In 2003, we implemented a new monitoring program for the the endangered arroyo toad (Bufo californicus) on Marine Corps Base Camp Pendleton (MCBCP). To address the problems associated with large variations in adult toad activity, we employed a spatial and temporal monitoring approach. In this approach, we track the presence of breeding arroyo toads over a wide geographic area rather than abundance at a small number of discrete sites.
ARMI (Amphibian Research and Monitoring Initiative, USGS) has adopted proportion of area occupied (PAO) as a standardized metric for mid-level monitoring of amphibian populations. We describe a monitoring program using this metric for the endangered arroyo toad (Bufo californicus).
Prolonged drought due to climate change has negatively impacted amphibians in
southern California, U.S.A. Due to the severity and length of the current drought,
agencies and researchers had growing concern for the persistence of the arroyo toad
(Anaxyrus californicus), an endangered endemic amphibian in this region. Range-wide
surveys for this species had not been conducted for at least 20 years. In 2017–2020,
we conducted collaborative surveys for arroyo toads at historical locations. We surveyed 88 of the 115 total sites having historical records and confirmed that the arroyo
toad is currently extant in at least 61 of 88 sites and 20 of 25 historically occupied
watersheds. We did not detect toads at almost a third of the surveyed sites but did
detect toads at 18 of 19 specific sites delineated in the 1999 Recovery Plan to meet
one of four downlisting criteria. Arroyo toads are estimated to live 7–8 years, making
populations susceptible to prolonged drought. Drought is estimated to increase in frequency and duration with climate change. Mitigation strategies for drought impacts,
invasive aquatic species, altered flow regimes, and other anthropogenic effects could
be the most beneficial strategies for toad conservation and may also provide simultaneous benefits to several other native species that share the same habitat
Habitat degradation, entwined with land cover change, is a major driver of biodiversity loss. Effects of land cover
change on species can be direct (when habitat is converted to alternative land cover types) or indirect (when
land outside of the species habitat is altered). Hydrologic and ecological connections between terrestrial and
aquatic systems are well understood, exemplifying how spatially disparate land cover conditions may influence
aquatic habitats, but are rarely examined. We sought to quantify relative effects of land cover at two different but
interacting scales on habitat suitability for the endangered arroyo toad (Anaxyrus californicus). Based on an
existing distribution model for the arroyo toad and available land cover data, we estimated effects of land cover
along streams and within entire watersheds on habitat suitability using structural equation modeling.
Relationships between land cover and habitat suitability differed between scales, and broader, watershed-scale
conditions influenced land cover along the embedded stream networks. We found anthropogenic development
and forest cover at the watershed-scale negatively impacted habitat suitability, but development along stream
networks was positively associated with suitability. The positive association between development along streams
and habitat suitability may be attributable to increased spatial heterogeneity along urbanized streams, or related
factors including policies designed to conserve riparian habitats amidst development. These findings show arroyo toad habitat is influenced by land cover across multiple scales, and can inform conservation of the species.
Furthermore, our methodology can help elucidate similar dynamics with other taxa, particularly those reliant on
both terrestrial and aquatic environments.
Species distribution models are used for numerous purposes such as predicting changes in
species' ranges and identifying biodiversity hotspots. Although implications of distribution
models for conservation are often implicit, few studies use these tools explicitly to inform
conservation efforts. Herein, we illustrate how multiple distribution models developed using
distinct sets of environmental variables can be integrated to aid in identification sites for use
in conservation. We focus on the endangered arroyo toad (Anaxyrus californicus), which
relies on open, sandy streams and surrounding floodplains in southern California, USA, and
northern Baja California, Mexico. Declines of the species are largely attributed to habitat
degradation associated with vegetation encroachment, invasive predators, and altered
hydrologic regimes. We had three main goals: 1) develop a model of potential habitat for
arroyo toads, based on long-term environmental variables and all available locality data; 2)
develop a model of the species' current habitat by incorporating recent remotely-sensed
variables and only using recent locality data; and 3) integrate results of both models to identify
sites that may be employed in conservation efforts. We used a machine learning technique,
Random Forests, to develop the models, focused on riparian zones in southern
California.We identified 14.37% and 10.50% of our study area as potential and current habitat
for the arroyo toad, respectively. Generally, inclusion of remotely-sensed variables
reduced modeled suitability of sites, thus many areas modeled as potential habitat were not
modeled as current habitat. We propose such sites could be made suitable for arroyo toads
through active management, increasing current habitat by up to 67.02%. Our general
approach can be employed to guide conservation efforts of virtually any species with sufficient
data necessary to develop appropriate distribution models.
The arroyo southwestern toad is a specialized and federally endangered amphibian endemic to the coastal plains and mountains of central and southern California and northwestern Baja California. It is largely unknown how long these toads live in natural systems, how their population demographics vary across occupied drainages, and how hydrology affects age structure. We used skeletochronology to estimate the ages of adult arroyo toads in seven occupied drainages with varying surface water hydrology in southern California. We processed 179 adult toads with age estimates between 1 and 6 years. Comparisons between skeletochronological ages and known ages of PIT tagged toads showed that skeletochronology likely underestimated toad age by up to 2 years, indicating they may live to 7 or 8 years, but nonetheless major patterns were evident. Arroyo toads showed sexual size dimorphism with adult females reaching a maximum size of 12 mm greater than males. Population age structure varied among the sites. Age structure at sites with seasonally predictable surface water was biased toward younger individuals, which indicated stable recruitment for these populations. Age structures at the ephemeral sites were biased toward older individuals with cohorts roughly corresponding to higher rainfall years. These populations are driven by surface water availability, a stochastic process, and thus more unstable. Based on our estimates of toad ages, climate predictions of extreme and prolonged drought events could mean that the number of consecutive dry years could surpass the maximum life span of toads making them vulnerable to extirpation, especially in ephemeral freshwater systems. Understanding the relationship between population demographics and hydrology is essential for predicting species resilience to projected changes in weather and rainfall patterns. The arroyo toad serves as a model for understanding potential responses to climatic and hydrologic changes in Mediterranean stream systems. We recommend development of adaptive management strategies to address these threats.
In 2003, we implemented a new monitoring program for the endangered arroyo toad (Bufo californicus) on Marine Corps Base Camp Pendleton (MCBCP). To address the problems associated with large variations in adult toad activity, we employed a spatial and temporal monitoring approach that tracks the presence of arroyo toad breeding populations by documenting presence of eggs and larvae. Sites are surveyed up to four times per year to calculate and account for imperfect detection probabilities. We also continued to conduct nighttime counts of adult toads from the monitoring program implemented by Dan Holland in 1996. In this presentation, we review the major trends and findings of the first three years of the spatial monitoring program and a decade of adult count transects. These include the findings that 1) toad activity has been highly variable among years, but relatively stable over the last decade, 2) associations between activity and rainfall are dependant upon hydroperiod, 3) proportion of wet area occupied appears to be the most stable monitoring metric, and 4) both proportion area occupied (PAO) and probability of detecting arroyo toads are negatively associated with the presence of non-native aquatic species.
This 2013 Wildland Fire Workshop focused on Southern California and landscape level fires occurring in the last decade. This workshop brought together land managers, researchers, and fire management personnel to continue the discussions on the topic of wildland fire impacts to at risk natural resources. The purpose of the workshop was to present, collaborate, and plan wildland fire-related research, management, responses, and future recovery as it applies to the “at risk†natural resources of San Diego County.
Rapid urbanization has led to the loss and degradation of riparian habitats in southern
California. In response to the need to protect and manage habitat for native species in the
South Coast Eco-Region of Southern California, the Natural Communities Conservation
Planning Program (NCCP) was initiated in 1991. The arroyo toad (Bufo californicus) and
western pond turtle (Clemmys marmorata) are covered species in the San Diego Multiple
Species Conservation Program (MSCP). However, the current status and distribution of the
arroyo toad and the western pond turtle within the MSCP is poorly known. Direct habitat loss in
conjunction with hydrological alterations and the introduction of nonnative species have caused
arroyo toads to disappear from about 75% of previously occupied habitat within the United
States. The western pond turtle is the only turtle native to southwestern California and was
historically abundant in most major drainages in San Diego County. Surveys conducted in
southern California in the late 1980's suggested that pond turtles no longer occurred in many
historic locations and that few viable populations of turtles remained. The US Geological
Survey conducted surveys for the arroyo toad and western pond turtle at select sites within the
San Diego MSCP in 2002. Arroyo toads were observed at two of the 7 sites surveyed and
western pond turtles were detected at 3 of the 26 sites surveyed. A suite of non-native aquatic
predatory species known to have deleterious effects on native amphibian species was detected
at 46% of the sites that contained surface water during the surveys. Non-native turtles were
detected at more locations than western pond turtles. Western pond turtles co-occur with nonnative
turtles at least at one location. Surveys for both, arroyo toads and western pond turtles
will continue during spring and summer 2003.
The U. S. Fish and Wildlife Service (Service) is required by section 4(c)(2) of the Endangered Species Act of 1973 (Act) to conduct a status review of each listed species at least once every 5 years. The purpose of a 5-year review is to evaluate whether or not the species? status has changed since it was listed (or since the most recent 5-year review). Based on the 5-year review, we recommend whether the species should be removed from the list of endangered and threatened species, be changed in status from endangered to threatened, or be changed in status from threatened to endangered. Our original listing of a species as endangered or threatened is based on the existence of threats attributable to one or more of the five threat factors described in section 4(a)(1) of the Act, and we must consider these same five factors in any subsequent consideration of reclassification or delisting of a species. In the 5-year review, we consider the best available scientific and commercial data on the species, and focus on new information available since the species was listed or last reviewed. If we recommend a change in listing status based on the results of the 5-year review, we must propose to do so through a separate rule-making process defined in the Act that includes public review and comment.
Observations of the federally endangered arroyo toad (Bufo californicus) within Cuyamaca
Rancho State Park in 1999 created the need for a park-wide study of this endangered
amphibian. At that time it was not known what the current distribution of the arroyo toad was
or how much suitable habitat for this amphibian occurred on state park properties in this
general area. USGS San Diego Field Station was contracted to address both issues. Surveys
were conducted in 2002 and 2003 in Cuyamaca Rancho State Park and in 2003 in the
adjacent Lucky 5 Ranch properties in Anza-Borrego Desert Sate Park. Habitat assessment
surveys were conducted during daylight hours, and follow-up presence surveys were
conducted after dark from June through September to clarify distribution. We used a habitat
quality rating system to classify habitats (i.e., drainage reaches) as high, good, marginal, or
poor quality for this endangered species. The presence/absence of physical features, known
to be highly correlated to the presence of arroyo toad populations were used to score each
drainage reach resulting in an overall habitat quality score. Four individual habitat patches
were identified as high or good quality within Cuyamaca Rancho State Park; no suitable
habitat was located within the Lucky 5 Ranch properties. Because high and/or good quality
habitat was found only in Cuyamaca Rancho State Park, focused surveys for arroyo toads
were only conducted there. For each arroyo toad observation we report the specific location
(latitude / longitude), environmental parameters, age class, and time of observation. Only two
observations of were made in 2002, while 43 individual observations were made in 2003.
The greater number of observations in 2003 than in 2002 was attributed to the greater amount
of rainfall and warmer nighttime temperatures in 2003. In addition, we documented breeding
(larvae) and recruitment (recent metamorphs) at two of the four high quality habitat patches.
It was also noted that this high-elevation arroyo toad population bred later in the season than
the coastal and foothill population in the same region. Introduced species including,
hatchery-stock rainbow trout (Oncorhynchus mykiss var.), threespine stickleback
(Gasterosteus aculeatus microcephalus), goldfish (Carassius auratus), and wild turkey
(Meleagris gallopavo var.) were all documented within Cuyamaca Rancho State Park and
were found to co-occur with the endangered arroyo toads. The po
In 2003, the USGS implemented a new monitoring program for the endangered arroyo toad
(Anaxyrus californicus) on Marine Corps Base Camp Pendleton (MCBCP). To address problems
associated with large variations in adult toad activity, we employed a spatial and temporal monitoring
approach to track arroyo toad breeding populations by documenting the presence of egg strings and
larvae. We survey sites within three major watersheds up to four times per year to calculate and account
for imperfect detection probabilities. We also conduct night surveys for adult toads, following a
monitoring program initially implemented by Dan Holland in 1996. This report details results and
analyses specific to the 2006 surveys, as well trends in occupancy, breeding and adult activity from
2003 to 2006.
Wide variations in seasonal rainfall have marked the past several years of arroyo toad
monitoring at MCBCP. In 2006, we received only half the normal average rainfall (138 mm).
Consequently, the largely ephemeral San Onofre and San Mateo Creeks remained partially dry
throughout the 2006 breeding season. Over all watersheds, 64% of potential toad breeding habitat
contained water during our survey efforts. However, 82.7% (se= 7.4) of the available wet habitat was
occupied by breeding arroyo toads. We recorded the highest occupancy in the Santa Margarita
Watershed (85.0%), followed by the San Mateo (22.3%) and San Onofre (0.0%) Watersheds.
Even in the wetted areas, San Mateo and San Onofre Creeks had unexpectedly low occupancy of
arroyo toads. In particular, we found a significant 74.1% decrease in occupied breeding habitat within
San Mateo Creek from 2005 to 2006. We hypothesize that this low occupancy for San Mateo and San
Onofre Creeks may be the result of reduced sand cover, which dropped from an average of 26-50% in
2005 to only 11-25% in 2006. In general, the creek beds became rockier with few sandy areas available
for arroyo toad breeding. Another possibility for the low occupancy of arroyo toads in San Mateo and
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San Onofre Creeks could be the cool temperatures and relatively late rainfall of 2006. These factors can
result in the absence of arroyo toad breeding activity.
Even though surface water availability was highly variable (44-95%) from 2003 to 2006, the
overall extant of breeding toads in wetted areas was relatively stable (77-95%) with no significant
change over the four year period. The night survey count data from 1996 to 2006 also showed
Internal Title "Studies of the Effects of Reservoir Releases on the Arroyo Toad and Coast Range Newt On the Upper San Diego River Watershed". INTRODUCTION: This study was commissioned in 1999 to investigate the potential downstream effects of
current and modified controlled water release regimes from Cuyamaca Reservoir into Boulder Creek on the resident populations of arroyo toad (Bufo californicus) and the coast range newt (Taricha torosa torosa). This study is intended to develop a scientific foundation upon which to base the issuance of United States Fish and Wildlife Service (USFWS) and California Department of Fish and Game (CDFG) endangered species take permits, as a part of the Helix Water District Natural Communities Conservation Plan (NCCP), pursuant to the State of California NCCP Act of 1991. Projects for which incidental take of sensitive species is sought are required to contribute to the recovery of the species through increased management and conservation, as required by state and federal environmental policy and legislation regarding take of endangered species. The development and study of alternative water release regimes is an important component of this project in that it will investigate means of reducing or avoiding adverse effects to these species, which is preferable to compensatory mitigation. The Implementing Agreement for the Helix Water District NCCP will include this research project as one of the conditions for ?coverage? for the arroyo toad and Coast Range newt. This report summarizes the first two years of the research project.
To address the problems associated with large variations in adult toad activity, we employed a spatial and temporal monitoring approach that tracks the presence of arroyo toad breeding populations by documenting the presence of eggs and tadpoles. In 2011, surveys did not officially start until early July due to a delay in the contract, which was later than optimal for full documentation of breeding. Under this circumstance, the contract and protocol were modified to adjust for the remaining available survey period. Sites were surveyed up to two times to detect breeding activity and the resulting occupancy modeling is limited to single- year analysis.
During 2011, seasonal rainfall totaled 320.5 millimeters (12.62 inches), which is 17% above to the historical normal average rainfall. Approximately 80% of suitable habitat contained water during the arroyo toad breeding season. Where surface water was present, we documented arroyo toad breeding at a majority of sites (82.5%), including those in the ephemeral watersheds.
Even though surface water availability was highly variable (34-95%) from 2003-2011, the overall extent of breeding toads in wetted areas remained relatively stable (77-95%) with no significant change over the nine-year period. Single-year models showed negative associations between occupancy of non-native aquatic species and arroyo toad tadpoles in 2011. Co-occurrence of arroyo toads and non-natives is largely within the Santa Margarita River. We previously documented negative associations in detection probability from 2004 to 2008, with a large peak in 2007. This association weakened in 2008 and disappeared in 2009. We attribute this partly to our bullfrog removal efforts in 2008, and to MCBCP base-wide efforts to remove bullfrogs, crayfish, and non-native fish, particularly in the Santa Margarita River since 2009. The increased association between presence of non-native aquatic species and absence of arroyo toads during 2010 and 2011 indicates that continued removal efforts support persistence of the arroyo toad in the river. We continue to demonstrate an important feedback loop between monitoring and management for this endangered species.
In 2003, we implemented a new monitoring program for the endangered arroyo toad
(Bufo californicus) on Marine Corps Base Camp Pendleton (MCBCP). To address the
problems associated with large variations in adult toad activity, we employed a spatial and
temporal monitoring approach that tracks the presence of arroyo toad breeding populations
by documenting the presence of eggs and larvae. Unlike adult toads, eggs and/or larvae
remain visible in the water for months before metamorphosis and have a much higher
probability of detection. This year, we began monitoring 89 km of potential toad breeding
habitat within MCBCP. We divided the habitat into approximately 60 blocks, each divided
into 6 survey site lengths. One site length within each block is surveyed yearly, while the
other site lengths are surveyed on a 5 year rotation. We implemented the first year of this
rotating panel design by comprehensively surveying 120 randomly stratified survey site
lengths (30 km). We then used a loglinear modeling program to model the data and correct
for varying detection probabilities. The program provides the framework for powerful
statistical analysis of trends in metapopulation dynamics and breeding, as well as the effects
of habitat, aquatic variables, and management actions on arroyo toad populations.
In 2003, 78% of potential toad breeding habitat contained water during our survey
efforts. Of these areas, 87.4% (se = 9.5) of the habitat was occupied by breeding arroyo
toads. The greatest occupancy was recorded on the San Mateo watershed (97.9%), followed
by the San Onofre (90.9%) and Santa Margarita (83.8%) watersheds. We evaluated over 14
habitat and survey specific variables in the models. These included landscape variables,
environmental variables, and the presence of nonnative plant and aquatic vertebrate species.
Results showed that the absence of crayfish was the single most significant predictor of the
presence of arroyo toad larvae. Larvae were 20 times (95% CI: 2-249) more likely to be
detected when crayfish were absent. Although data on the relationship between crayfish and
arroyo toads are sparse, crayfish are known to prey upon amphibian eggs, larvae, and adults,
and have been linked with declines in some amphibian populations. It is unknown whether
this is a direct link or if crayfish are an indirect indicator of less than favorable habitat
conditions.
In order to provide continuity with previous monitoring efforts, monitor n
The purpose of this study was to provide a risk assessment of the short-term and long-term
effects of Loveland Dam operations on arroyo toad (Bufo californicus) reproductive success and
population viability. Results of this study will be used in the development of the Sweetwater
Authority Subarea Plan of the Joint Water Agencies Subregional Natural Community
Conservation Planning (NCCP) program and will be used in the process of gaining scientific
justification for the United States Fish and Wildlife Service (USFWS) and California Department
of Fish and Game (CDFG) incidental take permits associated with the Sweetwater Authority
Subarea Plan (Fleury 2001). The goal is for Sweetwater Authority to maintain flexibility in the
management of their reservoirs while sustaining arroyo toad populations within the system
(Fleury 2001). Historical arroyo toad breeding, weather, hydrological, and Loveland Dam
release data were used to examine the risk associated with the short-term and long-term effects
of Loveland Dam operations on arroyo toad reproductive success and population viability. Dam
releases during the arroyo toad breeding season are the biggest concern for reproductive success
and the focus of this risk assessment. Using historical breeding occurrence data, rough upper
and lower bounds for arroyo toad cohort loss due to controlled dam releases during the arroyo
toad breeding season were estimated. In the analysis, risk due to dam releases was found to be
the highest in early March to late July when the greatest loss of egg masses, larvae and
metamorphs was estimated to occur, with the upper bound ranging from 28% to 63% of the
entire year's cohort. Over time, repeated loss of cohorts due to dam releases can decrease
population viability, but further study is required to determine the exact risk. Simply avoiding
controlled releases during the arroyo toad breeding season, especially from March to late July,
will greatly reduce the risk to arroyo toad reproductive success and population viability. In
addition, several other possible risks to arroyo toad reproductive success as a result of dam
operations were qualitatively examined. These included the effects of dam releases concurrent
with rain or spill events, the effects of dam releases during wet and dry years, the effects of the
intensification and lengthening of drought periods and the effects of the degradation of arroyo
toad breeding habitat from the increase in vegetative
From 2002 to 2004, California State Parks contracted with the U.S. Geological Survey to
conduct daytime habitat evaluation and focused nocturnal surveys to determine the
distribution of suitable habitat and presence of arroyo toads (Bufo californicus) within
Cuyamaca Rancho State Park (CRSP). The 2002 and 2003 surveys documented breeding
populations of arroyo toads at four high-quality sites along the Sweetwater River, but the
effects of the Cedar Fire in late 2003 on these populations were unknown. The purposes
of the 2004 surveys were to determine if there were changes in the distribution of arroyo
toads and arroyo toad habitat as a result of the Cedar Fire, and to determine fire severity
levels at the four previously known high-quality habitat locations. To accomplish this, we
used daytime habitat evaluation surveys, fire severity transects, and nocturnal presence
surveys. Each 250-m stretch of the river was re-evaluated based on the presence of key
arroyo toad habitat characteristics: 1) the channel substrate and banks being
predominately composed of depositional sand, 2) flat, exposed sandy terraces
immediately adjacent to the channel, and 3) channel braiding. Furthermore, the reaches
were surveyed diurnally and nocturnally for all life history stages of the arroyo toad and
other riparian-associated animal species.
Of a total 17.0 km (10.6 mi) of riparian habitat surveyed, 7.8 km, or nearly half of the
river within CRSP, was rated as high- (3.7 km) or good-quality (4.1 km) habitat for
arroyo toads. Arroyo toads (particularly the immature stages) were abundant in the lower
third of the Sweetwater River, found virtually continuously along a 5.2-km stretch of
river. Breeding individuals and large numbers of young were also detected in the middle
of the river within CRSP, thus documenting the presence and breeding of arroyo toads in
all four sites from the previous two years. In addition, we recorded a large adult female at
the highest known elevation (1,354 m; 4,442 ft) for arroyo toad occurrences in the
Sweetwater River watershed, in a severely burned, dry portion of the river several
kilometers upstream from the nearest surface water. Chytridiomycosis, a major infectious
disease affecting amphibians, was detected in one arroyo toad and one Pacific treefrog
which were collected dead during the surveys, possibly representing the first cases of the
pathogen in amphibians in the watershed. According to the fire severity transect
Rapid urbanization has led to the loss and degradation of riparian habitats within the Southern California Coastal Sage Scrub Region. In response to the need to protect and manage riparian and other sensitive habitats in southern California, the Natural Communities Conservation Planning (NCCP) Act was enacted in 1992. The San Diego County subregional plan under the NCCP is the San Diego County Multiple Species Conservation Program (MSCP). The MSCP has been designated to protect such sensitive species as the arroyo toad (Bufo californicus) and western pond turtle (Emys marmorata) within its boundaries by preserving lands with known populations, controlling non-native species, minimizing human impacts, and restoring or enhancing native habitats. Direct habitat loss in conjunction with hydrological alterations and the introduction of non-native species has caused the arroyo toad to disappear from about 75% of previously occupied habitat (Jennings & Hayes 1994) and has resulted in a decrease in the number of viable populations of the western pond turtle in southern California (Brattstrom & Messer 1988; Jennings et al. 1992; Jennings & Hayes 1994). Prior to this study, little was known about the current status and distribution of the arroyo toad and the western pond turtle within the San Diego MSCP lands.
In 2002 and 2003 the U. S. Geological Survey conducted focused surveys for the arroyo toad and western pond turtle within nine watersheds of San Diego County, eight of which fall within the MSCP boundaries. Daytime arroyo toad habitat surveys were conducted at 39 sites. Eighteen of these sites were determined to have potential for supporting arroyo toads because of the presence of suitable habitat and/or the close proximity of historical locality record(s) and were surveyed nocturnally for the presence of arroyo toads. Arroyo toads were located at five sites, all but one were previously known locations and all were within the MSCP boundaries. Visual and/or trapping surveys were conducted for western pond turtles at 68 sites for a total of 67 visual and 45 trapping surveys. Western pond turtles were detected at nine sites, six of which are within the MSCP boundaries, and all locations but one were previously known. Population sizes of both species appear to be small. Although mark-recapture data were not collected for arroyo toads and it is not possible to make population estimates, 18 was the largest number of arroyo toads detected at a site during the course
In 2002 The U. S. Geological Survey (USGS) was contracted by the Sweetwater
Authority to conduct a study examining the short-term and long-term effects of Loveland Dam
operations on the arroyo toad (Bufo californicus) below that dam in the Sweetwater River
channel. The first phase of the study was a risk assessment, which examined the short-term and
long-term effects of Loveland Dam operations on arroyo toad reproductive success and
population viability (see Madden-Smith et al. 2004). This report covers the second phase of the
study, which involved baseline surveys for arroyo toad habitat and arroyo toads below Loveland
Dam. During the 2003 arroyo toad breeding season, daytime habitat and nocturnal presence
surveys for arroyo toads were conducted at four sites along the Sweetwater River: 1) Sycuan
Peak Ecological Reserve, Sweetwater River; 2) San Diego National Wildlife Refuge, Sweetwater
River; 3) Cottonwood Golf Course along the San Diego National Wildlife Refuge border, and 4)
upper Sweetwater Reservoir. Habitat assessment included: percent vegetative cover, streambed
and bank vegetation type, substrate type, descriptions of arroyo toad habitat characteristics and
hydrologic descriptions including stream width and estimates of flow. Habitat assessment at
Sycaun Peak Ecological Reserve resulted in two reaches rated as high quality, two reaches rated
as good quality, three reaches rated as marginal quality and two reaches rated as poor quality.
Habitat assessment at San Diego National Wildlife Refuge and upper Sweetwater Reservoir
resulted in one reach of high quality habitat for each site. Habitat assessment at Cottonwood
Golf Course resulted in one reach of good quality habitat. Based on the results of the daytime
habitat assessment, nocturnal adult presence surveys were conducted at potentially suitable
arroyo toad habitat (habitat rated high or good quality). Nocturnal surveys were conducted for
six nights at each site and arroyo toads were not detected at any of the sites. Survey techniques
were in accordance with the recommended U. S. Fish and Wildlife Service (USFWS) Protocol
(USFWS1999b). For inaccessible areas, available arroyo toad abundance and distribution data
were used to fill in where current information is lacking. Management concerns (e.g., presence
of bullfrogs or other non-native predators, obstructive vegetative growth [native and non-native],
etc.) were also identified as part of the baseline surveys. Results
During the 2001 Arroyo Toad Surveys by USGS, arroyo toads were
observed at five of the twelve study sites. Arroyo toads were observed in the
months of May, June and July. The timing of the detectability of the arroyo toads
appears to vary between sites. Most notable is the delayed timing of the Deep
Creek population of arroyo toads. While arroyo toads were observed at five
other localities in the SBNF during the month of May, the first detected arroyo
toad from Deep Creek Hot Springs was from mid-June. Furthermore, the arroyo
toads in Deep Creek Hot Springs became more detectable by mid-July.
The lower Mojave River populations appear to have the earliest timing as
detected from the 2001 surveys. Larvae were present upstream from the Mojave
Forks Dam in the West Fork of the Mojave River from early May. Adults were
also detected during May in this location as well, with only one adult being
detected in Mojave Forks Dam vicinity in the month of June.
The Little Horsethief Canyon population of arroyo toads appears to be
timed in between the lower Mojave River populations and the populations higher
in Deep Creek. During early May, arroyo toads in Little Horsethief Canyon were
observed breeding. By the end of May, several adult arroyo toads were
observed as well as some larvae. Metamorphic arroyo toads were observed at
Little Horsethief Canyon by the middle of June.
The timing of the Bautista Canyon arroyo toads is unclear. Adult arroyo
toads were observed in Bautista Canyon during the months of May and June,
however no indication of breeding behavior or recruitment was observed. More
20
surveys from throughout the late winter and early spring are needed to determine
the timing and location of breeding events in this population of arroyo toads.
The populations of arroyo toads in the Mojave River, Deep Creek Hot
Springs, Little Horsethief Canyon and Bautista Canyon appear to be relatively
substantial populations based on their detectability in 2001. Some segments of
the Mojave River population appear to be impacted as lower detectability is
correlated with disturbance and habitat conversion (OHV usage and beaver
ponds) in specific localities. Other populations of arroyo toads in and near the
SBNF (Cucamonga, Cajon Wash, Whitewater) are located in areas that appear
to be more heavily impacted with less continuous overall suitable habitat than the
areas where arroyo toads were observed in 2001. These less detectable
populations sho
In 2003, we implemented a new monitoring program for the endangered arroyo toad (Bufo californicus) on Marine Corps Base Camp Pendleton (MCBCP). To address the problems associated with large variations in adult toad activity, we employed a spatial and temporal monitoring approach that tracks the presence of arroyo toad breeding populations by documenting the presence of eggs and larvae. Sites were surveyed up to four times per year to calculate and account for imperfect detection probabilities. We also continued night surveys for adult toads from the monitoring program implemented by Dan Holland in 1996. This report details the results and analyses of the first three years of the spatial monitoring program and a decade of adult count transects.
During this study, three years of highly variable rainfall had large impacts on arroyo toad breeding and breeding habitat. After a normal rainfall year in 2003, minimal rainfall in 2004 resulted in the complete lack of breeding and recruitment within the San Mateo and San Onofre watersheds, which were largely or completely dry. In 2005, twice the normal rainfall created huge surges in all watersheds. Scouring of stream and river channels substantially reduced aquatic vegetative cover and washed away portions of adjacent banks and floodplains.
In tracking both the proportion of area with surface water and the proportion of wet area occupied by breeding toads, we found that even though surface water availability was highly variable (44-95%), the overall extant of breeding toads in wetted areas was relatively stable (77-95%) with no significant change over the three year period. The night survey count data from 1996 to present also shows that arroyo toad activity has had extremely high annual variability (ranging +/- 44% of mean), but has been relatively stable over the last decade.
We found the probability of detecting arroyo toad larvae was positively associated with low flow shallow water and negatively associated with non-native species. These two variables were correlated with one another. During the arroyo toad breeding season, non-native species were associated with deep
1
and faster flowing water. Since the amount of low flow shallow water was highly variable within each season, this factor was predictive of detecting tadpoles on a given survey, but not of annual occupancy.
For annual occupancy and adult counts, we found compelling evidence that arroyo toad dynamics differ among the watersheds according t
An all day workshop was held on August 27, 2002 to review and revise the ongoing
monitoring protocol for arroyo toads at Marine Corps Base Camp Pendleton. The
revised protocol focuses on monitoring the extent of arroyo toad habitat on base and
monitoring the proportion area occupied (PAO) of arroyo toad habitat by arroyo toad
tadpoles and egg masses. Potential arroyo toad habitat will be divided into
approximately 50 blocks and each block will be subdivided into 5-7 sites approximately
200 meters long depending on the total amount of available habitat on the base. The
final number of sites and length of each site will be determined after an assessment of
the total amount of suitable habitat is completed. Sites will be surveyed for presence of
arroyo toad tadpoles and egg masses in a rotating panel design with an estimated 5 or
6 year rotation. One site in each block will be surveyed every year (permanent), while a
second site will be rotated within each block in different years (rotating). Most of these
sites will be surveyed a 1-2 times annually after breeding has initiated with the visits
occurring approximately one month apart. Eight of the 50 blocks will be considered
"intensive" blocks and will be surveyed four times.
Table 1. Recommended number of sites per watershed assuming a 5-year rotation.
Note: These numbers may be adjusted after the assessment of the amount of suitable
habitat on base is complete. In this example, a block is made up of 6 sites: 1 permanent
plus 5 rotating sites resulting in a 5 year rotation.
*
In addition, the eight intensive blocks should be used for short-term studies to refine key
components of the protocol including identification of factors associated with the
beginning of arroyo toad breeding, quantifying relationships between number of egg
masses, number of tadpoles, and number of adults, examining habitat characteristics
associated with tadpoles and egg masses, and examining the relationship between
amount of time spent searching, habitat structure, and detection rate of tadpoles.
Building upon previous pit-tagging work, toads at the 8 intensive sites will also be
scanned for existing pit tags in order to evaluate longevity. Additional research
recommendations are also discussed but are not included in the monitoring protocol.
Elements of the monitoring protocol are summarized in Table 2. In addition to the core
elements of the monitoring protocol, additional protocol refinement work
The purpose of this Biological Diversity Baseline Report for the Lawrence and Barbara
Daley Preserve is to provide the County of San Diego with information on existing
biological conditions to assist in the development of Area Specific Management
Directives. The approximately 597-acre1 Preserve is located in the south central portion
of San Diego County, in the community of Dulzura, north and east of Highway 94 and
south of Honey Springs Road. Technology Associates International Corporation
(Technology Associates) assisted by the San Diego Natural History Museum, conducted
baseline biological surveys at the Preserve on behalf of the County of San Diego
Department of Parks and Recreation.
Baseline surveys were conducted in the winter, spring, and summer of 2009-2010.
Biologists conducted the following surveys to assess the current status of biological
resources onsite: (1) mapping of vegetation communities, (2) a floral inventory including
rare plant surveys, (3) butterfly inventory surveys, (4) pitfall trapping for amphibians,
reptiles, and small mammals, (5) arroyo toad surveys, (6) aquatic herpetofauna surveys,
(7) diurnal avian point count surveys, (8) nocturnal avian surveys, (9) acoustic bat
surveys, (10) small mammal trapping, and (11) track and camera station surveys for
medium and large mammals. Due to the 2007 Harris fire that burned all of the Preserve,
results of these surveys may under-represent the diversity of plant and wildlife species
that occupy the Preserve.
Ten vegetation communities were mapped within the Preserve and consist of Diegan
coastal sage scrub, coastal sage-chaparral scrub, southern mixed chaparral, native
grassland, non-native grassland, southern riparian woodland, coast live oak woodland,
eucalyptus woodland, disturbed habitat, and urban/developed habitat. The most abundant
vegetation community on the Preserve is Diegan coastal sage scrub, which makes up
approximately 417.20 acres or 70% of the total area. Floristic surveys documented 355
plant taxa occurring on site. These include both native and non-native species along with
eleven sensitive (California Native Plant Society List 1-4) plant species, including: desert
fragrance (Ambrosia monogyra), San Diego needlegrass (Achnatherum diegoensis),
Palmer's sagewort (Artemisia palmeri), San Diego sunflower (Bahiopsis [Viguiera]
laciniata), delicate clarkia (Clarkia delicata), Palmer's goldenbush (Ericameria palmeri
var. palmeri), chocolate lil
This framework management and monitoring plan provides guidance to maintain and enhance the conservation values of the Ramona Grasslands Open Space Preserve. The Preserve supports many unique biological resources, provides a suite of important environmental services for the region, and preserves a rich cultural and historic heritage.
The Ramona Grasslands Preserve functions as a core habitat area within a regional network of existing and anticipated conservation lands. The coastal sage scrub, chaparral, and oak woodlands of the surrounding landscape, together with the grasslands, riparian habitat, and vernal wetlands of the core area, constitute an exceptional concentration of regionally and globally significant resources. That significance is reflected by the near complete overlap of the Preserve area by federal Critical Habitat designations (San Diego fairy shrimp, arroyo toad, and California gnatcatcher).
Current Status: The arroyo southwestern toad (Bufo microscaphus caiWornicus) is
listed as endangered. In California, it is known from 22 river basins in the coastal
and desert areas of9 counties along the central and southern coast. The range
extends into northwestern Baja California, Mexico.
Habitat Requirements and Limiting Factors: The arroyo southwestern toad
(arroyo toad) is endemic to primarily the coastal plain and mountains of central
and southern California and northwestern Baja California. These toads breed in
stream channels and use stream terraces and surrounding uplands for foraging and
wintering. Direct habitat loss due to urbanization, agriculture, and dam
construction is the main cause for the decline ofarroyo toads. Other threats
include water management activities and diversions; road construction,
maintenance, and use; livestock grazing; mining; recreational activities; loss of
habitat due to exotic plants; and predation by introduced species. Although the
species evolved and has survived in an environment periodically impacted by fire,
flood, and drought, the interactions ofnatural events with human alterations ofthe
habitat may lead to the extirpation of local populations ormetapopulations ~.
Recovery Priority: 9 on a scale of 1 to 18. The priority is based on its being a
subspecies (rather than a full species) with a moderate degree ofthreat and high
recovery potential. If the arroyo toad is made a full species, its priority rises to 8.
Recovery Objectives: Downlist to threatened status, then delist.
Recoverv Criteria
:
Downlisting to threatened status: The arroyo toad will be considered for
reclassification from endangered to threatened status when management plans
have been approved and implemented on federally managed lands to provide for
conserving, maintaining, and restoring the riparian and upland habitats used by arroyo toads for breeding, foraging, and wintering habitat. In addition, these
measures must maintain at least 20 self-sustaining metapopulations or
subpopulations ofarroyo toads at the following locations (minimum number of
populations for each agency and targeted river basins is indicated in parentheses):
Fort Hunter Liggett Army Reserve Training Center (1: San Antonio River basin);
Marine Corps Base Camp Joseph H. Pendleton (2: San Mateo/San Onofre Creek
basins, Santa Margarita River basin); Los Padres National Forest (4: Sisquoc
River basin, Upper Santa Ynez River basin [including In
Baseline surveys were conducted in the winter, spring, and summer of 2008. Biologists conducted the following surveys to assess the current status of biological resources onsite: (1) mapping of vegetation communities, (2) a floral inventory including rare plant surveys, (3) checklist butterfly surveys, (4) pitfall trapping to sample amphibians, reptiles, and small mammals, (5) focused arroyo toad surveys, (6) aquatic herpetofauna surveys, (7) diurnal avian point count surveys, (8) nocturnal avian surveys, (9) acoustic sampling and roost and foraging surveys for bats, (10) small mammal trapping using live Sherman traps, and (11) track and camera station surveys for medium and large mammals. Due to a series of drought years and recent wildfires that have burned much of the Preserve, results of these surveys may under-represent the diversity of plant and wildlife species that occupy the Preserve.
Nine vegetation communities were mapped within the Preserve and consist of southern coast live oak riparian forest, Diegan coastal sage scrub, southern mixed chaparral, mafic southern mixed chaparral, non-native grassland, coast live oak woodland, eucalyptus woodland, disturbed habitat, and urban/developed. The most abundant vegetation community on the Preserve is southern mixed chaparral. Floristic surveys documented 337 plant taxa occurring in the nine vegetation communities. These include both native and non-native species along with seven sensitive plant species: Brewer?s calandrinia, Humboldt?s lily, Cleveland?s bush monkey flower, felt-leaved monardella, Fish?s milkwort, Robinson?s pepper-grass, and Engelmann oak.
A total of 150 animal species were documented from the Preserve during the 2008
baseline surveys. These include 16 species of butterflies, three species of amphibians, 16 species of reptiles, 78 species of birds, and 37 species of mammals. No federally or state listed species were detected; however, 13 non-listed sensitive species were detected during baseline surveys.
Jones & Stokes conducted a baseline biodiversity study of the County of San Diego?s Boulder Oaks Open Space Preserve (Preserve) to provide the Department of Parks and Recreation with the biological data to develop Area Specific Management Directives (ASMDs). The Preserve consists of very high value natural communities and is located approximately three miles south of the unincorporated township of Ramona, between State Route 67 and Mussey Grade
Road, in central San Diego County, California.
During 2007, Jones & Stokes? biologists conducted the following studies, in addition to general, qualitative evaluation of the entire Preserve: (1) mapping of
vegetation communities, (2) a floral inventory including rare plant surveys, (3) a focused survey for Quino Checkerspot butterfly, (4) a habitat evaluation to
address Arroyo Toad, (5) pitfall trap arrays to sample amphibians, reptiles, and small mammals, (6) avian point counts, (7) a nocturnal bird survey, (8) acoustic
sampling and roost surveys for bats, (9) a track and sign survey for medium-tolarge mammals, and (10) a camera station survey for medium-to-large mammals.
Due to the low rainfall during the 2006-2007 winter, results of these surveys may under represent the diversity of plants and wildlife that occur within the Preserve.
The following report summarizes the results of sensitive species surveys conducted for the Southwestern Willow Flycatcher (Empidonax traillii extimus), Least Bell's Vireo (Vireo bellii pusillus), Southwestern Arroyo Toad (Bufo microscaphus califomicus), and Southwestern Pond Turtle ( Clemmys marmorata pallida). Surveys were performed on the Pine Creek, Bauser Creek, and Cottonwood Creek
drainages within the Pine Creek and Bauser Canyon Wilderness areas of the Cleveland National Forest. The purpose of these surveys was to determine both species presence, population number, and breeding status, as well as habitat conditions within the survey areas.
APPENDIX A?Biological Survey Report for the Santa Maria Creek Restoration Project: Stephens? kangaroo rat (Spencer and Montgomery 2007)
APPENDIX B?Wintering Raptors of the Cagney Ranch and Surrounding Ramona Grasslands (2003-2006) (Wildlife Research Institute 2007)
APPENDIX C?Biological Survey Report for the Ramona Grasslands Preserve (RECON 2005)
APPENDIX D?Biological Survey Report for the Santa Maria Creek Restoration Project: riparian birds (Lovio 2007)
APPENDIX E?Biological Survey/Monitoring Report for the Santa Maria Creek Restoration Project: arroyo toads (Hollingsworth et al. 2006)
APPENDIX F?Invasive Weed Report for the Santa Maria Creek Restoration Project: grassland and riparian invasive weed control efforts and results (Kelly & Associates 2007)
The Ramona Grasslands host a unique assemblage of resources:
? The southernmost population of the endangered Stephens? kangaroo rat;
? Unique vernal wetlands that support endangered San Diego fairy shrimp and several rare plant species;
? Santa Maria Creek and associated habitats are important for neotropical migrant songbirds and the endangered arroyo toad; and
? A diverse raptor community, including the largest population of wintering ferruginous hawks in San Diego.
Oak savannah, riparian woodlands, alkali playas, native perennial grasslands, and rock outcrops contribute to the diversity and ecosystem functions within the grasslands. These resources are imminently threatened by the indirect impacts of urbanization and thus require science-informed monitoring and management to ensure their persistence.
The Ramona Grasslands comprise a significant portion of the Santa Maria Creek subbasin of the San Dieguito River watershed. The Santa Maria Creek, which drains the urbanizing community of Ramona, flows westward through the grasslands, then through Bandy Canyon to its confluence with Santa Ysabel Creek. Below the confluence, the San Dieguito River flows through San Pasqual Valley into Lake Hodges, a City of San Diego drinking water reservoir. The creek corridor serves as both a hydrological and habitat linkage for numerous species. It also provides essential ecosystem processes, such as natural filtration of anthropogenic contaminants that may impair downstream water quality.
The Ramona Grasslands Preserve functions as a core habitat area within a regional network of existing and anticipated conservation lands. The coastal sage scrub, chaparral, and oak woodlands of the surrounding landscape, together with the grasslands, riparian habitat, and vernal wetlands of the core area, constitute an exceptional concentration of regionally and globally significant resources. That significance is reflected by the near complete overlap of the Preserve area by federal Critical Habitat designations (San Diego fairy shrimp, arroyo toad, and California gnatcatcher).
Adult and tadpole arroyo toad (ARTO) were observed within Santa Maria Creek west of Rangeland Road
within Ramona Grasslands Preserve (Preserve) during monitoring surveys performed in 2016. Historically,
this species is known to breed within Santa Maria Creek on the western areas within the Preserve. These
sections of the creek contain high quality habitat; however, ARTO abundance in these areas is less than
what has been reported in similar stream systems, and that is likely due to high abundance of bullfrogs.
Threat surveys performed in 2016 confirmed bullfrog presence within Santa Maria Creek within the
western areas. Also, an individual southwestern pond turtle was observed in 2016 in the western portion
of the Preserve. The goal of the project was to enhance the existing ARTO population and increase the
potential for a southwestern pond turtle population within Ramona Grasslands Preserve. The objective of
the proposed project was to implement a bullfrog eradication program within the Preserve and the
treatment ponds on the adjacent Ramona Municipal Water District (RMWD) property.
Chambers Group, Inc. was retained by the Bureau of Land Management (BLM), to conduct a literature review, a reconnaissance-level biological survey, and to prepare biological technical report of findings for the approximately 438-acre Internalional Fuel Break site. This report provides recommendations for sensitive plant and wildlife species potentially present on the property.
Technology Associates International Corporation (TAIC), assisted by the San Diego
Natural History Museum, conducted baseline biological surveys at Hellhole Canyon
Preserve on behalf of the County of San Diego Department of Parks and Recreation. The
purpose of these baseline surveys is to provide the County with information on existing
biological conditions to develop a Resource Management Plan (RMP) including Area
Specific Management Directives (ASMDs). The Preserve is located approximately six
miles northeast of Escondido in Valley Center, east of Valley Center Road and north of
Santee Lane in San Diego County, California, and is owned and managed by the County
of San Diego.