Biome: Deserts and xeric shrublands
Central latitude: 32.620000
Central longitude: -106.740000
Duration: 18 years, from 1989 to 2006
21 distinct species
Across the time series Uta stansburiana is the most frequently occurring species
MethodsMethods and locations. Pitfall trap grids have been installed at three creosotebush sites. three grassland sites. and three mesquite sites. and two tarbush sites. Each grid consists of 4 x 4 rows of traps at 15 meter intervals. Each pitfall trap is 40 cm deep. and lined with tin can cylinders. A polyethylene funnel is set on a container in each trap. Each trap has a ceramic tile cover which is used to close the trap during non-sampling periods. Traps were opened for two consecutive weeks every month for the period 16 June 1989 to 23 August 1991. For the period post-August 1991. traps were opened for two consecutive weeks quarterly (Feb. May. Aug. Oct). During the summer traps are checked every three days. during the winter they are checked once each week. Lizards are removed from the containers and information is recorded on data sheets. Objectives. Desertification is hypothesized to have altered the spatial and temporal availability of resources required by the biota. Results of desertification on the Jornada include changes to shrub dominated communities and major soil changes. We hypothesize that these shifts in vegetation have changed resources temporally for many of the consumers. If grassland systems respond to rainfall without significant lags. but shrub systems do not. then consumer species should reflect these differences. In addition. shifts from grassland to shrubland results in greater structural heterogeneity of the habitats. We have hypothesized that consumer populations. diversity. and densities of some consumers will be higher in grasslands than in shrublands. Diversity and/or densities are hypothesized to be related to the NPP of the sites. Data will be collected for the duration of the LTER program in order to provide data to test these hypotheses.Protocol for Lizard Pitfalls - OVERVIEW.A grid of 16 pitfall traps is located at each consumer plot. Each trap is 40 cm deep and contains an inner plastic container and funnel. A ceramic tile is placed over each trap. For a 2-week period each sample period. the tiles are raised on one side. and the traps are checked every 3 days in summer and once a week in winter. Individual lizards are taken from the traps. identified. sexed. measured. and weighed. Each lizard was clipped with a unique number using the codes on the diagram on the field data sheets. Toe clipping was done from 1989 to 1995. Starting in March 1995 toe clipping was terminated and lizards were instead marked with a black sharpie marking pen to provide a temporary mark to determine recapture status over a particular 2-week trapping period. A black mark is made posterior to the cloaca on the ventral base of the tail. Trapping grid is a 4x4 with 15 meter interval between traps.I. INTRODUCTION. In conjunction with net primary production studies. consumer and faunal studies are conducted at or near NPP sites using pitfall traps. We use live traps. not employing ethylene glycol or other killing/preservative agents. with traps checked once a week at the minimum. Sampling-with-replacement is used with the lizards but without replacement for the arthropods; thus any released arthropods. when possible. should not be let go in the immediate vicinity of the pitfall grids (Note: separate pitfall traps for arthropods were established in 1995 for LTER-III).Lizard pitfall studies are conducted quarterly over a period of two weeks: in February-March (following winter NPP). in May-June (following spring NPP). in August. and in October-November (following fall NPP). A. LOCATION: Pitfall grids consist of sixteen stations (four rows of four traps) located at the following ll sites (the old code. no longer used. is given in parentheses following each site*): T-WEST (TBA). T-EAST (TBB). M-RABB-A (MDA). M-NORT (formerly M-RABB-C (MDC). moved to M-NORT in 1995). M-WELL (MDB). G-IBPE-C (GLC). G-SUMM (formerly G-IBPE-A (GLA). moved to G-SUMM in 1995) G-BASN (GLB). C-SAND-B (CBB). C-CALI (CBA). and C-GRAV (CBD). Pitfalls formerly located at MB (mixed basin slope NE of weather trailer) and C-SAND-C (CBC) have been closed. No pitfalls are directly associated with the following NPP sites: P-COLL. P-SMAL. P-TOBO (because of flooding potential). T-TAYL. or G-SUMM. The pitfall for C-SAND is located NW of the NPP site (see site map). The location of each trap is marked by a rebar bearing a numbered aluminum tag. * (old codes may still be found in data books and vial labels)B. CONSTRUCTION: The LTER pitfall traps are walled by two large vegetable cans. 6 diameter; size 10 tomato cans (6 lbs. 3 oz. ca. 6 l/2 high) are most common. The ends of the cans are cut out and the cans stacked so that the top of the upper can is nearly flush with the ground. Similar-sized coffee cans may be used; the funnel (see below) should fit the can with little excess space. The collection container is a slightly tapered plastic beverage cup 5 l/2 deep with top diameter of 4 l/2; several small (ca. l/16) holes are drilled in the bottom of each cup to facilitate drainage. A polypropylene funnel with top diameter of 5 l/2 is placed in the cup to seal the trap and prevent escapes; the stem and lower funnel are cut off about 4 below the top. making a lower hole of ca. l l/2- 1 3/4 diameter. The cups are supported on small stones or wooden blocks to raise the top of the funnel nearer the top of the can (it should not be flush); elevation of cups is especially important in poorly drained sites. When not in use. the traps are sealed by a ceramic tile with dirt packed along sides (see procedure below). Trap numbers (l-16) originally were stamped on a small aluminum block fastened to a rebar next to each pit. Many of these blocks are now missing. More recently. sites have been numbered with aluminum tags attached to the rebar. If both the block and tag are missing. the number can be determined by counting from the northeast corner of the grid (l-4 north-south. 5-8 next line south-north. etc.). However. some sites. notably BASN. have a different numbering scheme so always check adjacent trap numbers if unsure.A SITE MAP IS INCLUDED WITH THIS PROTOCOLII. PROCEDURE: Traps are usually opened on a Friday; the tiles are excavated and propped open l to 2 at one end using wooden blocks or stones. Be sure the tile covers the trap as completely as possible. During spring and summer. collections are made the Tuesday and Friday the week after opening and again Tuesday and Friday (close) of the next week. In fall and winter. collections on Fridays are sufficient. Take care to look under the cup; both lizards and arthropods (especially scorpions and crickets) will readily hide there. Any lizards found are carefully grasped (don't grab tail!) and subjected to the measurements detailed in section A below. Be sure to use forceps on venemous arthropods. Note special procedures for juvenile lizards. Before leaving for the field. make certain that you have the bag with measuring equipment (below) and a box with labelled cups (w/lids) for the eleven pitfall sites plus an additional unlabelled cup for each participant. The data book should be on a clipboard which has a list of lizard species codes and identification information affixed. IMPORTANT: the clipboard should also had an updated list of the identification numbers previously used in toe marking for the period prior to 1995. Equipment for processing lizards includes a metric ruler. scales. forceps. plastic bags. black sharpie markers. pencils. and a reptile field guide. The scale is a PESOLA (l00 gram) spring-type; it is expensive so should be kept out of the dirt. Equipment kept in a zippered bag either in FH 117 or 236. The following information is recorded in the Jornada LTER II Lizard Pitfall data book for each lizard:l. Pit number (see above).2. Species code: Lizard species are recorded using a four letter code (first two letters of generic and species names). Cnemidiphorus tigris is thus CNTI. etc.3. Sex: record an M. F. or J (juvenile) for each lizard. The field guide and clipboard information may assist in sexing. which differs in different families.4. Rec.: If individuals have been previously marked with a black.5. sharpie marker. record an R (recapture). Record an N for unmarked adults.6. Markings. Prior to 1995: Toe mark: For newly captured adults. toes are clipped according to the numbering system shown on each page of the data book. Note that the ventral side of the lizard is shown in the diagram. With scissors. clip the first 2 mm or so of the required toes. As lizards have only five toes. numbers 6-9 are not used in the codes. Upon reaching number 6 one should skip to the next availble combination (e.g. HOMA 2046 would skip to 2050; UTST 56 would skip to 100. Close attention should be given to avoid toe clipping errors. It is also imperative that accurate and updated records be kept (on provided clipboard sheet) of numbers used; be sure this sheet is brought to the field each time. Severe problems have occurred in the past with skipped and duplicated numbers. In general. JUVENILES. especially small ones. should not be toe clipped as the required handling may injure them. Put a dash across the toe mark space for small juveniles. After 1995: Each new lizard is marked with a back sharpie marker at the ventral base of the tail posterior to the cloaeca.7. S-V: record length (in mm) from snout apex to vent for each lizard. Exercise great care in handling juveniles for any measurements. Estimates might be better for very small juveniles; the handling needed to position the lizard for measurement may be injurious. If the juvenile is not too active it can be measured in the cup.8. Total length: record total length in mm from snout to tail tip for each lizard.9. Weight: place lizard in plastic bag and clip bag to the scale. Keeping bag out of wind if possible. note weight in grams (subtract bag weight) and record in data book. Very small to small juveniles can be estimated at l gram.10. Tail: record as whole (W) or broken (B). If tail is broken and regrown. record as broken and make a note at the bottom of the page. A SAMPLE LIZARD DATA BOOK PAGE IS INCLUDED WITH THIS PROTOCOL III. CLOSING PITFALLS: on the last day of collections. close the pitfalls by lowering the tiles to the ground surface and covering the pitfall as well as possible. and then packing soil or sand tightly around the edges and top of the tile. Soil on top may discourage coyotes and help assure tight closure. A shovel or trowel is useful in closing the traps. Be sure to place a stone atop the tile or it may be difficult to find the trap again. Sloppily closed pitfalls will be deathtraps for any organisms getting in. so take time to seal them.IV. GENERAL PROBLEMSl. Poor drainage (or flooding) is a problem in several areas. especially tarbush and BASN. If traps and cups are flooded. pour the cup onto a flat surface and try to recover as many organisms as possible (note in book any not kept). Using the cup. bail as much water out of the trap as possible.2. Broken tiles: this has been a problem at the RABB sites which are open to grazing. Tiles from the LTER I transect have been used as replacements. An extra tile is usually kept with the pitfall box and a box of tiles has been kept in the annex.3. Broken funnels: plastic funnels eventually begin to crack and must be replaced. If broken funnels are noticed make a note for immediate replacement. Some funnels are available in the FH236 lab.4. Natural toe loss in lizards may have affected the toe marking system. If new captures had lost toes (usually only one foot will be affected). attempts were made to incorporate the digit into the marking scheme. Toe losses in marked recaptures may be told by reference to the marking lists and should be noted in the data book. 5. Escapees: large. active lizards are easily capable of escaping from one's grip and occasionally from untended traps with the tile off. Beware of lizards running up your arm as you attempt to pull them from traps- a quick grab is safer than slow fishing. If a lizard escapes. note as much information as you can about it and then write escaped across the rest of the row. Pitfall traps for lizards Unit of abundance = IndCountInt, Unit of biomass = Weight
Citation(s)Lightfoot, D. (2013) “Lizard pitfall trap data (LTER-II, LTER-III)”. Jornada Basin LTER. Available at: http://jornada.nmsu.edu/lter/dataset/49821/view, accessed 2016.