Relationships between characteristics of forest fragments and howler monkeys (Alouatta palliata...

8/7/2019 Relationships between characteristics of forest fragments and howler monkeys (Alouatta palliata mexicana) in sout

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e c o L o c : : ; ~ ANO CONSeRVADON

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RELATIONSHIPS BETWEEN FOREST FRAGMENTSAND HOWLER MONKEYS (ALOUATTA PALLlATAMEXICANA) IN SOUTHERN VERACRUZ, MEXICO

Erika M. Rodriguez-Toledo, Salvador Mandujano, and Francisco GarciaOrdua*1. INTRODUCTIONLos Tuxtlas, a region located in he 51ate of Veracruz, Mexico, is he masl northergeographic distribution oftropical rain foresl in America (Dirzo and Miranda, 1991). In thregion here are two species of primates, he howler monkey (Alouotlo palliata mexican

and spider monkey (Ate/es geoffroyi ve/lorosus). Populations ofboth species have decline90% (Estrada and Coates-Estrada. 1995). For this reason, these species are considered lO bvulnerable according to NOM-059-ECOL-1994 and endangered according to Appendix I oCITES (Rylands et al., 1995). In Mexico, hunting or capturing these primates is illegahowever, the practice conlinues in the region (Rodriguez-Luna et aL, 1987). Nevertheleslhe main reason ofreduclion in distrihution and abundance is the dramatic deforestation otropical rain forest (Silva-Lopez et al.. 1988; Estrada and Coates-Estrada, 1995). Loss1986 alone was eslimaled at 84% of the original forest (Dirzo and Garcia, 1992), bUI hpercentage is even higher today. As a consequence, there is relatively inlact habitat founonlyin the higher parts ofthe region's volcanoes, whle in Ihe lower areas many Aloualta anAleles groups have been forced to Ive in forest fragmenls (Garcia-Ordua, 1995). This iunfortunalely, Ihe mosl common scenario for Ihe monkeys, thus crealing urgency for thdevelopment of management plans designed to conserve Ihe primates nol only in relativeintact reserves, but also in the disturbed landscape.

.. Erika M. RodriguezToledo, Posgrado en Manejode Fauna Silvestre,lnstitutode Ecologa A. C.. km2.5 CarreAntigua aCootepcc No.351, Congregacin el Haya, Cf'91 070.Xalapa, Veracruz, Mxico. Salvador MandujanDepartamento de Ecologa y Comportamiento Animal, Instituto de EcologIa A. C., km2.5 Carrct. AntiguaCoatepec No.35 1. Congregacil\ el Haya. CP91070. Xalapa, Verzeruz. Mxico. Francisco G a r c i a O r d u ~ Instituto de Neuroc:tologa, Universidad Veracru:.eana, Ave. Dos Vistas sin. km2.5 Carret. XalapaVeracru0'91000. Xalapa. Veracruz, Mxico. Correspondence to S. Mandujano(cmail: [email protected]


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80 1::.1\1. RQDRIGUEZ.TQLEOO E.1',IIn (he last 30 years. dala about 1l101l11/tll and Ateles ecology in Los Tuxtlas has bee

gathercd (Estrada. 1982; Estrada and Coales-Estrada. 1995; Garcia-Ordua, 1995; JuanSolano, 2000; Silva-Lopezcl al., 1988). Spccifically, studies have providcd evidence that thfragmentalion nOuences certain dcmographic and behavioral faclOrs (Jimenez. 1992, SilvaLopez el al., 1993; Garcia-Ordua 1996, Estrada el al., 1999; JuanSolano. 2000). Studieon he relationships betwcen fores! fragment characteristics and AIOllatta group sizes, havbeen done in Ihis regon (Rodrguez-Luna el al., 1987; Silva-Lopez el al., 1988; Estrada anCoates-Estrada, 1995; Estrada el al.. 1999). The main result of these studies is lhal asfragmenl inereases in surfaee and quality, the size of the AtO/lGua groups also inereaseEvidently. this result provides us wilh initial knowledge of the passiblc eonsequences oforest fragmenlalion on primate speeies. In this chaplcr we present results on the relatiollshipbetween fragmenl characteristics and howler mOllkeys in this region bUI in another highlaltered landscape. If similar resulls are found in many fragments within Los Tuxtlas, thenmay be passible to make sorne gcneralizalions aboul the impact of fragmcntation on thprimale spccics and, from this, managemenl implieations.

\Ve think that fUrlher researeh is needed to understand the funetional relationshibetween l'll1dscape struClure and primate population dynamics at a regional scale. In threspect, metapopulalion theory could provide a feasible, conceptual, and methodologicaframework for Ihe development of this kind of researeh. A demonstrationofthe relationshipbetween forest fragment eharaeleristics and group size of monkeys is the firsl SICp iunderstanding how fragmentl!ion affeets population dynamics and extinetion-survivaprobabilities at a regional scale, In conservation applications, lhe usual question of interesis how mueh the viabililY of a species is affeeted by the number and size offragments withia region and by Ihe rates of movement of individuals among fragments (Hoopes anHarrison, 1998).

2. PROJECT OBJECTIVESThe principal objective is to analyze the possible effeets of forest fragmentalion odemography and behavior oflhe Alol/(jtf(j and Ate/es melapopulalions in the southern buffe

zone of Ihe Special Biosphere Reserve Los Tuxllas. An in sitll eonservalion program couldbe possible if we consider the spatial and lemporal metapopulation dynamics at n landscaplevel. \Ve willlhus be able lO define local population viability and effective population sizcThcse mcasurcs willlead to Ihe establishmenl ofcertain fragments as priority areas that needincreased eonneelivity through corridors. Therefore, this projeet is based on Ihe theory aOOmelhods of lalldscape ecology, population and metapopulation ecology, and conservalionbiology. \Ve inlcnd lO 1) develop actual and potential digitallandscape models; 2) analyzeIhe local primte grotlps (hereafter "subpopulations" or "local populations") and


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1I0WU:R /IIONKEYS IN FRAGMENTS

3. METAPOPULATION BACKGROUNDMelapopulalion lheory has becn used reccntly lO address the conservalion problem:lnim:lls in fragmenls (Harrison. 1994). The principal paradigm of Ihe metapopula

concept for conservalion is lO maintain equilibrium belween the cxlinClioncolonizaprocesses. Theorelically, the persistence of a metapopulalion al both lemporal and spascales depends on Ihe equilibrium between extinction and lhe rale of colonizalion of vafmgments (H:lnski. 1999). Metapopulalions exist as various local populalions of Ihe sspecies wilhin a fragmented system surrounded by an inhospilable matrix (McCullou1996). Vndcr ccrtain condilions. a local population may go extincl or may colopreviously uninhabiled fragmenls. Thus. metapopulations are maintained over a reg(Wiens,1996).The extinction rale depends on factors associaled with local populalions andlandscape. The main factor is Ihe struclure and abundance of the local population, becal a small size, evenls such as slochastic demography and environment, allelic effecl,genelc depletion, could increase the probabililY ofextinction(Gotelti. 1998).There areoimportant faclors Ihat affcct Ihe survival of thc local population wilhin the landscape, sas conneclivity among fragments, number, size, qualily and age of fragments, Ihe numlenglh, and qualily of corridors, and thc malrix characleristics surrounding each fragm(l3urkey, 1989). In general, it is expected that as size and qualily increase and isoladecreases. Ihe probabililY of extinclion diminishes and colonization increases. Thumetapopulalion within a landscape ofsmall size.lowquality, and high isolation offragmehas a grcater probabilily of extinclion because of a negative balance of colonizatextinclion rales (Hanski, 1999).First we need lO define metapopulalion. A metapopulation could be "natural" orresult of the segmenlalion of an original population (Hanski. 1999). Therefore, sfragmenls could have a fraction 01' individuals of the original population. This grouindividuab muy form a new local populalion thm, throughoul time, could have itsdemographic process. The viabililY of Ihis new local population will depend on intrifaclors such as the number of individuals and sex. age, and genelic composilion offmeton 01' lhe original segmented populalion. As a consequence, Ihe eXlinctionpersislence probabililY ofeach new local population wi 11 depend on its demographic dynaaOO Ihe movemenls 01' individuals among populations. Thus, a new non-natmetapopul:ttion could be formed ir three conditions are met: density dependence of lpopulationdynamies. spalial asynchrony in local populationdynamics.and limiteddisperlinking Ihe local populations (Hanski, 1991).In lhe original metapopulation model (Levins, 1970; ciled in Hanski, 1999),fragments areofequal quality, equaJly spaced, and dispcrsed. However, few metapopulalmeel lhis simplified definition (Harrison. 1994). AClually, there are olhcr concepl


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4. POSSIBLE METAPOPULATION SCENARIO IN LOS TUXTLAS

al a spalial seale comparable 10 a species' long-distance dispersal capabililies. Altcrnatively.habitats may be fragmented so finely lhose populations are nol reallf subdivided. or socoarsely tha! populalions are eompletely isolated from one another. 1n hese cases, we havea palchy population and a non-cquilibrium mctapopulation, respcclively. Also. veTY unevcnfragmentation may Icad lO mainland-island dynamics in which only he largest populationsand habitat fragments rea11y malter fOT persistence. Thus, niti al information about landscapestructure, fragmem occupatioll, population dynamics. and individual movements are ncededlO determine i f local populations are struetured as metapopulalions. From this, it will bepossible to analyze the information using melapopulation models.

Originally, howler and spider monkeys werc throughout the rcgion ofLos Tuxtlas. Thearea ofthis region was cstimated at 155,122 ha (Diario Oficial de la Federacin, 1988). andwas dominated by different types of tropical forest, principally tropical rain forest(Rzedowski. 1978). An imporlant aspect is that an abrupt disconlinuation of the originalvegetationdid nol existo This region was inhabited by one pandemic or genctically inlermixedpopulation of each primate species. However, the high rateofdeforestation as a consequenceof cattle breeding and crop production (Guevara et aL, 1997) has draslically reduced theoriginal vegetation (Dirzo and Garcia, 1992). Thus theoriginal populations were segmentedand the primates were forced into fragmenled habila!. As a consequence, {he originalpopulations of Aloualla and Aleles in Los Tuxtlas could be described as a "non-natural"metapopulation. Regardless. Estrada and Coates-Estrada (1995) describe the need forconservation of these primates at landscape and metapopulation sca1e.

According to predictions based on metapopulation theory at a regional scale. we expccta higher probability of persistence for Aloualla and Ate/esmetapopulations as long as morefragments are occupied and group sizes increase. Occupalion would depcnd on theprobability of fragmenl colonization. which in turn is determined by lhe size, quality. andconneclivity of fragmenls. The largest well connecled fragments and those with the beslhabitat conditions would have a greater likelihood of being occupied andlor colonized bythese primates. Furthermore. the larger a monkey group is. the lower Ihe likelihood of itslocal extinction due to effects such as stochasticity and/or demography. If the landscape hasbeen highly transformed due to deforestation so that the number, size. qualily, andconnectivityof fragments are quite low, the probabil ity of persistence on a regional scale wil!decrease due to limited fragment occupation and less colonization of emply fragmenls. Thistype of scenario c1carly indicatcs lhe pressing nced for a proposal ofmeasures to mitigale andreverse fragmentmion. Thus. an inilial s tep is to describe Ihe lnndscape structure andoccupation of fragments by primates lo know how lhe fragment characteristics are associaledwilh monkey presence/absence and group size. In this chapler we present an analysis oftheseaspecls only for A10lul/1{/. The Ale/es results are beyond lhe scope 01' this chapter.

E. M. RODRIGUE7..TLEDO ETAl..2


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1I0WLER MONKI10 m. In some cases, an ahad secondary vcgclation bUI l was


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84

+

E. M. RODRIGUEZ-TQLEIX> ETA

"Los Tuxtlas",Veracruz, Mxico

Gulf of Mxico


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IOWLER 1\I0NKEYS IN Jo'RAGME1"o'TS ss

"316000

+

314000

........+_ Fragmenlseontinuous lorest

+ +

+ + " +0 - /ISanta Marta .- . < " ~ . , ,...'" , , , 2000 m


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" E. i\1. RODRIGUEZTOLEI)() ETAand madc observations with billOCulaTS and vocalizations over a perio

\Ve eStimale he population density (DP"I') as

"pop=-Awhere 1I '" lhe sum oC individuals from all groups inhabiting he occupied fragrncnls andthe lotal surface of complete landscape.

Also, we estrmated lhe spccific ecological density (DsoI) of fragmenls as

D S e c o l = ~Ah,where Il j = lhe number of individuals from each group and Ah,= the surface of lhe fragmwhere the group is found. In lhis case, \VC estimaled ecological dcnsity considcring booccupied and unoccupied fragments. This procedure diminished lhe possible biasconsidering only occupied fragmenls for eSlimating ecological density. In Ihe I\VO casdcnsily \Vere exprcsscd as individuals pcr heclarc.

We eslimaled lhe distance of each group to lhe nearest-neighbor group and alsoisotation of each group with respecl 10 all groups in lhe landscape using ArcView. Thedislances are an indirect approximation of Ihe movements of individuals among groups.lhere is minor distance bel\Veen fragments, lhere is greater probabililY of dispersal byprimales IhroughoUl the landscape.

In arder to ascerlain Ihe relationship belween monkey prcsence ar absencc and grosize with cenain fmgmenl charaCleristics such as size, shape. isolating distallCc, avegetation height, independen! testsofChi squared were applied lo presenceorabsencedaand simple linear correlation tesIS \Vere applied lO group size data. Non-significant resuindicaled Ihal presence and srze were independent from fragment characleriSlics.

7. RESULTS AND DISCUSSION7.1. Fragmcnt Charactcrizations


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IIOWLER ~ I O N K E \ ' S IN F " " G M ~ ; r . . ' T S

support havc led lO an extensive conversion oflhe originallropical forest wilhin the Iast twdecades.

\Ve idcntified 64 fragments in this sludy (Figure 3). The range of elevation is frosea level to 700 rn. AH fragments were located on Ihe shores of the rivcrs and streams anjusI a few of thcm in the top of sorne inaccessible hitls. The slope of Ihe fragmenls is vesleep (>30'). Sorne of Ihe fragrnents near the sea coast had less severe slope bUI hapcrmanent illundalion. Thc inaecessibility ofthese fragments was the principal cause for Ihlack of deforestalion. Of the tolal fragmenls, 81 % are less lhan 5 ha, and only five fragmen(8%) 3reover ID ha (T3ble [l. The biggest fragment is 67 ha. Therefore, the actual [3ndscapis ch3r3cterized as a sm311 habit3t area for primales, divided inlo smatler fragments.

Using eanopy height as an indicator of Ihe original vegetation, disturbance might bconsidered a weak habitat quality indicator: however, there are sorne interesting comparisonfound in Ihis study. For instance, 27 fragmenls had relatively wel1-preserved canopy (treetaller than 15 m), while 37 fragmenls had diSlurbed vegetation CIrces 10 m height), whilc 58% of the fragments smaller than 10 ha had sufferedisturbancc 10 m height). This result was slatistically significant (Xl= 5.1. d.f. = 1, P0.02). Thus, Ihe landscape is charaeterized by many small fragmenls with some gradedisturbance in the arboreal stralum. There were no obvious relationships bclween fragmedisturbance and distance lO towns, since bolh well-preserved and disturbed fragments weequally spaced from the towns.

Many of Ihe fragments are narrow and long and follow slreams and rivers. Taking thimo account. 64 fragments (45%) had a re!atively irregular shape (Table 1). A more irregulfragment might increase the relationship ofsurface lO perimeler and could increase the edgeffec!. It was found Ihat the disturbance of Ihe fragments was dependent of their shape (X= [6.4. d.r. = 3. P = 0.001) and Iheir size (X l = 8.4. d.f . = 1, P = 0.005). The biggefragtnents had lhe most irregular shape (Table 1). To beller understand Ihis relalionshiplerms of primate survival. we would need to know the fioristic eomposition and to be ablO evaluate lhe edge effeel.

Relatively well-preserved and continuous forest is found at the top of the "Sierra SanMarta" and "San Martin Pajapan" vo!Canoes. In Iheory, the closer the fragment was to lhsource of continuous habilat lhe more likely the fragment would be colonized. The majoriof fragments are relatively far away fram a potential source habitat. At aH fragments, 85%were greater Ihan 1,000 m from continuous foresl with an average of 2,800 rn (Table 1).

Conversely, 85% of Ihe fragments were less than 200 m from the nearesl fragme(Table 1); the averagedislance from the nearest fragment was 123 m. However, this distanisastraighlline from fragmcnl to fragment and does nol necessarily mean Ihal there is a recorridor between them. In this site, Ihere is a lack of data about primates walking at grounlevel mov;ng from one fragment lO another. If the mean distante between fragmentsbeyond the nalural movements ofthe primates in a place wilh no corridors, then the group


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E. M. RODRIGUEZTOLEDO

fragments size

> 10 haD < 10 ha

San MartinPajapan~ - - - ' ~ , ~undlsturbed fragments

trces t.ller th.nUmhcight

an Martin


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1I0WLER MONKEYS IN FRAGMENTS "Table 1. Numberoffragments in the landscape (Iotal 3.987 ha) and {he numberoffragmenloccupied by at least one individual of Afollatta palliara mexicana in the study area aTatahuicapan de Juarez. Los Tuxtlas. Veracruz, Mexico.

Fragment Chllracteristics Number of Fragments Number of Fragmenlsin the Landscape Occupied by AlollatlaSize


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90 E. M. RODRIGUEZTOLEOO ETapens the possibility for a management plan for the conservation of primates throughunderslanding of the beneficial and ecological preservation of fragmenls by he people7.2. Howler Populalion

In Ihe sludy area theTe werc 16 fragments, 13 wjlh more Ihan one individualofAlOlland thrce wilh isolatcd individuals (Figure 4). Therefore. onty 25% of the 64 fragmentthe region were occupied (Table 1). Thisdistribution is very small compared lO the availnumber of fragmenls. whieh suggesls hal the primate survival in this landscape mayproblematic.

A total of 80 individuals of AfOl/atta were counted in the occupied fragments. Thcoflhe groups ranged from 2 lo 15 individuals; while the average group size was 6 ~ {Sindividuals. Three isolated males of Alouatla inhabited separate fragments. If thindividuals were in the process of dispersa! or lived permanently in these fragmentunknown. Because fragments are small and isolated, it is important 10 determine

.At. Gulf of...tt Mexico

San Martin


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1I0WLER MONKEYS IN FRAGMENTS

probability of local extinction and metapopulation persistence in this landscape. \Ve predtwo possiblc scencries in the near future: 1) a high risk of local extinction oC many grousimply by stochaslic demography and environmem and 2) an overpopulation of sofragmenls because ofthe small fragment size and lowconnectivity with other fragmems tlimits the dispersal of individuals.The population density (total number of individuals per entire landscape area) westimated as 0.02 individualslha. This eSlimale is very low because it ineludes Ihe emlandscape area. However, considering Ihe "ecological density" (tolal number oC individuper fragment arca) Ihe eSlimate was 0.28 j: 0.09 individualslha. This eSlimale is mrealistic because Ihe abundance is divided by habita!. It is very interesling to note thalfragment size decreases, lhe ecological density increases (Figure 5); and bigger fragmeshowa low ecological density. This resull means that overpopulation exists in some vsmall fragmenls throughout the study arca. Thus, potential imer-specific competilion amoindividual s could exist because of Ihe low carrying capacily in small fragmenls. The cffon survival and fecundity rales is unknown and rcquires urgent study.A very important result is that a relationship was observed between fragmcm size aAlollmTa presence in the fragments (Xl = 4.46. d.f. = l. p = 0.04). Of the fragments tmeasured under 10 ha. only 19% were occuped; in contrast, in those fragments larger th10 ha, groups wcre prescnt in 100% (Table 1). Group presence was also associated wcanopy hcight (Xl = 8.78. d.f. = 1,p = 0.(05), as 75% ofthe groups were found in fragmewith a well-preserved canopy (Table 1). In conlraSt. the presence of monkeys w

- -"" "ragment size ( ha )-"--, -----'


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92 E. M. ROORIGUEZ-TOLEOO Endependent from fragment shape (Xl:::; 0.104. dJ. = 1, P = 0.75). A similar numbgroups were found in regular- and irregular-shaped fragments (Table 1). Therc is a posassociation between monkeys who [ive in lurge fragmenls and those hal have apreserved canopy, which shows hat size and distribution do have an effeel over popul:tThereforc. howlers show a preference for the characteristics of fragmenls. An impoquestion is fhis preference is the result oran active selection ofthcse fragments by howor simply he result o f historie processes of i501alion for caeh group.

Group presence was nol significant as compared lO thedistance lO thecontinuous f(Table l. Xl = 1.4. dJ. = 2.p =:; 0.51). This result is important because it implies that howdo not depend on continuous foresl as sourcelmainland area. Therefore. lhe persislenlocal groups depends on demographic structure and on the movements ofindividuals amfragmenls. In conlinuous forest thcre is a high abundance ofprimates. So, crcating corrbetween fragmenls would possibly increase the isolaled subpopulalions.

The average distance ofthe nearest group was 393 328 m; while lhe average dislof a parlicular group to all OIher groups was 2,731 1,735 m. This result shows the crsilUation o f primates. since the isolation among groups is quite large. There is a negconsequenee to individuals and groups as a result of such long distances. The long distlO the nearest group could be an isolation factor preventing sorne individuals from dispeIfdispersal were attempted, there is a probabilityofmortalityduring Ihe movemenl fromgroup lo anolher. There is also a ehance that individuals remain isolated. For exampleobserved Ihree males that inhabited an isolated fragmenl. In either case, the consequena reduction of primates in this landscape.

Group presence lO the nearest town was not signifieant (Table 1. Xl =:; 2.1, d.f. = 20.35). A group's proximily to towns did not influenee a group's presence. Sorne grinhabil fragments very close to people, such as in Mirador Pilapa, Magaltanes, Lopez Aand Guadalupe Victoria. A possible reason for Ihis mighl be thal the i11egal hunlingcapture o f monkeys has reeenlly decreased. In sorne lowns we noled a slighl posmodification of Ihe people's perceplion of primates.

Finally, there was no relationship between group size and fragmenl size (r = -0.100.09, dJ. =: ; 1, ID, p = 0.77), fragment shape (r = 0.15, F = 0.20, d.f. = 1, 10, p = 0distance lO continuous forest (r = 0.001. F = 0.0002, d.f. = 1, la. p = 0.99), to the netown (r = -0.27, F = 0.72. d.r.::;= 1, 10, p = 0.42), and dislance 10 the nearest fragmenl0.31, F = 0.96, d.f. = 1, 10, p = 0.35). These resulls may be due lO the low numbindividuals that inhabit bigger fragmenls. In faet, we had tioped to find a greater numbindividuals in larger fragments, as had been found in olher studies (see Seclion 8 belo

8. COMPARISON WITH OTHERS STUDIESIt is interesling to compare OUT results with data reponed by Estrada et al. ([999)


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1l0WLER MONKEYS IN FRAGMENTS

Tablc 2. Comparison ofthe howler monkey in two different landscapes in LosTuxtlas.data for the north landscape were obtained from Estrada et al. (1999). South data arestudy.CharacteristicsLandscapc tOlal areaNumbcr of fragmcnlsFragmcnts total arcaFragmenls arca pcrecntagc respcet lO the landseape lotal arcaNumbcr of fragmcnls under eaeh eategory size


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94 E. M. RODRIGUEZTOLEOO ET AL

"..

,L u" " " " .. .. " '" ,., ... 00'foras! fragmenl size ( ha ).., ."E,-

observed group monkey sizeD &xpeeted group monkey size. 'igurc 6. Nurnbcr of A/ullulla individuals observe


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1I0WI.ER Jl.1ONKEYS IN FRAGMENTS

lakes place. In large. narrow fragments. Irees may fall from slrong winds Ihat blow fromGulf ofMexico in several months of the year. damaging fragment Slruclure.

Alollalfll presence and group size do not depend on the dislance from fragmenls 1continuous foresl. At this moment.areas with eXlensive and relatively undisturbcd vegetaare found in the high and intermediate parts of the San Martin Pajapan and Sierra SMarta volcanoes (Rodriguez-Luna et al.. 1987). It might be assumed Ihat Ihese arcasfunctioning as sources for primates and that the fragments are sinks. Although Ihis asrequires detailed analysis. our data do nol support Ihis explanation. as greater proximicominuous forest did nol mean a larger number of occupied fragments. Therefore. soareas should be seriously considered in managemenl planning. In the study arca, hogroups are isolaled and there is a high probability lhat they will disappear ducatastrophes. stochastic events, genetic deplelion, or social dysfunction (LandeBarrowdough, 1987). Hanski (1999) provides corroboration for Ihe concepl that wilincrease in fragment size. connectivity. and habilat qualitY.lhe arcas are more likely 1occupied anci/or colonized. It is Iherefore necessary tO preserve as much original vegetain fragments as is possible, giving priority to Ihose larger than 10 ha. Conccrning smfragments. priorilY should bc given 10 those Ihat have a canopy heighl of over 15 m. Tarc also unoccupied fragmenls that based on their characteristicscould function as pOlcngood habitats for groups of monkcys. It is thercfore necessary lO formulatc proposals focreation of corridors Ihat permit individual movement between fragmenls. thus facilitafragment recolonization. As the number of occupied fragments increases, so willprobability of persistence for monkey groups in this landscape, and Ihis in turn will asthe conservalion of Alo/larta populations in Mexico.

10. SUMMARYThe relationship between certain fragment characteristics (size, shape. isolation.

vegetation dislurbance level), Alollatta pall iata mexicana presence. and the numbeindividuals per group was analyzed in a section ofthe buffer zone found on the Los TuxSpecial Biosphere Reserve in Ihc slate of Veracruz. Mexico. Fieldwork was carried oearly 2001 and 2002. Sixty-four fragmenls were idenlified. representing 8.4% of the 3ha Ihat make up lhe study area. Oflhesc. 92% had a surface area ofunder 10 ha, while8% exceeded this size. In the larges! fragmenl measured (67 ha) only 42% had a reJatiwell-preserved canopy height (exceeding 15 m). Specifically, 100% of the fragmmeasuring over 10 ha had well-preserved eanopy. while ofthe total fragments under 1in size,58% showed signsofdiSlurbance and only 19%were occupied by howlers. Fortypercent had a relatively regular shape and were found principally in riparian zones.


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" E. M. RODRlGUEZ-TOLEDO Estraight-line distance between fragments, distance to the continuous forest, and distan(he nearest town. The actual distance belween groups i5 very large. Eighty-two pereentogroups were faund in fragmems with weJl-preserved canopy hcight. Clearly, manageproposals are urgently nceded to ncrease populalion size and the number of fragmentsprimates in this landscape. A management plan is nceded where regenerationreforestation offragmenls and corridors are a priority. It is urgent lO involve local peopconservation plans thal considcr their social and economics issues.11. ACKNOWLEDGMENTS

The aulhors would like lO thank physicist Rosario Landgrave and biologisl NoCorona for Iheir assistance in the analysis ofGeographic Information Systems as well afamily of Mateo Gutierrez, espccially Ruben, for his hospitalily and invaluable helpficldwork. Also lO Odellc Brunell for her field assislance. The firsl aulhor received a gfrom lhe Nalional Council of Science and Technology (CONACYT) for Ihe pursuposlgraduale research. We would also like to thank Ihe U.S. Fish and Wildlfe Service, wprovides assiSlance lO the Nalural Prolection through Conservation Program and theWilManagement Maslers Program thal form part of Ihe Latn Amercan Alliance of WilManagement Training. Finally, we are grateful to the Depanment of EcologComportamiento Animal of the Instituto de Ecologa A.C., for provding the supnecessary for the completion oflhis research. Actually, the American SocietyofPrimatobrings a grant lO help in sorne aspects of this sludy.12. REFERENCESBurkey. T. V., 1989, Extinlon in nature reserves: The cITeet of fragmentation and tlle importa.nee of migbelwcen reserve fragments. Oikos 55:75-81.DiarioOfeial de la Feder:;cin, 1994, NOM059-ECOt.,..I994, Organooel GobiemoConstitueional de los EUnidos Mexicanos. Tomo COLXXXVIII, 10. Mxico, D.F.Oirw, R" and Garda, M. c.. 1992, Ratcs ofdeforcstation in Los Tuxtlas. a Neotropkal arca in Veracrul. MCn",-av. 8i"l. 6:84-90.DrlO, R.. and Miranda, A., 1991. EllImile boreal de la selva tropical hmeda en el continente ameriContraccin de la selva y solucill de una controversia./II/ercinu:ia 16:240--247.Estrada. A .. 1982. Survey and census of 1I0wlcr monkeys (Alolllllra paUillla) in tlle rain forcst of Los TuVeraeruz. Mxico, Am. J. Primlllo/. 2:363-372.Estrada. A.. ano CoatesEstrada. R.. 1995, La contraccl1 y fragmentacin de las selvas y las poblacionprimates silveslres: El caso de los Tuxtlas. Vcracruz. in: Estudio,. Primlllolgico.r"" Mlxico, E. RodrfLuna. L. Cons, and J. MartfnelConlrcas. eds.. Universidad Veracruzana. Xalapa, Veracruz, Mxic

25-60.Estrada, A., Anzurcs, A., and Coatcs-Estrada, R.. 1999. Tropical rain foresl fragmcnlation, lIowler mo(AlOUGIIG palli{l/a), and dung bcetles at Los Tuxtlas, Mexico. AIIJ. J. PrillllUol. 48:253-262.Forman. R. T. T.. and Godron, M., 1986. Wnd.\'cGpt Ec%g)', Jotm Witey and Sonso Ncw York.


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GareiaOrdua, F., 1996. Dislribuci6n y abundancia del mono aullador AlrlflcJUa pal/ial{J y el mono al':la Ageoffroyi en fragmentos de selva del municipio de San Pedro Soleapan, Vcracru:t. Undcrgl":'ldualC lhUniversidad Veracruzana. Xalapa. Vel":'lcruz. M6ieo.Glander. K. E.. 1975. Habital and Resourcc Utiliz.alion: An ecological view of social organizalion in manhowling monkeys. Dissertalion thesis. Universily of Chicago. lIlinois.Gotelli, N. J., 1998. A Prima oj Ec%gy. Second Edilion. Sinaucr Associates. Ine .. Sunderland. MA.Guevara. S,. Laborde. J,. Liescnfcld. O,. and Barrel':l. O.. 1997. POlrerOS y ganadcra. in: J{i)'uria Noturol deTuxt/as. E. Gonz1ez-Soriano. R. Dirzo. and R. C. Vogl, cds., Universidad Nacional Aul6noma de MxMbtico. D.F.. pp. 43-58,Hanski.l.. 1991. Single-speciesmctapopulalion dynamics: Concepls. models, and observalons,BilA. J. UII/l,4l:17-38.Hanski, J., 1999, Melopopu/aliOlI Ec%gy. Odord Universily Press. London.Harrison, S., 1994. Melapopulations and conservalon. in: Large-Sea/e Ec%gy aud COIuervatioll Biology.Edwards, R. M. May. and N. R. Webb. eds.. lJlackwell Science, Osney Mead. Odord. pp. 111-128.Hoopcs, M. F.. and Harrison, S" 1998. Metapopulation. sourcesink and disturbanee dynamics. in: COIlJen'lSciellct' cmd Arlicm. W. J. Sutherland. ed.. lJlackwell Scicnce. Osney Merd. O ~ f o r d , pp. 135-151.INEGl. 1999. fotogl":'lfas areas, San Juan Volador. Lnea 4 a la 7. Escala 1:20,000, Instituto NacionaESladislca Geogrfica e Informtica San Juan Volador. EI5 A74.Jimnez. H. J., 1992. Distribuci6n y abundancia del recurso alimemicioen un fragmelllo de selva alta percnniy su uSO por Ate/es y A/mmlta en el ejido Magallanes (Municipio de Soteapan. Veracrul.). Undergradlhesis. Univcrsidad Vel":'leruzana, Xalapa, VCl':lcru:t. M ~ i c o .Juan-Solano. S., 2000. A comparativc sludy of resource use by howlcr rnonkey groups (A/oullllil pal/i"liisolalcd rainforeSI fragmenlS of lhe region of Los TuxllaS. Veracruz, Mexico, ASP B"I/eliu 24:8.Lande. R.. and Barrowclough. G. F.. 1987. Effective populalion size. genelic varialion. and lheir use in populamanagemcnl. in: V i a b l ~ I'OPlllatiollS jor CUIlIfrvatiOIl, M. E. Soul. ed.. Cambridge University PCambridge. UK. pp. 87-123.Mas. J.. andCorrea-Sandoval. J.. 2000. Anlisis de la fl":'lgmenlacill del paisaje en el rea prolegida "Los I'eleCampeche. Mxico. Bo/nlll dellllsliwlII dI' Gfograjfa. UNAM 43:42-59.McCullough. D. R.. ed" 1996. MerapIJplI/mifl/M' amI Wi/dliff CUlI)fn'atioll. lsland l'ress. Covelo. CA.Miranda. F., and Hemndez. X. E.. 1963. Los tipos de vegctacifl de Mxico y su clasificacin. Baldll dSociedad 801llim d Mxiro 28:29-178.Rzedowskl. J., 1978. Vt'getociII d Miro. Editorial Limusa. Mxico. D.F.RodrfguczLuna. E.. GarcaQrdua. F., Silva-L.pc:t. G.. and Canales-Espinosa. D.. 1987. l'rimale conservain Mexico. Prim. COIM"l!fV. 8:114-118.Rylands. A. n. , Minermcer. R. A., and RodriguC"l.-Luna. E., 1995. A specics lisl for lhe New World p r i m (Platyrrhini): Distribulion by eounlry. cndernism, and conscrvation stalus according lO lhe Mace-LSystem. NI'OIwpi. Prima. 3: 113-160.$aunders. D. A., Hobbs, R. J .. and Margulcs. C. R., 1991, Biological consequcnces of ecosyslem fl":'lgmcnla

A rcview. COIlUrv. 8/01. S: 18-32.SilvaL.pe1.. G .. GardaOrdua. F,. and RodrlguezLuna. E., 1988, The Slatus of Ale/es gl!(Jffroy/ and A/JIpallillla in disturbcd forst arcas of Sierra de Sanla Marta, Mexico, Primo Cfl/M'frv. 9:53-61.Silva-L6pe1.. G.. Benlez-Rodrguez. J., and Jimtnn-Huerta, J., 1993. Uso del hbilat por monos araa (Ag ~ o / f r o ) " i ) y aullador (AIOlwlla palliata) en reas perturbadas. in: sludim' Pril ll l l loigirm t"l MixicoRodrguez-Luna. L. Corts. and J. Martnel.-Comreas. eds., Universidad Vcraeruzalla, Xalapa, VeracMxico. pp, 421--435.Wicns, J. A., 1996, Wildlife in palchy cnvironmenlS: Melapopulations. masaics. and managementMt'/IIp


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INEGI. 1999. Fotografas areas. San Juan Vobdor. Unea 4 a la 7. Escala 1:20.000. Instiluto NacionalEstadistica Goognlfica e lnfonntica San Juan Volador. EI5 A74.Jimnez, H. J 1992. Distribucin y abundancia del rccursoalimentieio en un rr:lgmenlode selva alta pcrennifoy su uso por Ale/es y Alouaaa en el ejido Magallanes (Municipio de SOIeapan. Veraeru7.). Undergradulhesis. Universidad Veracru7.ana. Xalapa. Veracruz. Mxico.Juan-Solano, S., 2000. A comparalive sludy of resouree use by howler monkey groups (AlOlwlla palliata)isolated rainforest fragments of the region of Los Tuxllas. Verdcruz. M e ~ i c o . AS" Hul/niu 24:8.Landc. R.. and Barrowclough. G. F.. 1987. Effcclive populalon size. genclie varialon. and 1heiruse in populalimanagcmem. in: V i a b l ~ Populaliolll' fo r CmlJer\'alioll, M. E. Soul, cd .. Cambridge Uni"crsiIY PreCambridge. UK. pp. 87-123.Mas. J.. and Correa-Sandova1. J.. 2000. Anlisisde la fragmenlacin del paisaje en el ~ r c a prolegida "Los PcleneS

Campeche. Mxico, Bolniu delllll'liluliJ de GeograjTa, UNAM 43:42-59.MeCulloogh. D. R.. cd.. 1996. MerapoplllaliOlIJ ami Wi/d/ife C O I l J ~ r v a l i o l 1 . ls!and Press. CovcJo. CA.Miranda. F.. and Hcrnndez. X. E.. 1963. Los l ipos de vegelacin de Mxico y su clasificacin. Bole/ill deSoriedad 8muira d Mxiro 28:29-178.

R7.edowskl. J.. 1978. V/'gnaII de Mxiro. Editorial Limusa. Mxico. n.ERodrguez-Luna. E.. Garcla-Ordua. F.. Silva-L6pez. G .. and Canales-Espinosa. D.. 1987. Primate conscrvalin Mexico. Primo COIlJ/'rv. 8: 114-118.Rylands. A. B., Mitlcrmeier. R. A., and Rodrguez-Luna. E.. 1995. A spedes list for lhc New World prima(Plalyrrhini): Distribution by coun1ry. endemism. and conservalion status aceording !O lhe Mace-LanSyslem. N ~ ( } / r o p i . Prillla. 3: 113-160.Saunders, D. A., Hobbs. R. J., and Margules. C. R.. 1991. Biological consequences of ccosyslem fragmenlatiA review. Cmlurv. Biol. 5: 18-32.Silva-Lpez, G .. Garela-Ordua. F., and Rodriguez-Luna, E .. 1988. lbe stalus of Aleles g ~ o f f r o y i and A/ouapulliala in diSlurbcd forst arcas of Sierra de Sanla Mana. Me... ico. Prim. COI1l'erv. 9:53--61.Silva-Lpcz, G., Bentcz-Rodrguez, J., and Jimnez-Huena. J., 1993. Uso del h ~ b i l a l por monos araa ( A I ~ geoffroyi) y aullador (Alouallu pulliala) en reas perturbadas. in: E"lUdio," I'rimalOlgicos el1 Mb:ico,Rodrguez-Luna. L. Cons, and J. Marlncz-Contreas. eds., Universidad Veraeruzana. Xalapa. VeracrMxico. pp. 421--435.

Relationships between characteristics of forest fragments and howler monkeys (Alouatta palliata...

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