The two names of this organism tell quite different tales about its character. Lithobates palustris—literally, one who haunts stones in the marsh—reveals an aquatic frog closely related to bull frogs, leopard frogs, and wood frogs. Its common name, however, refers to its use by fishermen as bait for pickerel, a large fish in the pike family. As its use in this capacity is not too common, I would argue that L. palustris would be the more accurate name for describing this frog. Although in many ways an unremarkable “one who haunts stones in the marsh,” neither of its names let on its distinction as both an unusually beautiful frog, and an unusually poisonous one.
Pickerel frogs are medium-sized, brownish-hued true frogs. Despite being an aquatic species, they have unwebbed feet, which allow them to easily live terrestrially as well. They are very similar in appearance to the related northern leopard frog (Lithobates pipiens); however, the dark patches on the back of the leopard frog are much more circular in appearance. In contrast, those on the back of the pickerel frog resemble irregular rectangles—sometimes merging or rounded, but always basically rectangular. The pickerel frog is also identifiable by the brilliant yellow or yellow-orange coloration on the hidden inside surface of its thigh. Typically 45-75 mm (1¾-3 in) in length, the females are almost always larger than the males.
Pickerel frogs are unique among frogs native to the US in that they produce toxic skin secretions—essentially, they are poisonous. These secretions often irritate human skin, but can be distasteful or even fatal to many potential predators, such as snakes, mammals, or other amphibians. However, some predators, such as the green frog and bull frog, have evolved immunity to the toxin.
Pickerel frogs have life cycles similar to many other frogs. Awaking from hibernation in the spring, they immediately set about the task of finding mates. The male vocalization, often described as a deep “snore,” is used to attract females. After mating, females lay spherical egg masses of 700-3,000 tiny eggs and attach them to submerged branches. Once the tadpoles have hatched, 
they take around three months to metamorphose into frogs and leave the water. In another two years, they are will become sexually mature and able to reproduce themselves.
Spread throughout most of the north- and mid-eastern United States, these frogs are often found in or near the clear, cool water of streams, springs, and ponds. In the southern part of their range, they can be found in warmer waters or coastal swamps, as well. Although pickerel frogs hibernate burrowed in sediment at the bottom of their home bodies of water and mate and lay eggs there in the spring, they often range far afield into pastures or open areas during the summertime. Pickerel frogs are largely insectivores, although they also consume other small invertebrates. The tadpoles live on aquatic vegetation.
This frog was caught by Tom in the parking spot behind Lewis. It has likely already mated in the station pond, and is entering the terrestrial portion of its annual cycle. At around 60 mm in length, it could be either a male or a female.