The following article was taken from the Green Heritage Newsletter, spring 2010, and written by Park System Senior Naturalist Christopher Lanza...
Amphibians Through Time
Amphibians first appear in the geologic record during the Devonian Period that began 408 million years ago. They most likely descended from a group of “lobe-finned” fish whose modified fins allowed them to move on land for brief periods of time. This was a great competitive advantage in an age when the oceans were a crowded and dangerous place to live, compared to the almost vacant land. The fossils of one very early amphibian, Hynerpeton bassetti, have been found in Pennsylvania and the animal presumably lived in ancient New Jersey as well.
Biology—Defining a Double Life
Amphibians are best defined as a class of exothermic (coldblooded) land and water vertebrates that can breathe with lungs, gills, or through scale-less skin; and who generally lay their jelly-like eggs in water. Here, the young, who look quite different from their parents, remain until their metamorphosis into adult form. Thus, they lead a double life. Adults may or may not live on land, but, even if they do, they tend to stick near water or areas of high humidity. Life histories are specific to each species and some variation may occur.
Salamanders: Fire Myth & Secrets
|Northern Red Salamander|
Salamanders are often confused with lizards because they share a similar body plan: four legs, a long body, and a long tail; but lizards are no more closely related to amphibians than to any other reptile. Throughout history, salamanders have been linked to myths, especially myths dealing with fire. This may partly stem from the fact that salamanders often hide in dead logs that may have been used for firewood. Upon lighting the log in a hearth, the sight of a creature emerging (fleeing, really) from the flames clearly would have seemed supernatural.
In New Jersey, salamanders are divided into two distinct groups: mole and lung-less. Mole salamanders are burrowing animals as adults and breathe with their lungs. Lung-less salamanders breathe through their moist skin and mouth. The only newt found in NJ is the red-spotted newt and it differs from other salamanders because it has three distinct life stages: an aquatic larval form, a juvenile land stage, and, finally, the aquatic adult.
A number of NJ salamanders are unfortunately either threatened or endangered due to water quality or loss of suitable habitat, and another group are listed as species of special concern. Here in Monmouth County, the Marbled Mole Salamander is a species of Special Concern. Due to their secretive nature, it is likely that the true extent of population loss may never be clear, making management all the more difficult.
Call of the Wild—It’s a Frog, Not a Bird
Recently, a few visitors to the Manasquan Reservoir Environmental Center asked about the identity of an animal they often heard calling near their home at night. They were surprised to learn that the animal was a Northern Gray Treefrog and not a bird as they had assumed. The popular conception is that all frogs sound the same, but every species has a unique mating call and most call only during certain months. In most cases, the callers are male frogs announcing their location, and presumably their fitness, to females of the same species and even as a challenge to other males.
Frog vs. Toad—Can You Tell the Difference?
Frogs and toads seem to have developed after salamanders and first appeared in their modern form during the Jurassic period, 208 million years ago. Although more familiar than salamanders, people still question how to tell them apart. In truth, they are quite similar with many overlaps, and should be thought of as a continuum, ranging from highly aquatic to more terrestrial. However, with that thought in mind, three broad groups emerge.
- True Toads (genus Bufo) tend to have squat, chubby bodies with warty, spotty, and blotched skin. Their skin is colored to match their environment, in shades of green and brown. Their posture is more upright and they will have large (parotoid) glands behind their eyes that produce a self- defense poison. They lack teeth and the explosive jumping powers found in some frog species and move by walking or in a sequence of short hops. They are not bound to the water except for breeding purposes. The Eastern Spadefoot toad is a special exception to this category and not a “true toad.” It has few spots, no parotoid glands, and spends most of its time underground.
- Treefrogs and their kin. Treefrogs, cricket frogs, and chorus frogs are generally small and slender frogs that may be adapted to living in trees and, if so, will have adhesive discs on their fingers and toes. They are all found near water, but not necessarily in the water, as is generally the case with true frogs.
- True Frogs. For most people, “true frogs” are what they imagine when they hear the word “frog:” long legs, narrow waists, webbed toes, explosive jumping, and croaking. This group is normally found in the water, although some species will leave the water during certain periods.
A Sensitive SpeciesAmphibians are a unique group of animals. They play an important role in the environment–controlling insect pests, providing food for larger species, and acting as “first responders” to changes because of their sensitivity.
At the same time, more and more people, adults mostly, have come to me to ask what has happened to all the frogs, noting “they were everywhere when I was a child.” The sad truth is that we are to blame for their disappearance. World-wide, according to the International Union for Conservation of Nature (IUCN), over 1,000 are at risk–more than any other species.
Even simple changes to the environment can cause problems. For example, consider the Bullfrog. Historically, this large and dominant frog species was not found in the Pine Barrens due to the highly acidic water (where Carpenter Frogs and Pine Barren Treefrogs used to thrive). Due to pollution, however, the water has become less acidic allowing Bullfrogs to move in and to replace the Carpenter and Pine Barren Treefrogs. It is very easy to overlook these wildlife habitat changes, but we do so at our own peril. At some point the pollution and habitat loss we create may displace us too.
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