Accurate status assessments of long-lived, widely distributed taxa depend on the availability of long-term monitoring data from multiple populations. However, monitoring populations across large temporal and spatial scales is often beyond the scope of any one researcher or research group. Consequently, wildlife managers may be tasked with utilizing limited information from different sources to detect range-wide evidence of population declines and their causes. When assessments need to be made under such constraints, the research and management communities must determine how to extrapolate from variable population data to species-level inferences. Here, using three different approaches, we integrate and analyze data from the peer-reviewed literature and government agency reports to inform conservation for northwestern pond turtles (NPT) Actinemys marmorata and southwestern pond turtles (SPT) Actinemys pallida. Both NPT and SPT are long-lived freshwater turtles distributed along the west coast of the United States and Mexico. Conservation concerns exist for both species; however, SPT may face more severe threats and are thought to exist at lower densities throughout their range than NPT. For each species, we ranked the impacts of 13 potential threats, estimated population sizes, and modeled population viability with and without long-term droughts. Our results suggest that predation of hatchlings by invasive predators, such as American bullfrogs Lithobates catesbeianus and Largemouth Bass Micropterus salmoides, is a high-ranking threat for NPT and SPT. Southwestern pond turtles may also face more severe impacts associated with natural disasters (droughts, wildfires, and floods) than do NPT. Population size estimates from trapping surveys indicate that SPT have smaller population sizes on average than do NPT (P = 0.0003), suggesting they may be at greater risk of local extirpation. Population viability analysis models revealed that long-term droughts are a key environmental parameter; as the frequency of severe droughts increases with climate change, the likelihood of population recovery decreases, especially when census sizes are low. Given current population trends and vulnerability to natural disasters throughout their range, we suggest that conservation and recovery actions first focus on SPT to prevent further population declines.
The western pond turtle (WPT), recently separated into two paripatrically
distributed species (Emys pallida and Emys marmorata), is experiencing significant
reductions in its range and population size. In addition to habitat loss, two
potential causes of decline are female-biased road mortality and high juvenile
mortality from non-native predatory bullfrogs (Rana catesbeiana). However,
quantitative analyses of these threats have never been conducted for either species
of WPT. We used a combination of historical museum samples and published and
unpublished field studies shared with us through personal communications with
WPT field researchers (B. Shaffer, P. Scott, R. Fisher, C. Brown, R. Dagit,
L. Patterson, T. Engstrom, 2019, personal communications) to quantify the effect
of roads and bullfrogs on WPT populations along the west coast of the United
States. Both species of WPT shift toward increasingly male biased museum
collections over the last century, a trend consistent with increasing, female-biased
road mortality. Recent WPT population studies revealed that road density and
proximity were significantly associated with increasingly male-biased sex ratios,
further suggesting female-biased road mortality. The mean body size of museum
collections of E. marmorata, but not E. pallida, has increased over the last
100 years, consistent with reduced recruitment and aging populations that could be
driven by invasive predators. Contemporary WPT population sites that co-occur
with bullfrogs had significantly greater average body sizes than population sites
without bullfrogs, suggesting strong bullfrog predation on small WPT hatchlings
and juveniles. Overall, our findings indicate that both species of WPT face
demographic challenges which would have been difficult to document without the
use of both historical data from natural history collections and contemporary demographic field data. Although correlational, our analyses suggest that female-biased road mortality and predation on small turtles by non-native
bullfrogs are occurring, and that conservation strategies reducing both may be
important for WPT recovery.
Used radio telemetry to access nesting locations of four Western Pond Turtle from May to August 1989. Study was conducted in the Arroyo Laguna-Oak Knoll Creek drainage in San Luis Obispo, California. Habitat surrounding the arroyo is a mosaic of coastal steppe, coastal sagebrush and oakwoods. Found nests in the uplands of the arroyo hypothesized to be due to the WPT attempt to increase their reproductive success by avoiding seasonal floods washing away the eggs. Deemed the habitat corridor of up to 0.5km on either side of water courses should be protected year-round for nesting habitat and potential overwintering of the hatchlings in the nests.
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 as a way for California Department of Fish and Game and US Fish and Wildlife Service to jointly implement habitat conservation plans (HCP). The western pond turtle (Clemmys marmorata) is a covered species in the San Diego Multiple Species Conservation Program subarea (MSCP). However, the current status and distribution of the western pond turtle within the MSCP is poorly known. The western pond turtle is the only turtle native to southwestern California and was historically abundant in most major drainages in San Diego. Surveys conducted in Southern California in the late 1980's suggested that pond turtles no longer occurred in many locations from which they were known historically and that few viable populations of turtles remained. The United States Geological Survey began conducting surveys for western pond turtles in the San Diego MSCP in 2002. During these surveys, non-native turtles were detected at many more locations than were western pond turtles. Western pond turtles co-occur with non-native turtles at least one of these locations. Surveys will continue during spring and summer 2003.
This protocol documents standard visual survey techniques for southern populations of the
western pond turtle (Emys marmorata), hereafter referred to as pond turtle, in the southcoast
ecoregion of the United States (within the U. S. this extends from Santa Barbara, California to
the Mexican boarder). The purpose of this protocol is to provide standard guidelines for
determining pond turtle presence and relative abundance. The protocol also contributes
information on general habitat components and disturbances found at each location so that
hypotheses can be formulated and tested as to why a species occurs or does not occur in a
particular area. In addition, the techniques are effective at documenting other aquatic species
such as fish, amphibians, snakes, and other aquatic freshwater taxa. This protocol is based on
methods found in the USGS Aquatic Species and Habitat Assessment Protocol for Southcoast
Ecoregion Rivers, Streams, and Creeks (U. S. Geological Survey, 2006a).
This protocol documents standard trapping survey techniques for southern populations of the
western pond turtle (Emys marmorata), hereafter referred to as pond turtle, in the southcoast
ecoregion of the United States (within the U. S. this extends from Santa Barbara, California to
the Mexican boarder). The purpose of this protocol is to provide standard guidelines for
determining pond turtle presence, relative abundance, population demographics and provide
baseline information applicable to declines in pond turtle populations. The protocol, in
combination with the USGS Western Pond Turtle (Emys marmorata) Visual Survey Protocol for
the Southcoast Ecoregion, contributes information on general habitat components and
disturbances found at each location so that hypotheses can be formulated and tested as to why a
species occurs or does not occur in a particular area (U. S. Geological Survey, 2006a). In
addition, the techniques are effective at documenting other aquatic species such as fish,
amphibians, and other aquatic freshwater taxa. This protocol is based on methods found in the
USGS Aquatic Species and Habitat Assessment Protocol for Southcoast Ecoregion Rivers,
Streams, and Creeks (U. S. Geological Survey, 2006b).
More than 90% of southern California's riparian and aquatic habitats have been destroyed or modified by agriculture and urbanization. This has had profound effects on species dependant on these habitats including the western pond turtle, Actinemys marmorata, the only freshwater aquatic turtle native to southern California. We have been monitoring the southern California pond turtle populations since 2001 and have documented their decline. This decline is a result of the direct and indirect effects of urbanization including habitat loss, habitat alteration, habitat fragmentation, the introduction of non-native species, and recreation activities. Our trap efforts have detected a minimum of 15 species of non-native turtles in southern California with red-eared sliders and spiny softshell the most common. At sites occupied by non-native turtles, non-native turtles outnumber the native turtles. We have also documented a negative correlation between pond turtle presence and sites with recreational use, while non-native turtles are positively correlated with recreational use. Finally pond turtle presence is positively correlated with the naturalness of a site while non-natives were more likely to occur at modified or artificial sites. Only a few viable pond turtle populations remain in southern California, most populations are male-biased with little to no recruitment. Currently, we are developing programs such as long-term monitoring, genetics microsatellite analysis, habitat suitability assessment, habitat restoration and creation, translocation, head starting, and captive breeding to be used as tools to promote the recovery of self-sustaining populations of the pond turtles in southern California.
Determine the current distribution and population status of the western pond turtle in the San Diego MSCP and surrounding areas. Determine wetland and upland habitat value. Provide management recommendations for the
San Diego MSCP.
Data Summary. The U.S. Geological Survey (USGS) has been conducting research on the southwestern pond turtle (Actinemys pallida, WPT) for over 20 years, which includes data collection and
observations on their natural history, behavior, and conservation. This research provides
information for various land management agencies as the WPT has been identified as a species
of concern by the State of California (CDFW 2021) and has been in decline in southern
California since the 1980s (Brattstrom and Messer 1988). For example, Brattstrom and Messer
(1988) identified only eight populations in San Diego County and indicated that as few as five of
the populations south of the Santa Clara River were reproductively viable over the long-term. In
the 1980s and 1990s, studies began to examine the status and health of the populations in
southern California with lower Murrieta Creek being one of the study areas (Holland 1991,
Lovich 1998). The species is under review for listing under the Endangered Species Act (U.S.
Endangered Species Act [ESA 1973, as amended]) based on a 90-day finding issued in April
2015 (USFWS 2015, 80 FR 19259).
Data Summary. To document occupied areas in southern California, record demography of remaining pond turtle
populations and assess suitable habitat, the U.S. Geological Survey (USGS) conducted pond
turtle specific surveys throughout Los Angeles, Orange, western Riverside, and southwestern
San Bernardino counties. These surveys included habitat suitability assessments to determine
whether appropriate habitat existed at survey locations, as well as identifying threats from
invasive species, especially the presence of non-native turtles. Pond turtles were also detected
during surveys focused on other species, but no habitat assessment was done at those sites.
Data Summary. In 2001, Harmsworth Associates, an environmental consulting group, translocated 27 pond
turtles from Bommer Creek and an adjacent tributary to a pond in Shady Canyon to mitigate for
the loss of turtle habitat from the development of the Shady Canyon Golf Course and residences
near Bommer Creek. The pond at Shady Canyon was a former cattle pond that was reconstructed
in 2002 to better retain water and provide habitat for pond turtles (Harmsworth Associates &
Goodman 2002). The location of the pond in upper Shady Canyon is within the Nature Reserve
of Orange County (Figure 1). The pond was chosen because it had some protections being within
a nature reserve, it had suitable upland habitat, and it was relatively isolated from public access
(Harmsworth Associates & Goodman 2003). Since the translocation, pond turtles have
established a successful breeding population (Harmsworth Associates 2007, 2013). However, in
2005, the African clawed frog (Xenopus laevis), a non-native species, invaded the site and
established a successful breeding population. The American bullfrog (Lithobates catesbeianus)
has also been documented at Shady Canyon as recently as 2021, but in much lower numbers.
Both clawed frogs and bullfrogs directly compete with pond turtles for food. In addition, bullfrog
adults are known predators of juvenile pond turtles (Moyle 1973, Holland 1991)
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.
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.
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.
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
Data Summary. This study builds on the previous work by the USGS and its partners in support of pond turtle
restoration and management in the MSPA (Brown et al, 2020). Here we report on the search for
new pond turtle populations, continued monitoring of translocated individuals and removal of
nonnative aquatic species from 1 January 2020 to 31 December 2021. Specific activities reported
here are summarized in Table 1. This work is part of the larger study to assess the pond turtle in
San Diego, Orange, and Riverside counties. Pond turtle restoration and translocation has been a
collaborative effort between the USGS and our partners: San Diego Zoo, CDFW, SDMMP, San
Diego Association of Governments (SANDAG), City of San Diego (City), County of San Diego
(County), U.S. Forest Service (USFS), U.S. Fish and Wildlife Service (USFWS), Endangered
Habitats Conservancy (EHC), and The Nature Conservancy (TNC).
The Pacific pond turtle (Actinemys marmorata) is the only native aquatic turtle species in
southwestern California. While historically abundant in most major San Diego County
drainages: habitat loss, human disturbance, hydrologic alterations, and invasive species have
resulted in a significant decrease in Pacific pond turtle populations in San Diego and throughout
California (Madden-Smith et al. 2005). Evaluating and addressing these threats is critical for the
long-term persistence of Pacific pond turtle populations in San Diego County, and is a focus of
the Multiple Species Conservation Program (MSCP), an approved Natural Community
Conservation Plan (NCCP) in southern San Diego County. The Pacific pond turtle is a MSCP
covered species with an impact avoidance condition. The condition is as follows: "Maintain and
manage areas within 1500 feet around known locations within preserve lands for the species.
Within this impact avoidance area, human impacts will be minimized, non-native species
detrimental to pond turtles will be controlled, and habitat restoration/enhancement measures will
be implemented."
During a 2002-2003 study conducted by the United States Geological Survey (USGS), 72 sites
within the MSCP area were surveyed for Pacific pond turtle presence. Pacific pond turtles were
detected at only 5 of these 72 sites (Lake Murray, Los Penasquitos Canyon Preserve, Lusardi
Creek Preserve Lands, Santee Lakes, and Sycuan Peak Ecological Reserve), only 3 of which had
more than one individual (Los Penasquitos Canyon Preserve, Lusardi Creek Preserve Lands, and
Sycuan Peak Ecological Reserve along the Sweetwater River; Madden-Smith et al. 2005). The
surveys conducted by the USGS in 2002-2003, provided valuable information regarding the
distribution of Pacific pond turtles, and raised management concerns about their viability.
Following the 2002-2003 survey efforts, MSCP managers have sought to assess additional
unsurveyed sites, and to prioritize and implement restoration actions to ensure the persistence of
western pond turtles within the MSCP Preserve System.
The Boulder Oaks Preserve became a part of the MSCP preserve system in 2003 after
completion of the 2002-2003 USGS survey and has not been surveyed for Pacific pond turtles.
Boulder Oaks Preserve includes three ponds which are potential habitat for Pacific pond turtles.
Unlike other sites where restoration actions may be affected by human impacts (e.g., invasive
species i
Recent conservation planning for Orange County identifies the western spadefoot (Spea
hammondii) and western pond turtle (Emys marmorata) as species requiring protection
(NCCP/HCP, 1995). The western spadefoot is listed as a federal species of concern, a
California Department of Fish and Game (CDFG) species of special concern, Bureau of
Land Management (BLM) sensitive species and Natural Community Conservation Plan
(NCCP) County of Orange target species. The western pond turtle is listed as a federal
species of concern, a CDFG species of special concern, a BLM sensitive species, and a
United States Forest Service sensitive species. Initial surveys of Irvine Ranch lands for
the western spadefoot (coastal reserve only) and the western pond turtle were conducted
in 1995 and 1997, respectively. The United States Geological Survey (USGS) conducted
surveys in 2003 and 2004 to 1) identify currently occupied habitats and 2) assess
population status for these two locally rare species within the Irvine Ranch Land Reserve
(IRLR). USGS surveys encompassed portions of both the IRLR coastal and central
reserves. Western spadefoots were found to be widespread in the central reserve,
occurring in all six surveyed areas. In the coastal reserve, western spadefoots were
detected in two of the six surveyed areas. Western pond turtles were detected at 4 of the
32 surveyed area on Irvine Ranch lands, all west of Interstate 5. Western pond turtles
were detected at the University of California, Irvine's (UCI's) San Joaquin Freshwater
Marsh and adjacent portions of the San Diego Creek Channel. At two sites, Bonita
Canyon and Strawberry Farms Golf Course only a single western pond turtle was
detected. Currently the largest populations of western pond turtles within the IRLR are at
the Shady Canyon turtle pond mitigation site. The success of The Irvine Company's
(TIC) mitigation effort at the Shady Canyon turtle pond indicates successful turtle
habitats can be created and maintained. This report summarizes USGS's habitat
assessment of the baseline surveys of both the western spadefoot and western pond turtle
on Irvine Ranch Land Reserve, and provides recommendations for management to
conserve these species within the IRLR.
Many of the watersheds in northern coastal San Diego County south of MCBCP are severely impacted
by aquatic nonnative species and pond turtles are at high risk of extirpation in these drainages, if they
are not already extinct in most locations. Similar to the restoration for pond turtles at SPER, the
removal of nonnative aquatic species can release this pressure on extant pond turtle populations or
prepare a site for reintroduction of pond turtles (Brown et al. 2012). However, in the MHCP region, the
extent to which nonnative species are impacting pond turtle populations and habitat is unknown. Before
successful active management can be implemented in the northern coastal drainages of San Diego
County, the distribution and status of pond turtles and aquatic nonnatives must be determined and
suitable habitat must be identified. In 2012, USGS began work on the TransNet Environmental
Mitigation Program grant agreement 5001976 regarding the western pond turtle in order to assess the
distribution of native and nonnative turtles and suitable habitat for pond turtles in coastal northern San
Diego County south of MCBCP.
Southwestern pond turtle (WPT) has been identified as a focal species for management in the
draft Fiscal Year 2011 Land Management Grant Program. The San Diego Management and
Monitoring Program is trying to assemble information regarding potential management actions
to improve the status of WPT populations in San Diego County.