Northern leopard frog
|Northern leopard frog|
|A male Northern Leopard Frog in mid-croak.|
The Northern leopard frog (also called the Meadow or Grass frog) is a species of frog in the family Ranidae. It is a nocturnal frog that can live in wide variety of habitats and is often used in biology books and dissections because of its abundance. But its population has seen a considerable drop due to many factors, such as habitat destruction. Its lifecycle is metamorphic like most frogs; starting as an egg, progressing into a larval tadpole, then adult. It is, however, prone to malformation and will usually die before it reaches maturity when this occurs.
A frog starts as a tadpole that lacks lungs, but instead it has gills. As the tadpole undergoes metamorphosis it grows hind legs first, then front legs. The lungs begin to form replacing the gills and eventually loses its tail enabling the froglet is able to live on land. As an adult the Northern leopard frog has light-colored dorsolateral folds on its back and is a greenish-brown color with random dark spots edged in a lighter color , on its back and legs. Its stomach however is white. The size of the frog varies from 3 to 5 inches which is considered medium for a frog; the females are however a bit larger then the males.  Some people mix up the Northern leopard frog with the Pickerel Frog (see gallery for picture) because they are about the same color. The main difference is there spots the Pickerel’s spots are more square then the leopard frogs , also the Pickerel has bright yellow coloration under its legs and belly. You really need to be able to tell the two apart because the Pickerel’s skin is toxic to some animals and irritating to humans.  The skin of the leopard frog is moist because of mucus being secreted from glands in the skin. They also have glands in their skin that can secrete poison. The poison is not harmful to humans but they do help the frog get away from predators. The leopard frog also has very powerful vision which helps them in avoiding danger and finding food. The frog’s hind legs are also very powerful and are how they swim and jump so well. 
When male frogs are three to four years old they begin breeding. The breeding period is from the end of February all the way through May. The males call using their croak to attract a females, the female will also use her croak if she is being held by a male when she does not want to be. As the female swims the male holds on to her using his specialized thumbs as she releases her eggs in a mass of dark colored jelly which is in the water, the female will lay up to 3,000 eggs in the jelly. While the female releases the eggs the male fertilizes them. The fertilized eggs either get attached to under water plants or settle on the bottom of the pond.  The eggs will hatch in 10 to 20 days as tadpoles from there it will take until early August before the tadpoles mature into adults, and another two to three years before it is sexually mature.
Video of a Northern leopard frog calling for a mate.
The Northern leopard frog lives around ponds and marshes in North America and Southern Canada . But it can travel away from water, however it can only breed in water so it returns for breeding.
Their diet is very versatile because they will eat almost anything as long as it fits in their mouth. They do not chase there food; instead they wait until it passes them and then they pounce on it and eat it. They have been know to eat beetles, crickets, ants, flies, worms, smaller frogs, including their own species, and even birds and garter snakes.  As tadpoles they have a different diet: they eat plants, algae, even dead tadpoles or other dead invertebrates.  Along with being a predator in there food chain, the leopard frog also is prey to animals such as birds, reptiles, and other mammals. But they have many ways of protecting themselves: they jump into water, bury themselves in mud, or take several jumps and dive into vegetation.
Humans use the leopard frog for many uses such as food some people find frog legs a delicacy. Many times you will find them being dissected in a biology class or in your biology textbook. They also are very important in pest management as they tend to eat anything including pests that may eat crops or mosquitoes that may eat humans. 
Decline in Northern Leopard Frogs
There are many aspects that are causing a decline in Northern leopard frog population. The main one however is malformed frogs. In a total of 44 states there have been reports of malformed frogs of 60 different species. Especially in Minnesota the Northern leopard frog is exceptionally malformed. Studies by the Minnesota Pollution Control Agency showed 6.5% of 13,763 Northern Leopard frogs were malformed. You rarely find a malformed adult frog because the frogs have a difficult time living due to their malformations. There are many different ways a frog could be malformed some of them include malformed jaws, extra legs or feet, or a lack of legs feet or even an eye. These issues cause life for the frog difficult but not impossible. There are many things that can cause these malformations one of which is a parasite Ribeiroia ondatrae which burrow into the frog and if the frog is being severely infected with them it can develop some very intense deformities. There are many other theories on ways that the Northern leopard frog can be malformed including pesticides, man-made chemicals, and ultraviolet light. 
The Northern leopard frog is not only threatened in Minnesota it is also in danger in Alberta, Canada, which has had it designated as threatened since 1997. There are some theories on why the population is declining so rapidly in Canada. For example, pesticides could easily enter a frog through its skin which is very absorbent and if this did happen the pesticides could easily destroy the animal’s immune system causing it to be easily effected by disease. Also some other species of frogs such as the Common carp and the Bullfrog all eat the same foods so the more frogs competing for the same food the less there is for all of them.  These facts are very scary since frogs are considered a good bio-indicator species of ecosystem imbalances because of there permeable skin. If the frogs start dying then it could easily be an indicator that humans may soon be affected by our ecosystem. But the Canadians are not just letting it go that the frogs are dying instead they are trying to do something about it they are trying to re-introduce younger Northern leopard frogs back into there ecosystem to help there population grow back. Also they are trying to monitor the frogs so that they might have a better idea what is killing them and how to prevent it from continuing to kill the frogs. 
- Northern Leopard Frog taxonomy by Wikipedia
- Northern Leopard Frog Rana pipiens by Earlham College Biological Diversity 2001, Johanna Mutti, Hannah Putnam, Alexandra "Coco" Shea.
- Northern Leopard Frog by Dorota, Frogland.
- Northern Leopard Frog by the National Geographic.
- Who is the Pickerel Frog? by Western Connecticut State University herpetology.
- The Northern Leopard Frog by unknown Alberta citizen.
- Frog, Northern Leopard by the Calgary Zoo.
- Northern Leopard Frog by the Calgary Zoo.