Lizards move north

[herpguy]

http://news.yahoo.com/s/ap/20060711/ap_on_sc/new_gecko;_ylt=AnY.XHUPrycm0ljiwEovOmMPLBIF;_ylu=X3oDMTA0cDJlYmhvBHNlYwM-

 

Why are the geckos doing this? Does it have to do with global warming? Or is it because they need more room? Thanks in advance.

[AzurePhoenix]

It's possible that they're taking advantage of areas where the climate is newly welcoming to them, but it might just be that they're only recently making it up that far. Remember, they're a transplanted species, non-native.

 

Also, the geckos seem to depend pretty heavily on human habitation to thrive. Around here, I only ever see them in the town and suburb, never out in the surrounding desert, so it seems to me that they can only go as far as people are. When a new housing development opens up, the native lizards tend to rebound well enough and are right at home, but it take months for the geckos to start showing up and build a notable populace, despite having an open niche free for the taking. As far as I can tell form personal observation it's because their movement and spread is restricted by where people are.

[SkepticLance]

Allow me to live up to my name and be really sceptical on this one. The media love bad news and putting the worst twist on everything. Many, many media stories are the result of selective perception, in order to get this twist.

I think the most probable cause for this story is selectively perceiving that a lizard that has probably been there for who knows how long, is now 'discovered' to be further north than anyone knew.

 

Nothing new about this. I remember a case in Australia, where a large lizard thought to be extinct, was 'found' in a new region of the interior. When the scientists finally got around to asking the aboriginal people, they were told :

"You should have simply asked us. These lizards have been here forever, and we have been hunting and eating them all that time."

 

Let me give another example of selective reporting. Most westerners believe that the Sahara Desert is expanding and swallowing more and more of Africa each year. The truth is different. According to New Scientist (21 September 2002, page 4), what happens is that there are a few years of drought, during which the desert expands, followed by a few years of good rain, during which the desert shrinks. In the former, the media go nuts, and report all kinds of alarmist nonsense. Latterly, the media are silent. Net result ; everyone thinks the desert is expanding whereas, on average, it is about the same size as it was 200 years ago when first surveyed.

 

Moral of the story : do not believe everything you read in the news media.

[Mokele]

Well, firstly, I can easily refute that the lizard has always been there: it's an introduced species, and probably arrived in the US with the advent of increased shipping, so 200 years tops.

 

As to how recent this range expansion is, you're correct that it can be difficult to asses. However, this species is not exactly hard to find; their favorite hunting area is porch lights. The prof in my dept who works with a similar species collects them just by driving around neighborhoods at night and picking them off people's walls. Also, this species breeds extremely rapidly, so they don't exactly stay rare for long after they arrive. While it's difficult to establish the precise time of their arrival, I doubt they could have been around for more than 5 years without being noticed.

 

What puzzles me is how they deal with winter. I know this species from FL and Louisiana (though it's considerably more widespread), but OK winters can't exactly be pleasant, especially for a tropical gecko. Either winters have been warmer (interesting support of global warming) or the lizards have found a physiological or behavioral mechanism allowing them to survive the OK winters (also interesting). Either way, it's interesting.

 

Mokele

[AzurePhoenix]

Could they simply be spending the cold months in home walls and such? I know it doesn't exactly get cold where I am, but during the chillier months we do find them inside far more often.

[Mokele]

Very possible, though there's obviously a limit to it, else they'd've colonized Canada by now.

[herpguy]

SkepticLance, thanks for your reply, but the article didn't say anything about why they were doing this. I just wanted to know. The reason why I suggested climate change is because it's a fact that other animals, such as birds, are going further and further north. Good stories and examples, though.

 

SkepticLance, just to back up your point with some more examples, I have a story. Last year, i went to an area in northern Michigan and I went searching for salamanders. I found an eastern tiger salamander which wasn't supposed to live that far north. So I asked some herpetologists on another forum, and they said they have also found them more than 100 miles north of where they are supposed to live years back. So it really wasn't a big deal. That wasn't as good as your examples, but I do agree with you.

 

I would also like to mention that a reptile store near my house in Michigan has many geckos that escape. I've seen them outside during the summer, but they come back in during the winter. So I think AzurePhoenix's idea could be correct.

[SkepticLance]

From what Mokele said, it sounds like he is right. Just another bunch of feral aliens spreading out in all directions.

 

Sad. I thought my idea was a lot more fun!

[Mokele]

Well, hang on there: alien species do not spread without limit; most hit some sort of climatic or ecological barrier and stop. This particular species has been in the US for a long time, so it's had ample time to fill out its possible home range and reach a stable state.

 

Given that this home range is now expanding again, that means either the animals have found a way to circumvent the barrier, or that the barrier itself has moved.

 

Mokele