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Southern Pacific Pond Turtle Data, Elizabeth Lake, Los Angeles County, California, USA

Data for journal manuscript: The effects of drought and fire in the extirpation of an abundant semi-aquatic vertebrate from a lacustrine environment in the southwestern USA


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Lovich, J.E., and Yackulic, C.B., 2018, Southern Pacific Pond Turtle Data, Elizabeth Lake, Los Angeles County, California, USA: U.S. Geological Survey data release,


These data were compiled to study the effects of severe drought and a concurrent large wildfire on a large population of southern Pacific pond turtles living in a rapidly drying lake. The study was done in collaboration with biologists from Ecorp Consulting in Santa Ana, California with funding from the Desert Tortoise Council. Data were collected in August and September of 2014. This worksheet contains the data that were used to analyze straight-line carapace length in cm and create a histogram of the size distribution and sex ratio of the population of southern Pacific pond turtles (n = 122) in Elizabeth Lake, Los Angeles County, California (Figure 4 from manuscript.) Carapace length was measured with tree calipers accurate to within [...]


Point of Contact :
Jeffrey E Lovich
Originator :
Jeffrey E Lovich, Charles B Yackulic
Metadata Contact :
Jeffrey E Lovich
Publisher :
U.S. Geological Survey
Distributor :
U.S. Geological Survey - ScienceBase
SDC Data Owner :
Southwest Biological Science Center
USGS Mission Area :

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The purpose of the dataset was to use it to analyze the size structure, sex ratio, short-term survival rates and causes of mortality in a population of southern Pacific pond turtles inhabiting a lake in southern California. The data were collected during an epic drought and following a massive wildland fire to assess how the turtle population responded to those stressors. Data collection procedures are explained in the abstract above but repeated here. Carapace length was measured with tree calipers accurate to + or – 1 mm. Mark-recapture data were fit using Burnham’s version of the Jolly–Seber model in program MARK. This model estimates initial abundance, lambda (i.e., proportional change in abundance between two time periods including both survival and recruitment), survival and detection probabilities. Given the short period of the study we assumed no recruitment to the adult population over the course of the study when live turtles were collected. As a result, we set lambda equal to survival. Survival was calculated for all turtles captured (males, females and immatures) on a per day basis and assumed constant over the 24-day study period. Given variation in sampling effort and gear we estimated different capture probabilities for each day of sampling. Although we could have reached similar estimates of detection probability and survival using a Cormack–Jolly–Seber model, the main advantage of our approach was that initial abundance was estimated as part of the likelihood, as opposed to as a derived parameter. Future projections of population abundance were based on the maximum likelihood estimates of the initial abundance and the daily survival, as well as their associated covariances, and assumed that there was no future recruitment to the population. These data provide a benchmark against which researchers can compare and contrast results from future research, if turtles are able to recolonize the lake.


The author(s) of these data request that data users contact them regarding intended use and to assist with understanding limitations and interpretation. Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.



  • USGS Data Release Products
  • USGS Southwest Biological Science Center (SBSC)



Additional Information


Type Scheme Key
DOI doi:10.5066/F7FN154F

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