Survivorship and Spatial Patterns of an Urban Population of Texas Horned Lizards

Vesy, Miranda; Watters, Jessa L.; Moody, Raymond W.; Schauber, Eric M.; Mook, Jennie; Siler, Cameron D.

doi:10.1002/jwmg.22064

Cited by 3 publications

(2 citation statements)

References 96 publications

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“…Growth rates of THL in our study were greatest during their first 2 years and then slowed thereafter, which is similar to the findings of Vesy et al (2021). The growth rates of THL reported herein were slower than previously reported (Henke and Montemayor 1997), and THL in our study did not obtain the SVL size by their second year as reported by Ballinger (1974).…”

Section: Discussionsupporting

confidence: 92%

Feasibility and application of using Texas horned lizard scat to predict lizard size and age class

Huerta

Henke

Wester

et al. 2023

Wildlife Society Bulletin

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Texas horned lizards (Phrynosoma cornutum; hereafter THL) were once abundant throughout Texas; however, their distribution and abundance have decreased, and currently they are listed as a threatened species in the state. Detection of THL can be difficult because of their cryptic nature and sporadic distribution. Using indirect signs such as fecal pellets (i.e., scat) to determine occupancy is a widely practiced survey technique. However, it is unknown if scat size can be used to determine the age structure of THL. Our objectives were to determine 1) if THL scats were consistently produced and at consistent size in relation to lizard snout‐vent length (SVL), 2) if THL scats remain intact in the environment, and 3) if scat length and diameter could be used as an indicator of THL size, which could be used to determine population age structure. We tested the feasibility of using scat morphometrics to estimate age class ratios, body size, and population estimates for THL. Data collection was conducted in 3 phases, which occurred from 2001–2019. Scats were collected daily for 6 days from 6 hatchling, 10 juvenile, and 10 adult THL collected from southern Texas. Texas horned lizards were measured for snout‐to‐vent length (mm) and categorized as either hatchling, juvenile, or adults based on estimates from the literature. On average, THL produced one scat/day, typically in the morning. Scat length and width increased as lizard size (i.e., SVL) increased with each age class. Scat size of each age class of THL was consistent between days; thus, objective one was met. Scats were measured for length and width (mm) and placed in direct sunlight for 90 days, submerged in water for 2 days, and placed in typical summer weather conditions of southern Texas. Texas horned lizard scat did not shrink or swell in size or decay due to environmental conditions during the 90‐day experiment. Thus, THL scats do remain intact in the environment. We collected scat from 70 known‐size THL from south‐central Texas. Simple log‐log regression models demonstrated a linear relationship (r2 = 0.89) between loge (SVL) and loge (scat length, mm). Slopes were similar among age classes, but intercepts differed as expected. We tagged individual THL to follow growth rates through time. Thirteen of 20 tagged females produced 178 hatchlings, of which 56, 23, 19, and 6 were recaptured during their hatchling, 2nd, 3rd, and 4th year, respectively. Models for growth rates of known‐age THL were not equal (F6,69 = 44.6, P < 0.0001) among age classes. Growth rates were faster in year 1 (0.101 ± 0.003 mm d−1) and year 2 (0.099 ± 0.007 mm day−1) and slowed (0.076 ± 0.009 mm day−1) during their 3rd year. Scat from THL reliably can be used to estimate population age class structure, body size, and population estimates. However, our growth rate analyses suggest that THL appear to experience slower growth rates than during previous decades, and thus, THL require reevaluation as to what SVL size constitutes an adult THL.

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Section: Discussionsupporting

confidence: 92%

Feasibility and application of using Texas horned lizard scat to predict lizard size and age class

Huerta

Henke

Wester

et al. 2023

Wildlife Society Bulletin

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“…classes are sorely lacking in general across vertebrate taxa (e.g., aves - Cox et al, 2014;Dunn et al, 2017;marine megafauna -Hays et al, 2016;reptiles -Delaney and Warner, 2016;Vesy et al, 2021), and filling these gaps should be of paramount conservation concern (Roznik et al, 2009;Cox et al, 2014). Without an understanding of habitat use and selection by juvenile animals, our perception of a species' habitat requirements becomes framed around knowledge of adult animals.…”

mentioning

confidence: 99%

Microhabitat and stopover site selection by juvenile Western Rattlesnakes (Crotalus oreganus)

Howarth,

Bishop,

Larsen

2023

Front. Amphib. Reptile Sci.

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Studies on habitat selection are central to our understanding of animal ecology and play an important role in the conservation and management of species. However, habitat selection is not necessarily consistent across sectors of populations and failing to understand both similarities and differences between age classes, for instance, may be problematic. Knowledge on habitat use by juvenile vertebrates in general is sorely lacking, particularly for species with precocial offspring, and here we address this gap by describing habitat use by juvenile Western Rattlesnakes (Crotalus oreganus). We measured habitat at two scales for radio-telemetered juvenile snakes along active-season movement paths at a site in southern British Columbia, Canada, where seasonal migrations and habitat associations of adult animals have been particularly well studied. Despite the relatively short distances these animals travelled and their diminutive size, we found there was selection for structurally stable cover (e.g., woody debris, shrub, and rock cover) similar to that documented for adult snakes in the same region. Additionally, we tested for differences in microhabitat features at sites used for short-duration (fewer than seven days) and long-duration (seven days or longer) stopovers: we detected negative selection for leaf litter at long-duration stopover sites, but otherwise identified no difference in the microhabitat features associated with these two categories of locations. Overall, this study contributes rare data to our growing understanding of the complexity of habitat requirements for migratory snake species, including northern crotalid vipers, while underscoring the crucial role of habitat selection research across all segments of populations. Comparative data on habitat selection by early-age classes within reptile populations informs conservation planning for the long-term survival of wild populations.

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Personality assessment of headstart Texas horned lizards (Phrynosoma cornutum) in human care prior to release

Barrett

Anthony²,

Eliades³

et al. 2022

Applied Animal Behaviour Science

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Survivorship and Spatial Patterns of an Urban Population of Texas Horned Lizards

Cited by 3 publications

References 96 publications

Feasibility and application of using Texas horned lizard scat to predict lizard size and age class

Feasibility and application of using Texas horned lizard scat to predict lizard size and age class

Microhabitat and stopover site selection by juvenile Western Rattlesnakes (Crotalus oreganus)

Personality assessment of headstart Texas horned lizards (Phrynosoma cornutum) in human care prior to release

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