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Vernal Pool Indicators

Spotted salamander (Ambystoma maculatum): On seasonably-warm, wet nights in late winter and early spring, spotted salamanders emerge from their terrestrial hideaways and make long migrations (up to 600 feet or more) to seasonal pools to breed.

Spotted salamander (Ambystoma maculatum): On seasonably-warm, wet nights in late winter and early spring, spotted salamanders emerge from their terrestrial hideaways and make long migrations (up to 600 feet or more) to seasonal pools to breed. Photo credit to Lindsay D. Funk, USGS Patuxent Wildlife Research Center.

Seasonal pool indicator species rely on seasonal pools as essential habitat. These species, sometimes also referred to as obligate species, are dependent upon these unique pools for their continued existence.

One of the defining characteristics of the seasonal pool biotic community is a lack of permanent populations of predatory fish. Isolation and periodic drying keep predatory fish from colonizing and occupying the pool. This reduced-predator environment allows amphibian larvae and invertebrate larvae to thrive.

Different species of amphibian and invertebrate seasonal pool indicator species occur across the United States. In mid-Atlantic and northeastern United States, amphibian indicators include wood frogs (Rana sylvatica), eastern spadefoots (Scaphiopus holbrookii), and species in the mole salamander family (Ambystoma spp.). These amphibians depend upon seasonal pools for optimal breeding. Additionally, a crustacean group (the fairy shrimp) relies on these pools for their entire life cycle.

Seasonal pool indicator amphibians spend most of their adult lives in the terrestrial habitat surrounding seasonal pools. Seasonally, they migrate en masse to the seasonal pools to breed. The egg masses that adults leave behind will hatch into aquatic larvae. If the pool does not dry up too quickly and the eggs/larvae are not eaten by predators, they will eventually transform into juveniles and exit the pool.

Other animals that rely on seasonal pools have evolved strategies to deal with the pools' ephemeral nature. For example, fairy shrimp produce resting eggs that remain buried in the pool bottom and survive dry spells.

Amplexus between a male and female wood frog (Rana sylvatica) : The male wood frog (notice he is smaller in size and darker in coloration) clasps the female wood frog from behind while mating. Male wood frog vocalizations during the breeding season sound like duck quacks. As their common name suggests, wood frogs primarily inhabit deciduous woods. Adults migrate to fish-free pools to breed in late winter or early spring. Photo courtesy of: Northeast Amphibian Research and Monitoring Initiative, USGS

Amplexus between a male and female wood frog (Rana sylvatica): The male wood frog (notice he is smaller in size and darker in coloration) clasps the female wood frog from behind while mating. As their common name suggests, wood frogs primarily inhabit deciduous woods. Adults migrate to fish-free pools to breed in late winter or early spring. Photo courtesy of: Northeast Amphibian Research and Monitoring Initiative, USGS

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Biological Indicators | Aquatic Biodiversity | Statistical Primer

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