Spring Has Sprung: Frogs in My Swimming Pool!
This time of year we begin looking (hoping) for signs of spring – purple crocus peeking out from under early spring snow, the conk-a-lee! of red-winged blackbirds at the feeders. New to my list of spring heralds this year is a pool full of quacking wood frogs!
A neighbor’s abandoned backyard pool has turned into a man-made vernal pool (an ephemeral body of water replenished by rain and snowmelt). This type of habitat is perfect for development of young amphibians and insects because of the lack of competition or predation by fish; frogs and salamanders are free to look around for these habitats because of their amphibious nature – you can even help these little ones cross the road in the spring, if you feel so inclined! Note: uprooted trees (thank you, Sandy!) may create vernal pools in the empty space left by their root mass, so check it out next time you see one!
I have come to learn that Wood Frogs (Rana sylvatica) are pretty amazing creatures. First off, they are the state amphibian of New York (New Jersey does not have a state amphibian [?!]). Besides their political notoriety, they are also well known in the science world for their tolerance to freezing temperatures. Wood Frogs hibernate in leaf litter or in the soil close to the surface, and actually allow their blood and up to 65% of their body tissue to freeze! They are very terrestrial for a frog – their toes are only partially webbed to allow them to walk efficiently on land. They can be found in cool, moist ravines, forested swamps and even upland areas throughout the summer, and typically relocate to areas close to breeding pools in the fall to overwinter (so they don’t have far to go in the spring).
When the frogs emerge from hibernation (i.e. thaw out), they migrate to nearby pools where the males announce their availability with loud,
quack-like croaks. A mating embrace called amplexus follows, aided in part by the male wood frogs enlarged thumbs that give him a strong hold of the female. Eggs are attached to shallow, submerged vegetation and the algae that grows on them acts as camouflage from predators. Multiple females lay their eggs close together, keeping them a bit warmer than if they were laid separately. The first stage of development – egg to tadpole – depends on water temperature, and the second stage – tadpole to froglet – depends on temperature as well as food availability (tadpoles are omnivorous and feed on algae, decaying vegetation, and even eggs of other amphibians).
Since vernal pools are filled solely with storm water runoff, they can become full of non-point source pollutants like household chemicals, herbicides/pesticides, and road salt. It is important that the pool’s water is free of these types of impurities for it to host amphibian young (whose skin is very porous, allowing water to flow in and out of their bodies freely). Take the River Friendly Resident quiz to see if you are doing your part to reduce non-point source pollutants like these!
Come on down to Fairview Farm Wildlife Preserve to see if you can spot a wood frog in the pond, or take a walk on the trails looking for a vernal pool in the early months of spring! Raritan Headwaters engages in land preservation and stewardship to help protect habitat for amazing creatures like the Wood Frog, as do our partners at the NJDEP and Conserve Wildlife Foundation of New Jersey. Contact us for more information about how you can help!