The Northern Leopard Frog Is Known to Scientists As the Northern Rana Pipiens

Seeing Spots:

The northern leopard frog is known to scientists as The Northern Rana pipiens. This spotted frog should be one of the most commonly found amphibians in Pennsylvania. Historically, it was. However, recent information gathered in Pennsylvania and in other northern states suggests that the northern leop- ard frog has been declining in our wetlands and along our Leopard Frog waterways. People aren’t seeing “spots” where they should be. Biologists in other states have also noticed that this species by Andrew L. Shiels has declined. In 1996, the United States Fish and Wildlife Nongame and Endangered Species Unit Service began reviewing the status of this species in each of the states where it occurs. The agency is attempting to deter- mine, from a regional perspective, how northern leopard frogs are faring. Early reports are not encouraging. The Pennsylvania Fish and Boat Commission is featuring the northern leopard frog in 1999 as the latest species in a series of collectible nongame patches. We chose to focus on NORTHERN LEOPARD FROG this amphibian because the environmental factors that may be influencing its survival in the Commonwealth are typical of those affecting other species. Consider this frog’s life his- tory to identify and better understand this species. Identification Northern leopard frogs belong to the Ranidae family (true frogs). They get their name from the apparently random placement of spots on their bodies. Other similarly appearing species include the Pennsylvania endangered coastal plain leopard frog (Rana sphenocephala) and the pickerel frog (Rana palustris). Leopard frogs reach a maximum length of about Walke McDonald; graphic-Ted photo-Joe

58 Pennsylvania Angler & Boater Fishing & Boating Memories Last A Lifetime photo-Joe McDonald five inches. Pickerel frogs typically do outlined in black, which are aligned in active hunters, their basic method of not exceed four inches. Thus, overall two parallel rows on the back. Also, the prey capture is ambush. Their perfectly size can be useful in identification. belly and inside of the legs are white on adapted camouflage helps them avoid The coastal plain leopard frog is a northern leopard frog but yellow or becoming the main course in the meal found only in Bucks and Delaware orange on a pickerel frog. of a snake, snapping turtle, raccoon, or counties along the coastal plain near great blue heron. the Delaware River. It displays a white Reproduction While foraging, this species can be spot in the center of its tympanum (ear Like most frogs, northern leopard found a fair distance from water. They membrane) and has a longer snout than frogs attract mates by calling during the are often referred to as “meadow frogs” the northern leopard frog. In Pennsyl- spring breeding period. Both males and because they often forage in wet or vania, there is no overlap in the range of females vocalize. Although they may damp meadows and grassy areas away the two leopard frog species. This begin calling in March, breeding can from open water. Activity levels are makes it easier to distinguish between extend into June. Permanent and tem- greatest during the cooler periods of the leopard frog species. Incidentally, porary ponds as well as areas along the the day, such as dusk and dawn. For a the coastal plain leopard frog is endan- edges of lakes and streams are used for frog, dew-laden grass provides an ideal gered primarily because of habitat loss courtship and egg-laying. Females de- situation for comfortable hunting. and degradation in the relatively small posit up to 6,000 eggs in a jellylike area of Pennsylvania in which it histori- mass. The eggs hatch about 10 days Reasons for decline cally occurs. later with most of the tadpoles trans- Researchers around the world are The pickerel frog is widely distrib- forming into juvenile frogs during July reporting marked declines in the abun- uted across Pennsylvania and can be and August. dance of many amphibian species, in- found sharing habitats with the north- cluding frogs. People have also ern leopard frog. Thus, these two spe- Feeding reported declines of local amphibian cies are often misidentified by the Northern leopard frogs consume a populations with which they have per- casual observer. The most obvious dif- variety of foods. As tadpoles they are sonal experience. We have heard quotes ference between the two is their spot herbivores. Using specially developed such as, “I don’t hear frogs calling patterns. Northern leopard frogs dis- teeth, they forage on aquatic plants and along the river as I did 20 years ago,” or play round spots that are encircled by algae. After transformation into “When I was a kid, we went down to the white or light halos and are not distrib- froglets, they become carnivores and eat pond and caught frogs all the time; now uted in rows on the frog’s back. Pick- almost any small insect or invertebrate you rarely see one.” erel frogs have squarish spots usually they can catch. Although they can be

The northern leopard frog may be what ecologists call an “indicator species.” Its health and survival may reflect the environment’s health. The frog’s apparent decline may be a warning for us to examine closely our influence on the environment.

Fishing & Boating Memories Last A Lifetime Pennsylvania Angler & Boater 59 There is no doubt that these observa- reach ancestral breeding grounds of- photo-Andrew L. Shiels tions are accurate. There have been ten become nighttime mortalities, left many reasons offered and theories pro- on the road as food for crows and rac- posed to explain these noted declines. coons. These losses are not obvious to One of the most obvious is that habitat most people because scavengers often is lost or altered at an alarming rate. In consume the carnage by daylight. Pennsylvania, we have lost a majority of Amphibian road mortality studies the wetlands that were present at the were conducted at the Hawk Moun- turn of the 20th century. All of tain Sanctuary in Berks County in Pennsylvania’s frogs require water and 1997. On seven rainy nights during wetlands in which to lay their eggs so spring and early summer, more than that they may hatch into tadpoles and 100 amphibians (including frogs) per develop into juvenile frogs. Loss of wet- night, representing up to 13 species, land habitat results in the loss of wet- were recorded as mortalities on some land-dependent species such as frogs. three miles of road. When one consid- Even though outright wetland de- ers the vast amount of road mileage struction or degradation is obvious that bisects or borders wetlands and even to the casual observer, some other forested areas in Pennsylvania, the Pickerel frogs (above) can be identified by environmental alterations may be less potential losses of amphibians to the double row of squarish dark blotches or visible. New highways have been built, highway mortality are staggering. spots on the back. The spots are encircled and vehicular traffic has increased on Research conducted in central with dark or black lines. Northern leopard most older highways. Frogs and sala- Pennsylvania has unequivocally linked frogs (below left) have light halos encircling manders that need to cross roads to acid precipitation to the decline of round spots. photo-Rob Criswell wood frogs and several species of wood- land salamanders. These amphibians require seasonal temporary ponds for reproduction and rearing of young. Temporary ponds do not contain water year-round, so they do not support fishes that could be predators on the larval amphibians. Thus, the survival rates of larvae would be expected to ex- ceed those from ponds that do contain fish. However, many of these ponds occur in mountainous areas where the soil has a low pH (highly acidic), and where the soil is naturally poorly buff- ered. Thus, a further drop in pH caused by acid deposition causes the pH to drop to lethal levels, causing the eggs or larvae to die. Additionally, sublethal effects can cause deformities in the ani- mals that do survive. Depletion of the ozone layer has been shown to allow certain wavelengths of harmful ultraviolet (UV) radiation to reach ground levels. This radiation was probably filtered by the ozone layer to a greater extent in the past than it is to- day. Researchers in the northwestern United States have documented that damage to the DNA of certain amphib- ians can result from exposure to these radiation levels. Some species can with- stand higher exposure levels than other species. Similarly, some species are able to repair radiation damage to their cells, while others cannot. The early theories are that those species in great- est decline may also be those that are less able to repair radiation-damaged

60 Pennsylvania Angler & Boater Fishing & Boating Memories Last A Lifetime photo-Rob Criswell DNA. Researchers are testing various leopard frog populations still exist and Concerns for the future amphibian species to determine if cer- others have disappeared completely. The northern leopard frog may be tain patterns are evident. The natural environment has been what ecologists refer to as an “indicator Another reason for the decline of compared to the workings of an auto- species.” That is, its health and survival many amphibian species is that herbi- mobile. Certain parts of a car, like the may reflect the environment’s health. cides, pesticides, and other chemicals in wipers, radio, or some wiring, can be Perhaps their apparent declines are a the environment have been linked to removed and the car will still run– warning for us to examine closely our deformities and death in certain am- maybe not as well as before, but it will influence on the environment. Frogs phibians. Most amphibians and nearly still run. However, at some point a are both herbivores and carnivores, all frogs breathe through their skin in critical part, such as the fuel pump, bat- predator and prey, and they are associ- addition to their lungs. They travel tery or distributor coil, might be re- ated with wetlands where the quality of along the ground and are always in con- moved, thus causing the car to stop our drinking water is often determined. tact with the substrate. Because this is working. Perhaps we are damaging or They are an important component of where many toxins accumulate, frogs removing critical parts in the northern healthy ecosystems. If northern leopard are prime candidates for toxin-loading leopard frog’s environment. In some frogs are missing from an ecosystem when harmful agents are found in their areas they are gone already. In other where they historically occurred, how environment. Even though it may be areas it may be only a matter of time. does that affect the other components difficult to determine which chemicals Hopefully, the right answers will be of that system? Similarly, when do hu- are harmful, just think of all the herbi- found before it’s too late. man populations begin to reveal the cides, pesticides, deicing agents, clean- effects foretold by indicator species in ers, and solvents that are in use today. Commission efforts the environment in which we all live? Today’s “harmless” chemicals could be What is the Fish and Boat Commis- Based on the amount of media cover- tomorrow’s DDT! sion doing about leopard frog declines? age some of the more recent issues in- Other less obvious chemicals may be Presently, the Commission has directed volving frogs have received, there are affecting our frogs. Recently, deformi- funding from the Wild Resource Con- reasons to be optimistic that the public ties in fish and amphibians have been servation Fund to Dr. Arthur Hulse, of is beginning to recognize that we as hu- linked to human female hormones that Indiana University of Pennsylvania, to mans are linked to the health of frogs. have found their way into the environ- conduct the Herpetological Atlas Let’s hope so. Pennsylvanians would ment via birth control usage (“the pill”) Project of Pennsylvania. Since 1996, surely benefit from seeing more spots! and the local sewer system. amateur herpetologists have been Most recently, scientists working in- searching the woods and wetlands of Resources dependently in the United States and Pennsylvania to identify and document Australia have discovered a new fungus reptiles and amphibians for this Northern Leopard Frog Patch genus known as a chytrid fungus. It is project. Early reports have revealed that In 1999, the Commission continues believed to be killing frogs and toads northern leopard frogs have been en- its series of nongame species limited- around the world. There are still sev- countered only in 17 of the 34 counties edition patches with a northern leopard eral unanswered questions about this where they had historically occurred. frog patch. Each sells for $4.71 plus 29 latest discovery. It is Special attention will cents PA state sales tax for a total of known that this fun- be given to locating $5.00. Include $2.00 shipping and han- gus has been found northern leopard frogs dling for each order. on dead frogs. How- as this survey effort Contact: Publications Section, PA ever, it is unclear continues. The Fish & Boat Commission, P.O. Box whether this fungus baseline data collected 67000, Harrisburg, PA 17106-7000. caused death or ap- by the atlas project will peared after the frogs be crucial to identify- Pennsylvania Amphibians & Reptiles were weakened by ing long-term monitor- Another excellent resource on frogs some other agent, ing sites that are and Pennsylvania’s other reptiles and such as ultraviolet necessary to document amphibians is the Commission’s book, radiation damage. and understand frog Pennsylvania Amphibians & Reptiles, by Additional research is population changes. Larry L. Shaffer. needed to be certain. We will also continue The book sells for $9.43 plus 57 cents The research con- to monitor research PA state sales tax and $2.00 for ship- ducted so far suggests initiatives that seek to ping and handling (total of $12 for that the decline of solve the mystery of books sent to PA addresses). Contact frogs and other am- disappearing frogs. the Commission Publications Section phibians may not be Then, where possible, at the address above. caused by any single we will apply the scien- factor, but instead by tific data toward man- Frogs wall chart a combination of en- agement techniques to $ .94 plus 6 cents tax and $2.00 post- vironmental alter- halt the apparent de- age. Send order to the PFBC address ations. That may clines of this interest- above. explain why some ing amphibian.

Fishing & Boating Memories Last A Lifetime Pennsylvania Angler & Boater 61