Surveys Estimating Abundance of the Endangered Houston on a Primary Recovery Site Adam Duarte*, Donald J. Brown, Michael R.J. Forstner Department of Biology, State University–San Marcos, San Marcos, Texas 78666

Abstract The Griffith League Ranch is one of the primary recovery sites for the endangered Houston toad Bufo () Downloaded from http://meridian.allenpress.com/jfwm/article-pdf/2/2/207/2751817/072011-jfwm-041.pdf by guest on 25 September 2021 houstonensis. New recovery initiatives have recently been implemented to increase Houston toad abundance; however, no robust estimate of population size has been conducted in the last decade of study, nor from this recovery site. To assist with inferences regarding efficacy of current and future management actions, we estimated adult Houston toad abundance on the Griffith League Ranch. Houston were sampled at breeding ponds during the 2010 breeding season using a mark–recapture methodology. We analyzed the data using a modified Jolly–Seber open population model in Program MARK. Models were built whereby the probability of capture remained constant, the apparent survival varied with time or was constant, and the probability of entry varied with time. Model averaging was used to account for uncertainty and the derived adult male Houston toad abundance ranged from 201 to 307 individuals. Using a previously determined Griffith League Ranch Houston toad functional sex ratio of 5:1, we estimated the abundance of the total adult Houston toad population on this primary recovery site to be from 241 to 368 individuals. This study is the first to report a robust abundance estimate of a Houston toad population and provides a foundation for further research to quantify the impact of current and future management actions.

Keywords: abundance; Bufo houstonensis; ; POPAN; Program MARK Received: July 15, 2011; Accepted: September 9, 2011; Published Online Early: September 2011; Published: December 2011 Citation: Duarte A, Brown DJ, Forstner MRJ. 2011. Estimating abundance of the endangered Houston toad on a primary recovery site. Journal of Fish and Wildlife Management 2(2):207–215; e1944-687X. doi: 10.3996/072011-JFWM-041 Copyright: All material appearing in the Journal of Fish and Wildlife Management is in the public domain and may be reproduced or copied without permission unless specifically noted with the copyright symbol ß. Citation of the source, as given above, is requested. The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service. * Corresponding author: [email protected]

Introduction A number of factors have likely contributed to the range-wide population declines of the Houston toad. The Houston toad Bufo (Anaxyrus) houstonensis (Fig- Brown (1971) suggested loss and degradation ure 1) was the first listed under the federal were leading threats to remaining populations. Given Endangered Species Conservation Act (Gottschalk 1970), that the species is a habitat specialist, showing strong the precursor to the Endangered Species Act as amended preference for deep sandy soils and forest cover (USFWS (ESA 1973). Over the past 50 y this east-central Texas 1984; Buzo 2008), development and land-use changes endemic has been extirpated from 3 of the 12 counties in have undoubtedly been major contributors to local which it was known to occupy, with substantial popula- declines (Brown 1975; Brown and Mesrobian 2005). tion declines in the remaining counties (Forstner et al. Additional factors potentially contributing to population 2007; Supplemental Material, Reference S1; http://dx.doi. declines across the species’ range include prolonged org/10.3996/072011-JFWM-041.S1; Gaston et al. 2010). droughts (Forstner et al. 2007; Supplemental Material, Since the 1970s, the Lost Pines ecoregion in Bastrop Reference S1; http://dx.doi.org/10.3996/072011-JFWM- County has housed the largest populations of Houston 041.S1), interspecific competition and increased oppor- toads, and has remained the only county without a high tunity for hybridization caused by habitat alteration short-term risk of extirpation (Brown 1971; U.S. Fish and (Brown 1971; Hillis et al. 1984), by invasive Wildlife Service [USFWS] 1984). species (Freed and Neitman 1988; McHenry et al. 2010),

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Figure 1. An adult male Houston toad Bufo (Anaxyrus) houstonensis calling to attract females on the Griffith League Ranch, Bastrop County, Texas in 2010. Image used with permission from photographer Bei DeVolld. historically inadequate management toward the conser- scenarios to assist with recovery efforts (Hatfield et al. vation and recovery of the species (Peterson et al. 2004; 2004; Swannack et al. 2009). However, abundance Brown and Mesrobian 2005), and anthropogenic changes estimates are needed to assess the current status of to habitat likely reducing overall chorus sizes (i.e., populations and measure responses to management number of individual males calling), which, in turn, actions designed to increase Houston toad abundance, decreases reproductive success (Gaston et al. 2010). such as prescribed fire and head-starting (i.e., releasing Houston toad breeding activity occurs between late captive-reared Houston toads into the wild [Forstner January and early May (Hillis et al. 1984; Swannack 2007). et al. 2007; Supplemental Material, Reference S1; http:// This species is an explosive breeder (Wells 1977), where dx.doi.org/10.3996/072011-JFWM-041.S1; Brown et al. large aggregations of calling males occur at irregular 2011]). Previously documented abundance estimates intervals throughout the breeding season. Adult toads have been restricted to ‘‘very good guesses’’ (Forstner are rarely found above ground between breeding et al. 2007; Supplemental Material, Reference S1; http:// intervals (Price 2003; Swannack and Forstner 2007; Brown dx.doi.org/10.3996/072011-JFWM-041.S1), because de- et al. in press), and breeding activity has been correlated tection problems associated with the secretive behavior with minimum daily temperature, precipitation, and and rarity of the species have made abundance moon phase (Hillis et al. 1984; Dixon et al. 1990; Price estimates difficult to derive. 2003; Swannack 2007). Houston toad reproductive In 2001 we began a long-term Houston toad monitor- behavior is sex-dependent, such that individual breeding ing project on a primary recovery site for the species. males return to the same pond within a breeding season Unfortunately, reliable abundance estimates were not (Jacobson 1989), whereas individual breeding females feasible prior to 2010 because of low within-year rarely visit the same pond more than once within a recapture success coupled with low annual adult survi- breeding season (Price 2003). vorship (Swannack et al. 2009). However, several years of Auditory call surveys are the primary method used to active stewardship along with unusually high precipita- monitor Houston toads across their range (Jackson et al. tion rates during spring 2010 resulted in extensive 2006), and models have been built to estimate the Houston toad calling activity, allowing us to obtain probability of extinction for the species under different sufficient recaptures to conduct reliable mark–recapture

Journal of Fish and Wildlife Management | www.fwspubs.org December 2011 | Volume 2 | Issue 2 | 208 Houston Toad Abundance A. Duarte et al. analyses. Herein, our objective within the confines of this 1989). Conversely, successful mating does not appear to study is to present the first robust local abundance deter males from returning to breeding ponds (Hillis estimate for the endangered Houston toad on a primary et al. 1984; Jacobson 1989). It is also important to note recovery site. that our sampling design defines the population in this study as the number of adult males attempting to Methods reproduce on the GLR. Thus, for this purpose, ‘‘adult’’ is defined as a reproductively active male, and if a large We conducted this study on the Griffith League Ranch number of adult males did not participate in chorusing, (GLR), a 1,948-ha ranch in Bastrop County, Texas, owned then our analysis will likely underestimate the number of by the Boy Scouts of America (Figure 2). This large tract adult males. A body condition index was calculated for of land is located within designated critical habitat for each male toad by regressing body lengths (snout-to- the Houston toad (USFWS 1984) and is considered vent lengths) on weights and using residuals for the body essential for long-term persistence of the species condition index (i.e., positive and negative residuals indi- (Hatfield et al. 2004). The GLR is a primarily forested cate above- and below-average body condition, respec- Downloaded from http://meridian.allenpress.com/jfwm/article-pdf/2/2/207/2751817/072011-jfwm-041.pdf by guest on 25 September 2021 ranch, with an overstory dominated by loblolly pine tively; Schulte-Hostedde et al. 2005). We removed an , post oak , blackjack oak Q. obvious outlier, but did not transform the data because the marilandica, and eastern red cedar Juniperus virginiana, untransformeddatafitalinearrelationshipwell(r2 =0.8). and an understory dominated by yaupon holly Ilex We transformed adult male Houston toad individual vomitoria, American beautyberry Callicarpa americana, captures (Supplemental Material, Table S1; http://dx.doi. and farkleberry Vaccinium arboreum. The GLR contains 17 org/10.3996/072011-JFWM-041.S2) into encounter histo- ponds, with hydroperiods ranging from highly ephem- ries, resulting in 15 sampling occasions, and imported the eral (n = 2) to permanent (n = 3). During 2010 we data into Program MARK (White and Burnham 1999). encountered Houston toads at 12 of these ponds. All 12 Abundance was then estimated using the POPAN ponds held water throughout the breeding season and, software incorporated in Program MARK, which is a thus, remained potentially active breeding ponds during Cormack–Jolly Seber model design (Schwarz and Arnason each sampling event. 1996). This model assumes an open population, allowing We conducted call surveys at each of the ponds using for immigration, emigration, births, and deaths between the survey protocol detailed in Jackson et al. (2006). We sampling occasions. Treating the population as closed was primarily surveyed on nights when Houston toads were unreasonable because predation on adult male Houston most likely to be active based on perceived weather toads occurs during the breeding season (Dixon et al. preferences derived from past studies. When Houston 1990; McHenry et al. 2010). Also, toads do not enter the toad calling was detected we searched the ponds and population at the same time; therefore all toads were not surrounding areas, captured the toads present, recorded available for sampling across all occasions (Hillis et al. standard measurements (i.e., snout–urostyle length, 1984; Jacobson 1989; Swannack 2007). head width, and weight), collected DNA from a single Program POPAN incorporates four parameter esti- toe clip, and individually marked toads using Passive mates, including probability of capture (p), probability of Integrated Transponder (PIT) tags (Camper and Dixon entry (PENT), apparent survival (Q), and super-population 1988; Dodd 2009). Previous research determined that size (N). Probability of entry is the probability of an handling and PIT-tagging Houston toads during calling individual entering the population on a given occasion nights did not adversely impact behavior (i.e., toads and Q is the probability of an individual remaining continued to call after handling), or subsequent returns available for recapture (survived and did not emigrate). to breeding sites (Dixon et al. 1990). We started with a global model in which p, PENT, and Q In addition to call surveys, we monitored Houston toad were all time-dependent (p(t) Q(t) PENT(t) N). Using activity using 26 drift fences (Heyer 1994). Seven of these Program RELEASE we tested the global model’s good- drift fences were located adjacent to (i.e., within 10 m), ness-of-fit. Reduced models were then fit where variation and parallel with, a pond used by Houston toads during in the parameter estimates was modeled as a function of the 2010 breeding season. These drift fences consisted of time (t) or as a constant (.). Probability of capture should one 15-m linear arm, a 19-L pitfall trap at each end, and be constant because we based our sampling events to two double-throated funnel traps placed near the center optimize toad capture, used multiple trained observers on each side of the flashing. Because of a low number of each night, and searched the breeding ponds and Houston toads captured in traps, we did not include the surrounding area until no new individuals were captured majority of these monitoring data in this study. However, during each sampling event. Therefore, p was modeled when Houston toads were captured at the seven linear as a constant. Apparent survival was modeled to vary arrays mentioned above on call-survey nights, we with time or to be constant and PENT was only modeled considered them pond captures for that night, because to vary with time. All possible combinations between our we likely intercepted migration to or from a breeding global model and applied constraints yielded a candidate pond. set of three models. We restricted our analysis to the adult male segment When constructing the models, we assigned Q, p, of the population. The return of females to ponds within PENT, and N the link function logit, Mlogit1, and log. We a breeding season is dependent upon nonsuccessful used the logit link for Q and p because it constrains the reproduction on previous nights, which is rare (Jacobson estimates from zero to one, which is necessary given that

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Figure 2. Locations of the 17 ponds and 26 drift fences on the Griffith League Ranch, Bastrop County, Texas, USA. To estimate adult male Houston toad Bufo (Anaxyrus) houstonensis abundance in spring 2010 we used data collected from the 12 ponds with detected calling activity during the 2010 breeding season and the 7 drift fences that were located adjacent to, and parallel with, ponds used by Houston toads during the 2010 breeding season.

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Figure 3. Count of individual male and female Houston toad Bufo (Anaxyrus) houstonensis captures per day on the Griffith League Ranch, Bastrop County, Texas, in 2010. We began the x-axis in February because no successful captures occurred during January. both parameters are probabilities. We assigned the cˆ =1.BasedontheAICc weights, both models in which Mlogitl link to PENT because it constrains the sum of p was constant were supported (Table 1). However, the all time steps from zero to one. We used the log link for modelinwhichp was constant and Q and PENT varied N, which is required because the abundance estimate across time (p(.) Q(t) PENT(t) N) was the most should be .1. parsimonious (AICc = 355.04). The derived N estimate We assessed model fit using Akaike’s Information per survey occasion varied over time and ranged from 4 Criterion (AICc) corrected for small sample size (Burnham (range using SEs adjusted for minimum number of and Anderson 1998). Model selection was based on AICc individuals captured = 1–8) to 134 (101–167; Figure 4); weights (i.e., the best-fit model had the largest AICc however, these estimates are likely biased high because weight). To account for model uncertainty, we used the of random temporary emigration of individuals. The model-averaging procedure in Program MARK to aver- gross N estimate was 254 (6SE, 53). The Q ranged from age parameter estimates, their corresponding standard 0.43 (60.29) to 0.98 (60.04; Figure 5), and p was 0.24 errors, and derived estimates of N. (60.05).

Results Table 1. Models analyzed and summaries of model We conducted 33 call surveys at each of the ponds selection for abundance estimates of adult male Houston between 13 January and 22 April, and monitored activity toads Bufo (Anaxyrus) houstonensis sampled from the Griffith using drift fences from 31 January to 1 May. Out of the 33 League Ranch, Bastrop County, Texas, in 2010. sampling events, 15 nights resulted in $1 Houston toad Model capture. Successful nights occurred between 13 February Modela AIC DAIC AIC wt. likelihood nPar and 22 April. Intervals between nights with male c c c captures ranged from 1 to 13 d and captures varied p(.) Q(t) 355.04 0.00 0.74 1.00 30 across the breeding season for both males and females PENT(t) N p(.) Q(.) 357.16 2.12 0.26 0.35 17 (Figure 3). One-hundred three individual toads (90 males, PENT(t) N 13 females) were captured and marked at breeding p(t) Q(t) 385.38 30.35 0.00 0.00 43 ponds. For the male and female segments of the PENT(t) N population we had 32 and 1 recaptures, respectively, that occurred over the entire breeding season. Individual a p is the capture probability, Q is the apparent survival probability, male body condition index scores ranged from 24.9 to PENT is the probability of entry, and N is the super-population size. The characters in parentheses denote the constraint that was put on 4.1 across all ponds. each parameter: (.) represents a constant, (t) represents time The goodness-of-fit test run for the global model in variation. AICc is the Akaike Information Criterion corrected for Program Release indicated underdispersion (cˆ , 1) in our small sample size score, DAICc is the difference between the best model score (smallest AICc) and each model, AICc wt. represents the data. Underdispersion is not biologically meaningful; relative likelihood of the model, and nPar is the number of therefore, we conducted our model selection assuming parameters in each model.

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Figure 4. Model-averaged-derived abundance estimates of adult male Houston toads Bufo (Anaxyrus) houstonensis per survey occasion on the Griffith League Ranch, Bastrop County, Texas, in 2010. Error bars represent 1 standard error corrected for the minimum number of individuals captured.

Discussion once. The largest number of male captures at breeding ponds in one night was 37 individuals. This particular Our gross abundance estimate of adult male Houston night had the largest congregation of male toads at a toads (i.e., total number of adult male Houston toads single pond throughout the entire breeding season attempting to breed in 2010) was reasonable (201–307 (Pond 12; 35 individuals). It is noteworthy that the individuals). We could not estimate abundance of adult capture of 35 individuals was approximately equivalent female Houston toads in Program MARK because of low to the total number of males detected during each of the recapture success (1 female recapture). However, Swan- previous years, 2006–2009. nack and Forstner (2007) reported a functional male- Despite the large number of individual male toads biased sex ratio of 5:1 on the GLR. This ratio was estimated captured at Pond 12 in one night, subsequent survey from successful individual captures utilizing multiple nights at this pond (n = 21) detected dramatically fewer sampling methods over 4 consecutive y. Using this toads (n = 9), and only 9% of the individuals captured at functional sex ratio, we estimated the adult female Pond 12 throughout 2010 were recaptured. This is in Houston toad population to be between 40 and 61 contrast to several other ponds, where we obtained far individuals. Thus, the total adult Houston toad population fewer total captures, but a much higher rate of return. on the GLR in 2010 was estimated to be between 241 and For instance, we captured only five individuals at Pond 368 individuals. Though all sampling took place on the 15, but recaptured 60% of the individuals, with one GLR, intra- and interyear movement data from 2001 to the individual recaptured three times. We propose three present, alongside high-resolution population genetic hypotheses concerning the observed high recapture data including migration inferences (McHenry 2010), variability among ponds: 1) probability of detection (i.e., support the supposition that our population estimate capture) varied among ponds because of pond charac- represents the majority of the western habitat patch in teristics; 2) probability of detection (i.e., capture) varied Bastrop County centered on the GLR. among ponds because of heterogeneous individual toad The breeding-season activity pattern observed during behavior; and 3) within-season survivorship differed this study was similar to previous studies (Hillis et al. among ponds. 1984; Jacobson 1989; Price 2003; Swannack 2007). Male We address evidence supporting each hypothesis in toads were detected at the breeding ponds prior to the sequential order. The estimated probability of capture arrival of female toads, and Houston toad calling activity was 0.24 (60.05). It is important to note the estimate is a was greatest in mid-March (Figure 3). Males visited the function of two components: whether we detected an same breeding pond throughout the season, although individual that was present at a pond, and whether an only a relatively small proportion (26.7%) of the male individual was actually at a pond (and, thus, was able to segment of the population was captured more than be detected). Pond characteristics (e.g., size and vegeta-

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Figure 5. Model-averaged apparent survival estimates of adult male Houston toads Bufo (Anaxyrus) houstonensis per survey interval on the Griffith League Ranch, Bastrop County, Texas in 2010. Error bars represent 1 standard error corrected for the maximum probability of apparent survival. tion cover) could influence detection. Nevertheless, individuals at Pond 12 were inherently less likely to differences in pond characteristics probably had little or engage in calling activity on multiple nights than toads no influence on capture probability during this study calling at other ponds. because we conducted extensive pond searches when The third potential explanation is within-season toad calling was detected. Further, even at large ponds, survivorship differed among ponds. We estimated ap- Houston toads on the GLR typically aggregate in the parent survival to range from 0.43 (60.29) to 0.98 (60.04; same localized areas of the ponds night after night (D. J. Figure 5), meaning the likelihood of an individual Brown and M. R. J. Forstner, personal observation). Thus, surviving and returning to the study area (i.e., breeding probability of capture was likely high once toads were ponds) from one day to the next was between 43% and initially detected during the study. 98%. The current estimate of annual survivorship for The influence of individual differences in calling adult male Houston toads is approximately 15% (Swan- behavior on initial detection is more difficult to nack et al. 2009). Therefore, the lower apparent survi- dismiss. Although this was unlikely to be a problem val estimates were likely primarily a consequence of on explosive nights, it could have influenced detection emigration. However, it might also be caused by on nights with minimal calling activity. Calling is differences in predation among chorusing groups. An energetically costly, and energetic demands influence increase in chorus size might elevate exposure to a variety of parameters associated with calling activity predation. Unfortunately, we were unable to partition (reviewed in Wells 2007). Although body size has been emigration from mortality or derive pond-specific found to be a poor predictor of nights engaged in parameter estimates. Nevertheless, we believe among- calling activity (i.e., chorus tenure) in other toad pond differences in detection probability, migration, or species (Given 2002), body condition has been found survivorship, are all reasonable hypotheses for the to be positively associated with chorus tenure in observed recapture heterogeneity, and we encourage species (Murphy 1994; Judge and Brooks 2001). Thus, further investigations concerning this topic. differences in body condition of male Houston toads Our study reports the most extensive, robust estimate among ponds, potentially a function of habitat quality, of abundance for a Houston toad population to date. could account for among-pond variability in chorus From summer 2007 to autumn 2009, Bastrop County tenure. However, both extremes of the body condition experienced significant and exceptional drought condi- index range calculated were from individuals at Pond tions, which likely negatively impacted Houston toad 12. Also the mean body condition index score for Pond survivorship (Price 2003; Forstner et al. 2007; Supplemen- 12 was 0.05, indicating that mean body condition of tal Material, Reference S1; http://dx.doi.org/10.3996/ male toads at Pond 12 was comparable to toads active 072011-JFWM-041.S1). Thus, the 2010 abundance esti- at other ponds on the GLR. Thus, at least from an mate likely represents the adult population size at the energetic demands perspective, it is unlikely that lower bound because it follows a series of harsh years

Journal of Fish and Wildlife Management | www.fwspubs.org December 2011 | Volume 2 | Issue 2 | 213 Houston Toad Abundance A. Duarte et al. with low reproductive success (M. R. J. Forstner, unpub- in a southern USA pine forest. Journal of Fish and lished data). Wildlife Management 2(2):135–145. We assumed the high reproductive success observed Brown DJ, Swannack TM, Forstner MRJ. In press. in 2010 would have allowed the population to rebound, Herpetofaunal survey of the Griffith League Ranch in and the 2011 breeding season would have afforded us the Lost Pines ecoregion of Texas. Texas Journal of the opportunity to quantify the influence of a good Science. reproductive year on adult population size. Unfortunate- Brown LE. 1971. Natural hybridization and trend towards ly, another severe drought in Bastrop County in 2011 extinction in some relict Texas toad populations. resulted in no detected Houston toad calling activity on Southwestern Naturalist 16:185–199. the GLR for the first time since we began surveying the Brown LE. 1975. The status of the near-extinct Houston property. Regardless, this study provides baseline infor- mation regarding Houston toad population size on one toad (Bufo houstonensis) with recommendations for its of the primary recovery sites for the species, and will be a conservation. Herpetological Review 6:37–40. useful gauge to infer the efficacy of recovery initiatives in Brown LE, Mesrobian A. 2005. Houston toads and Texas Downloaded from http://meridian.allenpress.com/jfwm/article-pdf/2/2/207/2751817/072011-jfwm-041.pdf by guest on 25 September 2021 the future. politics. Pages 150–167 in Lannoo M, editor. 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Texas Austin, Texas. Parks and Wildlife Department, Research Publication Found at DOI: http://dx.doi.org/10.3996/072011-JFWM- 7100-159. 041.S1 (497 KB PDF). Dixon JR, Dronen NO, Godwin JC, Simmons MA. 1990. Table S1. Capture history of adult male Houston The amphibians, reptiles, and mammals of Bastrop toads at breeding ponds on the Griffith League Ranch, and Buescher state parks: with emphasis on the Bastrop County, Texas, in spring 2010. Houston toad (Bufo houstonensis) and the short-tailed Found at DOI: http://dx.doi.org/10.3996/072011-JFWM- shrew (Blarina sp.). Report to the Texas Parks and 041.S2 (18 KB XLSX). Wildlife Department, Austin, Texas. Dodd CK. 2009. Amphibian ecology and conservation: a Acknowledgments handbook of techniques. Oxford: Oxford University We are grateful to J. Bell, A. Harper, M. Vandewege, M. Press. Gaston, B. DeVolld, and J. Barnett for field assistance [ESA] Endangered Species Act of 1973, Pub. L. No. 93- during this study. The Capitol Area Council of the Boy 205, 87 Stat. 884 (Dec. 28, 1973). Scouts of America provided access to the GLR, and we Forstner MRJ, McHenry DJ, Gaston M, Villalobos L, Crump appreciate their continuing support of our research. B. P, McCracken S, Jackson J, Swannack T, Bell J, Gaertner Halstead, C. Dodd, J. Hatfield, and the Subject Editor J, Mays S, Hahn D, Dixon JR. 2007. The Houston toad provided valuable comments that improved an earlier 2007: annual summary of research and monitoring. version of this manuscript. Report to the U.S. Fish and Wildlife Service, Austin, This research was funded by the U.S. Fish and Wildlife Texas (see Supplemental Material, Reference S1; http:// Service, Texas Parks and Wildlife Department, and Environ- dx.doi.org/10.3996/072011-JFWM-041.S1). Texas Jour- mental Defense Fund. Trapping and handling permits were nal of Science 40:454–456. provided by the Texas Parks and Wildlife Department Freed PS, Neitman K. 1988. Notes on predation on the (permit SPR-0102-191), and the U.S. Fish and Wildlife endangered Houston toad, Bufo houstonensis. Texas Service (permit TE 039544-0). This research was approved Journal of Science 40:454–456. by the Texas State University - San Marcos Institutional Gaston MA, Fuji A, Weckerly FW, Forstner MRJ. 2010. Care and Use Committee (0810_0208_11). Potential component allee effects and their impact on The use of trade, firm, or product names is for wetland management in the conservation of endan- descriptive purposes only and does not imply endorse- gered anurans. PLoS One 5:e10102. ment by the U.S. Government. Given MF. 2002. Interrelationships among calling effort, References growth rate, and chorus tenure in Bufo fowleri. Copeia 2002:979–987. Brown DJ, Baccus JT, Means DB, Forstner MRJ. 2011. Gottschalk JS. 1970. United States list of endangered Short-term outcomes for juvenile amphibians after fire native fish and wildlife. Federal Register 35:16047–

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