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Map of the historical and current distributions for the Flat-tailed Horned Lizard in the United States and Mexico. Borrego Badlands, West Mesa, Yuha Basin, East Mesa, and Yuma Desert Management Areas and Ocotillo Wells Research Area are included.
Contexts in source publication
Context 1
... guide these efforts, an Interagency Coordinating Committee (ICC) was formed (FTHL ICC 1997) and five management areas (MAs) and one research area (RA) were designated. The MAs are located in the Yuma Desert (YDMA) of Arizona and in California in the East Mesa (EMMA), West Mesa (WMMA), Yuha Basin (YBMA), Borrego Badlands (BBMA), and the RA in Ocotillo Wells (OWRA; Figure 1). ...
Context 2
... of mortality due to EV around 20% suggest steady populations (= 1). A deviation due to EV of 25% or greater suggests population decline whereas a deviation of 15% or less suggests population growth for juveniles, sub-adults, and adults ( Figure 10A, B, and C). This suggests that extremes in environmental variability could have immediate impacts on FTHL populations. ...
Context 3
... percent mortality that results in a steady population size of FTHLs varies slightly for juveniles ( Figure 11A); however a value of 50% or less suggests population growth (> 1) for all three age classes. For juveniles, a mortality of 60% suggests a steady population, though any value above 60% suggests a steep population decline (< 1). ...
Context 4
... juveniles, a mortality of 60% suggests a steady population, though any value above 60% suggests a steep population decline (< 1). For sub-adults and adults, a mortality of 60% or more results in population decline, and between 50 and 60% suggests a steady population (= 1; Figure 11B and C). ...
Context 5
... annual rate of change for SD of K due to EV was very similar for all values tested ( Figure 13), revealing population growth ( > 1) when all other variables are held constant. This suggests that changes in the overall dynamic K from year to year may have little effect on population persistence. ...
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Long-term demographic monitoring from 2008 to 2018.
Range-wide PVA on Flat-tailed Horned Lizard populations
Citations
... A fundamental step in this process is to prepare conservation action plans, which brings together the needed actions for a given species or group of species (Fuller et al., 2003;IUCN/SSC, 2008). The main actions included in these plans are basic research to fill knowledge gaps (e.g., gathering information on life history traits to determine vital rates; e.g., Grimm et al., 2014;Meiri, 2018), population modeling (e.g., using vital rates to estimate time to extinction; e.g., Mazaris et al., 2005;Grimsley et al., 2017), population monitoring (e.g., to detect further declines; e.g., Burton and Rivera-Milán, 2014;Thapa et al., 2018), population and/or habitat management (e.g., to increase population growth; Corbett and Tamarind, 1979;Brito et al., 1999), translocation of individuals (e.g., reintroductions; Daltry et al., 2017;Wang et al., 2011), detection of priority areas to create PAs (see above), control and/or monitoring of invasive species (e.g., eradication of invasive predators; Jones et al., 2016;Hu et al., 2019), education programs (e.g., awareness workshops; Kaiser et al., 2013;Morrison et al., 2007), legislation and enforcement (e.g., trade prohibition; Mansergh et al., 1993;Fonseca et al., 2021), and ex-situ conservation (maintenance of captive populations in zoos; Odum and Reinert, 2015;Ziegler, 2015). A good example to illustrate the diversity of conservation actions that may compose an action plan is the plan for the EN Turks and Caicos Rock Iguana, Cyclura carinata (Havery et al., 2021). ...
There are over 11,700 reptiles throughout the world, 18% of them categorized as threatened in the IUCN red list, especially turtles and crocodilians. Most threatened reptiles have small ranges associated with decline in extent or quality of habitat. A variety of life history traits may contribute to the decline of reptiles, such as small populations, small ranges, low fecundity, and long lives. Reptiles are threatened mainly due to habitat loss/disturbance, overcollection, and invasive species. Well-delineated conservation planning associated with the implementation of carefully designed conservation actions would bring back many endangered reptiles from the brink of extinction.
... comm.). The YDMA population viability analysis suggested that age of first offspring, clutch size, and juvenile mortality have the strongest influence on Flat-tailed Horned Lizard population dynamics in this region (Grimsley et al. 2017). Further investigation of differences in survivorship (predation, prey, habitat, etc.) and reproduction across the two plots is recommended in concurrence with annual demographic and occupancy monitoring. ...
The Arizona Game and Fish Department completed the 15th consecutive season of Flat-tailed Horned Lizard (Phrynosoma mcallii) demographic monitoring within the Yuma Desert Management Area (YDMA) in September of 2022. The objectives for Flat-tailed Horned Lizard monitoring on the YDMA in 2022 were to: survey the two long-term demography study plots established in 2008; continue the collection of demographic information on populations within these plots; and estimate the population size, survivorship, recruitment, and population growth within the YDMA. This report summarizes the 2022 monitoring results and provides an analysis
of the Flat-tailed Horned Lizard demographic data for two demographic plots within the YDMA collected from 2008 through 2022. To examine population demographics in the YDMA, we utilized data from all 15 years (2008 – 2022) on both the YDMA1 and YDMA2 plots using robust design multi-year models with a Huggins p and c likelihood (Huggins 1989, Kendell and Nichols 1995) in program MARK (White and Burnham 1999). We gathered data on 3,852 captures, including 1,628 individuals marked with PIT tags over the past 15 years of monitoring. We removed 2013 YDMA1 data from the encounter history due to insufficient data (only four adult captures). Therefore, our final encounter history included 584 adult individuals (YDMA1, n = 327; YDMA2, n = 257). Populations of this r-selected species are expected to oscillate over time.
Estimated population sizes on each plot tended to slightly decline across 15 years, but the decline was not significantly different from a stable population. Since 2017, both study areas have shown increased population estimates. For 2022, YDMA1 showed slightly lower population estimates compared to the prior year (2022 𝑛 = 28.4, 2021 𝑛 = 69.6). YDMA2 population estimates are slightly above population estimates of the prior year (2022 𝑛̂ = 52.2, 2021 𝑛̂ = 45.8).
... comm.). The YDMA population viability analysis suggested that age of first offspring, clutch size, and juvenile mortality have the strongest influence on Flat-tailed Horned Lizard population dynamics in this region (Grimsley et al. 2017). Further investigation of differences in survivorship (predation, prey, habitat, etc.) and reproduction across the two plots is recommended in concurrence with annual demographic and occupancy monitoring. ...
The Arizona Game and Fish Department completed the 14th consecutive season of Flat-tailed Horned Lizard (Phrynosoma mcallii) demographic monitoring within the Yuma Desert Management Area (YDMA) in September of 2021. This report summarizes the 2021 monitoring results and provides an analysis of the Flat-tailed Horned Lizard demographic data for two demographic plots within the YDMA collected from 2008 through 2021.
... The average robust design adult survivorship estimate for the YDMA from 2008 to 2020 was 0.38 ± 0.03, lower than the adult survival estimate from the YDMA population viability analysis (0.47 ± 0.15; Grimsley et al. 2017). Estimates, though comparable, are likely due to different modeling methods and different datasets (Robust Design, 2008vs. ...
... comm.). The YDMA population viability analysis suggested that age of first offspring, clutch size, and juvenile mortality have the strongest influence on P. mcallii population dynamics in this region (Grimsley et al. 2017). Further investigation of differences in survivorship (predation, prey, habitat, etc.) and reproduction across the two plots is recommended in concurrence with annual demographic and occupancy monitoring. ...
The Arizona Game and Fish Department completed the 13th consecutive season of Flat-tailed Horned Lizard (Phrynosoma mcallii) demographic monitoring within the Yuma Desert
Management Area (YDMA) in September of 2020. This report summarizes the 2020 monitoring results and provides an analysis of the P. mcallii demographic data for two demographic plots within the YDMA collected from 2008 through 2020.
The objectives for P. mcallii monitoring on the YDMA in 2020 were to:
1) Survey the two long-term demography study plots established in 2008,
2) Continue the collection of demographic information on populations within these plots,
and
3) Estimate the population size, survivorship, recruitment, and population growth within the
YDMA.
... Our data suggest a reduction in P. mcallii presence across the YDMA (Figure 4), but as mentioned previously, estimates are above the trigger point requiring management action. This analysis, along with previous YDMA occupancy analyses (Grimsley and Leavitt 2016c, Grimsley and Leavitt 2017b, Grimsley and O'Donnell 2019, YDMA demographic analyses (Grimsley and Leavitt 2016a, Grimsley and Leavitt 2017a, Grimsley-Padron 2019, the YDMA population viability analysis (Grimsley and Leavitt et al. 2017), and corresponding range-wide population viability analysis ) and range-wide occupancy and demographic analyses (Leavitt 2013, Grimsley and Leavitt 2016b, help to inform managers on the status of P. mcallii in Arizona and throughout its range. ...
A part of a larger scale long-term monitoring plan by the FTHL Interagency Coordinating Committee for the conservation and management of Flat-tailed Horned Lizards across their range. This specific report shows the long-term occupancy monitoring results from 2011 to 2019.
... Demographic and occupancy monitoring at the five FTHL MAs and one RA over the past 18 years has resulted in a rich data set on FTHL demographics. A population viability analysis (PVA) was recently completed in the YDMA for FTHLs in Arizona (Grimsley et al. 2017), and is used here as the base format for carrying out a range-wide PVA. The last time a range-wide PVA was carried out on FTHLs was 20 years ago (Fisher et al. 1998). ...
... We used the statistical software program Vortex Lacy and Pollak 2015) to carry out a range-wide PVA on FTHLs, including a meta-population PVA and individual PVAs for each MA/RA as completed in the YDMA (Grimsley et al. 2017). Vortex allows us to evaluate the interaction of age-structured populations and life history parameters through Monte Carlo simulations (Lindenmayer et al. 1995). ...
... Though the demographic plots have distinct survey boundaries, emigration and immigration estimates may be impacted by the plots not being closed to movement. As such, we removed emigrating individuals from survival calculations in order to lessen the effects of 'false' deaths in our population (thus underestimating survival), as done in the previous YDMA PVA ( Grimsley et al. 2017). To do this, we first differentiated between captures within the core and the edge of each demography plot by creating a 100 m buffer from plot borders in ArcMap (ESRI, Redlands, CA). ...
Range-wide PVA on Flat-tailed Horned Lizard populations
... Monitoring provides the status of FTHL populations in relation to the trigger point designated by the Rangewide Management Strategy. This analysis, along with previous YDMA occupancy analyses , Grimsley and Leavitt 2016c, Grimsley and Leavitt 2017b, YDMA demographic analyses , Grimsley and Leavitt 2016a, Grimsley and Leavitt 2017a, the YDMA PVA (Grimsley and Leavitt et al. 2017), and corresponding range-wide analyses (Leavitt 2013, Grimsley andLeavitt 2016b) help to inform managers on the status of FTHLs in Arizona and throughout its range. ...
The Arizona Game and Fish Department completed the twelfth consecutive season of Flat-tailed Horned Lizard (Phrynosoma mcallii) occupancy monitoring within the Yuma Desert Management Area (YDMA) in 2022. A total of 75 plots were surveyed six times over the summer, including 8 plots on Bureau of Reclamation Lands and 67 plots on the Barry M. Goldwater Range West. To examine Flat-tailed Horned Lizard distribution and status from 2011 to 2022, we utilized robust design occupancy models in program MARK (White and Burnham 1999). Survey results were compiled into detection histories with twelve primary occasions (years) and up to six secondary occasions (sessions within a year). In 2022, there were 233 Flat-tailed Horned Lizard captures during 450 surveys with detections on 61 of the 75 occupancy plots, a naïve occupancy of 81%. There were fewer captures in 2022 (n = 233) than 2021 (n = 285), but more than 2020 (n = 97), and 2019 (n = 126). Occupancy estimates in each year of monitoring the YDMA are above the 30% trigger point recommended by the Rangewide Management Strategy. Our continued monitoring effort strengthens our findings that management goals are being met and that habitat conditions are stable to support Flat-tailed Horned Lizard throughout the YDMA.
The Arizona Game and Fish Department completed the eleventh consecutive season of Flat-tailed Horned Lizard (Phrynosoma mcallii) occupancy monitoring within the Yuma Desert Management Area (YDMA) in 2021. Occupancy and demographic monitoring are included within the larger range-wide effort outlined by the Flat-tailed Horned Lizard Interagency Coordinating Committee (FTHL ICC 2013). Occupancy and demographic monitoring support management and conservation strategies developed by the Flat-tailed Horned Lizard Interagency Coordinating Committee, whose primary objective is to "maintain self-sustaining populations" (FTHL ICC 2003). In order to meet this objective, reduce threats, and eliminate the potential need for federal listing under the Endangered Species Act, a strategy was devised to provide a standardized assessment of Flat-tailed Horned Lizard populations throughout the species’ range
to determine whether the population is stable, increasing, or decreasing (FTHL ICC 2003, 2008, 2009, 2013). Occupancy modeling within five management areas and one research area is part of that strategy. This report summarizes the 2021 occupancy season for the YDMA and provides an analysis of occupancy monitoring efforts from 2011 through 2021 to provide the most current information for trends in the YDMA of Arizona.
