FROGS AND TOADS

Identification
Frogs and toads are amphibians with four legs and no tail. They may have skin that is smooth and moist or dry and warty, but they have no scales or claws. The front legs are short, but the hind legs are muscular and elongated for hopping or jumping. The popular distinction between frogs and toads is somewhat artificial; basically, toads are a particular group of frogs. Throughout this chapter, the term frog will be used to include toads. North American frogs range in body size from the 11/16-inch (1.7-cm) little grass frog to the 8-inch (20-cm) bullfrog.

Range
At least 85 species of frogs are native to the United States, and there are three well-established exotic species. There is no part of the country that is not home to at least a few species.

Habitat
Frogs occur in almost all non-marine habitats. “True” frogs (genus Rana) and treefrogs predominate in the more humid east. In the drier Great Plains and western regions, toads and spadefoots are typically more numerous. Whereas some species are seldom found far from permanent water, others return to water only seasonally to breed. Some desert species spend most of their time beneath ground, venturing to the surface only following rains.

Food Habits
Most frogs have a two-phased life cycle, including an aquatic larval form (tadpole) and a terrestrial or semi-aquatic adult form. Tadpoles are primarily herbivorous, feeding on algae and decaying organic matter. Adults, on the other hand, are carnivorous, consuming almost any prey that can be overpowered. Although the diet consists primarily of insects, crayfish, and other invertebrates, larger frogs occasionally take snakes, other frogs, fish, mice, and small birds. In natural habitats, fish usually comprise less than 5% of the diet of the bullfrog. On fish farms, as many as 30% of bullfrogs have been found to contain fish.

General Biology, Reproduction, and Behavior
Although some species spend most of their adult lives away from water, most frogs native to North America must return to water to lay eggs. Some species breed during the cooler winter and spring months, whereas others breed during the warmer months. Following rain, males begin calling from breeding sites. Each species has its own distinctive call, and females respond only to the calls of their own species. Several recordings of frog calls are available, and four are listed at the end of this chapter.

Eggs are fertilized by the male as they are released by the female. Hatching occurs a few days later. The aquatic tadpole stage may last as little as 2 to 3 weeks in some species of spadefoots or as long as 2 years in some northern populations of bullfrogs.

Frogs are typically most active at night. Some species aggregate around artificial lights and feed on the insects attracted there. Frogs are an important component of the vertebrate food chain and are consumed by a variety of predators, including fish, snakes, turtles, wading birds, raptors, skunks, and raccoons. Individuals of many species may live 12 to 15 years, but life expectancy is much shorter in the wild.

Damage and Damage Identification
The greatest potential for economic damage is at fish farms and hatcheries. Tadpoles compete for food intended for fish, and adult bullfrogs may actually feed on the fish. Losses are said to be high at some fish farms. One study suggested that the mere presence of high densities of tadpoles retarded reproduction of fish. Although the bullfrog is native to most of the eastern United States, its introduction to portions of the west has seriously affected some native species. In at least some cases, these introductions may have resulted from the unintentional release of tadpoles during fish-stocking programs. Considerable labor is required to separate tadpoles from loads of fry.

Only in rare instances do frogs cause any significant damage. Some species (toads, for example) produce skin secretions that are toxic if ingested. This does not normally present a problem for people, and pets usually learn to avoid such frogs. A few species (giant toad, Colorado River toad) produce especially copious or toxic secretions, and there have been cases in which dogs have died after biting them.

The noise sometimes produced by large breeding choruses of frogs following heavy rains can be annoying to humans. These aggregations usually last only a few days, however, and seldom warrant control. Similarly, complaints sometimes arise when large numbers of young frogs leave the ponds en masse, but the frogs disperse quickly, and the “problem” will take care of itself in a few days.

Economics of Damage and Control
Frogs eat many insect pests. With the exception of fish farms, control measures for frogs are seldom warranted and, in most cases, should be discouraged. On fish farms, the economic damage depends in part on the unit value of the fish produced. There is data suggesting that a 350-pond farm that produced goldfish might sustain $42,000 in annual losses to bullfrogs, whereas the same facility might sustain only $12,600 in losses if it produced golden shiners, a less valuable species. It follows that losses might be still higher on farms specializing in valuable aquarium fishes.

Legal Status
Laws pertaining to frogs vary from state to state. Some rare species (for example, Houston toad, Wyoming toad, Pine Barrens treefrog) may be fully protected under federal or state laws. Seasons and bag limits may apply to other species (bullfrogs, for example). Permits to remove frogs that are causing damage are available in some states. Contact your state wildlife department to determine the legal status of frogs in your area.


Damage Prevention and Control Methods

Exclusion
Around hatchery ponds, keep vegetation closely mown and remove emergent vegetation and other types of cover.

Habitat Modification
Minimize emergent vegetation. Drain ponds and borrow pits where appropriate and permitted.

Frightening
Not applicable.

Repellents
None are registered.

Toxicants
None are registered.

Fumigants
None are registered.

Trapping
Funnel traps.

Capture
Capture by hand or gig at night. Egg masses may be removed with a fine-meshed net.

Shooting
Allowed in some states, but often not safe in areas requiring control. Some states permit shooting only during daylight hours.




ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).