Nest Site Selection by Colombian Slider Turtles, Trachemys callirostris callirostris (Testudines: Emydidae), in the Mompos Depression, Colombia

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Nest Site Selection by Colombian Slider Turtles Trachemys callirostris callirostris(Testudines Emydidae) in the Mompos Depression ColombiaAuthor(s) Adriana Restrepo Victor J Pintildeeros Vivian P PaacuteezSource Chelonian Conservation and Biology 5(2)249-254 2006Published By Chelonian Research FoundationDOI httpdxdoiorg1027441071-8443(2006)5[249NSSBCS]20CO2URL httpwwwbiooneorgdoifull1027441071-84432820062955B2493ANSSBCS5D20CO3B2

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Chelonian Conservation and Biology 2006 5(2) 249ndash254 2006 Chelonian Research Foundation

Nest Site Selection by Colombian Slider Turtles Trachemys callirostris callirostris(Testudines Emydidae) in the Mompos Depression Colombia

ADRIANA RESTREPO1 VICTOR J PINEROS

1 AND VIVIAN P PAEZ1

1Instituto de Biologıa Apartado 1226Universidad de Antioquia Medellın Colombia [restrepoadriana78gmailcom]

[victorpinerosyahoocomar] [vpaezquimbayaudeaeduco]

ABSTRACT ndash Nest-site selection by female Trachemys callirostris callirostris was studied on an islandin the Pijino wetland of the Mompos Depression of Colombia We quantified distances of nests tothe shoreline and compared vegetative cover and soil types at nest locations and at randomlyselected points on the island Nests sites were concentrated in the first 5 m from the shoreline andwere always located under vegetative cover Such cover might reduce thermal stress to nestingfemales lower the probability of nest detection by predators and buffer the incubating eggs fromenvironmental extremes Females preferentially nested under water hyacinth but it was not clearwhether they selected directly for this vegetative cover type or simply preferred dirt substrateswhere it dominated because dirt soils contained higher humidity

KEY WORDS ndash Reptilia Testudines Emydidae Trachemys callirostris callirostris turtlereproduction nesting nest-site selection Colombia

The nesting process has important fitness consequenc-

es for female turtles (Spencer and Thompson 2003)

Females are particularly vulnerable to predation at this

time (Tucker et al 1999 Spencer 2002) and eggs and

neonates also suffer predation during incubation and nest

emergence (Congdon et al 1983 Yerli et al 1997 Burke

et al 1998 Escalona and Fa 1998 Janzen et al 2000a

2000b) Microclimatic conditions within the nest such as

humidity and temperature also affect embryo survival

(Packard et al 1991 Burger 1993 Resetarits 1996) and

influence sex (Janzen and Paukstis 1991 Spotila et al

1994) incubation period (Yntema 1978 Packard et al

1987) and the size morphology yolk reserves growth

physiology and performance abilities of neonates (Burger

1991 Packard et al 1993 Bobyn and Brooks 1994

Tucker et al 1998a Steyermark and Spotila 2001

Filoramo and Janzen 2002 Janzen and Morjan 2002)

Given the apparent fitness consequences that nest-site

selection implies we predicted that female Trachemyscallirostris should nest nonrandomly with respect to

specific environmental variables Other studies of fresh-

water turtles have shown that females often oviposit in

sites that differ in various ways from randomly selected

points suggesting the existence of microhabitat prefer-

ences on their part (Wilson 1998 Janzen and Morjan

2001 Kolbe and Janzen 2002) Here the existence of

preferences for specific nesting-site locations was defined

statistically as the oviposition of eggs disproportionately in

sites that differed from randomly selected points within a

given constrained nesting area (Wilson 1998)

Various hypotheses have attempted to explain female

nesting-site preferences Some researchers have suggested

that females in species with temperature-dependent sex

determination select nest locations so as to manipulate

progeny sex ratios to consistently or alternatively produce

males or females (Vogt and Bull 1982 Roosenberg 1996

Spencer 2002) Other researchers have hypothesized that

females prefer to nest in areas shielded from nest

predators parasites or environmental extremes thereby

maximizing embryo survivorship (Burger and Montevec-

chi 1975 Burger 1976 Gochfeld 1979 Bodie et al 1996

Spencer and Thompson 2003) Finally others have argued

that females restrict their nesting activities to areas near the

shoreline to minimize their own predation risks while on

land at the expense of ovipositing in locations that are

suboptimal (Spencer 2002 Spencer and Thompson 2003)

In practice it is difficult to differentiate among the sex

ratio embryo survivorship and female survivorship

hypotheses (Schwarzkopf and Brooks 1987 Spencer and

Thompson 2003) given that nest-site selection in many

species probably represents a trade-off between the costs

and the benefits of these multiple sometimes contradic-

tory factors (Misenhelter and Rotenberry 2000 Wood and

Bjorndal 2000 Spencer and Thompson 2003)

Different habitat characteristics could serve as impor-

tant proximate cues to females during the nesting-site

selection process (Weisrock and Janzen 1999) Vegetative

cover is one of the most studied characteristics given its

association with nest temperature (Burger and Montevec-

chi 1975 Vogt and Bull 1984 Janzen 1994 Bodie et al

1996 Roosenberg 1996 Wilson 1998) Slope and soil

surface temperatures also have been proposed as important

cues in nesting-site selection (Burger and Montevecchi

1975 Stoneburner and Richardson 1981 Schwarzkopf

and Brooks 1987 Wood and Bjorndal 2000)

Advancing on work begun by Bernal et al (2004) that

described the basic nest characteristics of T callirostris in

the Mompos Depression of Colombia the objective of this

study was to evaluate whether females in the same area

nest randomly or whether they demonstrate preferences for

particular locations within the general nesting area

METHODS

The Mompos Depression is the largest wetland in

Colombia (CVS 2002) located in the Caribbean lowlands

and bounded by the Cauca River to the west the San Jorge

River and Ayapel wetlands to the east the Magdalena

River to the northeast and the Ayapel highlands to the

south (Garramuno 2001 Fig 1) Mean ambient temper-

ature is 298C but may attain extremes of 358C The annual

precipitation varies between 1000 and 2000 mm (Fundes-

cala 1997 Turbay et al 2000) with 2 dry seasons

occurring from December to mid-April and from July to

August During the 2 rainy seasons the region is subject to

periodic flooding of the principal rivers that pass through it

(Pena 1993)

This study was conducted on Leon Island in the Pijino

wetland complex (9817rsquo N 74824rsquo W) in Angostura county

of the Magdalena Department approximately 1 hour by

boat to the northeast of the city of Mompos The 12-hectare

island is private property used for raising cattle and swine

Most of the vegetation is low shrub The shoreline is

composed of a mud flat created by the marked fluctuations

in water levels each year where the predominant

vegetation is water hyacinth (Eichornia crassipes)

Trachemys callirostris (previously Trachemys scriptacallirostris) is a recently recognized species (Seidel 2002)

composed of 2 subspecies restricted to Colombia and

Venezuela respectively In Colombia Trachemys callir-ostris callirostris occurs from the western Gulf of Uraba

throughout the wetland systems of the Sinu San Jorge

and Magdalena drainages in the entire northern area of the

country except the Guajira desert (Castano-Mora 2002)

Trachemys callirostris is perhaps the most heavily

exploited turtle in Colombia for both direct consumption

and sale (Castano-Mora 1997) and is classified as NT

(nearly threatened) in the Colombia Red List (Castano-

Mora 2002)

Trachemys callirostris callirostris females in this area

predominantly oviposit nocturnally Nests were located

during the day by following tracks or by detecting other

evidence of nesting activity We recorded microhabitat

characteristics of nests and at randomly selected locations

on the island from 6 February to 15 May 2003 We

considered the potential nesting area as being the ring of

dry soil surrounding the perimeter of the island beginning

where the wet mud ended (hereafter the shoreline)

because no nests were encountered there and ending at

20 m inland of this point because more inland nesting was

rare (Medem 1975 Bernal et al 2004) Within the

potential nesting area we selected 80 random points as

follows from an arbitrary point on the shoreline we

defined a 20-m transect perpendicular to it then walked 15

seconds along the shoreline before defining the origin of a

second transect and so on until 20 transects were laid out

that covered the majority of the perimeter of the island In

each transect we selected 4 distances of the 20 possible

meter-unit distances by using a random number table to

define 80 random locations for study

For both the actual nests and randomly selected

locations we recorded the exact distance to the shoreline

and classified each site into 1 of 2 distance categories 0ndash5

m and 5 m Vegetative cover was categorized by placing

a 1-m2 quadrat with 10-cm subdivisions over each nest or

randomly selected location and recording for each subdi-

vision whether it contained primarily grass water hyacinth

or shrubby vegetation Each m2 was then classified as

belonging to one of these categories based on the dominant

coverage in its subdivisions or as mixed in cases where no

one coverage was present in more than 75 of the

subdivisions Soil type was classified by using the

methodology of Casanova (1991) yielding 3 main

categories of dirt clay and sand substrates and the possible

combinations of them (dirt-clay dirt-sand and clay-sand)

Twenty three of the 80 randomly selected locations

had distances to the shoreline greater than the maximum

distance recorded for an actual nest in this study (145 m)

and were thus excluded from the analyses Also no nests

were encountered in sites that were predominantly bare

substrate so this category was removed from the analyses

We used v2 goodness of fit tests to compare the number of

nests in each distance class the number of nests located in

each vegetative class (use by turtles) and the number of

randomly selected locations present in each vegetative

class (availability to turtles) Then we repeated the last 2

analyses (use and availability) after having removed the

most abundant vegetative class from consideration The

same approach was used in the analysis of soil types as

well as the comparison of the number of nests encountered

in the dirt soil type vs all other soil types pooled Finally

a v2 goodness of fit analysis was used to inspect for an

association between soil type and vegetative cover

Figure 1 Map of the Mompos Depression in northern Colombia(square) and the location of Leon Island in the Pijino wetland(circle)

250 CHELONIAN CONSERVATION AND BIOLOGY Volume 5 Number 2 ndash 2006

Heterogeneity v2 tests were used to compare use vs

availability of vegetative covers and soil types

RESULTS

We located 86 nests during searches around the island

The greatest distance of a nest from the shoreline was 145

m with a mean distance of 35 m There were significant

differences in the proportion of nests located in the 2

distance intervals (v2 frac14 268 df frac14 1 p 0001) with 67

nests (779) located within the first 5 m (Fig 2) There

were significant differences in the proportion of vegetative

cover types available on the island (v2 frac14 2092 df frac14 3

p 0001) but after eliminating the grass category

which was the predominant vegetative cover (Fig 3) there

were no differences in availabilities among the other 3

types (v2 frac14 235 df frac14 2 p 005) There also were

significant differences in the proportion of nests oviposited

under the different vegetative covers (v2 frac14 3577 df frac14 3

p 0001) Upon eliminating the hyacinth category from

consideration which was the predominant vegetative cover

selected by nesting females there were no significant

differences in the use of the remaining categories

(v2 frac14 235 df frac14 2 p 005) Obviously with grass as

the predominant vegetative cover and hyacinth as the

preferred vegetative cover type the difference in avail-

ability and use of the different vegetative covers was

significant (v2 frac14 922 df frac14 3 p 0001 Fig 3)

The relative availability of soil types on the island did

not differ significantly (v2 frac14 735 df frac14 5 p 005 Fig

4) but there were significant differences among soil types

in terms of their use for nesting (v2 frac14 15348 df frac14 5

p 0001) Upon eliminating from consideration the dirt

soil type where the majority (6512) of nests were

located there still were differences in the proportion of use

of the remaining soil types (v2 frac14 1933 df frac14 4

p 0001) as well as differences when use of the dirt

soil type was contrasted to the use of the remaining 2 soil

types pooled (v2 frac14 8598 df frac14 1 p 0001 Fig 4)

There were significant differences between the availability

and the use for nesting of the differing soil types

(v2 frac14 1629 df frac14 5 p 0001 Fig 4)

Water hyacinth was associated with the dirt soil type

In 78 of the cases where a randomly selected point or

actual nest was located in the hyacinth vegetative type it

also occurred in the dirt soil type (v2 frac14 2679 df frac14 1

p 0001) whereas no other vegetative type occurred

predominantly in that soil type

To evaluate whether the apparent preference by

nesting females for the hyacinth vegetation type was an

artifact of its association with the dirt soil type or vice

versa we combined the vegetative cover and soil-type

categories to compare availability and use of the 4 new

categories (hyacinth on dirt soils hyacinth on other types

of soils other vegetation types on dirt soils and other

vegetation types on other soil types) Apparently females

preferred both the hyacinth vegetation type per se and the

dirt soil type per se with the additive effects of these

preferences explaining the strong tendency to nest where

these 2 variables co-occurred (v2 frac14 2603 df frac14 3

p 0001 Fig 5)

DISCUSSION

The data on availability and use of vegetative cover and

soil types revealed that the T callirostris nests were not

randomly distributed within the general area used for

nesting suggesting that females were actively selecting

sites with specific characteristics for ovipositing The

previous study in this site by Bernal et al (2004) found

Figure 2 Proportion of Trachemys callirostris nests oviposited atdiffering distances (m) from the shoreline on Leon Island

Figure 3 Availability and use of differing vegetative covers bynesting females on Leon Island

Figure 4 Availability and use of differing soil types by nestingfemales on Leon Island (C-S frac14 clay-sand Dfrac14 dirt D-S frac14 dirt-sand S frac14 sand D-C frac14 dirt-clay C frac14 clay)

RESTREPO ET AL mdash Nest Site Selection by Colombian Slider Turtles 251

that 82 of the nests that year were located beneath

herbaceous vegetation (hyacinth or grass) consistent with

the results of this study in which 65 of the nests were

located under the same vegetative-cover types Medem

(1975) also reported 34 T callirostris nests from the

Totumo wetland in Bolivar Department Colombia as being

covered by grass shrub or second-growth vegetation

Selecting sites covered by vegetation for nesting

might reduce thermal stress to the nesting females as well

as lower the detectability of nests to natural predators

human hunters or their domesticated animals (Wilson

1998 Bernal et al 2004) Also nests under vegetation

might experience less variation in temperature or humidity

compared with those oviposited in exposed sites (Bodie et

al 1996 Wilson 1998 Bernal et al 2004) This preference

on the part of T callirostris females differs from that

reported for other tropical Trachemys species that tend to

nest in relatively open areas that receive direct sunlight for

at least part of each day (Moll and Legler 1971) This may

be a response to the higher mean nest temperatures

prevalent in this region of Colombia (Restrepo et al

unpubl data 2003) in comparison with those documented

for other tropical Trachemys nesting sites (Llanos de Cano

Negro Costa Rica mean 2628 6 148C SD with a range

of 2558C to 2828C Cabrera et al 1996 Juan Mina

Panama with a range of 228C to 308C Moll and Legler

1971) Apparently female nest-site selection behavior

varies geographically in response to prevailing climatic

conditions (Gibbons 1983)

In the Mompos Depression relatively few nests were

oviposited under grass (15) given its abundance (51)

indicating nonpreference of this coverage whereas

hyacinth was preferred (523 of all nests oviposited

under a cover that comprised only 177 of the total in the

area Fig 3) However in a previous year Bernal et al

(2004) failed to document preferential nesting for hyacinth

vs grass vegetative covers This difference may have been

a result of the exceptionally high temperatures during our

study and the fact that nests under hyacinth experience

incubation temperatures that are lower than those of nests

under other vegetative types (Restrepo et al unpubl data

2003) There were no differences among vegetative types

in terms of the other variables that we considered (hatching

success rates predation or parasitism rates incubation

periods hatching success rates hatchling sizes or sex

ratios Restrepo et al unpubl data 2003)

We also documented that nesting females preferred to

nest in the dirt soil type especially but not exclusively

when it was associated with the hyacinth vegetative cover

We detected no other associations between the other

vegetative covers and soil types Selecting for specific soil

characteristics may be related to the possibility or the ease

with which appropriate nest chambers may be constructed

there or also related to the relation between grain size and

water potential of the substrate Flexible-shelled turtle eggs

such as those of T callirostris benefit from incubating in

humid substrates in terms of the developmental rate of the

embryos and size of the resultant neonates (Congdon and

Gibbons 1990 Tucker et al 1998b)

Although we documented a preference on the part of

the nesting females for dirt soils Moll and Legler (1971)

argued that Trachemys in Panama nested irrespective of

soil type except that they avoided muddy areas In a

previous year Bernal et al (2004) found nests in our study

site predominantly in mixed dirt-sand soils However the

previous study was conducted in a year with considerable

flooding whereas our study was conducted during an El

Nino year with an exceptionally severe dry season This

suggests that female nest-site preferences not only vary

geographically but also temporally depending upon

climatic variation indicating a flexibility on the part of

the females similar to that documented in green sea turtles

Chelonia mydas (Bjorndal and Bolten 1992)

We found 779 of all nests within the first 5 m from

the shoreline concordant with the reports of Bernal et al

(2004) of finding the majority of nests on Leon Island that

year within the first 6 m and the study by Medem (1975)

that reported a mean nest distance from the shoreline of 45

m Also Zenteno and Bouchot (2001) reported a mean

nest distance to the shoreline of 35 m for Trachemysvenusta in Mexico despite the fact that many nests located

there were lost to natural predators In contrast in an area

with little human presence in Juan Mina Panama Moll

and Legler (1971) documented a mean nest distance to

shoreline of 50 m for T venusta with some nests located

almost 400 m from the shoreline Heavy hunting pressures

on nesting females in some areas may have led to a

tendency to confine nesting activities to the immediate

vicinity of the shoreline as has been shown experimentally

for Emydura macquarii where females increased their

mean nest distance to the shoreline by 10 m in response to

the removal of natural predators from some islands

(Spencer and Thompson 2003)

Many freshwater turtles appear to actively select their

nest-site locations but decisions are probably influenced by

complex trade-offs related to various fitness components

and it seems that the costs and benefits of different options

may vary both geographically and temporally for any given

species Unfortunately studies that merely characterize the

Figure 5 Availability and use of differing combined vegetativecover-soil type categories on Leon Island (O-O frac14 other-other O-D frac14 other-dirt H-D frac14 hyacinth-dirt H-O frac14 hyacinth-other)


microhabitat characteristics of sites where turtle nests

occur without also quantifying the general availability of

the different characteristics in the overall nesting area are

insufficient Only by rigorously documenting actual nest-

site location preferences will a complete understanding of

these complex fitness interactions be possible

ACKNOWLEDGMENTS

We thank the Centro de Investigaciones of the

Universidad de Antioquia for financing this study Brian

C Bock for his comments and help with the English Juan

Manuel Daza and Carlos Gutierrez for all their help and

encouragement and to the Grupo Herpetologico de

Antioquia and Fundacion Neotropico for use of their

facilities We also thank Lucia Lukas and our families

and all the residents of Angostura especially Carlos

Elvira and the children for receiving us into their homes

and making this project possible

RESUMEN

Realizamos un estudio sobre la seleccion del sitio de

anidacion por la tortuga Trachemys callirostrois callir-ostris en una isla perteneciente al complejo cenagoso de

Pijino Depresion Momposina Colombia Comparamos la

cobertura vegetal y el tipo de suelo de 86 nidos naturales

con 57 puntos elegidos aleatoriamente en la isla

Observamos que los nidos no se distribuyeron al azar

sino que se encontraban en sitios con caracterısticas

particulares Encontramos la mayor parte de los nidos en

los primeros 5 m de distancia al pantano debido

posiblemente a las altas tasas de depredacion que enfrentan

las hembras Siempre seleccionaron sitios cubiertos por

algun tipo de cobertura vegetal no encontrando ningun

nido en suelo descubierto Esto posiblemente se debe a que

los sitios cubiertos reducen el estres termal para las

hembras anidantes disminuyen la probabilidad de detec-

cion de los nidos por parte de los depredadores y

amortiguan las condiciones ambientales extremas para

los embriones en desarrollo Las pruebas estadısticas

indicaron que las hembras seleccionaban preferiblemente

sitios cubiertos por Buchon para depositar sus huevos Sin

embrago no pudimos establecer si las hembras elegıan

directamente esta cobertura o si este resultado fue debido a

la fuerte asociacion que encontramos entre el Buchon y el

suelo Limoso El suelo Limoso fue el seleccionado por las

hembras este posee un alto contenido de humedad la cual

favorece el desarrollo de los embriones

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BODIE JR SMITH KR AND BURKE VJ 1996 A comparison ofdiel nest temperature and nest site selection for two sympatricspecies of freshwater turtles American Midland Naturalist 136181ndash186

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BURGER J 1991 Effects of incubation temperature on behavior ofhatchling pine snakes implications for reptilian distributionBehavioral Ecology and Sociobiology 28297ndash303

BURGER J 1993 Colony and nest site selection in lava lizardsTropidurus spp in the Galapagos Islands Copeia 1993748ndash753

BURGER J AND MONTEVECCHI WA 1975 Nest site selection inthe terrapin Malaclemys terrapin Copeia 1975113ndash119

BURKE VJ RATHBUN SL BODIE JR AND GIBBONS W 1998Effect of density on predation rate for turtle nests in a complexlandscape Oikos 833ndash11

CABRERA J ROJAS JR GALEANO G AND MEZA V V 1996Mortalidad embrionaria y exito de eclosion en huevos deTrachemys scripta (Testudines Emydidae) incubados en unarea natural protegida Revista de Biologica Tropical 44

CASANOVA E 1991 Introduccion a la ciencia del sueloUniversidad de Venezuela Caracas Consejo de DesarrolloCientıfico y Humanıstico pp 71ndash72

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CASTANO-MORA OV 2002 Libro Rojo de los Reptiles Ame-nazados de Colombia Bogota Colombia Instituto de CienciasNaturales Universidad Nacional de Colombia p 160

CONGDON JD AND GIBBONS JW 1990 Turtle eggs their ecologyand evolution In Gibbons JW (Ed) Life History andEcology of the Slider Turtle Washington DC SmithsonianInstitution Press pp 109ndash123

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CVS (CORPORACION AUTONOMA REGIONAL DEL SUR DEL BOLIVAR)2002 Plan de manejo integral de los humedales subregion dela Depresion Momposina y cuenca del rıo Sinu MagangueColombia

ESCALONA T AND FA JE 1998 Survival of nests of the terecayturtle (Podocnemis unifilis) in the Nichare-Tawadu riversVenezuela Journal of Zoology 244303ndash312

FILORAMO NI AND JANZEN FJ 2002 An experimental study ofthe influence of embryonic water availability body size andclutch on survivorship of neonatal red-eared sliders Trachemysscripta elegans Herpetologica 58(1)67ndash74

FUNDESCALA (FUNDACION PARA EL DESARROLLO A ESCALA HUMANA)1997 Plan de manejo ambiental del complejo cenagoso de Pijino(Municipios de Pijino y San Zenon) Informe ejecutivoMagangue Colombia 15 pp

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the mud turtle Kinosternon subrubrum (Lacepede) Herpeto-logica 39(3)254ndash271

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JANZEN FJ 1994 Vegetational cover predicts the sex ratio ofhatchling turtles in natural nests Ecology 751593ndash1599

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JANZEN FJ TUCKER JK AND PAUKSTIS GL 2000a Experi-mental analysis of an early life-history stage avian predationselects for larger body size of hatchling turtles Journal ofEvolutionary Biology 13947ndash954

JANZEN F J TUCKER JK AND PAUKSTIS GL 2000bExperimental analysis of an early life-history stage selectionon size of hatchling turtles Ecology 812290ndash2304

KOLBE JJ AND JANZEN FJ 2002 Impact of nest-site selection onnest success and nest temperature in natural and disturbedhabitats Ecology 83269ndash281

MEDEM F 1975 La reproduccion de la icotea Pseudemys scriptacallirostris (Testudines Emydidae) Caldasia 1183ndash106

MISENHELTER MD AND ROTENBERRY JT 2000 Choices andconsequences of habitat occupancy and nest site selection inspage sparrows Ecology 81(10)2892ndash2901

MOLL EO AND LEGLER JM 1971 The Life History of aNeotropical Slider Turtle Pseudemys scripta (Schoepff) inPanama Bulletin of the Los Angeles County Museum ofNatural History No 11 102 pp

PACKARD GC MILLER K AND PACKARD MJ 1993 Environ-mentally induced variation in body size of turtle hatchlings innatural nests Oecologia 93445ndash448

PACKARD GC PACKARD MJ AND BENIGAN L 1991 Sexualdifferentiation growth and hatching success by embryonicpainted turtles incubated in wet and dry environments atfluctuating temperatures Herpetologica 47(1)125ndash132

PACKARD GC PACKARD MJ MILLER K AND BOARDAN TJ1987 Influence of moisture temperature and substrate onsnapping turtle eggs and embryos Ecology 68983ndash993

PENA DE 1993 Espacio y diacronıa en la conformacion de lasubregion momposina En I Encuentro Regional de Historia dela Costa Caribe Colombiana Mompos Edicion especialBoletın Historial No 26 Medellın 238 pp

RESETARITS W JR 1996 Oviposition site choice and life historyevolution American Zoologist 36205ndash215

ROOSENBERG WN 1996 Maternal condition and nest site choicean alternative for the maintenance of environmental sexdetermination American Zoologist 36157ndash168

SCHWARZKOPF L AND BROOKS RJ 1987 Nest-site selection andoffspring sex ratio in painted turtles Chrysemys picta Copeia198753ndash61

SEIDEL ME 2002 Taxonomic observations on extant species andsubspecies of slider turtles genus Trachemys Journal ofHerpetology 36285ndash292

SPENCER RJ 2002 Experimentally testing nest site selection

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SPENCER RJ AND THOMPSON MB 2003 The significance of

predation in site selection on turtles an experimental

consideration of macro - and microhabitat preferences Oikos

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SPOTILA JR ZIMMERMAN LC BINCKLEY CA GRUMBLES JS

ROSTAL DC LIST A JR BERGER EC PHILLIPS KM AND

KEMP SJ 1994 Effects of incubation conditions on sex

determination hatching success and growth of hatchling desert

tortoises Gopherus agassizii Herpetological Monographs 8

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STEYERMARK AC AND SPOTILA JR 2001 Effects of maternal

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morphology in snapping turtles Chelydra serpentina Copeia

2001129ndash135

STONEBURNER DL AND RICHARDSON JI 1981 Observations on

the role of temperature in loggerhead turtle nest site selection

Copeia 1981239ndash241

TUCKER JK FILORAMO NI AND JANZEN FJ 1999 Size-biased

mortality due to predation in a nesting freshwater turtle

Trachemys scripta American Midland Naturalist 141

198ndash203

TUCKER JK FILORAMO NI PAUKSTIS GL AND JANZEN FJ

1998a Residual yolk in captive and wild-caught hatchlings of

the red-eared slider turtle (Trachemys scripta elegans) Copeia

1998488ndash492


1998b Response of red-eared slider Trachemys scriptaelegans eggs to slightly differing water potentials Journal of

Herpetology 32124ndash128

TURBAY S GOMEZ GA LOPEZ AD ALZATE C AND ALVAREZ

OJ 2000 La Fauna de la Depresion Momposina Medellın

Colombia Editorial Lealon 102 pp

VOGT RC AND BULL JJ 1982 Temperature controlled sex-

determination in turtles ecological and behavioral aspects

Herpetologica 38156ndash164

VOGT RC AND BULL JJ 1984 Ecology of hatchling sex ratio in

map turtles Ecology 65582ndash587

WEISROCK DW AND JANZEN FJ 1999 Thermal and fitness-

related consequences of nest location in painted turtles

(Chrysemys picta) Functional Ecology 1394ndash101

WILSON DS 1998 Nest-site selection microhabitat variation and

its effects on the survival of turtle embryos Ecology 19(6)

1884ndash1892

WOOD DW AND BJORNDAL KA 2000 Relation of temperature

moisture salinity and slope to nest site selection in loggerhead

sea turtles Copeia 2000119ndash128

YERLI S CANBOLAT AF BROWN LJ AND MCDONALD DW

1997 Mesh grids loggerhead turtle (Caretta caretta) nests from

red fox (Vulpes vulpes) predation Biological Conservation 82

109ndash111

YNTEMA CL 1978 Incubation times for eggs of the turtle

Chelydra serpetina (Testudine Chlydridae) at various tem-

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ZENTENO CE AND BOUCHOT C 2001 Reproduccion de la tortuga

pinta (Trachemys scripta venusta) en una laguna de la planicie

costera Veracruzana Universidad y Ciencia 17(33)37ndash42

Received 18 September 2004

Revised and Accepted 12 October 2005


Chelonian Conservation and Biology 2006 5(2) 249ndash254 2006 Chelonian Research Foundation

Nest Site Selection by Colombian Slider Turtles Trachemys callirostris callirostris(Testudines Emydidae) in the Mompos Depression Colombia

ADRIANA RESTREPO1 VICTOR J PINEROS

1 AND VIVIAN P PAEZ1

1Instituto de Biologıa Apartado 1226Universidad de Antioquia Medellın Colombia [restrepoadriana78gmailcom]

[victorpinerosyahoocomar] [vpaezquimbayaudeaeduco]

ABSTRACT ndash Nest-site selection by female Trachemys callirostris callirostris was studied on an islandin the Pijino wetland of the Mompos Depression of Colombia We quantified distances of nests tothe shoreline and compared vegetative cover and soil types at nest locations and at randomlyselected points on the island Nests sites were concentrated in the first 5 m from the shoreline andwere always located under vegetative cover Such cover might reduce thermal stress to nestingfemales lower the probability of nest detection by predators and buffer the incubating eggs fromenvironmental extremes Females preferentially nested under water hyacinth but it was not clearwhether they selected directly for this vegetative cover type or simply preferred dirt substrateswhere it dominated because dirt soils contained higher humidity

KEY WORDS ndash Reptilia Testudines Emydidae Trachemys callirostris callirostris turtlereproduction nesting nest-site selection Colombia

The nesting process has important fitness consequenc-

es for female turtles (Spencer and Thompson 2003)

Females are particularly vulnerable to predation at this

time (Tucker et al 1999 Spencer 2002) and eggs and

neonates also suffer predation during incubation and nest

emergence (Congdon et al 1983 Yerli et al 1997 Burke

et al 1998 Escalona and Fa 1998 Janzen et al 2000a

2000b) Microclimatic conditions within the nest such as

humidity and temperature also affect embryo survival

(Packard et al 1991 Burger 1993 Resetarits 1996) and

influence sex (Janzen and Paukstis 1991 Spotila et al

1994) incubation period (Yntema 1978 Packard et al

1987) and the size morphology yolk reserves growth

physiology and performance abilities of neonates (Burger

1991 Packard et al 1993 Bobyn and Brooks 1994

Tucker et al 1998a Steyermark and Spotila 2001

Filoramo and Janzen 2002 Janzen and Morjan 2002)

Given the apparent fitness consequences that nest-site

selection implies we predicted that female Trachemyscallirostris should nest nonrandomly with respect to

specific environmental variables Other studies of fresh-

water turtles have shown that females often oviposit in

sites that differ in various ways from randomly selected

points suggesting the existence of microhabitat prefer-

ences on their part (Wilson 1998 Janzen and Morjan

2001 Kolbe and Janzen 2002) Here the existence of

preferences for specific nesting-site locations was defined

statistically as the oviposition of eggs disproportionately in

sites that differed from randomly selected points within a

given constrained nesting area (Wilson 1998)

Various hypotheses have attempted to explain female

nesting-site preferences Some researchers have suggested

that females in species with temperature-dependent sex

determination select nest locations so as to manipulate

progeny sex ratios to consistently or alternatively produce

males or females (Vogt and Bull 1982 Roosenberg 1996

Spencer 2002) Other researchers have hypothesized that

females prefer to nest in areas shielded from nest

predators parasites or environmental extremes thereby

maximizing embryo survivorship (Burger and Montevec-

chi 1975 Burger 1976 Gochfeld 1979 Bodie et al 1996

Spencer and Thompson 2003) Finally others have argued

that females restrict their nesting activities to areas near the

shoreline to minimize their own predation risks while on

land at the expense of ovipositing in locations that are

suboptimal (Spencer 2002 Spencer and Thompson 2003)

In practice it is difficult to differentiate among the sex

ratio embryo survivorship and female survivorship

hypotheses (Schwarzkopf and Brooks 1987 Spencer and

Thompson 2003) given that nest-site selection in many

species probably represents a trade-off between the costs

and the benefits of these multiple sometimes contradic-

tory factors (Misenhelter and Rotenberry 2000 Wood and

Bjorndal 2000 Spencer and Thompson 2003)

Different habitat characteristics could serve as impor-

tant proximate cues to females during the nesting-site

selection process (Weisrock and Janzen 1999) Vegetative

cover is one of the most studied characteristics given its

association with nest temperature (Burger and Montevec-

chi 1975 Vogt and Bull 1984 Janzen 1994 Bodie et al

1996 Roosenberg 1996 Wilson 1998) Slope and soil

surface temperatures also have been proposed as important

cues in nesting-site selection (Burger and Montevecchi

1975 Stoneburner and Richardson 1981 Schwarzkopf

and Brooks 1987 Wood and Bjorndal 2000)

Advancing on work begun by Bernal et al (2004) that

described the basic nest characteristics of T callirostris in

the Mompos Depression of Colombia the objective of this

study was to evaluate whether females in the same area



METHODS













(Pena 1993)




















Mora 2002)



























































RESULTS
























































p 0001 Fig 5)

DISCUSSION





















































































































ACKNOWLEDGMENTS











RESUMEN



























LITERATURE CITED




51(2)229ndash238













































2136ndash2144




102592ndash600






103ndash116




2001129ndash135







198ndash203




1998488ndash492

















1884ndash1892







109ndash111












METHODS













(Pena 1993)




















Mora 2002)



























































RESULTS
























































p 0001 Fig 5)

DISCUSSION





















































































































ACKNOWLEDGMENTS











RESUMEN



























LITERATURE CITED




51(2)229ndash238













































2136ndash2144




102592ndash600






103ndash116




2001129ndash135







198ndash203




1998488ndash492

















1884ndash1892







109ndash111












RESULTS
























































p 0001 Fig 5)

DISCUSSION





















































































































ACKNOWLEDGMENTS











RESUMEN



























LITERATURE CITED




51(2)229ndash238













































2136ndash2144




102592ndash600






103ndash116




2001129ndash135







198ndash203




1998488ndash492

















1884ndash1892







109ndash111




















































































































ACKNOWLEDGMENTS











RESUMEN



























LITERATURE CITED




51(2)229ndash238













































2136ndash2144




102592ndash600






103ndash116




2001129ndash135







198ndash203




1998488ndash492

















1884ndash1892







109ndash111
















ACKNOWLEDGMENTS











RESUMEN



























LITERATURE CITED




51(2)229ndash238













































2136ndash2144




102592ndash600






103ndash116




2001129ndash135







198ndash203




1998488ndash492

















1884ndash1892







109ndash111
































2136ndash2144




102592ndash600






103ndash116




2001129ndash135







198ndash203




1998488ndash492

















1884ndash1892







109ndash111










Documents

Nest Site Selection by Colombian Slider Turtles, Trachemys callirostris callirostris (Testudines: Emydidae), in the Mompos Depression, Colombia