Arroyo Southwestern Toad-Recovery Plan - Amphibian Specialist

128 Pages·2000·14.54 MB·English

ARROYO SOUTHWESTERN TOAD
(Bufo microscaphus caiWornicus)
RECOVERY PLAN
Region 1
U.S. Fish and Wildlife Service
Approved:
U.S. Fish and Wi V e Service Region 1
Date:
As theNation’s principalconservation agency,theDepartment of
the Interiorhas responsibility for most ofour nationally owned
public lands andnatural resources. Thisincludes fosteringthe
wisest use ofour land andwater resources, protecting our fishand
wildlife, preserving the environmental andcultural values ofour
nationalparksandhistorical places, andproviding forthe enjoyment
oflife throughoutdoor recreation. The Departmentassesses our
energy andmineral resources andworks to assure thattheir
developmentis inthe bestinterests ofall our people. The
Department also has amajor responsibility for American Indian
reservation communities and forpeople who livein island
Territories under U.S. administration.
DISCLAIMER
Recoveryplans delineate reasonable actions thatarebelievedto be requiredto
recover and protectlisted species. Plans arepublishedby theU.S. Fish and
Wildlife Service, and sometimes areprepared withthe assistance ofrecovery
teams, contractors, State agencies, and others. Objectives will be attained and any
necessary funds made available subjectto budgetary andotherconstraints
affecting the parties involved, as wellas theneed to address otherpriorities.
Recoveryplans do notnecessarily represent theviews nor the official positions or
approvalofany individuals or agencies involved in the plan formulation, other
thanthe U.S. Fish and WildlifeService. Theyrepresent the official positionof
the U.S. Fish and Wildlife Serviceonly afterthey have beensignedby the
Regional Director or Director as approved. Approvedrecovery plansare subject
to modification as dictatedby new findings,changes inspecies status, andthe
completionofrecoverytasks.
Literature citation ofthis document should read as follows:
U.S. Fish and Wildlife Service. 1999. Arroyo southwestern toad (Bufo
microscaphuscalifornicus) recoveryplan. U.S. Fish and Wildlife Service,
Portland, Oregon. vi 119 pp.
+
Additional copies may be purchased from:
Fish and Wildlife ReferenceService
5430Grosvenor Lane, Suite 110
Bethesda,MD 20814-2158
telephone: [phone] or 800/582-3421
fax: [phone]
e-mail: fwrs~fws.gov
Fees for plans vary depending onthe numberofpages.
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ACKNOWLEDGMENTS
This recoveryplan wasprepared by MarkR. Jennings, Biological Resources
Division, U.S. Geological Survey, and Grace S. McLaughlin, U.S. Fishand
Wildlife Service, Ventura Fishand Wildlife Office. Mark Jenningsprepared the
maps. Arthur Davenport, U.S. Fish and Wildlife Service, Carlsbad Fishand
Wildlife Office, assisted withthe development ofthe draftplan; heand other
Carlsbadstaffmembers provided inputfor the draftand finalplans. Several
Venturastaffmembersprovidedcomments; Kate Symonds inparticularprovided
considerable input and assistance. Weappreciate the input andcommentswe
received from PeterH. Bloom, Peter Famolaro,RobertN. Fisher, Erik W. A.
Gergus, WilliamE. Hans, DanC. Holland, BrianLeatherman, RubenRamirez,
Norman Scott, Shawn Smallwood, and Samuel S. Sweet; the Angeles, Cleveland,
Los Padres, and San Bernardino NationalForests; Marine Corps Base Camp
Pendleton, Departmentofthe Army Ft. HunterLiggett; the California Department
ofFish and Game; the Helixand Montecito WaterDistricts and the Sweetwater
Authority; and the TransportationCorridorAgencies.
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EXECUTIVE SUMMARY
Current Status: The arroyo southwesterntoad (Bufomicroscaphus caiWornicus) is
listed as endangered. InCalifornia, it is known from22 riverbasins inthe coastal
and desert areas of9 counties along the central andsoutherncoast. Therange
extends into northwesternBajaCalifornia, Mexico.
Habitat RequirementsandLimitingFactors: The arroyo southwesterntoad
(arroyo toad) is endemicto primarily the coastal plainandmountains ofcentral
and southernCalifornia and northwestern BajaCalifornia. Thesetoads breed in
stream channels and use streamterraces and surroundinguplands for foraging and
wintering. Directhabitat loss due to urbanization, agriculture, anddam
construction is the maincauseforthe decline ofarroyo toads. Otherthreats
include watermanagement activities and diversions; roadconstruction,
maintenance,and use; livestock grazing; mining;recreational activities; loss of
habitatdueto exoticplants; andpredationby introduced species. Although the
species evolvedandhas survivedin anenvironmentperiodically impactedby fire,
flood,and drought, theinteractionsofnatural eventswith humanalterations ofthe
habitatmaylead to theextirpation oflocalpopulations ormetapopulations
~.
Recovery Priority: 9 ona scaleof 1 to 18. Thepriority isbased onits being a
subspecies (ratherthanafull species) with amoderate degree ofthreat andhigh
recovery potential. Ifthe arroyo toad is madea fullspecies, its priority risesto 8.
Recovery Objectives: Downlistto threatenedstatus, then delist.
Recoverv Criteria
Downlisting to threatened status: The arroyo toad willbe considered for
reclassification from endangeredto threatened status when managementplans
have beenapprovedand implemented onfederally managed lands to providefor
conserving, maintaining, and restoringthe riparian and uplandhabitats usedby
Metapopulation: apopulationofsubpopulations in somewhat
geographically isolatedpatches, interconnectedthroughpatterns ofgene
flow,extinction, and recolonization(see page 13).
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:
arroyo toads forbreeding, foraging, andwinteringhabitat. In addition,these
measures mustmaintain at least20 self-sustainingmetapopulations or
subpopulations ofarroyo toadsat thefollowing locations (minimumnumber of
populationsfor each agency andtargeted river basins is indicated inparentheses):
Fort HunterLiggett Army Reserve TrainingCenter (1: San Antonio Riverbasin);
Marine CorpsBase CampJoseph H. Pendleton(2: San Mateo/San Onofre Creek
basins, SantaMargarita River basin); LosPadres NationalForest (4: Sisquoc
Riverbasin, UpperSanta YnezRiver basin including Indian andMono Creeks,
Sespe Creekbasin, PiruCreekbasin); AngelesNational Forest (3: Castaic Creek
basin, LosAngeles Riverbasin including Big Tujungaand Alder Creeks, Little
Rock Creekbasin); San BernardinoNational Forest (1: Mojave Riverbasin
including WestFork ofthe Mojave River,Little HorsethiefCanyon, andDeep
Creek); ClevelandNational Forest (8: San JuanCreek basin, San MateoCreek
basin, Upper SantaMargaritaRiver basin, San Luis Rey Riverbasin, San Dieguito
Riverbasin, SanDiego River basin, Sweetwater Riverbasin, TijuanaRiver
basin); andtheJacumba (In-Ko-PahMountains) WildernessStudy Area(1: Pinto
Washbasin) managed bythe BureauofLand Management. Self-sustaining
populations or metapopulationsare thosedocumented ashaving successful
recruitment(i.e., inclusion ofnewlymatured individuals intothe breeding
population)equal to 20percent ormore ofthe averagenumberofbreeding adults
in7 of10 yearsofaverage to aboveaverage rainfall amountswith normal rainfall
patterns. Self-sustainingpopulations ormetapopulations require little or no direct
human assistance such ascaptive breedingorrearing, ortranslocation oftoads
betweensites.
Delisting: Thearroyo toadwill be consideredfor delisting whenthe genetic and
phenotypic variation ofthe arroyo toad, throughoutits range inCalifornia,is
securedby maintaining 15 additional self-sustaining subpopulationsor
metapopulations ofarroyo toadson coastalplain, coastal slope, desert slope, and
desert lands, includingknown subpopulations and metapopulations outside of
Federaljurisdictioninthe Mojave Riverbasin (SanBernardino County); the
Whitewater Riverbasin (Riverside County); the San Juan Creek basin(Orange
and Riverside Counties); SantaMargarita Riverbasin(SanDiego and Riverside
Counties); and the San LuisRey River, San Dieguito River/SantaYsabel Creek,
San Diego River, SweetwaterRiver, Otay River/Dulzura Creek, andTijuana River
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basins (in San Diego County).
ActionsNeeded
1) Stabilize and maintain populationsthroughoutthe range ofthe arroyo toadin
Californiaby protectingsufficient breeding andnonbreeding habitat.
2) Monitorthe status ofexisting populations to ensure recoveryactions are
successful.
3) Identify and secure additional suitable arroyo toadhabitat and populations.
4) Conductresearch to obtaindatato guide managementefforts and determine
the best methods forreducing threats.
5) Develop and implement an outreachprogram.
Costs (minimum) Year Year’s cost
1999 $992,000
2000 469,000
2001 369,000
2002 205,000
2003 195,000
2004 155,000
2005 155,000
2006 155,000
2007 155,000
2008 155,000
2009 155,000
2010
Total EstimatedCostofRecovery (minimum) $3,315,000
Date ofRecovery: Delisting could be initiated in 2010, ifrecovery criteria aremet.
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TABLE OF CONTENTS
I. Introduction
BriefOverview 1
Descriptionand Taxonomy 4
Distribution and Population Status 12
Life History and Ecology 31
Reasons forDecline andCurrentThreats 38
Conservation Measures 53
Recovery Strategy 67
II. Recovery
Objectives 75
Recovery Criteria 75
RecoveryTaskNarrative 78
III. Literature Cited 87
IV. ImplementationSchedule 91
Appendix: Summary ofthe Agency andPublic Comments onthe
Draft Recovery Plan forthe Arroyo Southwestern Toad 104
..
Figures:
Figure 1 Historic andcurrent distributionofthe arroyo toad 2
Figure2 Larval and adult arroyo toads 5
Figure 3 Arroyo toad larvae 7
Figure 4 Egg clutches and adultarroyo toads inamplexus 8
Figure 5 Larvae ofarroyo and Californiatoads 10
Figure 6 Embryos and envelopes ofthe arroyo and Californiatoads.. 11
Figure 7 Historic and currentdistribution ofthearroyo toad inthe
northernpart ofits range 15
Figure8 Historicand currentdistribution ofthearroyo toad inthe
centralpart ofits range 22
Figure 9 Concept ofstreamorder 33
Table:
Table 1 Recovery units forthe arroyo toad 73
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I. INTRODUCTION
BriefOverview
OnDecember 16, 1994, theU.S. Fish and Wildlife Service (Service)determined
thearroyo southwestern toad (Bufo microscaphus caiWornicus) to be an
endangered sj,ecies (Service 1994).
Thearroyo southwesterntoad (arroyotoad) was scientifically described from
individualspecimens collected atSanta Paula, VenturaCounty onMay 22, 1912,
and Big TujungaWash near Sunland, Los Angeles Countyon April 1, 1904
(Camp 1915). Overthe next 70years, collections andobservations by zoologists
foundthe arroyo toad in coastand desert drainages from southern California south
intonorthwestern BajaCalifornia, Mexico (Stebbins 1951, 1985; Figure 1).
Because relatively little wasknown aboutthis animal anditwas often confused
with the Californiatoad (Bufo boreas halophilus), whichis very common in the
sameregion, detailed studiesofthe natural historyofthe arroyo toad were not
conducted until the 1980’s (Sweet 1992). These studiesrevealed thatthe northern
populations (from MontereyCounty to the SantaClara Riverbasin, Los Angeles
County) exhibithabitat specializationthat favorsthe shallowpools and opensand
and gravel floodterraces ofmedium- to large-sizedintermittent or perennial
streams thatare floodedon afairly regularbasis. However, additional studies and
observations in the central portion oftherange (Los Angeles County south ofthe
SantaClara Riverbasinthrough San Diego County) haveshownthat arroyo toads
also breed in smaller streams (lowerorder streams, as explained in figure 9, page
33), deep canyons (where breeding sites may be patchily distributed), andutilize
upland habitatsasjuveniles, subadults, and adults (Dan C. Holland, Ph.D.,
Principal Investigator, CampPendleton Amphibian and Reptile Survey,
California; in litt. 1997; RobertN. Fisher, Ph.D.. University ofCalifornia at San
Diego, pers. comm. 1997). These differences in ecologymay be due to the
differences in landscapes and available habitat overtherange ofthearroyo toad.
The arroyo toad hasevolved in asystemthat isinherently quite dynamic, with
marked seasonal and annual fluctuationsin climatic regimes,particularly rainfall.
Natural climatic variations as wellas otherrandom events such as fires and