Revision of Portal Project - Mammals from Tue, 2010-06-22 12:55
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Overview:
The Portal Project is a long-term ecological study that has been monitoring small mammal community responses to climate and experimental manipulation of dominant rodent species since 1977 in southeastern Arizona.
Ecological Level: Community
Biome: Desert
Location: Southeastern Arizona (Lat/Long)
Spatial Scale of data: Each plot is .25 ha. There are 24 plots.
Timespan: 1977-2002
Frequency: Monthly
Observational/Experimental: Experimental (but with long-term controls).
Manipulation: Removal of kangaroo rats (Dipodomys spp.) and removal of all rodents.
Dataset Location:
Data collection summary: All plots are trapped for one night each month. Each plot consists of 49 permanent trapping locations. Around the new moon, a sherman trap is placed at each stake. Data is collected for each animal that is caught.
Data Collected: Species, gender, reproductive information, location caught, weight, hindfoot length, individual tag.
Issues:
1) "Monthly": While data collection is meant to be monthly, things happen. Trapping follows the new moon, so some years there are 13 sample periods because there were 13 new moons in a 12 month period. Weather, airline delays, etc, can cause sample periods to be missed, so some years will have less than 12 sample periods. The take home message: different years can have different sampling intensities. Do not simply sum all sample periods within a year and compare across years.
2) The reproductive status and age columns appear to be reversed, with age actually occurring after reproductive status, not before.