Wednesday, August 17, 2011

Day 78: Costs

The last insect transect. This is the story of the last morning that I had to be out the door, jars and gun in hand to collect insects from 5 pitfall traps. It is a sad story. I have already explained on August 11 why I am doing the insect transects for the Godwit team, to gather more data for the mismatch hypothesis. The last godwit chick would have hatched (if the nest wasn't deprecated, predated on) on August 15th. So if it would have hatched successfully, which is somewhat doubtful due to the storms we've just had the last two days and that most of the godwits have already begun to flock, then the collection of insects the last two days would show how much food would be available to these chicks. Not much, as it turns out. Just a few spiders and a few springtails and a few parasitic mites. 

Springtail or Collembola. These can get so abundant during
the season that we don't measure each individual one like
we do for the rest of the insects. We just count how many there
are which can get to several hundreds or even thousands in a
single sample.

The bugs in general have been decreasing in abundance, including the mosquitos. I haven't seen any bulldogs for several weeks and the mosquitos are becoming more an more rare to the point that I haven't seen them the last couple of days. The blackflies are another story. These lovely little things have still managed to maintain large numbers, and surging to higher numbers after the rain we have just received. 

But back to the insect transect. Why is it such a sad story? First, I have to explain something about traps, target species, and nontarget species. Whenever a trap is set up to catch something it is meant to catch a specific animal or plant or fungus or human or what ever it is you are trying to catch, your target species. So you use the right bait, peanut butter of a mouse or a homemade apple pie for a human. You use the right scale of trap, decide on live trap or something that might kill what you are catching, depending on the study. 

For the insect study, the insects are sometimes dead and sometimes alive. I don't like it when they are dead because the information we are gathering doesn't require that they be dead. The length and number could be measured if they were alive as well, though it is difficult to trap insects alive. Though I don't like it when they are dead because it doesn't seem right, I also don't like it when the spiders especially are alive. The spiders tend to cling onto the spoon that I'm trying to fish them out of and then climb swiftly up to my fingers, obviously making me drop the metal and push my chair away from the table. I logically know that they won't harm me, but they still freak me out when they move like that! But that is a bit off topic.

The topic is to explain the tragedy of nontarget species. This is when you catch something you didn't want to catch. So I put a homemade apple pie out and I get a bunch of ants, not what I wanted. But this isn't such a bad thing as an unwanted thing. As far as catching nontarget species, this isn't so bad. The ants get a meal, and I just have to bake a new pie. The worst part of capturing nontarget species is when they die because of the capture.

A researcher up here is trying to capture small rodents to find parasites that can be transferred from the rodents to her study animal, the fox, because the fox eat the rodents. She hasn't caught very many rodents, it is a low year in the cycle of lemmings. However, she has caught a frog and two birds in her trap and only one rodent. Her trap is designed to kill the rodents, so she can study gut parasites. This means that the frog and birds were killed too.

They are so cute too...

So why is my last day doing insects sad, besides killing some insects, which is sad enough? I killed a vole. In the third cup, I found a curled up fur ball. It had drowned in the dilute ethanol. It's the second rodent killed in these cups. The only good thing was that I could give these to the fox researcher. Unfortunately, this death of nontarget species is rather common in capture studies. It's always a balance between the benefits of the study and the negative side effects. Is there enough of a benefit? How can you measure it?

No comments:

Post a Comment