 ABSTRACT
In recent studies chemical analyses show that highest levels of contaminants
in surface water and dry particulate samples in the Sierra Nevada Mountains,
CA are pesticides applied in the Central Valley, CA during heavy use periods
in summer. Don Sparling, Gary Fellers, and Laura McConnell (2001) have recently
found significant levels of pesticides (chlorpyrifos, diazinon, and endosulfan)
in tissues of adult Pacific treefrogs, Hyla (Pseudacris) regilla, (Silva
1997) collected in the Sierra Nevadas.
This study tests the null hypothesis that pesticides are not having adverse
effects on H. regilla tadpoles. H. regilla tadpoles were translocated
in cages among sites located in Lassen, Yosemite, and Sequoia National
Parks, and held in place to metamorphosis. Suspected impacts to be evaluated
include: (1) increased mortality of larvae due to direct toxicity, cholinesterase
(ChE) inhibition, or physical malformations; (2) reduced survivorship
of tadpoles; (3) increased percentages of malformations at metamorphosis;
(4) increased genetic damage in exposed larvae (measured by flow-cytometry);
and (5) elevated body burdens of pesticides and ChE inhibition.
Discovery of detrimental effects in Pacific treefrog larvae and newly
metamorphosed frogs may provide significant information towards the evaluation
of ranid amphibian declines in the Sierra Nevada Mountains.
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INTRODUCTION
Broad scale field sampling compared with historical analyses of museum records
shows an ecosystem level decline of amphibians in the Great Central Valley
in California. Counties most affected are Sacramento and those of the San
Joaquin Valley (Fisher and Shaffer 1996). The collapse of a regional frog
fauna, 5 of 7 species, in the Yosemite area of the California Sierra Nevada,
has also been documented (Drost and Fellers 1996). Jennings (1996) reported
that all 5 native ranid species in the Sierra Nevada are in need of protection.
The Cascade frog (Rana cascadae) is in serious decline and the northern
leopard frog (R. pipiens) has disappeared from 99% of its range (Jennings
and Hayes 1994). The California red-legged frog (R. aurora draytonii) is
listed as threatened (Miller 1994). The foothill yellow-legged frog (R.
boylii) is in decline (Drost and Fellers 1996) and the mountain yellow-legged
frog (R. muscosa) has disappeared from over 75% of study sites where it
was formerly found in California (Bradford 1991, Bradford et al. 1994).
H. regilla was chosen as a surrogate species for testing because ranid
frog numbers are seriously low. This treefrog species occurs in the same
areas as the ranids and is widespread and abundant. However, their exposure
to water is much less than that of ranid frogs and this may help to explain
why they are still abundant in areas of ranid frog declines. If adverse
effects of pesticide exposure is found in H. regilla, ranid frogs may
be undergoing similar effects at an increased rate based on length of
exposure.
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OBJECTIVES
 We
propose to test the null hypothesis:
Agricultural pesticides have no significant adverse effects on frogs in
the Sierra Nevada Mountains, California
Possible impacts to be evaluated include: (1) increased mortality of larvae
due to direct toxicity, cholinesterase (ChE) inhibition, or physical malformations;
(2) reduced survivorship of tadpoles; (3)increased percentages and type
of malformations at metamorphosis; (4) genetic damage in larvae and adults;
and (5) elevated body burdens of pesticides and ChE inhibition.
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Phase 1
Prior to tadpole translocations, sampling transects will be established
from coastal to mountain locations (see map below).
H. regilla tadpoles, adult males, sediment, and water will be collected
along transects at 3 sites per location (red dots indicate locations).
Residue analyses will be conducted on all samples; ChE analyses will also
be done on tissues.
Broadscale sampling will (1) provide a baseline of information for the study;
(2) will enable us to more clearly define trends in pesticides levels and
effects from coastal to mountain areas; and (3) aid in our interpretation
of translocation data.
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Phase 2
Tadpoles (Gosner stage 21-25) were translocated among each of the 3 parks
(June 1-Sept.7, 2001).
Tadpoles were held in place in a field-tested design cage (Harris and Bogart
1997)made of Nitex® nylon (see diagram below).
Tadpoles were fed boiled romaine lettuce, and sampled at 28 days exposure
and at metamorphosis (Gosner stage 45-46).
Cages were monitored daily; water temperatures, water depth, dissolved
oxygen, nitrites/nitrates, pH, ammonia, hardness, and turbidity were measured.
A floating platform was placed in the cage for metamorphosed frogs when
tadpoles reached Gosner stage 42 (appearance of front limbs).
Post exposure, larvae and metamorphosed frogs will be analyzed for ChE
inhibition, DNA damage, and body burdens of pesticides. Data collected
in the field will be evaluated for rate of physical malformations, abnormal
behavior, and mortality due to direct toxicity.
 Criteria
for site selection (Fall 2000):
3 meadow/ponds per park
Approximate elevation
of 7000 ft
Appropriate access Presence of H. regilla
Accommodation of
cages Absence of fish
Each pond selected held 9 cages, 3 cages containing tadpoles per each
park (27 cages per park)
Dummy cages were put out 2 weeks prior to the start of the study (and
during study) for curious bears.
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Preliminary Results Phase 2
Survivorship of tadpoles to metamorphosis was greatest at Lassen Volcanic
National Park
Malformations of hind limbs, brachymelia, (first segment of hind limb truncated;
see photo below) observed in tadpoles and newly metamorphosed frogs at all
three parks.
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LITERATURE CITED
Bradford, D.F. 1991. Mass mortality and extinction in a high-elevation population
of Rana muscosa. Journal of Herpetology 25:174-177.
Bradford, D.F., Graber, D.M. and Tabatabai, F. 1994. Population declines
of the native frog, Rana muscosa, in Sequoia and Kings Canyon National Parks,
California. Southwestern Naturalist 39:323-327.
Drost, C.A. and Fellers, G.A. 1996. Collapse of a regional frog fauna in
the Yosemite area of the California Sierra Nevada, USA. Conservation Biology
10:414-425.
Fisher, R.N. and Shaffer, H.B. 1996. The decline of amphibians in California’s
Great Central Valley. Conservation Biology 10:1387-1397.
Harris, M.L. and Bogart, J.P. 1997. A cage for evaluation of in situ water
quality using frog eggs and tadpoles. Herpetological Review 28:134-135.
Jennings, M.R. 1996. Status of Amphibians. Sierra Nevada Ecosystem Project:
Final Report to Congress, volume II—Assessments and Scientific Basis
for Management Options. Report 37. University of California Davis, Davis,
CA. USA.
Jennings, M.R. and Hayes, M.P. 1994. Amphibian and reptile species of special
concern in California. Rancho Cordova: California Department of Fish and
Game, Inland Fisheries Division.
Miller, K.J. 1994. Endangered and threatened wildlife and plants: Proposed
endangered status for the California red-legged frog. Federal Register
59,
no.22 (2 February): 4888-95.
Silva, H.R. 1997. Two character states new for hylines and the taxonomy
of the genus Pseudacris. Journal of Herpetology 31:609-613.
Sparling, D.W., Fellers, G.M. and McConnell, L.L. 2001. Pesticides and Amphibian
Population Declines in California, USA. Environmental Toxicology and
Chemistry:
20:1591-1595.
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ACKNOWLEDGMENTS
This study is the result of collaboration among investigators and resource
managers from USGS, USDA-ARS, Texas A&M University, USFWS, and NPS.
Many thanks to all who have contributed advice and logistical help in the
planning of this project. Special thanks to field technicians: Erika Cowman,
Shenandoah Marr, Deborah Purce, and Pamela Widder, and to Patrick Kleeman,
USGS Western Ecological Research Center, Point Reyes National Seashore,
Point Reyes, CA, for all his help in the field.
Maps of California were made by Carlos Hinojosa and Amy Hays of the Land
Information Systems, Texas A&M University.
Funding is provided for this study by USGS, Amphibian Research and Monitoring
Initiative and USFWS, Endangered Species, Region 1.
 
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Translocation Areas
