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A Behavioral Analysis of Male-male Combat in the Eastern Massasauga (Sistrurus catenatus)

Herpetological Review 53(3), 2022
Herpetological Review, 2022, 53(3), 381–384.
© 2022 by Society for the Study of Amphibians and Reptiles
A Behavioral Analysis of Male-male Combat in the
Eastern Massasauga (Sistrurus catenatus)
Since the early observations of Shaw (1948), the occurrence
of male-male combat events has been reported for an increasing
number of snake species (Carpenter 1986; Gillingham 1987;
Shine 1994; Schuett et al. 2001). While previous and more
recent accounts provide a comprehensive list of species level
occurrence of male-male combat, the specific behaviors are not
often quantified or analyzed beyond simple descriptions (but see
Carpenter et al. 1976; Carpenter 1979; Schuett and Gillingham
1989). Consequently, details specific to the behaviors displayed
during male-male combat events are lacking, particularly for
free-ranging snakes. Because male-male combat events are not
homogeneous for all snake lineages in which they occur (Shine
1994), describing and analyzing the associated behaviors of
combative and aggressive male-male interactions at the species
level is crucial for understanding the consequences of these
social events.
The inherent difficulty of observing male-male combat and
interaction in free-ranging snakes has contributed to the lack
of behavioral descriptions and analyses (but see Andrén 1986;
Madsen et al. 1993). Combat events between snakes within
the genus Sistrurus have rarely been observed, with only one
previous report providing detailed descriptions and an analysis
of the observed behaviors (Carpenter 1979). While this work
provided a foundation for assessing combat behavior in Sistrurus,
the descriptions and analysis were based upon a single combat
event that took place in an artificial environment between two
different Pygmy Rattlesnake (S. miliarius) subspecies (Carpenter
1979). Aggressive male-male behavior and combat between male
S. catenatus has only been reported twice (Shepard et al. 2003;
VanDeWalle 2005), and while these accounts were informative
and documented the occurrence of combat in this species,
no formal analysis of the specific behaviors of the male-male
combat was offered.
Here, we used a video recording of a combat event between
two free-ranging male Eastern Massasaugas (S. catenatus) to
describe (e.g., Martin and Bateson 2007; Stanton et al. 2015)
and quantify the combat behaviors. In addition, we used radio
Department of Biological Sciences, Sam Houston State University,
Huntsville, Texas 77341, USA;
Current aliation: Illinois Natural History Survey, University of
Illinois at Urbana-Champaign, Champaign, Illinois 61820, USA
Department of Biological Sciences, Sam Houston State University,
Huntsville, Texas 77341, USA
Department of Biology, The College of New Jersey,
Ewing, New Jersey 08628, USA
*Corresponding author; e-mail:
Table 1. An ethogram and codes of the behaviors observed during a
Sistrurus catenatus male-male combat event.
Behavior (Code) Description
Tongue flicks (TF) A snake protrudes its tongue outside of the
mouth, so it is visible and subsequently
moves it back into the mouth in a quick,
darting motion.
Intertwined (IT) Both snakes are in an extended postion
and have a majority of their bodies
intertwined, with heads close together,
while maintaining extensive contact with
the substrate. There is little movement
associated with this behavior.
Disengaged (DE) A snake lowers itself, typically to an angle of
30°, often while assuming a position
facing away from the opponent, with a
majority of its body either immediately
above or in contact with the substrate.
Raised (R) A snake has the anterior portion of its body
raised off the ground at an angle typically
45°, usually in either an S-shaped position
or a vertical position.
Raised and engaged (RE) Both snakes are in a raised position (as
defined above) and are maintaining
substantial body to body contact with one
Topping attempt (TA) While in a raised position (as defined
above) a snake utilizes the medial and
superior portions of its body in an attempt
to force the opponent to the ground.
Topping (T ) While raised and engaged (as defined
above), a snake successfully utilizes the
medial and superior portions of its body
and forces the opponent to the ground.
Herpetological Review 53(3), 2022
Fig. 1. Chronological progression of behaviors displayed by male Sistrurus catenatus during combat. The
timestamps for each of the six images captured from the 00:17:04 video recording are reported: A) intertwined
(00:02:10); B) disengaged (00:03:50), MS-04 (left) and MS-05 (right) with female MS-01 in the vegetation im-
mediately between the two males; C) raised and engaged (00:05:05), MS-05 (left) and MS-04 (right); D) top-
ping attempt (00:05:10) initiated by MS-05 (right); E) topping (00:05:12) of MS-04 (below) by MS-05 (above);
F) disengaged behavior of MS-04 (left) while MS-05 (right) remains raised (00:13:44).
Herpetological Review 53(3), 2022
telemetry to observe the full progression of behaviors in the S.
catenatus combat event. This allowed us to describe the combat
and subsequently analyze and compare the behaviors displayed
with respect to the outcome of the combat event.
MaTerials and MeThods
Snakes and Study Area.—Our observations involved three
adult S. catenatus: MS-01 (gravid female; 51.0 cm SVL, 194 g),
MS-04 (male; 50.4 cm SVL, 149 g), and MS-05 (male; SVL and
mass not measured but appeared larger than MS-04 based
upon visual comparison by ZEP). MS-01 was equipped with a
surgically implanted radio transmitter. We observed interactions
among these snakes periodically over 4 d (30 July–2 August 2021)
in Cranberry Township, Venango County, Pennsylvania, USA.
Observations and Recordings.—All field observations (by ZEP)
were possible through radio telemetry and the daily monitoring
of a female S. catenatus (MS-01). The male-male combat event
was observed and digitally recorded using an iPhone SE (2020).
The 00:17:04 (i.e., 1024 s) timestamped video recording was
subsequently used to describe and quantify the frequency and
duration of the different combat behaviors observed.
Video Analysis.—An ethogram (e.g., Martin and Bateson 2007;
Stanton et al. 2015) of observed behaviors was constructed from
the video recording by evaluating snake position, body posture,
and contact. Our ethogram focused on identifying and defining
general behaviors that were observed multiple times during the
combat event. Behaviors previously described during male-male
combat events in rattlesnakes (Carpenter et al. 1976; Carpenter
and Ferguson 1977; Carpenter 1979) were used and served as a
reference for defining behaviors in our ethogram (Table 1). The
seven behaviors observed and described were: tongue flicks (TF),
intertwined (IT), disengaged (DE), raised (R), raised and engaged
(RE), topping attempt (TA), and topping (T). Microsoft Windows
Media Player® was used to view the video frame by frame so
that we could distinguish different behaviors, and the timestamp
on each video frame was used to accurately determine both the
frequency and duration of each behavior observed.
While monitoring a telemetered gravid female S. catentus
(MS-01), we encountered a non-telemetered male S. catenatus
(MS-04) coiled within 0.5 m of the female on 30 July 2021. This
male was captured, processed, and immediately returned
to its capture location near the female, with the hope of not
disrupting a potential mating event. Despite this observation of
mate accompaniment (Mauger and Wilson 2005) of MS-01 by
MS-04, copulation or courtship behavior between MS-01 and
MS-04 was not observed at any time during the 4-d period. On
1 August 2021 a second non-telemetered male S. catenatus (MS-
05) was observed in the vicinity of MS-01 and MS-04, which led
to the recorded male-male combat event. During the combat
we observed seven separate combat-related behaviors (Table
1). We provide still images from the video recording and show
the sequence of combat behaviors and events observed during
the encounter (Fig. 1). On 2 August 2021 the progression of this
event culminated with male MS-05 successfully copulating with
female MS-01. Despite careful searching, male MS-04 was not
observed in the vicinity of the copulating pair after the combat
activity on 1 August.
Based on our analysis (Table 2) the behavior with the longest
duration for both male snakes was raised and engaged (RE),
accounting for 64.9% (665 s, ca. 11 min) of the 1024 s video
recording (Fig. 1C). The behavior with the second longest
duration for both snakes was disengaged (DE; Fig. 1B). Male MS-
04 was disengaged for 23.3% of the event (239 s, ca. 4 min), and
MS-05 was disengaged for 14.0% of the event (143 s, ca. 2.5 min).
Although the raised and engaged behavior was displayed for
the greatest duration by both snakes, MS-05 spent considerably
more time in a raised position and less time disengaged than
did MS-04 (Table 2; Fig. 1F). Raised (R) behavior was the third
longest duration for MS-05 (13.4%, 137 s, ca. 2.25 min), and the
fourth longest duration for MS-04 (5.1%, 52 s, ca. 1 min). MS-04
and MS-05 were intertwined (IT) for 5.8% of the event (59 s, ca. 1
min), making this the third longest behavioral duration for MS-
04 and the fourth longest for MS-05 (Table 2; Fig. 1A).
The remaining three behaviors (tongue flicks, topping
attempt, and topping) were abrupt, short duration behaviors (1
s). Consequently, we focused on the overall frequency of these
behaviors during the male-male combat event. Tongue flicks
were the most frequently observed behavior, with MS-04 and
MS-05 tongue flicking a total of 30 and 42 times, respectively.
During the combat event a combined total of 23 topping attempts
were displayed by both males. MS-04 displayed eight topping
attempts (34.8% of total attempts) and MS-05 displayed this
behavior 15 times (65.2% of total attempts). Of the eight topping
attempts by MS-04, only one was successful (12.5% success
rate), whereas male MS-05 was successful in topping (Fig. 1D,
E) on five of 15 attempts (33.3% success rate). Our observations
Table 2. Numeric summary of all observed behaviors by two male Sistrurus catenatus (MS-04 and MS-05) showing the frequency of each
behavior and the total and mean (SE) duration in seconds of each behavior displayed over the 1024 s video record of the male-male combat
event. The sum of all behavioral durations for each snake (excluding tongue flicks) equals 1024 s. Tongue flicks (TF) were displayed with other
behaviors and overlapped in duration.
Male MS-04 Male MS-05
Behavior (Code) Freq Total duration Mean duration Freq Total duration Mean duration
Tongue flicks (TF) 30 30 1.0 (0.0) 42 42 1.0 (0.0)
Intertwined (IT) 2 59 29.5 (27.5) 2 59 29.5 (27.5)
Disengaged (DE) 12 239 19.9 (2.2) 8 143 17.9 (3.3)
Raised (R) 2 52 26.0 (9.0) 7 137 19.6 (3.5)
Raised and engaged (RE) 32 665 20.8 (2.9) 32 665 20.8 (2.9)
Topping attempt (TA) 8 8 1.0 (0.0) 15 15 1.0 (0.0)
Topping (T) 1 1 1.0 (0.0) 5 5 1.0 (0.0)
Herpetological Review 53(3), 2022
from mate accompaniment to male-male combat to successful
copulation, suggests that male MS-04 (the male that initially
accompanied the female) was eventually displaced by male MS-
05 as a result of the combat event. The successful male (MS-05)
exhibited longer duration of raised behavior, shorter duration
of disengaged behavior, and higher frequencies of both topping
attempts, and successful toppings (Table 2).
Although male-male combat behavior in the genus Sistrurus
has previously been observed (Carpenter 1979; Shepard et al. 2003;
VanDeWalle 2005), our results offer the first detailed description
and analyses of the frequency and duration of the behaviors dis-
played during combat in free-ranging S. catenatus. Furthermore,
the consistent presence of the focal female (MS-01) throughout
the different stages of this event (e.g., Fig. 1B) and the observed
(ZEP) successful copulation between the winning male (MS-05)
and the focal female (MS-01) are novel observations for Sistrurus
combat. These extremely rare observations allowed us to not only
describe and quantify the observed combat behaviors, but more
importantly allowed us to compare the quantified behaviors of
the two competing males to ultimately identify how male MS-05’s
behavior during the combat event led to winning the combat and
successfully copulating with the female of interest (MS-01).
Similarities of body position, topping, and continuous posteri-
or body contact between the male-male combat of Sistrurus cate-
natus and S. miliarius (Carpenter 1979) were described by VanDe-
Walle (2005). We also observed these three behavioral similarities
in the combat of male S. catenatus. In addition, we identified an
intertwined behavior, which occurred uninterrupted for nearly
one minute. While intertwined behavior in male-male combat
events is not novel for all snake lineages (Carpenter and Ferguson
1977), this behavior has not been described for the genus Sistru-
rus. In addition, during our observed combat event S. catenatus
exhibited extensive bouts in which both snakes were raised, as
defined in our ethogram and shown in Fig. 1C. Such behavior
was reported as infrequent and of short duration for S. miliarius
(Carpenter 1979). This difference in the frequency and duration
of vertical body positioning in these two Sistrurus species could
be a species-specific attribute or the result of observations under
natural field conditions versus those in an artificial environment
and behavioral arena.
Our observations and analyses suggest that the successful
snake was more persistent and engaged in the combat confron-
tation. Specifically, our analysis supports the contention that the
longer duration of raised behavior, the shorter duration of disen-
gaged behavior, and the higher frequency and success of topping
attempts are the behaviors that appear to establish superior-
ity in crotaline male-male combat events (Carpenter et al. 1976;
Carpenter 1979; Gillingham et al. 1983). Additionally, previous
work on Viperidae combat (Madsen et al. 1993; Schuett 1997) has
shown that larger male snakes virtually always win combat events,
supporting our assertion that MS-05 (the victor) was the larger of
the two male massasaugas observed.
Observation of combat behavior by snakes is an opportunistic
event. Consequently, detailed behavioral descriptions and analy-
ses as performed here are particularly rare under natural field
conditions. Such behaviors have clear implications for reproduc-
tive success at both the individual and species levels, and detailed
analyses of combat behavior may prove useful in an evolutionary
context by allowing for potential phylogenetic comparisons with
regard to reproductive success and fitness (Schuett et al. 2001).
Acknowledgments.—We thank B. Scott Fiegel, B. Reich, and
B. Miller for field assistance, and we are indebted to James White-
house Sr. for his help in so many aspects of this project. We espe-
cially thank the landowners for permission to conduct research on
their properties. All research was approved by Institutional Animal
Care and Use Committee (IACUC) at Sam Houston State University
(protocol # 2021-1131) and The College of New Jersey (protocol #
1901-006HR1A1). Sampling was conducted under Pennsylvania Fish
and Boat Commission (PFBC) Scientific Collector’s permits (per-
mits #2021-01-003, 2021-01-0082, and 2021-01-0084). Funding and
resources were provided by the Department of Biological Sciences
at Sam Houston State University, the Department of Biology at The
College of New Jersey, a Sigma Xi Grant in Aid of Research, and the
Pennsylvania Fish and Boat Commission.
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Collected detailed behavioral observations over 7 yrs on a small population of adders (21–34 Ss) in southern Sweden in order to conduct a quantitative analysis of the behavioral determinants of male mating success. Results show that the number of matings obtained by a male adder was enhanced by higher male mobility, mate-finding ability, and ability to defeat rival males in combat bouts. In combination, variation among males in these 3 abilities accounted for 55% of the variation documented in male mating success. Male success rates in combat bouts were strongly dependent on body size (and hence, age), and reproductive tactics shifted concomitantly. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Courtship, mating and agonistic behavior in a freeliving population of adders, Vipera berus (L.)
andren, c. 1986. Courtship, mating and agonistic behavior in a freeliving population of adders, Vipera berus (L.). Amphibia-Reptilia 7:353-358.
Variation and evolution of stereotyped behavior in reptiles
carpenTer, c. c. 1979. A combat ritual between two male pygmy rattlesnakes (Sistrurus miliarius). Copeia 1979:638-642. ---. 1986. An inventory of combat rituals in snakes. Smithsonian Herpetol. Info. Ser. 1-18. ---, and g. W. Ferguson. 1977. Variation and evolution of stereotyped behavior in reptiles. In C. Gans and D. W. Tinkle (eds.), Biology of the Reptilia, Volume 7, pp. 335-555. Academic Press, New York, New York. ---, J. c. gillinghaM, and J. b. Murphy. 1976. The combat ritual of the rock rattlesnake (Crotalus lepidus). Copeia 1976:764-780.
Sistrurus catenatus (eastern massasauga). Mating activity
  • D Mauger
  • T P Wilson
Mauger, d., and T. p. Wilson. 2005. Sistrurus catenatus (eastern massasauga). Mating activity. Herpetol. Rev. 36:327-328.