Sunday, February 1, 2009

Love is in the Water

Reproduction is one of the driving biological forces and often commands readers attention. This photo shoot was done under difficult conditions. Toads are one of the first amphibians to mate in our northern climates and often beat out other species by a month. Here in New York these toads will only mate for two days in the ice cold waters in the early days of April. The mating starts at dusk and is most active if there has been rain. So there you have all the conditions that make up an enjoyable photo shoot – 40 degree weather, light rain, dark, and I am wearing a wet suit and in water knee deep. On this photo shoot I also had an assistant holding a remote flash as I used the underwater camera. The goal was to get a solitary male with a huge inflated air sack as the male calls to the females. The males call in the females, as well a jockey for prime territory. The females will answer with a deeper sound, and I am sure there are frequencies involved below the human hearing range. The males will often mount another male, but with out the correct sounds will quickly identify that something is wrong and go back to calling. Once the male finds a female and is accepted he will hold on until the female lays the eggs and external fertilization takes place. After three nights the mating was over and I still did not get the shot I was seeking – I will return this spring.

This image shows the male firmly positioned, awaiting the egg laying . The male is on top while the female is on the bottom. The female is larger than the male due to she has to carry a large percentage of her mass in eggs. On a rainy night in the summer you can collect toads hopping on the roads. If you take the weight of each of the toads you find and make a bar graph of number of frogs vs their weight - you will see the data points are bunched together. Such a graph will show the average weight a toad gains each year – thus you can determine the age of a toad that you find. The oldest toad I have found was six years old, although I suspect there are older ones. The especially large toads I run across I call toadzilla.

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