Biodiversity, Abundance, and Breeding Success of Amphibians in Urban, Suburban, and Rural ...

44 Pages·2013·2.3 MB·English

by  Annie Hor

Biodiversity, Abundance, and Breeding Success of Amphibians
in Urban, Suburban, and Rural Ponds
in San Joaquin and Stanislaus County, California, USA

Felicia C. De La Torre
Advisor: Dr. Marina Gerson
Internship from January through July 2013

California State University, Stanislaus
One University Way
Turlock, CA 95382
Final Report Submission Date: July 31, 2013
TABLE OF CONTENTS
PAGE

ACKNOWLEDGEMENTS ................................................................................................... 3

EXECUTIVE SUMMARY ................................................................................................... 5

PROJECT OBJECTIVES ...................................................................................................... 7
Introduction ............................................................................................................................ 7
Project Goals .......................................................................................................................... 8
Project Tasks .......................................................................................................................... 8
Potential Career Pathway ....................................................................................................... 9

PROJECT APPROACH ........................................................................................................ 10
Site Selection ......................................................................................................................... 10
Timing of Surveys.................................................................................................................. 11
Amphibian Surveys ................................................................................................................ 11
Potential Predator Surveys ..................................................................................................... 14
Voucher Specimens ............................................................................................................... 14
Habitat Variables ................................................................................................................... 14
Data Analysis ......................................................................................................................... 15

PROJECT OUTCOMES ........................................................................................................ 17
Amphibian Abundance .......................................................................................................... 17
Amphibian Species Richness ................................................................................................. 17
Amphibian Breeding Success ................................................................................................ 17
Amphibian Deformities ......................................................................................................... 18
Potential Predators and Other Wildlife .................................................................................. 18
Habitat Variables and Water Quality ..................................................................................... 19

CONCLUSIONS.................................................................................................................... 21

REFERENCES ...................................................................................................................... 22

APPENDICES
Backyard Pond Flyers ............................................................................................................ 25
Other Sites (Not Included in This Project) With Evidence of Breeding Attempts………… 26

TABLES ................................................................................................................................ 27

FIGURES ............................................................................................................................... 30

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ACKNOWLEDGEMENTS

First and foremost, I would like to express my gratitude to all of the field technicians of
my “Frog Team” that volunteered their time and efforts to help me during night and day surveys:
Kelly Baker, Esther Buie, Paul Coates, Mitchell Court, Breanna Crist-Hill, Rick De La Torre,
Yolanda De La Torre, Dr. Marina Gerson, Elizabeth Grolle, Michelle Lopez, Alison Loux,
Adam Parikh, Jacob Pohl, Loren Pohl, Sandy Pohl, Nicole Siemens, and Felisha Walls.
I am especially grateful of my advisor and chair of my thesis committee, Dr. Marina
Gerson, who always set aside time to meet with me, help me shape the project, and ultimately get
it into motion. I would also like to thank my other committee members, Dr. Ann Kohlhaas and
Dr. Kenneth Schoenly, who have also provided on-going support and loaned me materials for
fieldwork.
In addition, Dr. Matthew Cover, coordinator of the Master Program of Ecology and
Sustainability, has also been a huge part of this project. He allowed me to borrow his water
quality equipment for the extent of the project and even set aside time to train me in using all of
it. This aspect of the project would not have been possible without his assistance.
I want to also extend my appreciation to all of the landowners, managers, and
organizations that allowed me to use their ponds, lakes, and/or other water bodies for my
research. Without the sites, I obviously would not have been able to complete my project. In no
specific order: Duane Johnson and Norm Winchester - US Army Corps of Engineers (Knights
Ferry Unit), Ray and Geri Hamilton, Steve Dutra and Kathy Grant - Lodi Lake Park, Michael
Blevins - Turlock Golf and Country Club, Phil Brown - Spring Creek Golf and Country Club,
Matt Rascoe - Micke Grove Golf Links, Karen Honer - White Slough Water Pollution Control
Facility, Steve Wilson - Turlock Water Quality Control, Kayo Armstrong - Woodbridge by Del
Webb, David Henry - IPC International Corporation, Laurie Barton and Darren Teeples -
Stanislaus County Public Works Department, Jami Aggers and Mae Song - Stanislaus County
Parks and Recreation, Cheryl Jackson - Woodward Reservoir, Tom Dias - Modesto Reservoir,
Dan Madden and Michael Cooke - City of Turlock (Municipal Services Department), Susan
Maxwell - Timberlake Condominium Association, Dan Keyser and Ray Thatcher - Grupe
Commercial Company (University Park), Steven Jaureguy and Staff - CSU Stanislaus (Police
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Department), Bill Burke, Debbie Burke, Joel Burke, Debbra Hunt, Bob Loux, Judy Loux, Loren
Pohl, and Sandy Pohl.
Last, but definitely not least, I want to recognize specific people and organizations that
referred me to other contacts, contributed to resource development, provided research advice,
allowed me to post notices/talk to the public about my project, etc. In no specific order: Kevin
Lunde - Regional Water Quality Control Board and UC Berkeley, Claudia Hidahl – Modesto
Irrigation District (Water Quality Lab), Sal Salerno – Stanislaus Audubon Society, Anita Young
– Sierra Club (Yokuts Group), Edgar Ortega – Central Valley Herpetological Society, Pete
Mostoufi and Amos Snider – IEH-JL Analytical, Matthew Grieger, John Maguire, and Sameer
Sharideh – San Joaquin County Public Works, Keith Nienhuis - San Joaquin Mosquito Vector
Control, Rhiannon Pintabona – East Side Mosquito Abatement District, Monica Patterson -
Turlock Mosquito Abatement District, Rob Edmundson – Modesto Reservoir, Bill Bischoff –
Bischoff Custom Design, Kyle Nelson – Swenson Park and Van Buskirk Golf Courses, Christine
and Zac White, Monica Della Maggiorre, Dave Williams, Deni Sullivan – Creative Water
Gardens, Monte Corley, Bethanie Martinez, Thomas and Rebecca Miller, Chris Mathis, Elena
Lombardo, Jeremy Shuman, and local Starbucks, Panera, Jamba Juice, Modesto Feed Store,
Tropical Haven Fish and Pet Supply Store, Pet’s Choice Store, and Discount Pet Food Store.

This project was supported by Agriculture and Food Research Initiative
Competitive Grant no. 2011-38422-31204 from the USDA National Institute of Food and
Agriculture. Additional grants from California State University, Stanislaus, that helped
support included: the Center for Excellence in Graduate Education (CEGE) Graduate
Assistantship Award (spring 2012) and the Biology Research Committee (BRC) Award
(granted in fall 2012 and summer 2013).

All work was carried out under California Department of Fish and Wildlife
Scientific Permit SC-12035 and with approval of the California State University, Stanislaus
Animal Welfare Committee.

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EXECUTIVE SUMMARY

This report summarizes findings from the field work season (March through May 2013)
for a Master’s thesis project entitled: Biodiversity, Abundance, and Breeding Success of
Amphibians in Urban, Suburban, and Rural Ponds in San Joaquin and Stanislaus County,
California, USA.
San Joaquin and Stanislaus Counties are generally known for their productive agricultural
status and high rate of human population growth (California’s Central Valley. 2006. Just the
Facts, Public Policy Institute of California. Available from www.ppic.org [Accessed 1 June
2013]). In areas such as these which are converted or human-dominated, wildlife is often
ignored—especially flora and fauna that are typically hidden from the public eye. The lack of
documentation for the effects of urban development on the wildlife in my hometown sparked a
project idea: I wanted to document current wildlife populations and collect baseline data on the
statuses of these populations. The presence of Western toads (Anaxyrus boreas) in the ponds at
my apartment complex led me to ask whether amphibian populations are able to persist despite
development.
The purpose of my project was to document biodiversity, abundance, and breeding
success of amphibians in urban and suburban ponds via visual encounter surveys, auditory
surveys, egg mass counts, and presence of larvae, in order to direct future decisions on urban and
suburban waterway management and development. This project took place at scattered sites in
San Joaquin County and Stanislaus County. Surveys took place an average of five to six nights a
week from March 3, 2013 through April 20, 2013 and intermittently thereafter until May 23,
2013.
I found that amphibian presence was greater than expected (including at 12 sites where
the landowners/managers stated they had never seen amphibians). Twenty-one out of 25 sites
had presence of at least one amphibian species. Four species of anurans (frogs) were documented
by my study: Western toad (Anaxyrus boreas), Pacific treefrog (Pseudacris regilla), Western
Spadefoot (Spea hammondii), and American bullfrog (Lithobates catesbeiana).
In terms of highest amphibian biodiversity, one site had presence of all four anuran
species simultaneously. Unfortunately, even with evidence of breeding attempts, that is at least
two individuals were heard calling or observed in amplexus (the mating embrace performed by
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most anurans; Fig. 1), at 17 of the sites, the number of sites showing breeding success to the
larval stage was low (only six).
The results of this study could vary from other years since amphibians are highly
dependent on rain. For the past few years, rain has been scarce in the Central Valley and summer
conditions have come earlier. Thus, it would be useful to repeat this study over time to establish
general trends and see how breeding success is related to yearly rainfall. Another factor at play
was the water quality and habitat characteristics at each site. These have been known to have
effects on amphibian presence and abundance (Dodd 2010; Egan and Paton 2008; Hamer and
MacDonnell 2008; Heyer et al. 1994). Breeding success has also been tied to the presence of
predators and/or invasive species presence and may even be negatively correlated with the
abundance of these species (e.g. Donnelly Park had hundreds of carp fish and no presence of
amphibians, this could be due to the fact that the carp seem to be voracious and will consume
whatever they can).
In conclusion, amphibians are indeed found in multiple urban and suburban ponds in the
Stanislaus and San Joaquin area. Their abundance, biodiversity, and breeding success, compared
to that in rural areas or even those that are not accessed by humans as much, are definitely lower,
therefore showing that natural areas provide better habitat for these creatures. These results do
not negate the fact that water bodies located in urban and suburban areas can help large
populations disperse and may add connectivity of meta-populations at a landscape level.

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PROJECT OBJECTIVES

Introduction
Today there are 7,100 living species of amphibians in existence globally (Worldwide
Amphibian Declines. 2009. Amphibiaweb. Available from http://amphibiaweb.org/declines/
declines.html [Accessed 9 June 2013]). The three orders of amphibians are: Anura (frogs and
toads), Caudata (salamanders and newts), and Gymnophiona (caecilians). While many people
don’t tend to think about these magnificent creatures, they serve a vital role in many
communities. They are an important part of the food web as natural pest control. They also serve
as prey for higher trophic level predators, such as large birds. Anuran larvae have also been
found to help break down leaf and tree matter in streams to provide extra sources of energy
(Conrad, J. 2010. Backyard Nature. Available from
http://www.backyardnature.net/n/a/tadpole.htm [Accessed 9 June 2013]). In addition, native
amphibian presence in most areas serves as an indicator of a healthy environment. Since their
skin is permeable, they can show the effects of any pollutants sooner than do humans and other
wildlife (Lannoo 2005). More important to look for than just presence is species biodiversity,
also known as species richness.
While species richness varies by area, it is evident that the majority of countries and
continents support a minimum of one amphibian species to over 100 amphibian species
(excluding Greenland and Antarctica; Worldwide Amphibian Declines. 2009. op. cit.). Despite
this high presence, nearly one-third (32%) of the world’s amphibians are considered to be
threatened. (IUCN, Conservation International, and NatureServe. 2006. Global Amphibian
Assessment. Available from http://www.globalamphibians.org [Accessed 1 June 2013]). The
declines have been attributed to a combination of direct and indirect anthropogenic factors such
as: habitat destruction, chemical pollution, chytridiomycosis (an amphibian-specific fungal
disease), unsustainable harvesting, and introduction of invasive species (Lannoo 2005; Hamer
and MacDonnell 2008; Vitt and Caldwell 2009). The Central Valley of California, comprised of
three regions (i.e. Sacramento Valley, San Joaquin Valley, and Coastal Region), is no exception
to the declining amphibian trend. Fisher and Shaffer’s (1996) study of amphibians in California’s
Central Valley showed that only 3 of 28 counties surveyed in 1990-1992 retained all of their
historical native amphibian fauna. While exotic species were one of the main factors correlated
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with the decline, it was surprising that the San Joaquin Valley had the fewest exotic species
introduced, yet still experienced drastic declines. This was most likely due to the San Joaquin
Valley being converted from open grasslands with wetlands to the top-producing agricultural
area of the three regions and the state overall (Umbach 1997). In addition, the San Joaquin
Valley also contains two counties (San Joaquin and Stanislaus) that have ranked third and fourth
place, respectively, in terms of greatest human population growth in California in the past decade
(Epodunk. 2007. U.S. Census Bureau. Available from
http://www.epodunk.com/top10/countyPop/coPop5.html [Accessed 9 June 2013]; Stanislaus
MLS. 2012. Available from http://www.free-mls-online.com/real-estate/stanislaus.html
[Accessed 9 June 2013]). In light of these changes, it is not surprising that amphibian diversity
has dwindled, but studying the amphibians that are still present is necessary to give insight to
those that are more resilient than others to urbanization.

Project Goals
The specific goals of my study were to:
1) Document diversity and abundance of pond-breeding adult amphibians at urban,
suburban, and rural sites in San Joaquin and Stanislaus Counties.
2) Correlate landscape and pond features to presence and abundance of pond-breeding
amphibians.
3) Measure breeding success based on anuran courtship calls, observations of amplexus,
and/or egg-mass counts, to be followed by larval presence.
4) Determine the effect of exotic species and predators on the presence and abundance of
native pond-breeding amphibians and their breeding efforts.

Project Tasks
The following tasks were completed for my internship (continued analysis of results, research of
journal articles, and thesis development will continue beyond the internship period):
1) Used Google Earth and GIS Software to locate and map out pond locations.
2) Contacted city and county advisors and landowners for land use permission and access.
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3) Ordered and gathered necessary materials for fieldwork; contacted water testing lab to
determine pricing and efficiency for submitting samples for pesticide analyses1.
4) Performed preliminary site visitations to determine suitability of the site characteristics
(whether it was most likely be an active site, inactive site, or if the conditions were too
hazardous).
5) During breeding season – performed auditory surveys (listened for anuran courtship calls),
visual encounter surveys, collected morphological data on individual adult amphibians
(snout to vent length, weight, and sex determination (if possible) based on features such
as: size, thumb pads, and throat color), and estimated abundance (individuals per square
meter).
6) Collected and euthanized individuals as permitted for submission as voucher specimens to
the Museum of Vertebrate Zoology, University of California Berkeley.
7) Followed-up surveys at sites with evidence of adult amphibian breeding, to look for egg
masses and performed egg mass counts (estimated using random quadrat placement).
8) Followed-up surveys of sites with egg masses to determine larval success and estimated
counts.
9) After conclusion of data collection, data organization and analysis was performed using
Microsoft Excel and statistical programs such as PC-ORD, Ecosim, and Piface.
10) Letters of appreciation with summary of site results were sent to all persons involved
with site permissions of access.

Potential Career Pathway
My career goal is to become a wildlife biologist and preferably to work with animal
communities within urban and agricultural settings to facilitate conservation. I have gained much
experience with herptofauna (reptiles and amphibians) through this project and previous work
and would not mind furthering my development in this specific field of study. On the other hand,
I am also open to broadening my horizons and learning to work with wildlife of all sorts. The
USDA is an excellent organization in which I can fulfill this career goal because there are
components within the agency that require research on wildlife and habitat effects, especially

1 Due to financial constraints, all water quality tests were limited and performed on-site with borrowed equipment.

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when dealing with agricultural development. I would love to work through the NRCS (Wildlife
Habitat Incentive Program or related), APHIS (Wildlife Services), or the USFS (Wildlife
Biology) in which I can attain hands-on experience with animals and take part in monitoring,
restoration, and habitat development and creation.

PROJECT APPROACH

Site Selection
Survey sites were identified using satellite images from Google Earth (Google Earth.
2012. Available from http://www.google.com/earth/index.html [Accessed 23 May 2012]),
recommendations from colleagues and organizations (e.g. Mosquito Abatement District), and
public outreach at relevant local club meetings (i.e. Sierra Club, Audubon Society, and Central
Valley Herpetological Society). Contacts for privately-owned pond sites were obtained by word-
of-mouth and by posting flyers (Appendix A) at local coffee shops, cafés, pet stores, feed stores,
etc. Sites were regionalized to determine which would be feasible to travel to and between,
especially for the time-restrained night surveys (Table 1). Initial contact with land owners and
managers was attempted via e-mail or phone call to discuss what the project entailed.
Once permissions were granted by city, county, and/or department officials, site locations
near permitted areas were targeted in order to create clustered regions of sites. Sites were also
categorized (i.e. urban, suburban, rural) and tallied in order to be sure to have enough
experimental units. Access was granted to approximately 90 water bodies within San Joaquin
County and Stanislaus County of California. Realistically, in order to be able to handle and
sufficiently monitor sites, the list was filtered down to a maximum of 40 sites. An arbitrary
minimum of 20 sites was set in order to gather enough data for statistical significance. As sites
were grouped and routed, some remote sites were removed from the list; these sites would have
required excessive travel time and reduced the number of total sites that could be sampled. Other
site features that were taken into consideration for inclusion in the project were: site safety
(especially during evening hours), access to perimeter of the water body, and hydroperiod (how
long water body holds water throughout the season).
In San Joaquin County, the main cities represented were: Ripon, Manteca, Stockton, and
Lodi. In Stanislaus County, the main cities were: Modesto, Salida, Turlock, and Oakdale.
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