Site by Bennett Web & Design Co.
2006 SOUTHEASTERN NATURALIST 5(2):227–234
Characteristics of the Foreclaw Display Behaviors of
Female Trachemys scripta (Slider Turtles)
R. Brent Thomas1,* and Ronald Altig2
Abstract - A common assumption is that titillation by adult female Trachemys
scripta (Slider Turtles) always represents female participation in courtship, but there
is only limited empirical support for this assertion and some data may contradict this
supposition. Behavioral interactions were staged among wild-caught T. scripta
throughout the local season of activity for this species (April–October). Each of 47
trials involved 6 turtles (total = 282 turtles: 94 melanistic males, 94 nonmelanistic
males, 94 females) videotaped for 3 h (total = 141 h). During our study, titillation
behaviors initiated by females were largely intrasexual, exhibited no peak during the
local mating period, and did not stimulate males to attempt copulation. We concluded
that such characteristics were inconsistent with the traditional assumption of a
courtship function and were more consistent with the characteristics of agonistic
signals, signals that communicate sender identity, or compound signals with multiple
communicative functions that may change ontogenetically or in different social
contexts. Because the communicative value(s) of these displays is not yet fully
understood, we argue that the traditional term “titillation” that has been used to refer
to these displays is inappropriate and should be replaced with “foreclaw display”
which is neutral with respect to the potential communicative function(s).
Bradbury and Vehrencamp (1998) define communication as an exchange
of a signal between a sender and a receiver to the benefit of both parties and
divide the types of information communicated into categories based on the
type of information being exchanged: (1) sender identity, (2) sender location,
and (3) specific contexts. Sender identity refers to signals that provide information
regarding individual, species, sex, or social group recognition. Sender
location signals relay information about the distance, altitude, or compass
angle of the receiver relative to the sender. Signals in the contexts category
involve such information as conflict resolution, territory defense, sexual
interactions, parent-offspring interactions, social integration, environmental
contexts, and autocommunication. However, a given signal may provide
information dealing with information in all three categories simultaneously.
Many turtles of both sexes in the family Emydidae perform elaborate
display behaviors often referred to as “titillation” (Ernst et al. 1994). Jackson
and Davis (1972a) described titillation as a complex, stereotyped series of
movements in which the adducted forelimbs of the male are brought parallel
to the head of the female, and the claws of the forelimbs are drummed and
1Division of Natural Sciences and Engineering, University of South Carolina Upstate,
800 University Way, Spartanburg, SC 29303. 2Department of Biological Sciences,
PO Drawer GY, Mississippi State University, Mississippi State, MS 38762.
*Corresponding author - email@example.com.
228 Southeastern Naturalist Vol. 5, No. 2
vibrated against the eyes and interocular region of the female. In this context,
titillation is commonly assumed to be a courtship signal (Carpenter and
Ferguson 1977, Ernst et al. 1994, Fritz 1991, Kramer and Burghardt 1998,
Lovich et al. 1990a, Seidel and Fritz 1997). Adult males (Cagle 1950, Jackson
and Davis 1972a, Taylor 1933, Zappalorti 1976), adult females (Jackson and
Davis 1972b, Jackson 1977, Lovich et al. 1990a, Zappalorti 1976), and
juveniles of both sexes (Cagle 1955, Kramer and Burghardt 1998, Morris
1976, Rives 1978) initiate and receive titillation behaviors. The receiver
sometimes reciprocates the behavior toward the initiator (Ernst 1971, Rives
1978, Wahlquist 1970, Zappalorti 1976). Titillation behaviors performed by
adults of either sex are thought to represent courtship displays, and juvenile
titillation is thought to represent some form of precocial courtship (Kramer
and Burghardt 1998). Suggestions that titillation may serve other functions
(Cagle 1955, Rives 1978) have not been explored, and studies designed to
specifically examine other possible communicative functions of female titillation
behaviors have not been performed.
The functions of any form of communication must be understood before
conducting studies of sexual selection (e.g., mate-choice studies). Previous
researchers of sexual selection in turtles assumed that titillation displays by
either sex always represented at least a part of courtship regardless of context
and that female choice is an important selective force within all species that
perform such displays (see Berry and Shine 1980). It is important to examine
the specific evidence that forms the basis for the conclusion that the titillation
behavior by female emydids constitutes initiation of or participation in courtship.
Ernst (1971) observed female Chrysemys picta (Schneider) initiating
titillation on “several occasions” (number not specified), and males attempted
to copulate subsequent to female titillation on three occasions. Lovich et al.
(1990a) reported that female Trachemys scripta Schoepff sensu Seidel directed
5 titillations toward males during 47 trials, and in all cases males remained
passive. Wahlquist (1970) reported a single observation of a captive, immature
female Graptemys flavimaculata (Cagle) reciprocating the titillations of an
adult male conspecific. Jackson and Davis (1972b) videotaped 1 male and 1
female Pseudemys concinna (Le Conte) in captivity for 8 h/day over a 10-day
period in April and reported that the female “occasionally” (number not
specified) performed titillation behaviors. Jackson (1977) reported female
initiation of titillation between a single pair of adult Pseudemys nelsoni (Carr)
in a tank that also contained several other species. Zappalorti (1976) stated that
female C. picta stroke the forefeet of the male with their foreclaws to signal
receptivity, but provided no data or citations to support this conclusion.
Three attempted copulations preceded by titillation initiated by a female
(Ernst 1971) provide the only support for the idea that titillation by
females represents some part of courtship. All others mentioned above
simply report that females performed titillation. Additionally, all such
reports have been rather cursory during only a small fraction of the activity
season, did not consider the possibility of intraspecific (or intrasexual)
variation, and did not quantitatively examine the social contexts of the
displays in order to question the potential communicative function(s). We
2006 R.B. Thomas and R. Altig 229
suggest that the assumption that titillation by females represents their
participation in courtship is at best premature and that the literature provides
very little supportive evidence.
Some evidence seems to conflict with the assumption of a courtship
function. For example, observations of immature individuals performing titillation,
interspecific titillation, and the titillation of foreign objects such as food,
pencils, and fingers (Rives 1978) suggests that titillation may communicate
other types of information. The general rationale seems to be that if an emydid
turtle of any sex titillates, then all members of that population and all members
of all populations titillate under the same presumed behavioral scenario.
Likewise, it has been commonly assumed that the communicative function of
titillation behavior remains the same in every population, environment, social
context, and season. Intraspecific and intrasexual variations in behavior are
now considered normal, and typological attitudes regarding courtship behaviors
are in conflict with current views (Foster and Endler 1998, Gross 1996).
The purpose of our study was to quantitatively examine the characteristics
of the titillation displays of female T. scripta in a controlled laboratory setting.
If the longstanding assumption that female titillation constitutes female participation
in courtship is correct, then the occurrences of these behaviors
should have at least some of the following characteristics: (1) females should
direct titillation toward adult males more often than toward females, (2)
females should reciprocate the titillations of adult males more frequently than
those initiated by other females, (3) the peak frequency of female titillations
should occur more often during the local mating season (Sept. through Oct.;
Thomas 2002, Thomas et al. 1999), and (4) female titillations should stimulate
copulation attempts from males at some reasonable but unknown rate. We
quantified the frequency and direction of female titillations, the frequency
and direction of reciprocal titillations, and the number of times that copulation
was attempted by a male after being titillated by a female, and examined
seasonal variation in the frequency of these behaviors.
Hoop traps and basking traps were used to collect Trachemys scripta in
several adjacent sewage lagoons near the campus of Mississippi State University,
Oktibbeha County, MS (33°27'N, 88°47'W). Traps were usually checked
every day from April through October 1997, and all individuals with elongated
foreclaws, a cloaca positioned posterior to the carapace margin, and a plastron
length greater than 110 mm were considered adult males. Individuals with a
plastron length greater than 160 mm and lacking these secondary sex characteristics
were considered adult females (Gibbons and Greene 1990).
Turtles were haphazardly assigned to individual tanks (60 x 90 x 35 cm)
for 24–48 h to allow them to adjust to laboratory conditions. Turtles were
marked (Cagle 1939) and released at their point of capture after the completion
of a trial. Individuals were not used more than once for any purpose in
any of the trials, and individuals removed from the same trap at the same
time were not used in the same trial.
230 Southeastern Naturalist Vol. 5, No. 2
The plastic experimental tanks were 70 x 145 x 40 cm. The tanks were
drained, cleaned (first with soap, then with alcohol), rinsed, filled with fresh
water to a depth of 30 cm, and allowed to age for at least 24 h after each trial.
Wide-spectrum lighting provided a 12D:12L photoperiod, and the water
temperature was maintained between 22 and 25 °C. All trials lasted 3 h and
were conducted between 1030 and 1330 CST. Observational trials were
recorded with an 8-mm video camera situated above the tank. Researchers
were not in the laboratory at any time during a trial.
The morphology and behavior of melanistic male T. scripta differs from
that of nonmelanistic males and females, e.g., titillation behaviors of
nonmelanistic males apparently serve a courtship function while the titillations
performed by melanistic males are probably not associated with courtship
(Thomas 2002). Because of these differences, we used the stages
described by Tucker et al. (1995) to quantify stage of melanism (0 =
nonmelanistic; 1 = limited melanic expression; 2 = fully melanistic) and, a
trial consisted of placing two adult individuals of each of the following
categories in the tank: (1) melanistic males (stage 2), (2) nonmelanistic
males (stage 0 or 1), and (3) females. An identification number assigned to
each turtle was written on the carapace with a grease pencil.
The occurrence of titillation, reciprocal titillation, copulation attempts,
and the identity of both the initiator and recipient were recorded
from the tapes. A copulation attempt was defined as an individual attempting
to mount by shifting into a position to copulate with another
individual (see Davis and Jackson 1970), but the inability to actually see
intromission required all of these to be conservatively considered as attempts.
We noted whether or not a female initiated titillation prior to a
copulation attempt by a male. Forty-seven trials (3 h/trial, total = 141 h)
involving 6 turtles per trial (total = 282 turtles: 94 melanistic males, 94
nonmelanistic males, 94 females) were conducted as follows: April
(N = 5), May (N = 7), June (N = 11), July (N = 9), August (N = 6),
September (N = 6), and October (N = 3).
The use of chi-squared statistic would be innappropriate given that
observations within a trial were probably not independent. However, the
results of each trial were independent of each other. Therefore, we followed
the advice of Kramer and Schmidhammer (1992) and used
ANOVA to compare both the mean number of titillations initiated by
females across categories and mean rate of female reciprocations across
categories (i.e., melanistic males, nonmelanistic males, and females).
Separation of means was accomplished using Fisher’s LSD (Sokal and
Rohlf 1994). A Kruskal-Wallis test compared the median monthly trial
totals of female initiation of titillation (Conover 1971), i.e., the median of
the total number of times that females initiatiated titillation in each of the
individual trials conducted during a specific month. The Bonferroni procedure
was used to adjust the type-I error rate for the three tests (i.e.,
0.05/3 = 0.017; Sokal and Rohlf 1994).
2006 R.B. Thomas and R. Altig 231
Female Trachemys scripta initiated titillation during 33 (70.2%) of the 47
trials. Female initiated titillation occurred 198 times and 113 of these displays
were directed toward females, 39 toward melanistic males, and 46 toward
nonmelanistic males. On average, female T. scripta directed titillations toward
the other female 3.5 times/trial, toward melanistic males 1.2 times/trial, and
nonmelanistic males 1.4 times/trial. Females directed their titillation behaviors
toward the other female significantly more often than toward melanistic or
nonmelanistic males (F = 4.923; d.f. = 2, 93; P = 0.009). Mean separation
procedures indicated no significant difference between the number of female
titillations directed toward melanistic and nonmelanistic males (P = 0.789).
Females received a total of 597 titillations: 188, 296, and 113 from melanistic
males, nonmelanistic males, and females, respectively. Reciprocal titillation
by female T. scripta was observed during 18 (38.3%) of the 47 trials (Table 1).
In response to receiving titillation, females reciprocated titillation 39 times
(melanistic males = 16, nonmelanistic males = 3, females = 20). The overall
reciprocation rate for all trials (percent of time that females responded by
reciprocating the titillation bout initiated by another individual of a specific
category) was 17.4, 8.6, and 1.0% for females, melanistic males, and
nonmelanistic males respectively. Females reciprocated the titillations of other
females significantly more frequently than those of melanistic and
nonmelanistic males (F = 4.749; d.f. = 2, 83; P = 0.011). However, the results of
mean separation procedures indicated no significant difference between female
reciprocation rate for titillations received from melanistic and
nonmelanistic males (P = 0.937). Males attempted copulation 233 times during
the trials, but none of these attempts occurred subsequent to female initiated
titillation toward a male. The median monthly trial totals for female titillations
were not significantly different (H = 9.312; d.f. = 6; P = 0.157; Table 1); thus, no
peak in the median monthly trial frequency of female titillations was observed.
If the sole purpose of titillation by female T. scripta is participation in or
elicitation of courtship, then at least an indication of the predictions stated in
Table 1. Number of trials during each month, mean (± SE), median, and range of monthly trial
totals for female initiation of titillation followed by the percent of trials in which females
initiated or reciprocated titillation.
% trials % trials
with female with female
Month # trials Mean (± SE) Median Range initiation reciprocation
April 5 6.2 (4.8) 3.0 0–25 60.0 20.0
May 7 1.7 (1.4) 0.0 0–10 42.9 14.3
June 11 5.1 (1.6) 3.0 0–18 90.9 45.5
July 9 6.9 (2.4) 3.0 0–21 88.9 55.6
August 6 2.7 (2.5) 0.0 0–15 33.3 16.7
September 6 2.3 (0.9) 2.0 0–5 66.7 50.0
October 3 2.3 (0.9) 2.0 1–4 100.0 66.7
Overall 47 4.2 (0.9) 2.0 0–25 70.2 38.3
232 Southeastern Naturalist Vol. 5, No. 2
the introduction should have been observed. We observed the converse of
each of these predictions and found no evidence to support the idea that female
titillation is any sort of courtship signal. Specifically, female titillation behaviors
were directed toward females more frequently than toward other males,
exhibited no obvious peak during the local mating period, and did not stimulate
males to attempt copulation. We suggest that signals with such characteristics
are more likely to communicate something about the identity of the
sender or information relevant to some yet unknown aspect(s) of conflict
resolution (see Rives 1978 for similar arguments). Similarly, titillations by
melanistic male T. scripta may not serve a courtship function, but titillation
may function as a courtship signal for nonmelanistic males (see Thomas
2002). Melanistic males and females are on average larger, older, and probably
more experienced than nonmelanistic males (Lovich et al. 1990b). It is
possible that these larger individuals use titillation to communicate different
types of information than the smaller nonmelanistic males, and thus the
communicative functions of these behaviors likely change ontogenetically.
Further research should address the influence of the relative size of individuals,
density of individuals, sex ratio, age, experience, or other demographic
factors on the display behaviors of T. scripta. For example, the current study is
not sufficient to determine to what extent (if at all) female T. scripta alter their
display behaviors in the presence of different numbers of conspecifics. Likewise,
the possibility of geographic variation cannot be dismissed. The possibility
that our results were solely an artifact of an unnatural lab situation, while
possible, seems unlikely. The initiation of social behaviors occurred within a
few minutes of the beginning of a trial, and turtles did not spend a great deal of
time swimming around the perimeter of the tank in an attempt to escape. Trial
animals were not long-term captives (i.e., only held 48 h or less prior to a trial),
and corticosterone levels (an indicator of stress) of (non-trial) T. scripta housed
under trial conditions were comparable to those of wild T. scripta (W.B. Cash,
Maryville College, Maryville, TN, unpubl. data). The photoperiod was held
constant during all trials rather than changing photoperiod seasonally to reflect
natural patterns of day length, and it is possible that the lack of seasonal
differences in female initiation of titillation could have been the result of an
“unchanging” photoperiod. While possible, it may be premature to make such
an inference given the paucity of studies that specifically examine the impact(s)
of photoperiod on turtle behavior (see Burger 1937, Cash 2000). Additionally,
non-melanistic male T. scripta were tested under exactly the same set of
“unchanging” conditions and exhibited significant seasonal differences in
regards to initiation of titillation behaviors in spite of the constant photoperiod
(Thomas 2002). Therefore, if constant laboratory photoperiod influenced the
behavior of test animals, then it must have differentially influenced female and
nonmelanistic male T. scripta. Further research on the specific impact(s) of
photoperiod on turtle behavior/physiology is needed before such issues can be
In summary, we found no evidence to support the assumption that titillation
by female T. scripta serves a courtship function and the evidence in the
literature is not sufficient to support this widely accepted assertion; in some
2006 R.B. Thomas and R. Altig 233
cases, the data seem contradictory to a courtship explanation (e.g., Rives
1978). We conclude that courtship may not be the purpose (or at least not the
sole purpose) for female titillations and that such displays may communicate
other types of information. To avoid similar logical errors as discussed above,
we note that it is premature to dismiss the possibility that female titillation
may serve a courtship function in other situations or social contexts (e.g.,
different density, species composition, size/age composition, or sex ratio). We
further argue that the term “titillation” explicitly provides the connotation that
these displays are exclusively involved in courtship. Given that the available
evidence is insufficient to support such connotations, we suggest that the term
should be replaced with “foreclaw display,” a neutral term with respect to the
potential communicative function(s) of such behaviors.
All animals were collected under MSU-IACUC protocol approval number 96-
010. We wish to acknowledge the support of Mississippi State University Department
of Biological Sciences and the University of South Carolina Upstate Division
of Natural Sciences and Engineering. We also thank C.M. Taylor, W.J. Diehl, P.
Gerard, and W.S. Parker, and two anonymous reviewers for their helpful comments
on previous versions of this manuscript.
Berry, J.F., and R. Shine. 1980. Sexual size dimorphism and sexual selection in
turtles (order Testudines). Oecologia 44:185–191.
Bradbury, J.W., and S.L. Vehrencamp. 1998. Principles of Animal Communication.
Sinauer Associates, Inc., Sunderland, MA. 882 pp.
Burger, J.W. 1937. Experimental sexual photoperiodicity in the male turtle,
Pseudemys elegans (Wied). American Naturalist 71:481–487.
Cagle, F.R. 1939. A system for marking turtles for future identification. Copeia
Cagle, F.R. 1950. The life history of the Slider Turtle, Pseudemys scripta troostii
(Holbrook). Ecological Monographs 20:32–54.
Cagle, F.R. 1955. Courtship behavior in juvenile turtles. Copeia 1955:307.
Carpenter, C.C., and G.W. Ferguson. 1977. Variation and evolution of stereotyped
behavior in reptiles. Pp. 335–554, In C. Gans and D.W. Tinkle (Eds.). Biology of
the Reptilia. Academic Press, New York, NY. 722 pp.
Cash, W.B. 2000. Behavioral and physiological ecology of the Slider Turtle: Laboratory
and field studies integrating hormonal and behavioral aspects. Unpublished
Ph.D. Dissertation. University of Mississippi, Oxford, MS. 153 pp.
Conover, W.J. 1971. Practical Nonparametric Statistics. John Wiley and Sons, Inc.,
New York, NY. 462 pp.
Davis, J.D., and C.G. Jackson, Jr. 1970. Copulatory behavior in the Red-eared
Turtle, Pseudemys scripta elegans (Wied). Herpetologica 26:238–240.
Ernst, C.H. 1971. Observations of the Painted Turtle, Chrysemys picta. Journal of
Ernst, C.H., J.E. Lovich, and R.W. Barbour. 1994. Turtles of the United States and
Canada. Smithsonian Institution Press, Washington, DC. 578 pp.
Foster, S.A., and J.A. Endler. 1998. Geographic Variation in Behavior: Perspectives
on Evolutionary Mechanisms. Oxford University Press, New York, NY. 352 pp.
234 Southeastern Naturalist Vol. 5, No. 2
Fritz, U. 1991. Balzverhalten und systematik in der subtribus Nectemydina 2.
Vergleich oberhalb des artniveaus und anmerkungen zur evolution. Salamandra
Gibbons, J.W., and J.L. Greene. 1990. Reproduction in the Slider Turtle and other
species of turtles. Pp. 124–134, In J.W. Gibbons (Ed.). Life history and Ecology
of the Slider Turtle. Smithsonian Institution Press, Washington, DC. 368 pp.
Gross, M.R. 1996. Alternative reproductive strategies and tactics: Diversity within
sexes. Trends in Ecology and Evolution 11:92–98.
Jackson, Jr., C.G. 1977. Courtship observations on Chrysemys nelsoni (Reptilia,
Testudines, Testudinidae). Journal of Herpetology 11:221–222.
Jackson, Jr., C.G., and J.D. Davis. 1972a. A quantitative study of courtship display
of the Red-eared Turtle, Chrysemys scripta elegans (Wied). Herpetologica
Jackson, Jr., C.G., and J.D. Davis. 1972b. Courtship display behavior of Chrysemys
concinna suwanniensis. Copeia 1972:385–387.
Kramer, M., and G.M. Burghardt. 1998. Precocious courtship and play in emydid
turtles. Ethology 104:38–56.
Kramer, M., and J. Schmidhammer. 1992. The chi-squared statistic in ethology: Use
and misuse. Animal Behaviour 44:833–841.
Lovich, J.E., W.R. Garstka, and W.E. Cooper, Jr. 1990a. Female participation in
courtship behavior of the turtle Trachemys s. scripta. Journal of Herpetology
Lovich, J.E., C.J. McCoy, and W.R. Garstka. 1990b. The development and significance
of melanism in the Slider Turtle. Pp. 233–254, In J.W. Gibbons (Ed.). Life
History and Ecology of the Slider Turtle. Smithsonian Institution Press, Washington
DC. 368 pp.
Morris, M.A. 1976. Courtship-like behavior of immature turtles. Herpetological
Rives, J.D. 1978. A comparative study of courtship-related behavior in immature
emydid turtles of two species. Unpublished M.Sc. Thesis. University of Southwestern
Louisiana, Lafayette, LA. 114 pp.
Seidel, M.E., and U. Fritz. 1997. Courtship behavior provides additional evidence
for a monophyletic Pseudemys, and comments on Mesoamerican Trachemys
(Testudines: Emydidae). Herpetological Review 28:70–72.
Sokal, R.R., and F.J. Rohlf. 1994. Biometry. W.H. Freeman and Company, New
York, NY. 887 pp.
Taylor, E.H. 1933. Observations on the courtship of turtles. University of Kansas
Science Bulletin 21:269–271.
Thomas, R.B. 2002. Conditional mating strategy in a long-lived vertebrate: Ontogenetic
shifts in the mating tactics of male Slider Turtles (Trachemys scripta).
Thomas, R.B., N. Vogrin, and R. Altig. 1999. Sexual and seasonal differences in
behavior of Trachemys scripta (Testudines: Emydidae). Journal of Herpetology
Tucker, J.K., R.J. Maher, and C.H. Theiling. 1995. Melanism in the Red-eared Slider
(Trachemys scripta elegans). Journal of Herpetology 29:291–296.
Wahlquist, H. 1970. Sawbacks of the Gulf Coast. International Turtle and Tortoise
Society Journal 4:10–13.
Zappalorti, R.T. 1976. The Amateur Zoologist’s Guide to Turtles and Crocodilians.
Stackpole Books, Harrisburg, PA. 208 pp.