Original investigation Diversity of mammals in the Bladen Nature Reserve, Belize, and factors affecting their trapping success

12 Pages·2001·6.9 MB·English

by  T M Caro

88 BrigitteA. Reutteretal.
Zusammenfassung
Biochemische Bestimmung dreiersympatrisch vorkommenderApodemus-JKrten mittels
Elektrophoresevon Blutproteinen
Mittels Elektrophorese von Blutproteinen wurde das Allelbandenmuster von Albumin und eines
„General Protein 1" derdrei in den Alpen sympatrisch vorkommenden Waldmausarten Apodemussyl-
vaticus, A.flavicollis und A. alpicola untersucht. Die Methode erwies sich als ein zuverlässiges Werk-
zeug zur Unterscheidung der drei Arten. Ihre Bestimmung anhand äußerer morphologischer Merk-
male ist nicht immer einfach, vor allem, wenn es sich um juvenile Tiere handelt. Mit dieser
Methode können lebende Individuen aller Altersklassen bestimmt werden, was eine Anwendung in
ökologisch ausgerichteten Felduntersuchungen erlaubt.
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common shrew Sorex araneus and Millet's ruhe, Germany.
Mamm. biol. 66 (2001) 90-101 äfflfe Mammalian Biology
© Urban & FischerVerlag
http://www.urbanfischer.de/journals/mammbiol '^BsP' Zeitschriftfür Säugetierkunde
Original investigation
Diversity of mammals in the Bladen Nature Reserve,
Belize, and factors affecting their trapping success
ByT. M. Caro, Rachel Brock, and Marcella Kelly
DepartmentofWildLife, Fish and Conservation Biology, UniversityofCalifornia, Davis, California, USA
ReceiptofMs. 12. 11. 1999
AcceptanceofMs. 20. 04. 2000
Abstract
The presence of33 non-volant mammalspecies was recorded in the Bladen Nature Reserve, an area
of subtropical wet forest in south central Belize, as determined from Walking transects and using
Sherman and Tomahawk traps to capture mammals. Using trapgrids over 6075 trapnights, the ef-
fects oftrap design, bait, moon phase, logging, elevation, and proximity to a river on three mea-
sures of trapping success were examined Systematically. Open wire mesh traps yielded somewhat
higher trapping success than Sherman traps; oats and molasses produced higher trapping success
than other kinds of bait; and trapping success was higher in selectively logged than in unlogged
forest, and marginally higher at lower elevations and dose to a river. Moon phase had no effect
on trapping success. These results provide baseline data on mammal diversity in a relatively un-
exploited area ofcentralAmerica and, though preliminary, indicate which aspects oftrapping tech-
nique need to be standardized when comparing species diversity and abundance across neotropical
sites.
Key words: Mammals, trappability, diversity, Bladen, Belize
Introduction
Most ecological studies of neotropical 1997; Malcolm 1997), loss of top predators
mammals require data on species diversity (Wright et al. 1994; Terborgh et al. 1997),
and abundance. For example, questions and mammal exploitation (Dirzo and Mir-
about population dynamics (e.g., O'Con- anda 1991; Glanz 1991; Wright et al.
nell 1989), population demography (e.g., 2000) on communities of mammals. In the
Torres-Contrera et al. 1997), Community neotropics data on mammal communities
structure (e.g., Asquith et al. 1997), and re- are growing (Voss and Emmons 1996) but
gions of mammal abundance (e.g., Mares they still come from only a handful ofloca-
1992) all require information on the num- tions, the most notable ofwhich are La Sel-
ber of mammal species or their relative va in Costa Rica (Timm 1994a), Los Tuxlas,
abundance in an area. Conservation studies Mexico (Estrada et al. 1994), Barro Color-
similarly require data on diversity and ado Island, Panama (Glanz 1990), Cosha
abundance in order to understand the ef- Cashu, Peru (Janson and Emmons 1990)
fects of habitat fragmentation (Lynam and near Manaus, Brazil (Malcolm 1990)
1616-5047/01/66/02-090$15.00/0.
Diversityofmammalsin the Bladen Nature Reserve 91
which limits our ability to make generaliza- mal densities being lower (Eisenberg et al.
tions about how mammalian communities 1979) and small mammal abundance being
are organized. higher in logged sites (Kasenene 1984; Isa-
As studies ofmammals inthe neotropics in- biyre-Basuta and Kasenene 1987; Mal-
crease, and comparisons between areas be- colm 1995). Increased elevation has been
come more feasible, researchers must stan- found to change species diversity in some
dardize their techniques for estimating areas of the tropics (Rickart et al. 1991)
mammal abundance, or at least be aware while proximity to seasonally flooded areas
of the biases inherent in different methods close to rivers may alter species diversity
of mammal estimation (Wilson et al. and abundance in complex ways (Janson
1996). We therefore investigated six differ- and Emmons 1990). Therefore the aim of
ent factors that influence trapping success this study is to investigate the diversity of
outside the neotropics and might therefore species at a new site in the neotropics and
be of importance elsewhere. Two of these to analyse factors affecting trapping success
were methodological factors (type of small in this environment.
mammal trap and characteristics of the
bait) and four were ecological factors
(phase of the moon, selective logging, ele-
Material and methods
vation, and proximity to rivers).
Trap design can influence trapping success
The study was conducted in and adjacent to the
substantially in temperate regions (Sealan- Bladen Nature Reserve in the Maya Mountains,
der and James 1958) and this problem has Toledo District, Belize (Fig. 1). The reserve en-
been identified in at least one neotropical compasses 350km2 of the watershed of the Bla-
site (Woodman et al. 1996). We therefore den River between latitudes 16°36'18" and
compared measures of trapping success 16°24'34"N and longitudes 88°42'16" and
using hand-made wire mesh small mammal 89°04'51"W. Elevation ranges from 50 to
mm
traps which could be seen through with 1000m. Rainfall averages around 3000 per
Standard Sherman traps which obscure visi- annum or more; January to April are the driest
bility. It is also well known that baits can af- mthornotuhgsh Nwiotvhemrbaeirn.sMtaeratinngmofnrtohmlyJutneempeornawtaurrdess
fect trapping success in temperate zones rängefrom 16°to33°CinBelize.Muchofthere-
(e.g., Buchalczyk and Olszewski 1971). serve is composed ofCoban formation limestone
Although far less work has been carried andvolcanicrock. The reserve contains subtropi-
out on this problem in the neotropics, preli- cal wet forest (Hartshorn et al. 1984) with the
minary evidence suggests that bait is not an lowest parts, along the main flow of the river
important factor in mammal trapping where we worked, supporting alluvial soils and
(Woodman et al. 1996). Increased moon- tall broad-leavedforest. Most ofthe Bladen Nat-
light lowers trapping success in open habi- ure Reserve is unlogged; selective logging has
t1a9t8s8)inbetceamupseerastmeallremgiaomnmsal(sBroofwtnenesthoalw. kbboenreodnwern,prhauhcnottwiiecnvegedrp.irmeTsmsheuderieartbeesyleyrlvoceoaulitspsiesdouepbljeietcsftoertaogstauemnre-n
changes in activity in accordance with a re- meat.
duction of predation risk from visually The study was conducted during four periods of
hunting aerial and terrestrial predators fieldwork: June and July1994, June through
(Clarke 1983). Although moonlight is August1995, March1997 and July1998. Some
known to influence activity patterns of rain feil in each of these periods but trapping
some tropical mammals (Fenton et al. was suspended under extremely wet conditions
1977; Emmons 1987; Alkon and Saltz because we were concerned about hypothermia
of captured individuals. All the work was con-
1988), it hasreceived little systematic atten- ductedadjacenttothe easternentrance ofthere-
tion in small neotropical mammal trapping serve, 1-3kminside, and0.5kmoutside it.
studies. Selective logging has many influ- Mammal diversity was assessed in three ways:
ences on mammal Community structure in through night and daytime walks in which obser-
tropical environments with arboreal mam- vations and calls ofmammals were noted, by in-
92 T. M. Caroetal.
Fig. 1. Belizeandthe locationofBLaden Nature Reserve (in black) inthe country.Top rightinsetshows Location
ofBelizein centralAmerica. Bottom rightinsetshowsthe boundaryofBladen Nature Reserve (dashed Line) and
the Bladen Branch Riverand itstributaries (solid Lines). The entrancetothe reserveis at Forest Hillshown as a
blackdot.Three2 kmtransectswerelocated (i)justinsidethereserveboundaryrunningsouthwesttonortheast
terminating at Forest Hill; (ii) between Forest Hill and the Richardson Creek (fifth tributary upstream from the
entrance) confluencesouth and paralleltothe Bladen River; (iii) andoutsidethereservefromanddue northeast
ofForestHill. Alltrapgridswithinthereserveweresetsouthofthe Bladen Riverbetween ForestHillandthesec-
ondtributaryupstream from theentrance. Trapgridsoutsidethe reserveweresetwithin 500m ofthereserveen-
trance. Blackbardenotes 10km;arrowshowsnorth (adaptedfrom Hartshornetal. 1994).
Diversityofmammalsin the Bladen Nature Reserve 93
terpreting mammal tracks in the mud, and greenorripe bananas, raisins, or a fruit found on
through live trapping. Abundances of certain the forest floor, Warre Cohune palm, Astrocar-
mammal species were estimated through repeat ynrri mexicanum. These traps were set approxi-
trapping using Standard Sherman, custom-made mately50-450mfromtheriver.Inonesetoftests
small mammal traps, and three sizes of Toma- these traps were placed at a height of 1-2.5m in
hawk traps. We used the field guide of Emmons trees and baited with oats and molasses in order
(1990) to identifymammals inthe field. Twopre- to estimate squirrel abundance.
vious mammal surveys had been conducted in We also set large Tomahawk traps
the Bladen (Brokaw and Lloyd-Evans 1987; (65x22.5x22.5cm) in a 6x8 grid with traps set
TheNature Conservancy 1993). 50m apart. These were baited with either green
We set up three 2km transects that were walked or ripe bananas, Astrocarynm mexicanum fruit,
at a pace of 1km/hour. One was located within commercial cat food or fresh fish; these latter
the reserve and followed an abandoned logging two baits were combined in bait analyses since
track that serves as the main road into the re- they both contained animal protein and smelled
serve; the second was further inside the reserve similar. In none of the trapping protocols were
on the south side and parallel to the Bladen Riv- different baits run at the same time oneitherthe
er; the third was located adjacent to but outside same ordifferentgrids.
the Reserve in a selectively logged area. Night Traps were usually set for 5consecutive nights
walks (N= 18) were conducted between 18.30 although a small minority was set for fewer or
and21.00h and animalswerespottedusingflash- more nights (ränge 1-7). Traps were set either in
lights; day walks (N=28) took place between unloggedforest with a tall thick canopy and rela-
05.30and07.30h.Tracksofmammalswereexam- tively open understory inside Bladen Nature Re-
ined opportunistically and in specially prepared serve, orin the area east ofthe reserve where se-
flats ofmud, at the center at which was placed a lective logging allowed light to penetrate,
commercialcarnivore olfactoryIure. producing a thicker understory of Vegetation.
Small mammals were trapped using Standard Trapswere opened andbaitedbetween 16.00and
Sherman traps (23x8x8cm), or traps of the 17.00h and checked next morning between 06.00
same dimensions custom-made entirely out of and 09.00h. Captured animals were individually
galvanized wire mesh (by the late R.Schwab) marked by cutting small patches of für since we
save for a galvanized aluminum plate door that were only interested in recaptures over a maxi-
was part of the floor until the door swung up- mum of 7days. Quarter of the moon was noted
wards on closure (see also Emmons 1984). Traps during each sequence of trapping; in some ana-
wereusuallysetinan8x8or7x7 gridwith traps lyses traps set during the first and last quarter
10m apart; infrequently they were set along a spanning the new moon, and then the second
transect precluding calculation of density. Grids and third quarters spanning the füll moon were
ofsmall mammal traps were baited either with a combined.
mixture ofoats and molasses, with peanut butter, We recorded number of species caught, percen-
with green or ripe bananas, or with a medley of tage capture success, individual mammals caught/
fruit consisting of apple, banana, and coconut 100trapnights, and densities when traps were set
mixed together. Ripe and green bananas were in a grid square. Percentage capture success was
the numberofcapturesdividedby the numberof
lumped together in bait analyses because green
bananas quickly ripened in traps making it diffi- ttrhaepnniugmhbtser(io.fe.n,ignhutmsboenrwhoifchtratphseymwueltrieplsiete)d;ibny-
cult to distinguish between the two. Traps were dividual mammals caught per 100trapnights was
uaspuparlolxyimseatteolnyt2h0e-2fl0a0tmvalfleryomfltohoreoBflathdeenreRsievrevre vthiedendubmybtehrenofumdbifefreroefnttrianpdniivgihdtusalxs1c0a0;ptaunrdeddedni--
bank. In another protocol, trapgrids were set at sities were calculated by dividing the number of
higher elevations on the steep limestone slope individuals captured by the area covered by the
b1o0r0dmerianbgovtehetheflvoaoldlpelyaifnlooarpparnodxi2m0a0t-e2l5y0m50fraonmd tgroiodketxhpirsesasreeda atsonbuembtheerdoifmienndsiivoindsuaolfs/tkhme2.gWried
the river. plus 5m either side (i.e., 70mx70m or 4900m2
We set two types of Tomahawk traps in a 7x7 grid) because paucity ofcaptures made
(40x13x13cm and 40x17x17cm) which we it difficult to calculate maximum distance be-
termed middle-sized traps. These were usually tween captures ofknown individuals. We did not
set in a 6x8 grid with traps 50m apart. Traps use mark-recapture techniques to estimate den-
were baited either with oats and molasses, with sitybecause recapturerateswere solow.
94 T. M. Caroetal.
Data were analysed by comparing trapgrids non-volant species (n= 18grids; 3521 trap-
although the number of trapnights that these re- nights). With the middle-sized Tomahawk
presented is also presented for clarity. Non-para- traps, we caught only two species, Ototyl-
metric statistics were used as number of species omys phyllotis and Tylomys nudicaudas.
was an ordinal measure, and captures/trapnight
and individual mammals caught/100trapnights Trap success was low at 0.7% (sd+ 1.0), or
producedtoomanyzeroes (nocaptures) tojustify 0.6individuals/100trapnights (sd±0.8)
normalizing the data required for parametric sta- (n = 9grids; 1354trapnights). Density of
tistics. The use of non-parametric statistics made these two species was 2/km2 and
itdifficulttocontrolforconfoundingvariables;in- 10/km2, respectively (n =5 grids; 1200trap-
steadweconductedaseriesofcarefullycontrolled nights). With the large Tomahawk traps,
comparisons among grids by excluding variables we caught Didelphis marsupialis, Didelphis
thatwere found to be important inprevious ana- virginianus, Dasypus novemcintus and a
lyseseventhoughthese resultedin a reductionin Tylomys nudicaudus giving an average per-
sample sizes. awas set at0.05; nevertheless pVa- centage trap success of 4.3% (sd±4.3), or
hleslyingbetween0.1 and0.05 arenotedanddis-
cussedwithappropriatecaution. 3.9individuals/100trapnights (sd±3.9)
(n= 9 grids; 1218 trapnights). Density of
these species was 28/km2 8/km2 2/km2
Results and 2/km2, respectivel,y (n=, 5 grids;,
1 152trapnights). Excluding bats, we calcu-
lated a Shannon-Wiener index of2.021.
Captures
In this study, twenty eight species of non-
Factorsaffectingtrapping success
volant mammals were identified inside and
outside but within 0.5 km of the Bladen Type of trap: Compared to Standard Sher-
Nature Reserve, althoughtwo ofthesewere man traps, custom-made wire mesh traps
equivocal identifications (Tab. 1). In our of the same dimensions caught marginally
study all of these species except five, Phi- more terrestrial mammal species (n= 6;
lander opossum, Urocyon cinereoargenteus, 20grids, respectively; 618, 3618trapnights,
Conepatus semistriatus, Leopardussp., and Means (Xs) = 1.0 (sd±0.9), 2.1 (sd±1.4)
Panthera onca were found inside the re- species, Mann-Whitney Utest, z =-1.763,
serve; in a previous study conducted by the P= 0.078), demonstrated marginally higher
Rapid Ecological Assessment Team in 1993 percentage capture success (Xs =2.2%
a jaguar and a small felid had been identi- (sd±3.0), 7.7% (sd±6.1) respectively,
fied inside Bladen (The Nature Conser- z =-1.951, P=0.051), and caught a margin-
vancy 1993). Our results, combined with ally greater number ofindividuals per trap-
those of the two earlier surveys (Tab. 1), night (Xs=2 (sd±3), 7 (sd±6) indivi-
showthat the Bladenareaholds aminimum duals/100trapnights respectively, z=-
of 33 non-volant species including large 1.830, P=0.067).
predators such as Felis concolor and Type ofbait: For small mammal traps, there
Panthera onca. were significant differences in the number
Employing small mammal traps, we cap- of species caught (n = 26grids; 4236trap-
tured five non-volant species, Heteromys nights, Kruskal-Wallis test, H= 11.444,
desmarestianus, Ototylomys phyllotis, Tyl- P= 0.01), percentage trap success (H=
omys nudicaudus, Marmosa robinsoni, Or- 8.464, P = 0.037), and individuals captured/
yzomys couesi and an unknown species of 100trapnights (H =7.888, P= 0.048) de-
batwith an average percentage capture suc- pending upon the type of bait offered. On
cess of 6.5% (sd±5.9), or 5.6individuals/ each measure, oats and molasses were most
100trapnights (sd±5.6) (n=26grids; successful followed by green and ripe bana-
4236trapnights). These traps yielded re- nas combined, and then the fruit medley
spective densities of 6836/km2 270/km2 (Tab. 2). There were no significant differ-
183/km2 925/km2 and 2127/km2 f,orthefive, ences between baits onmeasures ofdensity,
,
Diversity ofmammalsin the BLaden Nature Reserve 95
Table 1. Listofspeciesofmammalsinandimmediatelyadjacentto BLaden Nature Reserve.
1994-1998 this study: Tp:trapped; 0: observed; Tr:tracks; H: heard; I/O: inside or outside Bladen Nature Re-
serve. 1. refers to species noted by the 1993 Rapid Ecological Assessment Team (The Nature Conservacy 1993);
2. refersto species noted bythe 1987 Manometsurvey (Brokawand Lloyd-Evans 1987). * species may have been
Marmosamexicana;+speciesmayhavebeenLeoparduswiedii(Margay).
Scientificname Common name Tp 0 Tr H I/O
Marsupilia
Dideiphismarsupiatis Commonopossum X I
Dideiphisvirginianus2 Virginiaopossum X I
Philanderopossum Commongrayfour-eyedopossum X 0
Chironectesminimus1 Wateropossum X I
Micoureusalstoni1 ALston'swollymouseopossum
Marmosarobinsoni* Robinson's mouseopossum X I/O
Xenarthra
Tamanduamexicana Northerntamandua X I
Dasypusnovemcinctus Nine-banded Long-nosedarmadillo X I/O
Chiroptera
Balaniopteryxio1 Leastsac-winged bat
Noctiboleponnus Greaterfishing bat AV T1
Unidentifiedspecies AY T1
Primates
Alouattapigra 1 Mexican blackhowlermonkey X I/O
Atelesgeoffroyi1, 2 CentralAmericanspidermonkey X I
Carnivora
Urocyoncinereoargenteus Grayfox X 0
Nasuanarica 1 White-nosedcoati A T1
Potosflavus Kinkajou X I
Mustelafrenata1 Long-tailedweasel
Eirabarbara2 Tayra X I
Conepatussemistriatus Striped hog-nosedskunk X 0
Lontralongicaudus2 Neotropicalotter X I
Leoparduspardalis+1 Ocelot X 0
Pumaconcolor2 Puma X I/O
ranineraonca i Jaguar x o
Perissodactyla
Tapirusbairdii1, 2 Baird'stapir X I/O
Artiodactyla
Tayassutajacu 1 CoUared peccary
Tayassupecari1, 2 White-lipped peccary X I/O
Mazamaamericana 1, 2 Red brockeddeer YA tl//Un
Odocoileusvirginianus 1, 2 White-taileddeer
Rodentia
Sciurusyucatanensis Yucatansquirrel X I
Säurusdeppei1, 2 Deppe'ssquirrel X I
Heteromysdesmarestianus Forestspinypocketmouse X I/O
Oryzomyscouesi Coues'ricerat X I/O
Tyiomysnudicaudus1 Naked-tailedclimbing rat X I/O
Ototybmysphyllotis Big-earedclimbing rat X I/O
Agoutipaca 1, 2 Paca X I/O
Dasyproctapunctata1, 2 CentralAmericanagouti
96 T. M. Caroetal.
Table 2. Mean (X) and Standarddeviation (sd) measuresoftrappingsuccessinallsmalAmammaLtrapsseparated by
typeofbait; roundbrackets referto numbersoftrapgridsortrapLines,Squarebracketstothenumberoftrapnights.
Oatsand Peanutbutter Bananas Fruitmedley
moLasses
(7) (3) (14) (2)
[1973] [502] [1461] [300]
kINlUiIiMmUhCo!rnuifcbnpocnL'ioccb x 3.1 0.7 1.6
sd 0.9 0.6 1.2 1.4
rerceniage uapsullcss AV U.D D.D l.U
sd 1.0 0.6 6.8 1.4
Individuals/100trapnights X 7.5 0.6 6.5 0.4
sd 1.3 0.6 6.8 0.6
(7) (1) (10)
[1973] [245] [1303]
Individuals/km2 X 8600 6100 12200
sd 14300 0 12400
* trapsweresetina Line, ratherthangrid, so estimatesofdensityareunavailable.
however. When analyses were restricted found that percentage capture success and
only to small mammal wire mesh traps, the individuals/trapnight were significantly
number of species captured still differed greaterin loggedforest outside Bladen than
significantly by type of bait (n = 20 grids; in unlogged forest inside (n = 7,13 gridsjre-
3618trapnights, H = 7.792, P = 0.02) alt- spectively; 741, 2877trapnights, Xs=
hough this was no longer the case for mea- 12.2% (sd±5.4), 5.3% (sd±5.1), z =2.260,
sures ofpercentage trap success and indivi- P = 0.024; Xs = 12 (sd±4), 4/100trapnights
duals/100 trapnights. There were no effects (sd±6), z =2.539, P = 0.011). In the Toma-
ofbaitforanymeasureinthemedium-sized hawk traps, a slightly greater number of
or large traps. species was captured in the unlogged than
Moon phase: Considering either small, in the logged forest in the medium-sized
medium-sized or large traps, there was no (n = 7,2_grids, respectively; 1312, 42trap-
effect of moon phase on number of species nights, Xs = 0.7 (sd±0.5), 0 (sd±0) species,
captured, percentage capture success, num- z - 1.690, P = 0.091) and in the large traps
ber of individuals caught/100trapnights, or (n = 7,2_grids, respectively; 1200, 18trap-
density either when quarters were analyzed nights, Xs = 2.0 (sd± 1.0), 0.5 (sd±0.7) spe-
separately or when quarters respectively cies, z = 1.869, P = 0.062).
spanning the new andfüll moonswere com- Elevation: We obtained amarginallygreater
bined. number of species, percentage capture suc-
Selective logging: Somewhat more indivi- cess and number of individuals/100trap-
dual mammals were captured in logged for- nights on the valley floor than at higher ele-
est than in unlogged forest using small vations on the slope above the Bladen River
mammal traps (n = 11,15 grids, respectively; (n=24,2grids, respectively; 3876, 360trap-
956, 3280trapnights, n= 8 (sd±7), 4 nights, Xs =2.0 (sd± 1.3), 0.5 (sd+0.7) spe-
(sd±4) per 100trapnights, Mann-Whitney cies, Mann-Whitney U test, z- 1.642,
Utest, z = 1,664, P = 0.096) but there were P = 0.1; Xs = 0.7% (sd±0.6), _ 0.3%
no significant differences on the three other (sd±0.4), z= 1.832, P= 0.067; Xs= 6.1
measures. Restricting analyses to the cus- (sd±5.6), 0.3 (sd+0.4), z= 1.832, P=
tom-made traps that were somewhat more 0.067). Two of these three results still held
effective in catching small mammals, we after analyses were restricted to custom-
DiversityofmammaLsinthe Bladen Nature Reserve 97
made small mammal traps placed in un- tal period; Timm (1994b) documented
logged areas only (n= 11 low and 2higher 50species for La Selva in Costa Rica over
elevation grids; 3258, 360trapnights, 20years; and Glanz (1990) reported
Xs= 2.4 (sd± 1.6), 0.5 (sd±0.7) species re- 39species on Barro Colorado Island, Pana-
spectively, z= 1.610, P=0.107; Xs= 6.3% ma, which had been studied for 13 years at
(sd±5.0), 0.3% (sd±0.4) respectively, the time.
z= 1.781, P= 0.075; Xs =4.7 (sd±3.5), 0.3/ Small mammal trapping success in Bladen
100trapnights (sd±0.4) respectively, (6.5%) was comparable to that in other
z= 1.781, P=0.075). Tomahawk traps were neotropical wet forests such as Cockscomb.
not placed above the valley floor. For example, trapping success in the Gi-
Proximityto the river: Finally, we compared gante Peninsula, Panama was 4.2% for the
m
traps Set within <50 of the river bank wet and 7.3% for the dry season
with those placed further away (50-200m). (McClearn et al. 1994). In contrast to mea-
Results showed that the number of species sures of mammal diversity, it is difficult to
captured was marginally higher close to the make many direct comparisons of species'
river than further away from it densities with other sites as data for many
(n= 11,11 grids, _respectively; 2239, of the same species are unavailable. Didel-
1349trapnights, Xs=2.4 (sd+ 1.6), 1.2 phis and Dasypus densities appeared low
(sd±0.9) species, Mann-Whitney Utest, compared to Barro Colorado Island and
z = 1.793, P=0.073) but there was no effect south American sites (Glanz 1990),
on percentage trap success or individuals/ whereas Marmosa densities were higher
100trapnights. When analyses were re- than either at Barro Colorado oreven Gua-
stricted to custom-made traps set on the topo, Venezuela (Eisenberg et al. 1979).
valley floor in unlogged areas, however, Oryzyomys densities were extremely high
proximity to the river resulted in greater in comparison to Barro Colorado, Guatopo,
numbers of mammals caught on all three Cosha Cashu and Cabassou, French Guiana
measures (n = 8,3 grids next to and away (Charles-Dominique et al. 1981; Glanz
from the river, respectively; 2103, 414trap- 1990) possibly because some traps were set
nights, Xs =2.9 (sd± 1.5), 1.0 (sd±1.0) spe- in selectively logged habitats.
cies, z = 1.763, P=0.078; Xs = 7.9%
(sd±4.6), 1.9% (sd±2.8) trap success re-
Factorsaffectingtrapping success
spectively, z = 2.041, P =0.041; Xs = 5.7
(sd±3.2), 1.9individuals/100trapnights There is a substantial literature on the ef-
(sd±2.8) respectively, z= 1.837, P=0.066). fectsoftraptypeontrappingsuccessintem-
perate regions (e.g., Sealander and James
1958;Sladeetal. 1993).Thefewstudiesthat
Discussion have beenconducted inthe neotropics have
comparedlive traps to snap traps andfound
the latter to catch more species and indivi-
Captures
duals (Pizzimenti 1979; Woodman et al.
Bladen Nature Reserve and land immedi- 1996). The only studies to compare wire
ately adjacent to it held a minimum of mesh and Sherman traps were conducted in
33 species of non-volant mammals which is temperate climates (Holdenreid 1954;
comparable to othercentral Americansites. O'Farrelletal. 1994).Inbothcasesagreat-
Rabinowitz and Nottingham (1989) docu- er proportion of captures was made using
mented 39species of non-volant mammals wire mesh traps and heteromyid rodents in
in the Cockscomb basin which is almost ad- particular were captured in mesh traps.
jacent to the Bladen; Medelon (1994) re- O'Farrell et al. (1994) found that custom-
ported 48species in Selva Lacondona, made wiremeshtrapscapturedtwotothree
Chiapas, Mexico but these were compiled times more individuals than Sherman traps.
over 10years as opposed to our6month to- Our results from the neotropics replicated