170 ARTICLES

Herpetological ReI,iell'. 2011, 42(2). 17()"177.© 2011 by ociely for the lUdy of Amphibians and Reptiles

Using Scrape Fishing to Document Terrapinsin Hibernacula in Chesapeake Bay

Chesapeake Bay's Diamondback Terrapin (Malaclemysterrapin terrapin) population ha made considerable recov­ery from the commercial exploitation that led to its near ex­tirpation in the late 19'" and early 20'" centuries (Carr 1952;McCauley 1945). Nevertheless, it continues to face increas­ing threats from human population growth, degradation ofthe Bay, exposure to man-made hazards (Butler et al. 2006;Roo enburg 1991; iegel and Gibbons 1995), and, during theperiod of this tudy (2003-2005), continued commercial har­ve t in the Maryland portion of the Bay. The state of Mary­land maintained an active terrapin fishery that was closedonly during the terrapin ne ting season (May-July), had nodaily or ea onal catch limit, and exclu ively targeted breed­ing-age female, i.e., terrapins with plastron length ;,,15.2cm. Although the fi hery was perceived a small, with littlemarket demand, the long season and 'no limit' regulation leftthe fishery vulnerable to overharvest. Concern over this vul­nerability led us to examine the method of traditional winterharvest and characteri tics of terrapins occupying hibernac­ula. Although generations of Chesapeake Baywatermen havepursued winter harvest of terrapins, fishing methods, loca­tions of hibernacula, and the terrapins occupying them havenot previously been documented.

Here we utilize watermen fishing skills and harvest meth­ods to locate, ample, and de cribe terrapins occupying es­tuarine bay hibernacula. Because the region has long been acenter for the commercial harve t of Blue Crabs (Callinectessapidus), we al 0 examine terrapin capture for potential ef­fects of selective by-catch mortality of mall terrapins associ­ated with decades of commercial crab pot use in the region(Roo enburg et al. 1997; Warner 1977; Wood 1997).

MATERIALS AND METHODSWe sought collaboration with a former terrapin harvester

to learn fishing methods and to access hibernacula in theTangier ound region of Che apeake Bay (Fig. 1). TangierSound is bordered by extensive brackish tidal marshes andhistorically has harbored large terrapin populations (Mc­Cauley 1945). ampled hibernacula were chosen to be

G. MICHAEl HARAMIS'*e-mail: mharamis@usgs.govPAULA P. F. HENRY'e-mail: phenry@usgs.govDANIEL D. DAY'e-mail: dday@usgs.gov

I U.S. GeologicalSurvey, Patuxent Wildlife Research Center,do BARC-EAST Bldg 308, 10300 Baltimore AvenueBeltsville, Maryland 20705, U5A

*Corresponding author

geographically separated and to represent a selection of sitesof former terrapin harve t. Four ite were chosen near largemarsh i lands ca. 8-12 km off hore (Smith I land, outhMarsh Island, and Bloodsworth Island) and two addition­al sites were located near the mainland (Janes Island and

anticoke River; Fig. 1). Two ites located within tributaries( anticoke River and Janes Island) and a third located withininterior outh Marsh Island were within zones where com­mercial crab potting is prohibited by state regulation. Theremaining three sites ( mith [Iand- , mith Island-S, andBloodsworth Island) were within areas of heavy potting activ­ity. We also selected St. Jerome Creek, a site of fonner harveston the western shore of Chesapeake Bay that differed in be­ing located in a navigable tidal creek having forested hore­line in lieu of exten ive bordering salt mar h.

To capture terrapins watermen adapted a dredge, orscrape, used to capture molting blue crabs from shallow,near-shore waters using locally built, shallow-draft ve sel(also called crapes; Warner 1977). Being hand-made, terra­pin scrape vary in ize, but most are ba ed on a 1.5 m wideblue-crab design. In 2003, we u ed a blue crab scrape that wamodified by attaching a larger mesh catch bag and welding12 short 7.6 em teeth every 13 cm along th scraping bar. Thelarger mesh bag (8 cm) helped minimize fouling and the teethdug terrapins from bottom sediment. In 2004 and 2005, weused a slightly larger scrape framed from heavier 2 cm diam­eter steel stock. Its entrance measured 1.7 m x 0.4 m and itsoverall length was 2.4 m (Fig. 2a). The noteworthy differenceof this scrape was the addition of numerous (30), longer (15cm), and more clo ely spaced (6 cm) teeth on the scrape bar.

The scrapes were towed in a circular pattern behind a 12m work boat and retrieved by hydraulic winch. The length ofthe tow rope was critical to proper operation as it adjustedthe drag or "bite" of the scrape in bottom ediment. Capturesuccess wa measured by the number of terrapins capturedltow. Although there was no fIXed time limit for each tow, sev­eral hundred tows averaged about 7 min in length, or a rate of8.6 tows/h. While some commercial crapes were equippedwith ide baffles to help gUide terrapins into the catch bag,neither of our scrapes had baffles.

Captured terrapins were given a visible mark by drilling a5 mm diameter hole in the lOt" right marginal cute throughwhich we attached a erially numbered monel fish tag (tagnO.l005-3: ational Band and Tag Co., P.O. Box 72430, ew­port, Kentucky 41072). Passive integrated tran ponders, orPIT tags (model TX1400L: Biomark, Inc., 7615 West RiversideDrive, Boise, Idaho 83714), were used as permanent mark.Size dimorphi m and tail characteristics (tail length and anusposition in relation to edge of carapace) were the primary

H~rp~t%gical Rroi~ 42(2), 2011

ARTICLES 171

FG. 1. Che apeake Bay and vicinity howing Tangier ound andthe location of ite of winter ampling of Diamondback Terrapin,2003-2005: I) Blood worth Island, 2) outh Mar h I land, 3) mithI land- onh, 4) mith Jsland- outh, 5) jane I land, 6) anticokeRiI"er, and 7) l. jerome Creek.

criteria u ed to sex terrapins (Carr 1952). Because only terra­pin about 10 year of age (YOA) Or younger could be aged byannular growth rings (as read from plastral pectoral scutes),we eparated captures into two ba i age classe : those s10and tho e >10 YOA. Body mas wa mea ured with a digi­tal electronic balance to the nearest g and midline plastronlength (PL) wa measured with calipers to the neare t mm.

To di pel concerns about po ible d trimental physiolog­ical effect a ociated from removal of terrapin from hiber­nacula, we conducted a field tudy to determine if hart-termacute effect did occur. Thi que tion ha management r 1­erance becau e we observed commercial terrapin harve terleaving capture on boat decks for up to everal hour beforeorting their catch and returning cull to the bay. In our ex­

periment, one et of 12 newly captured terrapin (6 of eachex) were maintained in bay water (5°C) while imultane­

ou Iy exposing a econd set of 12 terrapins in a heated boatcabin at ca. 24°C, a temperature ~ ell above the range of am­bient air temperatures (lO-iSOC) experienced on a boat deckon a mild winter day. Both et of terrapin were held for a

DCDE

®\,

TANGIER/SOUND

Io

ISOKM

FIG. 2. ) A crap ,or dredge, u ed to harve t DiamondbackTerrapinin winter in he apeake Bay. De ign i ba ed on a crape u ed to har­ve t blue crab but with heavier con truction, addition of teeth onth rape bar, and a larger me h catch bag ( ee text for detail ). B)retri ved crape resting on the boat gunwale howing a good catchof terrapin. The crape did not injure terrapin and a many a 24were captured in a ingle tow. C) Two female caught] 8 March 2005from t. jerome Creek demon trate size and age in the diamondbackterrapin. The female on the left (body rna of 1922 g, PL of 202 mm)wa known to be 20 years of age by previou marking on the nearbyPatuxent River (w. Roosenburg, per. comm.). The female on theright i of unknown age and wa the large t terrapin caught duringour tudy (3022 g, PL of228 mm). Thi pecimen approximate themaximum size for the specie within the he apeake Bay and likelywithin the pecie ' range.

H~rp~/ologicalRftj,roJ 42(2), 2011

172 ARTICLES

TABLE 1. Numbers and sex ratios of Diamondback Terrapin capturedfrom ix hibernacula in Tangier Sound and the t. Jerome Creek iteon the western hore of Chesapeake Bay, winter 2003-2005. ite areIi ted by rank in cumulative ex ratio given a proportion female (pf).

ite o. captures ex ratio (pf)

t. Jerome Creek 33 0.970 A"

mith IsJand- 74 0.784 BJane Island 222 0.734 B

mith Island- 377 0.719 Bouth Mar h I land 141 0.709 B

Bloodsworth I land 160 0.588 Canticoke River 168 0.345 D

Totals 1175b 0.660

•Value sharing the arne letter are not different: individual 2-tailedz-test of proportions (n =0.05).

bTotals exclude between-year recapture ( =22).

25

C

20.2003

~ 0200'

': 02005.. 15co~

~ ,.co..~

~

FIG. 3. A composite hi togram of year- and ite-specific terrapin cap­rure rate (mean ± E capture ftow) using a modified crab scrape in2003 and a lightly larger crape in winter 2004-2005. Capture ratehad marked year and site effects (P < 0.001, individual te t using Kru­kal-Walli one-way ANOVA on rank ). Mean within site haring the

I arne letter do not differ: Dunn's multiple comparison test (n =0.05).

period of 2 h. Following the holding period, all terrapins werereturned to the location of capture and placed in a 1.8 m x 2.4m x 1.8 m wire holding cage made of 2.5 cm mesh galvanizedchicken wire. The cage at on the bottom and extended abovetide level. After 3 weeks, the cage was retrieved and urvivaland outward condition of the terrapin asse ed.

We used SigmaStat 3.1 (Sy tat oftware, Inc, Point Rich­mond, California 94804) to evaluate assumption of nor­mality and homogeneous variance and to conduct analysesof variance. When nece sary, we either transformed data tomeet normality and equal variance or applied the nonpara­metric Kruskal-Walli OVA test on rank. Contrasts weretested using Tukey' test (parametric) or Dunn's method(non-parametric). ex ratios and proportion of females <10

YOA were tested by 2-tailed z-tests of binomial proportions( okal and Rohlf 1995). We generated a simple Lincoln-Pe­tersen e tirnate ba ed on site-specific between-year recap­tures to estimate hibernaculum population size (Seber 1973).This estimate is made under the as umption of populationclosure and equal catchability. We te ted for two potentialeffects of selective by-catch mortality of maller terrapinsin crab pots as noted by Dorcas et al. (2007) and Wolak etal. (2010): larger size of both sexes based on PL and reducedpresence of younger female terrapins. Data were combinedacross year within pot and no pot sample sites.

RESULTSHibernacu.la.-Hibernacula were located in semi-pro­

tected estuarine bays in near-shore shoal waters adjacent toexten ive salt marsh. Sites had bottoms of moderately softmud and were deep enough (1.5-3.5 m) to offer little riskof dewatering even under unusually low storm tides. Mostbottoms were relatively clean of shell and organic debri ; allwere expo ed to good tidal circulation but limited wave en­ergy because of reduced wind fetch. Because terrapins wereoften buried in soft mud, continued scraping at such sitesoften increased capture succe s. On firm bottoms terrapinswere only partially buried or not at all. Terrapins were notinjured by capture and only rarely were they marked by themetal teeth or frame of the scrape (Fig. 2b).

Capture success.-During February and early March,2003-2005, we captured 1175 terrapins from seven hibernac­ula (Table 1). Capture rate had a marked site and year effect(P < 0.001: individual tests, Kruskal-Wallis one-way A OVAon ranks; Fig. 3). Capture rate for ite in Tangier Soundaveraged 4.18 ± 1.02 SE captures/tow ( = 18), or about 36terrapins/h. Capture rate generally increased in 2004 and2005 with the u e of the heavier scrape with longer, moreclosely paced teeth (Fig. 3). The exceptions were the Smithlsland- site where harvest activity was suspected to havedepleted the population in 2004 and 2005, and the St. Jeromesite where capture uccess was low in all years (mean = 3.1terrapin /h). St. Jerome Creek wa the deepe t site ampledat 3.5 m and during three winters produced the fewest (32female and one male), but on average the largest terrapins.The largest, a 3022 g female with PL of238 mm, was consider­ably larger than a known-age 20-year-old terrapin capturedat the same site (Fig. 2c) and marked previously on the Patux­ent River (w. Roo enburg, Ohio University, pers. comm.).Mass of26 females averaged 2151 ± 56 g and PL ranged from191 to 228 mm (mean 205 ± 1.6 mm). At our South Marsh site,heavy growth of eelgrass (Zostera marina) precluded captureof terrapins in 2003. However, in the absence of vegetationin 2004, capture success increased sharply, and in 2005, thesite was our mo t productive hibernaculum, averaging19 ter­rapins/tow, or 160 terrapin /h (Fig. 3).

Sex ratio.- ex ratio across all site and years favored fe­males: 0.66 proportion female (pf), or 1.94 females/male ( =1175; Table 1). Cumulative yearly sex ratio declined from 0.730

Ht'rpt'/ological Rt«IJirw 42(2 ), 2011

------ - ~ - ------- ---

ARTICLES 173

TABLE 2. Mean mass of male and female terrapin captured at six site withinTangier ound and t. Jerome Creek on the we tern hore of Che apeake Bay,winter 2003-2005. Includes only unique adult capture (exclude between-yearrecapture) of female >10 year of age and male >9 year of age. For the ixTangier ound ite there wa no rank correlation between ite- pecific meanmass of males and female (r =0.54, P> 0.05, 4 dO.

• One-way OVA found marked ite effect for female ma s (Fs.sI< =52.2, P <0.001). Mean within columns sharing the arne letter do not differ: Tukey' te t(et = 0.05).

b Insufficient sample size.c One-way OVA on In transformed data found a marked site effect for male

mass (F5.J63 =16.0, P < 0.00l). Mean within column haring the ame letter donot differ: Tukey's te t (et = 0.05).

180

10 YO""n-8

170160150140

y = O.000787xUS51

R'=O.995

Plallron Length mm

130120

5 YO""n-8

Mean mas

Female Male

26 2150.6 ± 56.4 At _b

49 1589.2 ± 34.1 B 16 455.2 ± 5.03 N

236 1386.7 ± 17.3 C 104 407.3 ± 5.0381 1324.8 ± 34.5 0 63 436.5 ± 7.91 AB72 1285.8 ± 34.0 CO 32 390.9 ± 13.03 CDIII 1248.1 ± 23.2 0 53 358.3 ± 7.14 046 1181.7 ± 30.9 0 101 412.3 ± 5.39 BC621 1393.5 ± 22.6 369 407.3 ± 3.19

but only 22 terrapins, 21 females (2.6% of female captures),and a ingle male (0.25% of male captures) were recapturedduring winter ampling. All 22 recaptures were recorded atthe ite of original capture. Recaptures were sufficient to e ti­mate hibernaculum population size only at the mith Island­N site, where sampling was increased a part of an ongoingpopulation study. Based on 13 female recaptures in 2005,

FIG. 4. Growth curve for 5- to 10-year-old female terrapin capturedduring winter ampling in the Tangier Sound region of Che apeakeBay. Age was determined by counting growth annuli on pia tral pec­toral cute. Points are means; bracket are ± E. mall ample sizein 5-year-old re ulted from general ab ence of the e and younger( mailer) terrapin in e tuarine bays in winter. mall ample ize of10-year-old terrapins re ulted from hell wear that ob cured growthannuli and limited the number that could be identified.

II 1400

1200

1000

.. 800

:600

400

200

0

100 110

Site

t. Jerome Creekmith I land­

Smith 1 land-NBloodsworth I landSouth Marsh IslandJane 1 land

anticoke RiverCombined

pf in 2003 to 0.654 in 2004 and 0.641 pf in 2005 (P< 0.05: individual 2003 vs 2004, and 2003 vs 2005z-tests of proportions). Discounting po sible yeareffects, the decline in sex ratio was likely a resultof use of the larger crape with more numerousand closely spaced teeth that increased captureefficiency of males.· ot only were generally moremales captured, but the minimum size wa low­ered in ome cases by as much as 15 mm. For sitewithin Tangier ound, year- and site-specific sexratio varied from a low of 0.32 pf to a high of 0.91pf. The anticoke River, a site of known frequentterrapin harvest, was the only site where malecapture outnumbered females (Table 1).

Estimate offemale recruitment.-Using growthannuli to age terrapins, we found females s10YOAto compri e 19.2% (145) of764 captures. Site- andyear-specific percentages varied from 0 to 39%.We estimated annual recruitment by a suming100% annual survival in the 6-to-9 YOA classesand averaging the percent of these year classesto total annual female captures. Terrapins <6YOA were not included because only 9 were cap­tured (8 five-year-old and 1 four-year-old); andlO-year-old were excluded because advancedshell wear obscured growth annuli limiting thenumber that could be identified ( =8). The 128 terrapins inthe 6-to-9 year-old age classes represented 10.4%, 18.3% and21.6 % of female captures during the respective three winterand yielded estimates of annual recruitment of 2.6%, 4.6%,and 5.4% (mean = 4.2 ± 0.83).

To eliminate potential error a ociated with readinggrowth annuli, we additionally estimated recruitment ba edolely on size metrics. We used mean ize tatistics from 44

known 9-year-old female, i.e., mean ma s (1043 g). PL (165mm). and mass-to-pla tron ratio (6.340 g/nun), to separatefemale s9 YOA from aU older female . The re ulting meane timates of percent annual recruitment were about 50%higher than those based on growth annuli: 6.0 ± 0.29% basedon PL, 6.5 ± 0.35% based on mass, and 6.7 ± 0.16% based onmass-to-PL ratio. Although we recorded 19.2% of females s10YOA, only 29 3-to-8-year-old males (7.9% of male captures)were so captured (X2 =22.8, P < 0.001, 1 dO. We concludedthat too few male in the younger age c1as es were capturedto provide a meaningful estimate of recruitment.

Growth rate.-Females in the 5-to-1O-year-old age classesexhibited marked growth as mean mass increased by a factorof 3 (from 397 to 1184 g) and mean PL increa ed 50% (from115.9 to 174.0 mm; Fig. 4). Based on the Maryland harvestregulation of a minimum PL of 152 mm, mo t female terra­pins would reach harvestable size at between 7 and 8 YOA.Too few males were captured to adequately interpret growthin the 5-to-9-year-old age classes.

Recaptures.-We recaptured 102 terrapins (8.7% of cap­tures) by variou means up to four years after initial capture,

Herpetological Rrview 42(2), 2011

174 ARTICLES

TABLE 3. Mean plastron length (PL) for male and female terrapins and the proportion of young female (pf) sl 0 years of age (YOA) captured atix ites within Tangier ound, winter 2003-2005. Ranking in relation to zone with and without crab potting i shown. PL means include only

unique capture (excludes bet\veen-year recapture) of female >10 YOA and male >9 YOA.

Mean plastron length (mm) ± ECrab potting Site Male Rank Female Rank pfslOYOAzone ( ) ( )

Pots 120.9 ± 1.16 A" 186.8 ± 1.33 N 0.157 AB<(16) (49)

Pots Bloodsworth Island 118.3 ± 0.73 A 2 176.3 ± 1.49 BC 3 0.133 B(63) (8l)

Pot mith I land- 116.2 ± 0.59 AB 3 179.2 ± 0.72 B 2 0.135 B(104) (236)

No pot anticoke River 115.2 ± 0.57 B 4 167.8 ± 1.40 0 6 0.300A(101) (46)

o pots outh Marsh Island 113.7 ± 1.24 BC 5 174.5 ± 1.43 C 4 0.309 A(32) (72)

o pot Jane I land 111.5 ± 0.84 C 6 173.9 ± 0.98 C 5 0.186AB(53) (Ill)

Combined 115.6 ± 0.33 178.2 ± 0.53 0.192(369) (595) (764)

Rank

4

6

5

2

3

• Kru kal-Walli one-way A OVA te t on rank found a marked site effect for pia tron length (1-1 = 48.0, P < O.OOl, 5 df). Means within column sharing the sameleiter do not differ: Dunn's lest (n = 0.05).

b One-way A OVA found marked site effect for plastron length (Fs.SIIO= l8.3, P < 0.001). Means within column sharing the ame leiter do not differ: Tukey's te t

(u = 0.05).

<Value haring the same leiter are not differenl: individualZ-tailed z-tesl of proporrion· (n =0.05).

a mark-recapture estimate of 1210 female populated thesite in winter 2004 (normal 95% C.L: 684-1737; Seber 1973).Males were excluded from the estimate becau e no malewere recaptured. However, ba ed on the 2004 ample ex ra­tio of 0.744 pf, the estimate increases to 1613 when males areincluded. Based on capture rates, populations at two oUlerhibernacula, Janes Island in 2004 and 2005 and SOUUl Mar hIsland in 2005 (Fig. 3), likely exceeded uli estimate.

ize charaeteristics.-Off- hore sample site near Blood­sworth, Smith, and oum Marsh Islands, had lightly heavierfemales than the near- hore ite ofJanes I land and ule an­ticoke River (Table 2). The largest females were at the St. Je­rome site and me mallest at me Nanticoke River, a site offre­quent harvest. imilarly, the mean rna of adult males (all >9YOA) was highe t for off-shore Smim Island-S/Blood worthIsland sites and lowest for near-shore Jane I land (Table 2).As e entially all male are immune to commercial harve tby virtue of their mall size, anticoke River males rankedcomparatively higher in site-specific mean mas (Ulird) ver-u the females captured there that ranked sixth (la t). For

the ix Tangier ound ample sites, site-specific mean massof males and female was not correlated ( pearman rank r =

0.54, P > 0.05, 4 df). Consistent with the known dimorphismin the species, the mean mas of female terrapins (1276 g,=767) was about three time greater than that for males (401g, = 399). Only 4.6% of females (35 of 767) fell below a PLmeasurement of the large t male (138 mm).

Effects ofcrab pot bycatch.-We tested for the effect of se­lective crab pot mortality on female size and found female PLto be greater in pot versus no-pot zone (one-way ANOVA:FI.593 =47.7, P < 0.001; mean PL, pot zon =179.6 ± 0.61,366; mean PL, no-pot zone = 172.9 ± 0.73, = 229). Becausethe male PL distribution was found to be non-normal, weapplied ule Kruskal-Wallis ANOVA test on ranks and founda larger median value in pot versus no-pot zones (H = 25.6,P < 0.001, 1 df; pot zone median PL = 117, = 183; no-potzone median PL = 114, = 186). Site-speciiic tests showeda marked pattern of larger PL means at ites with crab pot­ting that produced a consi tent alignment of ranks to potand no-pot zone (Table 3). We also found females to havea higher proportion of young s10 YOA in no-pot versus potzone (one-way A OVA: FI.I3= 5.2, P < 0.04; mean proportionno-pot zone = 0.26 ± 0.13, = 8; mean proportion pot zone= 0.11 ± 0.11, = 7). Individual ite-specific tests produced a

H~rptfologi{Ql ReviroJ -12(2 ). 2011

imilar pattern of a higher proportion of female at site inno-pot zones with a consi tent alignment of rank to pot andno-pot ite (Table 3).

Testing for acute effects.--Dn initial placement of the 24terrapin in the holding cage, three individual were activeenough to wim to the top of the water column. Thi indi­cated that their metaboli m had increa ed enough to be­come active wimmer, but none were ob erved to breatheair at the urface. The swimming activity cea ed shortly afterplacement ugge ting that any increase in body temperatureand metabolism was quickly rever d by return to cold wa­ter. All other terrapins were Ie s activ and simply sank to thebottom of the cage. Following the three-week holding periodin February 2005, all terrapin were alive and observed to

behave normally, i.e., were luggi h but active; there wa noign of morbidity.

DISCU SlOOur discovery that upwards of a thou and or more terra­

pin can be concentrated at heavily populated hibernacuJaunder core the vt1lnerability of the pecie to winter scrapeharve t. Our capture of 160 terrapin /h at outh Marsh I landdemon trate how, in certain in tance ,hundred of terra­pin can be removed from a local area in a matter of hours,a majority of which would be harvest -size females. Becau eterrapin population trait include low recruitment, delayedmaturity, long life, and limited di per al (Gibbon et al. 2001;Harden et al. 2007; Tucker et at. 2001), high urvival of long­lived adult i critical to ustaining population (Mitro 2003).It follows that harvest removal of a large portion of breeding­age female would be deva tating to local population. Ter­rapins, like other long-lived turtles, have no compensatorymean to replace uch 10 se (Brook et at. 1991; Congdon etal. 1993; Heppe1l1998) and recovery would be predicted to bee pecially protracted.

As e tuarine bay hibernacula have never been studiedpreviou Jy, no comparative data exi t on numbers, size,and sex ratio. Moreover, we hav no knowledge of how ourcapture characteristics have been altered by the confound­ing influence of two principal anthropogenic effects: 1) thedirect 10 of females to commercial harvest and 2) seJectivmortality of mall terrapin as bycatch in crab pot (Roosen­burg et at. 1997; Roosenburg 2004). Becau e our data howthat heavy terrapin harve t would quickly devastate the adultfemale portion of the population, the prevalence of a femalebia ed ex ratio in Tangier ound i trong evidence of mini­mal harve t activity in the region in the recent past. Terrapinmortality in recreational (not commercial) crab pots primar­ilyaffect maller terrapin (male and young females) thatoccupy habitat near hore where they are at ri k to recre­ational crab pots (Roosenburg et at. 1997; Roo enburg 2004).Terrapin expo ure and ub equent mortality in commercialcrab pot in Tangier ound therefore seem mediated by vir­tual re triction of commercial pots to offshore u e. Indeed,Roosenburg (2004) sugge ted that Maryland' deep-water

1

ARTICLES 175

re triction on commercial crab potting likely has averted thedecimating los e to Bay terrapin populations such a ha ebeen reported in Florida ( eigel 1993), outh Carolina (Dor­ca et al. 2007; Gibbon et al. 2001; Hoyle and Gibbons 2000;Tucker et al. 2001), and more recently, Georgia (Gro e et al.2009). onethele ,decade of crab pot expo ure eem ap­parent as our re ult indicate an effect of increased ize ofboth exe and reduced number of young females. The eresult are consi tent with demographic effect attributedto elective crab pot mortality in tidal creek of the KiawahRiver, outh Carolina (Dorcas et aI. 2007), and at the Good­win Island at the mouth of the York River, Virginia (Wolak etal. 2010). Although other interpretations are possible, a non­normal PL distribution for male, in contrast to a normaldistribution for female, lend upport to an active mortalityproces affecting males. Additionally, and most significantly,we found the proportion of young female in the no-pot zoneto be 2.4 time that in the pot zone. It follows that this ap­parent 10 s of female to crab pot, and the projected loss inrecruitment it represents, would have the greatest long-termeffect on terrapin productivity in Tangier ound.

Our winter ampled ex ratio and the ex- and age­related vulnerability of terrapin to crab pot al 0 may bedriven by a fundamental di tribution proce related to ize,i.e., larger terrapin dominating open-water e tuarine bayand mailer terrapins seeking protected areas in tidal creekand interior alt mar h. Roo enburg et al. (1999) provide evi­dence of larger adult female moving farther and pendingmore time offshore while mailer male and juvenile remainin near-shore shallow water. Finding from our ummer cap­ture at mith I land upport thi notion as our interior altmar h bait-trap captures yielded maller terrapin of moreven sex ratio (0.58 pf) and open-water Bay-shore fyke net

captures produced primariJy large females (0.87 pf; P. Hen­ry, U G , pers. comm.). That terrapins overwinter in inte­rior tidal creeks and creek bank at a ha been documented(Yearick et at. 1981). Our amples show that few female <6YOA (with mean PL of 134 mm and mean mass of 560 g) andfew males <6 YOA (mean PL of 105 mm and mean mass of300g) occupy estuarine bays in winter.

The comparatively pristine nature of Tangier ound, incontra t to highly developed areas of the Bay, likely providere ilience to terrapin population ,a evidenced by our e ­timated female recruitment rate of 4-7%. Thi recruitmentIe eJ eem favorable and et a bench mark for future win­ter ampling, but its relation to population statu i unclearwithout knowledge of other vital population tati tic, e ­pecially an e timate of population growth rate (Mitro 2003).Further demographic tudy i needed to better establi h thetatu ofTangier ound terrapin population.

Although terrapins were gen rally abundant in Tangieround, the paucity of number in t. Jerome Creek, a former

harve t site, is enigmatic. The los of terrapins at this for­merly productive site may be related to harve t or perhapa broader population decline do ument d during long-term

Herpetological Review 42(2),2011

,

176 ARTICLES

study of terrapin on the nearby Patuxent River (w. Roosen­burg, Ohio University, pers. comm.).

CONCLUSIO SThe nature of adult female terrapins to aggregate in hi­

bernacula often in high densities and in easily accessibleestuarine bays has made them exceptionally vulnerable tocommercial winter harve t. Such harvest, if unregulated, canbe devastating to local terrapin population. Although no ex­act history can be reconstructed, winter scrape fishing mayhave played a part in the near extirpation of the species inChe apeake Bay in the early 20'h century (Carr 1952; Ernstand Lovich 2009; McCauley 1945). In 2007, a well-organizedconservation movement successfully lobbied the Marylandlegislature to permanently close the terrapin fishery. Com­mercial harvest of diamondback terrapins is now prohibitedthroughout Chesapeake Bay.

ow that the commercial terrapin fishery is closed,adopting scrape fi hing as a winter sampling method couldbe of particular value in assessing the past effects of har­vest and recovery of terrapin population. Scrape fishing ofhibernacula offers unique access to a large portion of theadult female segment of the population, including femaleapproaching breeding age. Moreover, scrape sampling offersa novel mean to advance scientific study of terrapins in win­ter, an aspect of the biology of the species that has been littleaddre sed. In thi light, we recommend further work be con­ducted to better understand physiological effects of removalfrom hibernacula and effects on long-term survival. We be­lieve winter scrape sampling could be an important elementof terrapin population and scientific study in ChesapeakeBay and perhaps elsewhere throughout the north temperaterange of the species.

Acknoru/edgments.-This study could not have been conducted

without the boating kills and pecial knowledge of terrapin hiber­

nacula and harve t methods provided by Smith I land re ident D.

Mar hall. Hi willingne to hare his intjmate knowledge of terra­

pins has made this a very pecial experience. Additional thank go to

W. Roosenburg for a sisting with marking techniques and freely shar­

ing hi pecial knowledge of terrapin from hi exten ive research onthe Patuxent Rjver. dditional thanks are extended to C. Driscoll and

K. Brittingham for field as i tance and . Beyer, M. Erwin, E. Grant

and W. Link for review of an early draft of the manu cript. Animal

welfare protocols u ed herein were detailed in a peer-reviewed tudy

plan and approved by the U G Patuxent Wildlife Re earch Center's

Animal Care and Use Committee.

LITERATU RE CiTED

BROOKS, R. J., G. P. BROWN, ADD. A. GALBRAITH. 1991. Effects of a sud­den increase in natural mortality of adults on a population ofthe common napping turtle (Chelydra erpentina). Can. J. Zool.69:1314-1320.

BUTLER, J. A., G. L. HEINRICH, AI DR. . EIGEL. 2006. Third workshop onthe ecology, status, and conservation of diamondback terrapin

(Ma/aclemys terrapin): result and recommendations. Chelon.Con erv. BioI. 5:331-334.

CARR, A. 1952. Handbook ofTurtle . Cornell University Press, Ithaca,ew York. 542 pp.

CO GDON, J. D., A. E. Du HAM, A DR. . VA LOBEN ELS. 1993. Delayedexual maturity and demographic of Blanding' turtle (Emydoi­

dea b/alldingit1: implication for con ervation and managementof long-lived organism . Con erv. BioI. 7:826-833.

DORCA, M. E., J. D. WILLSON, AND j. W. GIBBON. 2007. Crab trappingcauses population decUne and demographic change in diamond­back terrapin over two decade. BioI. Con erv. 137:334-340.

ERNST, C. H., ADJ. E. LoVl H. 2009. Turtle of the United States andCanada. 2nd ed. John Hopkin University Press, Baltimore, Mary­land. 827 pp.

GIBBO S, J. w., J. E. LoVlCII, A. D. TUCKER, . FITZSIMMONS, DJ. L.GREEI E. 2001. Demographic and ecological factors affecting con­ervation and management of the diamondback terrapin (Mala­

c/emys terrapin) in outh Carolina. Chelon. Conserv. BioI. 4:66-74.GROSSE, A. M., J. D. VAN DIlK, K. L. HOLCOMB, ADJ. C. MAERZ. 2009. Dia­

mondback terrapin mortality in crab pots in a Georgia tidal mar h.helon. Con erv. BioI. 8:98-100.

HARDEN, L. A., . A. DILUZIO, J. W. GIBBON', AND M. E. DORCAS. 2007. pa­tial and thermal ecology of diamondback terrapins (Ma/ac/emysterrapin) in a South Carolina alt marsh. J. North CaroUna Acad.ci. 123:154-162.

HEPPELL, . . 1998. Application of life hi tory theory and populationmodel analysis to turtle conservation. Copeia J998:367-375.

HOYLE, M. E., AND j. W. GIBBO S. 2000. U e of a marked populationof diamondback terrapins (Malaclemys terrapin) to determineimpact of recreational crab pots. Chelon. Conserv. BiDI. 3:735­737.

MCAULEY, R. H., JR. 1945. The Reptiles ofMaryland and the District ofColumbia. Privately printed, Hager town, Maryland. 194 pp.

MITRO, M. G. 2003. Demography and viability analy es ofa diamond­back terrapin population. Can. J. Zool. 81:716-726.

ROOSENBURG, W. M. 1991. The diamondback terrapin: habitat require­ments, population dynamic, and opportunitie for conservation.[n A. Cbaney, and j. A. Mihursky (ed .), ew Perspectives in theChe apeake Bay System: A Re earch and Management Partner-hip, pp. 227-234. Proceedings of a sympo ium. Chesapeake Bay

Con ortium Publication No. 137, Solomons, Maryland.--.2004. The impact ofcrab pot fisheries on terrapin (MaLac/emys

terrapin) population : where are we and where do we need to go?[n C. warth, W. M. Roo enburg, and E. Kiviat (ed .J, Conservationand Ecology ofTurtle of the Mid-Atlantic Region: A Symposium,pp. 23-30. Bibliomania, Salt Lake City, Utah.

--,W. CRESKO. M. MODESITIE, A'D M. B. RonBI . 1997. Diamondbackterrapin (Malaclemys terrapin) mortality in crab pots. Conserv.BioI. 11:1166-1172.

--, K. L. HALEY, AND . M GUIRE. 1999. Habitat selection and move­ments of diamondback terrapins, Malaclemys terrapin, in a Mary­land e tuary. Chelon. Con erv. BioI. 3:425-429.

SEBER, G. A. F. 1973. The E timalion of Animal Abundance. HafnerPres, ewYork, ewYork. 506 pp.

E1GEL, R. A. 1993. Apparent long-term decline in diamondback ter­rapin populations at the Kennedy pace Center, Florida. Herpetol.Rev. 24:102-103.

--, AD]. W. GIBBONS. 1995. Workshop on the ecology, statu, andmanagement of tile diamondback terrapin (Malac/emys terrapin),avannah River Ecology Laboratory, 2 August 1994: final results

and recommendations. Chelon. Conserv. Biol.l:240-243.OKAL, R. R., AD F. J. ROHLF. 1995. Biometry: The Principle and Prac­

tice of tati tic in Biological Re earch. 3nl ed. W. H. Freeman, ewYork, ewYork. 887 pp.

H~rp(tological &uiroJ 42(2 ).201J

TUCKER, A. D., ). W. GIBBONS, D). L. GREE E. 2001. Estimate of adultsurvival and migration for diamondback terrapin: con ervationinsight from local extirpation within a metapopulation. Can. ).Zool. 79:2199-2209.

WARNER, W. W. 1977. Beautiful wimmers. Penguin Book, ewYork,ewYork. 304 pp.

WOlAK, M. E., G. W. GILCHRIST, V. A. RUZICKA, D. M. AllY, A 0 R. M.CHAMBER. 2010. A contemporary, ex-limited change in body sizeof an e tuarine turtle in response to commercial fi hing. Con erv.BioI. 24:1268-1277.

HerpetologiCflllleuiew. 2011. 42(2). 177-1BO.(;) 2011 by ociety forthe Study ofAmphibians and Reptiles

ARTICLES 177

WOOD, R. C. 1997. The impact of commercial crab trap on northerndiamondback terrapin , Malaclemys terrapin terrapin. 1/1 J. anAbbema (ed.), Proceedings of a yrnposium: Con ervation, Re ­toration, and Management of Tortoises and Turtle -An Interna­tional Conference, pp. 46-53. ewYorkTurtle and Tortoise ociety,

ewYork, ewYork.YEARICK, E. E, R. C. WOOD, A 0 W. . JOH 0 '. 1981. Hibernation of the

northern diamondback terrapin, Malaclemys terrapin terrapin.E tuarie 4:78-80.

A Large-Scale Snake Mortality Event

Road mortality has been shown to constitute a consider­able threat for a variety of herpetofaunal pecie. A numberof po ible explanations for movement onto or across roadresulting in mortality have been proposed, including sea on­aI movements between habitats (Bernardino and Dalrymple1992; mith and Dodd 2003), ea onal dry-down of suitablehabitats (Are co 2005; Bernardino and Dalrymple 1992; Engeand Wood 2002), de ire to access resources on the other ide(Andrews and Gibbons 2005), movement to new areas forbreeding (Lebboroni and Corti 2006), and movement and for­aging follOWing rainfall events (Ashton and Ashton 1988; Carr1963; Cook 1983; Gibbons and Dorcas 2004; Tennant 1997).

In addition to the hazards of entering or attempting tocross roads, it appears that aspects of snake natural hi torymay put them at a greater ri k of road mortality than otherherpetofaunal species. Snakes are known to use warm roadsurfaces for thermoregulation (Bernardino and Dalrymple1992; Enge and Wood 2002; Ro en and Lowe 1994). Andrewsand Gibbon (2005) report that nake road kill may be mag­nified by immobilization behavior with some nake speciesstopping on the road during crossing. Some authors haveuggested that snakes are commonly intentionally targeted

by drivers (Ashley et al. 2007; Rudolph et al. 1999; Shepard etaI.2008).

In March of2006, we ob erved a snake roadkill event alonga newly opened road leading into the Southwest Florida In­ternational Airport located in Fort Myers, Lee Co., Florida,USA (26.5123° ,81.7726°W). The airport developed a new

..........................................................................................................................

JENNIFER EVANS*LAURA WEWERKA**EDWIN M. EVERHAM IIIand

A. JAMES WOHLPARTFlorida GulfCoast University, Fort Myers, Florida 33965, USA

<Corresponding outhor; e·moil: jevons4@Cfemson.edu"Lee County Conservation 20/20, Fort Myers, Florida 33916, USA

terminal, which included the opening of this new road to thepublic in September 2005. The initial report of a snake road­kiJI event came from ob ervations taken on 12 March 2006,suggesting that the majority of dead-on-road (DOR) nakewere killed during the preceding week (5-11 March). The ob­servations were made along 1.5 km of the new airport accesroad; no snake carcasses were found before or after this sec­tion of the road. We documented this large-scale snake road­kill event, which appears to have been greater in magnitudeand density than any other snake mortality event reported inthe literature for this small of an area for this short of a timeperiod (Beck 1938; Hellman 1956; Smith and Dodd 2003).with the exceptions of mass snake roadkill events associatedwith a hurricane (Carr 1963) and a snake migration event(Tennant 1997).

Methods.-The airport expansion included constructionof a new four-lane roadway and creation of a canal (Figs. lAand IB). The roadway consisted of both an east and west­bound terminal road with a grassy median separating them.The speed limit was 45 mph. Bike paths were located exte­rior to the roadway and had a width of 1.6 m as comparedto a single road lane width of 3.6 m. Grassy shoulders werelocated exterior to the bike paths. The southern shoulder ex­tended 10-12 m to a low (0.5 m) berm which eparated thehoulder from a 20-25 m wide tormwater treatment swale.

A second berm (1.5 m high and 15 m wide), located south ofthe swale, ran parallel to the canal which was approximately15 m in width.

From 19-22 March, 2006, 1.5 km of the eastbound ter­minal road (Fig. IB) heading toward the Southwe t FloridaInternational Airport was walked and snake species were re­corded. The road was divided into 10 m egments. The loca­tion of each roadkilled nake along the eastbound ide wasrecorded as follows: in the left hand lane of the road nearthe median, in the right-hand lane of the road near the bikepath, on the bike path, or on the grassy shoulder. The areaof grass along the road edge that could be reliably observed

H"peto1ogicol Review 42(2). 2011