechlorification kits available to help make tap water safe for hermits to drink! Also, people don't think about it, but many species of hermit crabs need a source of seawater as well! Seawater has calcium in it, which helps to build up their exoskeletons after they molt. It also has a lot of salt they need to keep healthy. Give your crabs a source of seawater too, you can find kits at the pet store for this as well.
  
• Extra shells - Hermits spend a lot of time in their shells and are very picky when it comes to which house they prefer. Give your crab a lot of options. You'll notice that it will examine every millimeter of a potential new home as it turns the shell over and over before deciding whether or not to make the switch. If it does, then it will line them up and quickly hop into the new one. You also might notice that they will switch back and forth between shells, taking each for a "test drive" before settling on the perfect one. New shells are also important because each time a hermit molts, it grows. Having a few slightly bigger ones will allow your hermit to make a move to a bigger place before actually growing to fit in!
  

Hermit crabs are a social species. Hermit crabs have been studied by biologists for a long time because they are social animals. If you are getting one, you might as well get two or three! It takes no more work and costs very little extra. Plus, you and they get the benefits of having more friends!

Hermit crabs can live a long time. In fact, they can live much longer than dogs and cats. Well-cared-for hermits can live up to 30 years (depending on the species), so it's important to keep them healthy and happy!

Hermit crabs are low-maintenance, but won't bark or meow when they need something. This is probably the hardest part for me. Like plants, hermits won't complain when the humidity is too low or their water needs to be changed or they need food. In fact, they are a bit harder than plants because they don't start to wilt if they have trouble! So, to keep them happy, you have to make sure they need everything before they start showing signs of being unhealthy. The best way to do this is to keep a schedule of what needs to be done on a calendar. This is also a good way to divide up care so your sister or brother or classmates can all help care for the hermit crabs together!

I love hermit crabs as pets, and they are great pets for almost everyone. They do require work and commitment, so don't buy one before you consider all the things you need to do for your little hermit before you get one (or several).

Have fun!

Back in the US

After a few hectic days and the end of the strike in Tahiti, I'm back at home. I also traveled home with seven hermit crab friends, three Strawberry hermits and four ruggies. I managed to get some of my goals accomplished, but a few weren't. That's part of doing things in the field, sometimes things just don't go the way you want them to!

I will have a few more posts on what I did over there, but for now, I'm resting after traveling for 24 hours. More to come!

How to Collect Stomatopods

Animals live in some crazy places. Up high on mountains, down in the depths of the sea, underneath antarctic ice. Life, through evolution, has found a way to live in just about every extreme environment on Earth (and possibly beyond). To study these animals, often biologists have to go to some of these crazy places, so biologists are also hikers, mountain climbers, sailors, and divers.

The animals that my friend Molly studies are stomatopods, or mantis shrimp. They come in a lot of different sizes and colors and live in different places in the ocean, but the species that she studies lives in the sandy-bottoms of the back reef on tropical islands. The sandy-colored males and pink females live in burrows that they dig that are shaped like the letter "U" and up to 12 inches deep. To study them, she needs to take them back to California, and to do that, we need to dig them up. Since they live under the water, we do this SCUBA diving.

SCUBA stands for "Self-Contained Underwater Breathing Apparatus," and is a way for people to spend some time under the water and sometimes go very deep to study and enjoy marine life. You saw all the equipment for diving in the first Packing for Moorea video. Here we will be using it to collect Molly's stomatopods!

Step 1: Find their burrows

Once you've geared up and jumped in the water, you need to find a stomatopod burrow. Stomatopods like to stalk their prey from the entrances of their burrow, and their little white eyes look just like two more sand grains on the surface. These holes are flush with the surface and look almost like two paper-punch holes that sit about 4-8 inches apart. Sometimes, there are a lot of holes and you're not sure which ones match up, so you have to make a guess. Here is a picture of a stomatopod burrow:



Step 2: Dig and dig and dig...

The best way to dig up a stomatopod burrow is to start by digging on either sides of the two holes so that the sand falls away from the burrow itself. That way, you can follow the burrow holes as you dig and tell when you've reached the bottom of the burrow (without the stomatopods getting scared and swimming away). Here is a burrow that I've partially dug up:



You have to keep digging until you see the burrow bend into a U or otherwise, you won't get the whole things, and your stomatopods will get away!

Step 3: Put the burrow in a plastic bag

The way we collect and transport stomatopods back to the lab is in a plastic zipping bag, like your parents might use to store vegetables or meat in the freezer. When you get to the bottom of the burrow, you take your shovel and scoop as much of the sand in the bottom of the hole (hopefully this includes the burrow) into the bag and zip it shut as fast as you can. I'm not always quick enough, and so sometimes I have to chase the stomatopods around and try to scoop them in the bag if they get out. Here is a bag full of a family of stomatopods (a male, a female and eggs):



Step 4: Transfer back to lab and put into cups

When we are done diving, we bring all the bags full of sand, water, and stomatopods up on the boat and drive back to the lab. From there, Molly has to sort out and catch the stomatopods with a turkey baster and put them in cups with some sand. They quickly dig new burrows. When it's time to fly back to Berkeley, she'll put them in plastic tubes and make sure that they have new air on the way back home. They do really well like this, even though it seems like the would be pretty cramped in a tube!

Molly and I both think this is pretty fun work!

Questions - part 2

Here are some new questions and answers for Mrs. Waldrop's class!

Sean asks, Is using the anemometer fun? Is it working right?

The anemometer is pretty fun to work and setup. Taking data is a little boring though, like you saw in the video it is a lot of sitting around and waiting and clicking buttons on the computer. But I am hanging out in a pretty nice place, so it's not too bad at all.

As far as working right, it has been mixed. It is pretty flaky sometimes, the program that runs and takes the data from the anemometer has been not working properly all the time. I sometimes have to close it and open it again so that it saves the way it should, and that is annoying. The thing that has been the worst problem is battery life of the computer, which is around 2.5 hours. I didn't think about this when I was packing and didn't get an extra battery, so I can only use it for that long even though I stay on the motu for usually 4-5 hours at a time.

Maria asks, How do crabs see?

Crabs see a lot like we see. They have eyes like us that use lenses to focus light onto cells that send signals to their brain. But they also see differently. They have compound eyes (like flies) which basically means instead of having one lens per eye (like you), they have a lot of lenses that go all the way around their eyes. This makes it easier for them to see things move, which is really useful if you don't want to get eaten by something! But they are not as good as we are at making out details. Crabs would need some crazy reading glasses!

Emily asks, How many different species of crabs are there?

There are two big groups of crabs that are related to, but a little bit different from, each other. Together, they have about 850 species. Crabs are part of a really big group of animals known as crustaceans. Crustaceans are all things with segments that have exoskeletons and are usually marine (but there are some that live on land). There are about 200,000 species of crustaceans, making it one of the largest and most diverse group of animals alive!

Keri asks, What is the weather like?

French Polynesia is in the southern hemisphere (it is below the equator). It is winter right now here, so it is a little colder and drier than it would be if I were here during November to March. It still rains a lot (like on Sunday!) and is very humid. It is about 80 degrees at night and 85 during the day, so I get to wear shorts and flip-flops everywhere and still be warm. It is not too windy, but last year I was here in July when the trade winds start blowing, and it can be very windy then. I like the weather, except when it rains a lot.

Sarah asks, How many babies do crabs have at once?

Crabs are different than mammals like people or dogs. When they reproduce, they lay eggs, kind of like chickens. Except they lay between 20,000 and 500,000 eggs at a time! Also like chickens, the mom crab will protect her eggs and carries them on her belly until they are ready to hatch. When they are, she shakes her tail and the new tiny babies, called larvae, swim away to grow in the water.

Great questions, y'all! Keep it up! And if you're not in Mrs. Waldrop's class, you can still leave your questions in the comments or email me at lwaldrop[at]berkeley[dot]edu.

The Mis-Adventures of Field Work

I haven't posted in a few days because we are very busy here in Moorea trying to get some last things done before I leave on Tuesday.* Don't worry, I will post some in the following days about collecting stomatopods (mantis shrimp), the motus, and an interview with one of the graduate student scientists who is also doing research at the station. But for now, I wanted to tell you about what happens when things don't quite go as planned when you're doing work in the field.

As anyone who has ever had a picnic rained-out can tell you, doing anything outside is sometimes risky. There are a lot of things you can't control outdoors like the weather. This makes trying to do science, which relies on being able to control as many things as possible during an experiment, sometimes very difficult. You can plan and prepare for things to not work (having extra things in case one breaks, having alternate plans and more time in case something happens), but some things you just aren't expecting and wouldn't even think about happen! Friday and Sunday were two of "those days."

On Friday, we went to the motus (small islands) off the coast of Moorea so I could gather more wind measurements and collect some small hermit crabs. When I got there, I set up the computer and the anemometer, just like always, and started to collect some data. What I wasn't expecting was that three dogs came by with a woman who wasn't watching them very closely. These dogs were very friendly but huge and not well-trained. I got jumped on and scratched by one very excited dog, and since I was in a bathing suit, it was pretty painful. I have some deep scratch marks and bruises along the inside of my left leg now, but luckily they are healing nicely. The dogs also were playing in the water and the sand. Now, sand and saltwater don't tend to make computers and anemometers very happy, so I had to work very hard to cover them up with my clothes so they wouldn't get sprayed with sand and also to try to lure the dogs away from that area. And at the same time, take the data that I needed! It went very slowly because the dogs liked me a lot (even though I was telling them to shoo!) and they decided to hang out for a couple hours. By the time they left, my computer battery was dead and I had only taken one set of measurements when I really needed three. Sometimes, as I learned that day, things happen that you can't predict, and you have to just make-do the best you can!

Sunday was quite the adventure as well. Molly and I were diving to collect more stomatopods, and our morning dive went fine. In the afternoon, it started to pour rain (as it does in the tropics), which wasn't a big deal because we were going to be underwater anyway. We loaded our gear into the boat and drove out to the dive site. We did our dive (it was still pouring rain) and then started to go back to the station. Well, our boat had other plans. About half way home, the motor stopped working. We were stranded in the water, and it was getting dark! Luckily, we were shallow enough that we could anchor the boat and swim back to shore. We walked back to the station in our wetsuits (and got some pretty strange looks from people driving by), then got someone to tow our boat back to the dock with another boat. We were very wet, pretty miserable, and extremely tired, although nothing a hot shower, dinner, and a good night's sleep can't fix.

Some people say that science is boring. Those people are not field biologists. Science in the field can be dramatic, scary, and dangerous. It is also thrilling and exciting when you figure something out for the first time or collect some animal that no one has ever seen before or see an animal in its natural environment do something that defies easy explanation. I love science because it is unpredictable and exciting, although sometimes I wish that it would rain a little less.


* I should say "might" leave on Tuesday because the fire-fighters in French Polynesia are on strike, the airport is closed, and all flights to and from Tahiti have been canceled. I might have to stay a few days longer than planned.

Moorean Science Fair

On Monday I was lucky enough to be able to attend the GK-12 Moorean Science Fair, put on by the fifth graders of Moorea. It was pretty fantastic, and I took a lot of pictures and talked to a lot of interesting kids. We couldn't talk too much because I don't speak French, and they didn't speak English! But we did talk a little bit through Molly or Rayo, a Tahitian lady who was helping Molly out with the fair.

The kids on Moorea learn a lot about the plants and animals that live on and around their island. They learn about invasive species that threaten the natural plants and animals, too. They learn about the ecosystems in and around the island that the plants and animals live in.



Here are some posters that they drew. You can see that they have a lot of tasty fruits, and they are learning about where they live and the names of the plants in both French and Tahitian.




They also learned about the marine animals that live there. On Saturday, Molly, Sho, and I did a dive to collect some animals for them to see. We collected some sea cucumbers, a pin-cushion star (see photo), a black pearl oyster (see photo), and a slipper lobster (see photo). They call the slipper lobster, "cigar del mare" which means "sea cigar!"

They even did some science experiments. In this one, they tested whether or not motor oil would affect the way seeds sprouted. They found that not as many seeds sprouted if they had been sprayed with water mixed with motor oil. This is why you shouldn't pour things like that down the drain!



I had a lot of fun helping out at the fair. And even though I don't speak French, it sure looked like they were having fun too!

First visit to the motu

On Sunday evening, we drove out to the other side of Opunohu Bay and kayaked over to the small islands that are on the northwest corner of Moorea. It is a very short kayak, maybe a quarter of a mile, across a 40-50 ft deep channel. When we arrived, there was a great view of the north face of Moorea with a rainbow.

There were three other researchers with me. Molly, my friend who studies mantis shrimp, spent a little time digging up them and their burrows in the sand flats that had about 2 ft of water over them. We saw a black tip reef shark cruising very close to her, looking for flatfish, and we had to call out "shark!" But Molly wasn't worried, because sharks are actually pretty cool and it didn't want to stick around after it realized we were in the water anyway.

Sho is a post-doc (already has her Ph.D.) working on crab larvae. She and I went out to the end of the motu to set up a light-trap to catch larvae, which are attracted to light like moths. We also saw a pretty cool sunset on the motu.

Pete is an etymologist (someone who studies insects) working with the Moorea BioCode project. He was collecting moths to study their diversity on the island; he also used a light trap to attract them.

I waited until dark and then used a headlamp to walk around and collect large hermit crabs. I saw probably two dozen really big ones, ranging in size from a plum to a baseball! The hermit crabs come out at night to scavenge for food and to return to the sea to fill up their shells with water, which prevents them from drying out during the day. I saw two species that are closely related: the Strawberry hermit and the ruggie hermit.

I still haven't taken pictures of them, but I'll update the blog when I do!