Octopus (33 page)

There are two main techniques to ensure that captive octopuses remain captive. One is to leave a lip around the top of the tank with a material that an octopus cannot get a grip on. The other is to seal the lid on, making sure there are no spaces the octopus can pry open. The first method is popular with public aquariums. They often use large tanks and display the octopuses in a way that hides the equipment. This approach leaves them room to put a barrier around the top of the tank to keep the octopus in. This barrier must be large enough that the octopus cannot reach across it and grab onto something on the other side, and must be coated with a material that octopus suckers cannot grip. For large octopuses, Astroturf is often used. But this material doesn't work for smaller species with smaller suckers, which are able to grab onto the blades of fake grass. Open-cell foam, screening, and rough synthetic cloth will work. Most home aquariums and research tanks use the seal-it-shut method. Acrylic lids are easy to custom make. Holes can be drilled for the intake and return tubes of pumps and for air lines. Clamps, weights, or Velcro straps can be used to secure the lid to the tank.

Octopuses can escape through almost any pipe, fitting, or filter in the tank that is big enough for them to squeeze through or weak enough for them to pull apart. Octopuses are born with the ability to get into and out of things. Even hatchling octopuses can get into places they don't belong; hatchling octopuses crawled up the inside
-in. (3 mm) air line tubing that was used to send water into the octopus rearing chamber. Octopuses like secure, dark, narrow places for their homes: under-gravel filter beds or behind fiberglass backdrops are ideal. Under-gravel filters should not be used in the octopus tank and all backdrops, pipes, drain holes, and plumbing to and from the filter should be secured, sealed, or covered with material that can't be held onto. Not only does the aquarium and filtration have to be octopus proof, anything else that is added to the system also needs to be secured.

Not only can octopuses hide behind things in tanks, they can also open valves, pull corks out, and open containers, especially if they are large.
Most folks don't have the space required for a giant Pacific octopus, but the curator of fishes and invertebrates at the Oregon Coast Aquarium does. A truly large giant Pacific octopus was on display in a 200,000-gallon (790,000-l) tank; she weighed over 100 lb. (45 kg). The aquarium installed a small ROV (remote operated vehicle) in the tank. For a fee, the public could guide it around the aquarium. According to the manufacturer of the ROV, it takes a long-handled strap wrench to open its 6-in. (15-cm) acrylic dome back port. One morning, the octopus grabbed the ROV, unscrewed the back port, and proceeded to gut the electronics. After all, she had been given enrichment items like lidded jars, so why not try this? Saltwater flooded into the housing and destroyed the circuit boards and color video camera. Finding no food inside, she released the ROV fairly quickly. Fortunately, the unit was not energized so the animal was not shocked. Only some of the ROV was salvageable.

What to Feed Your Octopus

All octopuses are generalist carnivores. In the wild, they primarily eat crabs and mollusks, but individual octopuses can have preferences. We have had success feeding octopuses live fish, crabs, and shrimp, and we have had success occasionally feeding them thawed, previously frozen crustaceans, fish, and squid. To coax a reluctant octopus to accept frozen shrimp, thaw the shrimp and then skewer them on a shish kabob skewer. Then “swim” them around the tank. The motion usually attracts the attention of the octopus. When a new octopus is adjusting to captivity, we usually feed it live food for a month or so while it settles in, before switching to frozen food.

Newly hatched octopuses will only accept live food. They will not grow on frozen or prepared food. Amphipods or mysid shrimp are ideal first foods for hatchling octopuses. Adults can be often fed a variety of frozen seafood that can be purchased at your local grocery store. Once acclimated, an octopus eats a surprising amount of food. There is some anecdotal evidence that a long-term diet based on freshwater animals, particularly feeder goldfish, can cause liver problems in octopuses. Until further studies are completed, we recommend only offering marine-based foods.

A healthy octopus has a healthy appetite. Newly purchased octopuses may still be shy, but most will quickly learn where the food comes from. An octopus that is offered a live marine shrimp and crab and doesn't eat it for days is likely very sick. How much to feed your octopus? About 5 to 10 percent of its body weight per day is the scientific answer, but then you have to know the weight of your octopus, and obtaining that is a challenge in itself. The best method is to carefully watch how the octopus responds to the food you give it. If the octopus takes but only eats part of what you offer, you are offering too much food and should cut back.

Remember, most species of octopuses are nocturnal, a plus if you are a college student. If you are a night owl, we advise feeding at night; if society
forces you to wake up early, try feeding early in the morning. In our experience, feeding at a regular time almost guarantees that you will see your octopus at least once a day, true for most octopus species.

Octopuses should be kept in a tank dedicated to them. They view most fish, crustaceans, and mollusks (including smaller octopuses) as food, though there are a few other animals that can be kept with them. Echinoderms such as sea stars, brittle stars, and sea urchins are usually safe tank mates. Reef tank inhabitants such as corals and sponges should be safe for your octopus, although he or she may not approve of your interior arrangement and will do some redecorating. Large, heavy rocks are less moveable.

Octopuses do not need any specialized spectrum or high-intensity lighting, a definite advantage for those of us who are on a budget or are still confused by the myriad lighting possibilities and their ramifications. Given a choice, an octopus probably prefers no lighting for its tank. But of course we humans do like to view our pets. A compromise of one or two standard inexpensive white fluorescent bulbs will work just fine. We prefer to turn the lights on and off with a timer, to add one more constant to the system.

Enrichment

Enrichment, practiced with large octopuses in the Seattle Aquarium, is the animal husbandry practice of enhancing the quality of captive animal care by identifying and providing species-relevant environmental stimuli necessary for optimal psychological and physiological well-being. Enrichment has been a hot topic in animal care in the past decade. But until recently, enrichment had been only applied to vertebrates, especially mammals. Roland and James have been among the first to argue that all animals live in complex environments, and therefore all animals should be considered for enrichment when they are kept in captivity.

We used the giant Pacific octopus as an example of an invertebrate that would benefit from enrichment. At the time, we didn't have any scientific evidence that enrichment for these invertebrates mattered. However, we argued that in the absence of evidence, it was best to assume that enrichment could benefit all captive animals. Although there has still been no study on the effect of enrichment in octopuses, shortly after we published our arguments for including enrichment for animals other than vertebrates, a 2000 study by Ludovic Dickel proved that cuttlefish raised in
enriched environments develop better mental ability than those raised in unenriched environments.

Enrichment comes in many forms. One form is a complex environment with hiding places and things to interact with. The primary predators of octopuses—marine fish, mammals, and birds—are all visual predators. Cephalopod adaptations reflect the pressure of these predators. Providing an environment where the octopus can hide, can dig holes, and move rocks is one way to provide enrichment. Materials safe to use as enrichment and decoration in marine aquariums include live rock (usually corals, from the ocean), limestone, or other aquarium-safe rocks, seashells, PVC pipe caps, and glass jars. Octopuses should never be kept in environments where they cannot hide in a dark lair if they wish.

The size of the aquarium is also important. Small species such as the Florida pygmy octopus can be kept in 10-gallon (38-l) aquariums. Mediumsized octopuses such as the Caribbean reef octopus are best kept in aquariums that are at least 30 gal. (114 l). Larger octopuses should be kept in aquariums that are at least 55 gal. (200 l). The giant Pacific octopus can grow to 100 lb. (45 kg) in captivity. These huge octopuses are too large for most home aquariums, since they should be kept in systems of at least 500 gal. (2000 l). Keep in mind that there are many different species and that size at maturity varies considerably even within a species. Also remember that a young, healthy, well-fed octopus will grow considerably. No harm can be done except to your wallet by having a tank that is too large. During a power outage, a large tank will be depleted of oxygen much slower, and a large volume of water may effectively dilute ink. While smaller tanks than those recommended have been used, especially small sterile tanks used by researchers to successfully raise octopuses, we suspect that the animals' quality of life and development are worse (see plate 38).

Another form of enrichment is offering a variety of food. In the wild, animals have to work for their food—they have to locate, capture, and prepare it. Live food is enriching, since the octopus has to capture and process it. Also, food can be placed in puzzle boxes that the octopus has to pull apart. Recently, many public aquariums have started using both these approaches, to enrich their octopuses and as a display to the public of octopus abilities.

Octopuses are fascinating animals, and with some precautions and patience they can be successfully kept throughout their natural life span in captivity. The large-egged species can even be raised from eggs in captivity.

References

Books, Articles, and Papers

Alexander, R. M. 2003. Principles of Animal Locomotion. Princeton, New Jersey: Princeton University Press.

Ambrose, R. F. 1984. Food preferences, food availability and the diet of Octopus bimaculatus Verrill. Journal of Experimental Marine Biology and Ecology 77: 29–44.

Ambrose, R. F. 1986. Effects of octopus predation on motile invertebrates in a rocky subtidal community. Pubblicazioni della Stazione Zoologica di Napoli, Marine Ecology Progress Series 30: 261–272.