frog farming 00

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                           Commercial Frog Farming
                                     Louis A. Helfrich, Richard J. Neves, and James Parkhurst*

Introduction                                                                                               Edible Frogs
Raising and selling frogs on a commercial basis has                                                        A number of species of frogs, including the green frog
not proven to be successful economically in Virginia                                                       (Rana clamitans), the leopard frog (Rana pipiens),
or elsewhere in the United States to our knowledge.                                                        and the pickerel frog (Rana palustris), are harvested
Although farming for frog legs sounds promising,                                                           from the wild and sold as a luxury food - frog legs - in
operating a profitable frog farm seems to be more of a                                                     expensive restaurants. However, the bullfrog (Rana
myth than a reality. Those few individuals who claim                                                       catesbeiana) has the greatest potential for culture.
to be successful frog farmers generally are distribu-
tors engaged in the selling of adult frogs, tadpoles, or                                                   The common bullfrog, often referred to as the ÒGiant
frog eggs, frequently harvested from the wild.                                                             FrogÓ or ÒJumbo Frog,Ó is the largest native North
                                                                                                           American species, often reaching 8 inches in body
Many Òfrog farmsÓ turn out to be natural marshy                                                            length. Because of its large size, the bullfrog is the
areas, swamps or shallow ponds with abundant food                                                          most preferred and commonly attempted species for
and habitat suitable to the needs of wild frogs. At                                                        farming.
some frog farms, culture methods simply consist of
increasing the shoreline area, erecting a fence to
                                                                                                           Breeding and the Life Cycle
exclude predators and retain the frogs, and stocking
                                                                                                           Bullfrogs lay their eggs in shallow standing water
wild frog eggs or tadpoles. The frogs usually are left
                                                                                                           during the Spring (April and May) in temperate cli-
to raise themselves.
                                                                                                           mates. The large, floating, jelly-like egg mass pro-
Intensive indoor frog culture techniques have been                                                         duced by a single female may cover an area about 3-5
developed for the production of laboratory frogs used                                                      feet square and include from 10,000 Ð 25,000 individ-
in medical and biological research. At present, how-                                                       ual eggs. The eggs hatch in 1 Ð 3 weeks, depending
ever, it is doubtful that these indoor culture tech-                                                       on the water temperature, into larval frogs that com-
niques can be applied economically to the culture of                                                       monly are called tadpoles. Bullfrog tadpoles chiefly
large frogs for human consumption.                                                                         are vegetarians, spending most of their time grazing
                                                                                                           on microscopic plants and bottom algae.

                                                                                                           Slow Growth
                                                                                                           Frogs and other amphibians are coldblooded animals
                                                                                                           that grow slowly, not a particularly desirable trait for
                                                                                                           farming. The rate of growth of the bullfrog tadpole
                                                                                                           varies with the climate, length of the growing season,
                                                                                                           and available food supply. Even in temperate cli-
                                                                                                           mates, it may take a year or more to transform the
                                                                                                           tadpole into a young bullfrog. Another year or more
*Extension Specialists, Department of Fisheries and Wildlife Scinces, Virginia Tech

                                       Virginia Cooperative Extension programs and employment are open to all, regardless of race, color, religion, sex, age, veteran status,
                                     national origin, disability, or political affiliation. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative
                                              Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department
                                                 of Agriculture cooperating. J. David Barrett, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg;
VIRGINIA POLYTECHNIC INSTITUTE                                   Lorenza W. Lyons, Administrator, 1890 Extension Program, Virginia State, Petersburg.
     AND STATE UNIVERSITY                                                                    VT/028/1101/1.5M/221612/420255                                                          VIRGINIA STATE UNIVERSITY
is required to produce a mature, marketable-size bull-       behavior firmly limits the number of frogs that can
frog. Therefore, in the mid-latitude states like Virginia,   coexist in a small area. Available shoreline area (the
development from egg to a mature bullfrog of har-            ratio of land to water edge) is a critical factor. The
vestable size may take over 3 years, even under ideal        total size of the pond is not as important as shoreline,
conditions.                                                  because frogs use shallow shorelands to rest and feed.
                                                             Large expanses of deep, open water are seldom used
                                                             by frogs.
Artificial Feeding
Feeding is the critical process in culturing frogs suc-      Regularly shaped round or square ponds have less
cessfully. Poorly fed frogs are susceptible to disease       shoreline in proportion to area than small irregular-
and frequently resort to cannibalism (eating younger         shaped ponds. Therefore, increasing the length and
bullfrogs and tadpoles), thereby reducing the har-           irregularity of the shoreline by constructing long nar-
vestable population. Frogs and tadpoles reared out-          row ponds with numerous islands, shallow bays, or
doors will obtain some natural foods, but for intensive      coves will increase the carrying capacity of frogs in a
commercial culture of frogs in high densities, supple-       given area. Some growers increase the amount of
mental food must be supplied.                                shoreline, by constructing ponds as a series of narrow
Bullfrog tadpoles are mainly vegetarians and will con-       ditches.
sume most soft plant matter and some animal feed.
                                                             Ponds should be deep enough to protect the adult
Acceptable tadpole foods include such items as boiled
                                                             frogs and tadpoles from extremely hot or cold temper-
potatoes, meat scraps, or chicken viscera. Recycling
                                                             atures. Accordingly, the depth of the pond must vary
butchered frog scraps is a convenient way to reduce
                                                             with the climate. In the southern U.S., water from 1-2
food costs, but may transmit disease.
                                                             feet deep is adequate, but in the North, much deeper
Once the tadpole has metamorphosed into the adult            water (6-12 feet) may be required to assure the over-
frog (i.e., the legs are fully developed and the tail is     winter survival of frogs hibernating in the bottom
absorbed), feeding becomes especially difficult. Adult       muds. Most of the pond should be shallow (2 -12
frogs feed exclusively on moving animals, primarily          inches deep), because frogs normally rest and feed in
small insects. They generally refuse to eat dead or at       shallow waters.
least non-moving food. Japanese researchers report-
                                                             Predatory fish, snakes, snapping turtles, cats, foxes,
edly have been able to induce frogs to eat dead silk-
                                                             and water birds that feed on adult frogs and tadpoles
worm pupae by using small motorized trays that
                                                             should be fenced out. Enclose the pond with a mesh
mechanically roll the silkworms back and forth to
                                                             fence about 3 feet high. A vertical fence, topped with
simulate live animal motions.
                                                             wings, one inclined outward and the other inward,
Live animals, such as minnows, crayfish, and insects,        will exclude predators and keep frogs in. Birds are
also are placed in these trays to condition the frogs to     especially difficult to exclude, but, in small ponds, a
feeding from these mobile platforms. Although this           wire net stretched above the shallow shoreline area
technique may work, most American frog farmers rely          may offer some protection. Some loss due to predato-
on stocking or attracting live food animals. Smaller         ry animals should be expected.
species of frogs, tadpoles, crayfish, and minnows can
be stocked as food items for bullfrogs although the          Water Quality and Quantity
expense of live feed is high.                                An abundant supply of high quality water must be
                                                             readily available to the frogs throughout the growing
The use of strong flood lights to illuminate the shore-      season. For good growth, water temperature should
line at night will attract flying insects and provide        remain relatively constant at 20¡ to 26¡ C. The pH of
additional food for frogs. However, this technique is        the water should be slightly acidic. Dissolved oxygen
not sufficient to supply enough food to sustain the          always should be present because tadpoles, as fish,
high frog densities needed for a commercial opera-           breathe by gills and are dependent on the available
tion. At present, live food, adequate in quantity and        oxygen. Pesticides and other dangerous chemicals
quality, remains the greatest problem for would-be           often are toxic to frogs, and even non-lethal concen-
frog producers.                                              trations could restrict the sale of frog legs for human
                                                             consumption. Pesticides can be distributed widely by
Pond Design                                                  winds and water currents. However, with care and
A mature bullfrog may require as much as 21 feet of          intelligent site selection, most pollution problems can
shoreline as its exclusive feeding territory. Territorial    be avoided.
Geographic Limits                                           Economic Factors
                                                            Good management and operational skills are critical
In aquaculture (farming aquatic animals), successful
                                                            to an aquaculture enterprise. The success of aquatic
results seldom are transferable from one geographic
                                                            farming depends largely on the cost to grow and mar-
region of the country to another. Climate often limits
                                                            ket for the product. Before attempting to raise frogs
aquacultural enterprises. The growing season for
                                                            or any other aquatic crop, the prospective culturist
frogs is longer in tropical than temperate climates,
                                                            should conduct a survey of the local or regional mar-
therefore the potential for frog farming may be better
                                                            kets to determine the current supply, present and
in South America or Louisiana than in Virginia or
                                                            expected demand, price elasticity, extent of competi-
other temperate climate states. Clearly, outdoor frog
                                                            tion, and other socioeconomic factors.
farming in the Northern states would not be advisable.
                                                            Large numbers of wild frogs imported into the United
Other important variables to consider are the lower
                                                            States or captured locally and sold at low prices will
labor costs, greater water availablility, and the high
                                                            reduce the potential profitability of frog farming.
demand in Southern states where frogs, crayfish, cat-
                                                            Market price fluctuations of frog legs are volatile.
fish, and other aquatic animals are traditional foods.
                                                            Prospective frog farmers realistically should assess
                                                            their own financial status because most aquaculture
Harvesting                                                  enterprises require a high initial investment, have a
Techniques for collecting and harvesting pond-cul-          number of associated ÒhiddenÓ costs, and produce low
tured bullfrogs are the same as those used in capturing     realized return on short term investments. Expectations
wild frogs. These methods include nets, hand capture,       of large or easy profits are extremely unrealistic.
spearing, and fishing with a hook and line. Hooks
baited with live insects, earthworms, or artificial lures   As in agriculture, aquatic farming a risky business. A
(a piece of red cloth or yarn) are dangled in front of      number of unpredictable and uncontrollable catastro-
the frog. Spearing and band capture techniques are          phes include prolonged droughts, severe floods, toxic
done most effectively at night, using a bright spotlight    chemicals, intense predation, infectious diseases, and
to momentarily daze and immobilize the frog.                contagious parasites literally can destroy an entire
Obviously, new methods to efficiently harvest large         yearÕs crop overnight. Prospective frog farmers
numbers of frogs need to be developed.                      should be well aware of these and other associated
                                                            risks and be prepared to sustain some periodic losses.
The most common disease of frogs, red-leg disease, is       Future Potential
due to a bacterial infection (Aeromonas), often result-     At present, there is no well-established frog farming
ing from overcrowded conditions. The best preventa-         industry in the United States. Current practices and
tive methods are adequate nutrition and space.              past efforts at commercial frog farming have been
Infected individuals should be isolated immediately,        unsuccessful largely because of physical, chemical,
and treated with antibiotics. In severe cases, it may       biological, and economic constraints. Opinions con-
be necessary to drain the ponds and allow them to dry       cerning the feasibility of frog farming in Virginia
out for several weeks.                                      range from the optimistic to those that maintain it is
                                                            not possible economically.
Considering the current state of the art, frog farming     and other forms of environmental pollution, but the
as a commercial venture appears to have severely           exact causes for the rapid disappearance of frogs and
limited potential. However, as intensive hunting and       other amphibians are unknown. Researchers fear
increased drainage of natural wetlands continue to         extinction of many species of amphibians worldwide.
reduce the wild frog populations, the demand for           This decline will reduce the supply of wild frogs for
frogs may reach a critical point, permitting skilled       food and for farming operations. It also may impose
culturists to profitably farm frogs.                       new regulations and restrictions on frog farming
Declining Wild Amphibian                                   In Virginia and most other states, it is lawful to cap-
Populations                                                ture and possess no more than a few wild native or
Wild populations of frogs, toads, salamanders and          naturalized amphibians for private use and not for
other amphibians are declining throughout the world.       sale. A permit for capturing, holding, propagating,
Scientists suspect greater atmospheric ozone and the       and selling of wildlife, including amphibians, is
increased incidence of ultraviolet radiation, acid rain,   required in most states.

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