The northern leopard frog (Rana pipiens) is a formerly abundant frog that has experienced
significant declines across its range and is considered endangered in some parts of the range but
still abundant in other parts of the range. Various factors have been invoked to explain population
declines in the northern leopard frog, including habitat destruction, diseases, chemical
contamination, acidification, increased ultraviolet light due to loss of the ozone layer, introduced
predators, overcollecting, climatic changes, and general environmental degradation. However, no
one cause has emerged as the primary factor behind population declines in any area. Probably,
multiple causes contribute to population declines of the species, and these causes most likely vary
from site to site. Of course, northern leopard frogs are still abundant in some areas, implying that
factors leading to population declines in other areas are absent or less important where the species
is still common.
Conservation of this species depends on minimizing habitat alteration, removing introduced
species, especially introduced predaceous fish, from breeding ponds, reducing the spread of
diseases such as chytridiomycosis, ranavirus, and bacterial diseases from pond to pond, reducing
chemical contamination and acidification, and eliminating overcollection where it occurs.