Study ID 59

Long-term monitoring and experimental manipulation of a Chihuahuan Desert ecosystem near Portal. Arizona. USA

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Realm: Terrestrial
Climate: Temperate
Biome: Deserts and xeric shrublands
Central latitude: 30.322600
Central longitude: -103.501000
Duration: 26 years, from 1977 to 2002

427 records

29 distinct species

Across the time series Dipodomys merriami is the most frequently occurring species


Ernest, S., Valone, T.J. & Brown, J.H. (2009) Long?term monitoring and experimental manipulation of a Chihuahuan Desert ecosystem near Portal, Arizona, USA. Ecology, 90, 1708-1708.


1. Site descriptionWithin the 20 ha study area there are 24 experimental plots. Each plot has anarea of 0.25 ha and is fenced to regulate rodent access to the plot. Access is regulated using gatescut into the fencing. Large gates (3.7 ? 5.7 cm) allow all small mammals to access plots. Smallgates (1.9 ? 1.9 cm) exclude kangaroo rats (Dipodomys) whose inflated auditory bullae make theirskulls too large to pass through the gates. Rodent removal plots do not contain any gates andanimals caught on those plots are removed and released outside the cattle exclosure fence.On each plot there are 49 permanent trapping stations marked by rebar stakes forming a 7 ? 7 grid.Every stake on a plot has a unique identifying number denoting the coordinate of that stake on thatplot. For example. stake 11 is the first stake on the first row. Rows are numbered 1 through 7going from the most northern row to the most southern. Columns are numbered 1 through 7 goingfrom the most western column to the most eastern (See metadata.htm. Fig. 1).Treatments: See metadata.htm. Table 1. for details on treatment assignments for each plot.Data Collection Period. Frequency: From 1977?2002. plots were trapped around each newmoon ? which occurs approximately once a month. though occasionally blue moons do occur.resulting in 2 separate surveys in a month. Occasionally. months are missed. Months that areentirely missed are not noted in the database. Sometimes weather or other unforeseen occurrencesprevent the complete trapping of a survey. these are noted in the database (see Table 1 below).3. Research MethodsField: The site is surveyed for rodents approximately once each month. The survey occurs asclose to the new moon as possible to minimize external effects on trapping success which could bemisconstrued as actual changes in populations. During a survey. each plot is trapped for one nightwith treatments divided evenly between nights to eliminate differences between controls andtreatments caused by environmental differences on different nights. When a plot is surveyed. allgates are closed to ensure that only resident individuals are captured. At each stake. one Shermanlive-trap is placed and baited with millet seed. Traps are collected the next morning andindividuals processed. Each individual was tagged and data on species. location caught (plot andstake). sex. reproductive condition. weight. and hindfoot length were recorded. Until 1993.individuals were tagged using either ear tags or toe tags. After 1993. individuals werepredominately tagged using Passive Integrated Transponder (PIT) Tags. Use of PIT tags wasE090-118-D1-Rodent metadata from 1997?2000 while we waited for a patent infringement lawsuit to be resolved againstthe company that supplied our tags and scanning system (Troyvan). In 2000 we resumed using PITtags. using a different system (Biomark). It is noted in the database if either an animal escapedbefore all information was gathered. was removed from the site because it was caught on a plot itwas supposed to be excluded from. or died during trapping.Most data has been consistently collected over the timespan of the study. The one exception is thatinitially data were also collected on the location of the burrow for Dipodomys spectabilis andNeotoma albigula. This was discontinued after 1994.Taxonomy and systematics: Taxonomy and identification of species is consistent with Mammalsof Arizona by Hoffmeister (1986). with the exception that some species identified as Perognathusin Hoffmeister (1986) are now a separate genus (Chaetodipus). Unit of abundance = AggregatedCount, Unit of biomass = NA