Wednesday, October 12, 2005

Geog 316 journal - The Island Foxes

So I'm really excited because Liam just started the Island biogeography lectures, something I've been looking forward to since the beginning of class. I feel lucky that I work at a place where I get a chance to interact with people who know these concepts. Over the past 5 years I've done a few projects at Santa Cruz Island - a change detection analysis, some cartography, and database design for the pig eradication project.

The topic that has dominated Santa Cruz Island is the Island Fox. I've been so caught up in the drama of the pig eradication that I always took the natural history for granted. And when Liam mentioned that Lori blogged about the foxes I was compelled to do my own research.

Google scholar searches showed the consensus to be that the grey fox rafted to the northern Channel Islands (NCI), probably during a storm event. But it seems crazy, what did they eat? Apparently they are omnivorous and will eat berries as well as mice. The populations of the southern Channel Islands were brought by the Chumash people as they were far more isolated.

Fox fossil remains at Santa Rosa Island date to 10,400-16,000 years ago and during that time (the end of the Pleistocene) sea level was much lower connecting all the NCI's into one large island called Santarosae. We learned in class that sea level was about 100m lower on average. So I took my research one step further by doing a quick GIS analysis using a digital elevation model. I wanted to see how far these foxes had to raft in these conditions. I colored up the DEM so that the 0-100m contour highlighted the ancient shoreline (map above). As it turns out they would only have to raft 7 miles from the mouth of the Santa Clara River. This seems more plausible than the idea that the slender salamander came down from the north coast on a redwood tree....but that's a whole other entry.


Anonymous said...

This is a beautifully rendered map. It clearly illustrates the process that you refer to.

Anonymous said...

The information here is great. I will invite my friends here.