Sunday, February 27, 2011

Sexy Selection

I've been meaning to write this post for...well probably for weeks now. But here it is. Aren't you excited? I was looking at some pictures of funny looking ducks that could dive to some pretty extreme depths a while back. The males had all these weird feather tufts on their wings and a big crest-like feature on their heads. It all seemed like it would really get in the way of effectively moving underwater. I thought, for a split second, why on earth would these ducks have evolved features that seemed counter-productive to getting food?

Then I remembered: Oh, right. Sexual selection. Perhaps you've heard about this process before but thinking about it in that light reminded me of what a powerful process sexual selection is. Sexual selection is the process that runs parallel to natural selection but has to do with individual animals choosing their mates. This is why you end up with extreme sexual dimorphism (when the male and the female of a species look very different from one another) and why you end up with ridiculous features like crests and bright colors that seem like they would get the creature killed in its quest for survival. These features often do run counter to surviving and that is why I think sexual selection is such an interesting topic: it can and usually does overpower the processes of natural selection.

The most impressive forms of sexual selection are probably found in the birds. That picture that reminded me of its power was a duck but the classic example (stop me if you've heard this) is the peacock tail. I can remember my professor clearly stating that the peacock's tail does slow it down to the point where it becomes difficult to get away from its predators. And what are peacocks predators? Well they are native to India and what big carnivores live there? Tigers. One of the worlds most capable hunters. The process of sexual selection has created a feature, this tail, that slows an animal down even under the selection pressures being exerted by one of the worlds most exceptionally effective carnivores. Natural selection is constantly trying to shorten and lighten the tail so the poor male peacock can get away from hungry tigers. But those pesky peahens are always choosing the males that have the biggest tails (actually the statistic seems to be the most "eyes," the bright blue spots peacocks have on their tails, that females are interested in) to mate with. That selection dictates that no matter how slow it makes the males the ones with more eye spots and therefor larger and heavier tails are getting to reproduce. As long as they get to sexual maturity and mate with a female it really doesn't matter if they then end up as tiger lunch.

So the next time you're out in the backyard, when the spring finally comes back, you can look at those bright red male cardinals and their bold crests and wonder at how those features came to be in the face of the selection pressures of peregrine falcons and other would-be predators.

Monday, February 14, 2011

Buteo jamaicensis

Several days ago I was greeted during my breakfast by this bird roosting in the ginko tree in our yard. It's a red-tailed hawk, the most common hawk in North America. Their range extends over nearly the entire continent except the very northernmost part and into Central America and Jamaica (hence the species name). There are three distinct "morphs" or forms and a total of fourteen subspecies with fairly different color patterns, most of which lack the distinctive red tail, which can make identification between this bird and some of the other common North American hawks a little tricky. However, because they are so common, if you see a hawk in North America it is very likely to be a red tailed hawk.

These birds of prey prefer areas where they can roost fairly high and watch over a wide flat area for prey. In New England they feed mostly on mammals such as rabbits, squirrels and mice. In the desert parts of the continent they feed mostly on snakes. To protect themselves from bites the red tailed hawk has a thick scale covering on its legs. After landing on the snake it will pin the prey item's head as quickly as possible to prevent retaliation.

Usually you can see these birds in flight, circling in the air watching for prey. I also hear their calls a fair amount even in the city.


Frances, Peter (senior editor) (2007) Bird. DK Publishing: New York, New York.

Wednesday, February 2, 2011

Climate and Weather

If you've been reading the mycelial network you know that I tend to avoid topics of climate change and other more politicized areas. This isn't so much that I'm afraid to talk about them but more because I'd rather spend my time nerding out and explaining how cool the tentacles on different animals are.

But as I mentioned yesterday, this season has been exceptional and there's been a lot of talk as to whether this is evidence for or against climate change. Plus, climate and weather are a part of nature so I figured I would weigh in briefly. Or rather, I would let actual climate scientists weigh in. Here's a great video sent to me by a colleague.

Tuesday, February 1, 2011

Remember Color?

Winter is dead to me. I had a slightly negative affect towards the season up until this year but as we endure what I'm assuming must be the billionth snow storm this year (since I've lost count and a billion sounds high and about right) it's becoming official. Winter and I are no longer on speaking terms. So I thought I'd post a photo to remind everyone that color exists. It'll be back. Rejoice.

That We Know Of

Recently a colleague of mine and I have been talking about using the phrase "that we know of" in science education. I found myself using it in a rather extreme case. A student of mine commented (and I don't remember what lead into this) that there "are no animals on the moon." I retorted: "that we know of." I was half joking but I stand by the point I was making. Researchers are discovering things all the time and just because we assume there are no animals on the moon doesn't make it true. Just two days ago I read this article: . It's about tardigrades (also known as water bears) being able to survive the vacuum and radiation of space. They're not on the moon but it's not really all that far off.

Field biologists have also recently discovered a new, very large species of crayfish in Tennessee. You can read about them here and here. So if you had said last month "There are no undiscovered species of giant crayfish in the rivers of Tennessee" you would have been dead wrong. If you had been a good science educator and said "There are no undiscovered species of giant crayfish in the rivers of Tennessee that we know of" you would have been exactly right.

It's just amazingly cool that researchers can still find relatively large animals that are basically in our backyards (well, not my backyard but probably someone's). And that is the essential spirit of the phrase "that we know of." Science is not a project of finding out what does not exist. We can never be certain about that. Ever. What we can be certain of are the things that do exist. So the next time you catch yourself making an exclusionary claim about the natural world, do your audience a favor (especially those of you who do work with young scientists) and add those four words.