Roll over you bears! (Part 2)
Joseph Grinell (center) and team, in 1908Last time, I wrote briefly about the history of grizzly bears in California and how there are no grizzlies in California anymore (an irony, given the animal's image on many of our state's symbols). The story of the grizzly's demise in California is the same narrative for many other large mammals throughout the world over the last few centuries: habitat loss, plus human hunting, does a number on mammal populations, especially mammals that have very large individual geographic ranges (bears, lions, elephants). Grizzly bears can still be seen in their native habitat, but the contraction of their range of the past 200 years limits these places to remote, unsettled tracts in Canada and the northwestern US states.
How has habitat change affected the distribution of mammals over this time? What kind of role has climate change played? Researchers at the UC Museum of Vertebrate Zoology (MVZ) are actively working to understand these questions, and others, through the Grinnell Resurvey Project. In the early part of last century, Joseph Grinnell, the founding director the MVZ, was one of the first naturalists to create systematic collections of living vertebrates with precise natural history data (taking weight measurements, identifying the sex of the individual animal, or recording the day and place of collection). Grinnell and his students recorded this information for large parts of California (and other western states), creating an archive of natural history data (in the form of field notes) that is unrivaled in its breadth, content, and precision. Since Grinnell's time, the landscape and climate of California has changed in many ways, and many people (politicians, economists, and scientists alike) are eager to know how animal communities have changed as well.
Using Grinnell's data as a baseline, MVZ researchers now are in the process of retracing his footsteps through California, and undertaking new surveys of the exact same places that Grinnell sampled. In doing so, researchers are recording new data about the presence, abundance and kind of species that now live in these habitats. By comparing what's found now with what was there 100 years ago, researchers will be able to see how the composition of mammal communities has changed over this period. Detailed records of climate change in the same places over the last 100 years can also be added to the analyses, to show how concomitant changes in rain or temperature might also have affected mammal communities.
All of the science in the project hinges on the foresight of Joseph Grinnell, who, at a time when ecology not even a real discipline, understood how the value of natural history collections can well outlast its creators. Read more about some early results from the Grinnell Resurvey Projects here:
Nick Pyenson is a PhD candidate at the University of California, Berkeley, in the department of integrative biology and the museum of paleontology.
latitude: 37.8642, longitude: -122.286