16 March 2010

Slug weighing operations resume

In this post I introduced an ongoing research project involving the eastern North American slug Megapallifera mutabilis. Basically, we are trying to deduce the population cycle of this species by monitoring the sizes of the slugs during a year.

Last weekend's rains and the sudden rise of the temperature were the signals I had been waiting for to start this year's data collecting. I was able to go out to the park near my house for about 45 minutes this morning to search for slugs. Luckily, I found and weighed 3 of them.


Here is a preliminary graph showing the slug weights toward the end of the fall and near the beginning of the spring.

Red dots are for 2009; blue squares are today's data. The X-axis is not to scale.

It appears that the largest slugs that are present early in the fall die off before the winter comes (compare the weights of the slugs in the picture in the previous post with that of the slug in the picture above). However, adults do survive the winter and they will probably start mating pretty soon.

Updates may be provided.


Lisa said...

Hi, this is interesting to me, but how do you know that the heavy slugs died off? Maybe the slugs on your graph are just the ones that you found.


Lisa, of course, one can suppose that all growth stages are always present but that certain ones come out only during certain times of the year. However, when we follow them throughout the year we begin to see patterns. For example, babies appear in the summer, the biggest ones are not present late in the fall or early in the spring. When there are such patterns, it is more meaningful to conclude that there is a population turn over.