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Faking death to avoid male coercion:
extreme sexual conflict resolution in a
dragonfly
I spent the summers of 2014 and 2015 in the Swiss Alps,
collecting the eggs of odonates (dragonflies and damsel-
flies) for laboratory experiments on larval responses to
temperature. This involved many hours spent waiting
beside ponds to capture females as they came to the water
to lay eggs. On 5 July 2015, while I was waiting at a pond
near Arosa, at about 2000 m elevation, I witnessed a drag-
onfly dive to the ground while being pursued by another
dragonfly. I grabbed my camera and started filming
(Video S1). As I approached the two insects, I realized
that they were Aeshna juncea (moorland hawker or sedge
darner), that the individual that crashed was a female,
and that she was lying motionless and upside down on
the ground. Upside down is an atypical posture for a
dragonfly. The male hovered above the female for a
couple seconds and then left. I expected that the female
could be unconscious or even dead after her crash landing,
but she surprised me by flying away quickly as I
approached. The question arose: did she just trick that
male? Did she fake death to avoid male harassment? If
so, this would be the first record of sexual death feigning
in odonates and probably the fifth in the animal kingdom
after a nuptial gift- giving spider (Bilde et al. 2006, Hansen
et al. 2008), two species of robber fly (Dennis and Lavigne
1976), and a European mantis (Lawrence 1992). Kaiser
(1985) described motionless hiding by females in another
dragonfly (A. cyanea; blue hawker), but did not indicate
that they were faking death. I also wondered how common
this behavior might be. The observation near Arosa
prompted me to remember several other instances during
the previous season in which I had seen dragonflies diving
into the ground or vegetation. Aeshna juncea is common
at each of the ponds where those observations occurred;
could sexual death feigning occur regularly in this species?
To answer these questions, I studied the reproductive
behavior of A. juncea for 72 h in July and August 2015 at
two sites (the Arosa pond, 46.80°N, 9.67°E and another
pond near Lenzerheide, 46.73°N, 9.55°E) from 10:00 to
16:00. In both ponds, the bank vegetation, where most
egg laying takes place, was relatively dense with most
patches not exceeding 60 cm height. As for many other
dragonflies, the female reproductive episode of the
moorland hawker may be divided into four important
sequential events: female arrival at reproductive site, cop-
ulation, oviposition, and departure from reproductive site.
To summarize, mature males remained close to the water
waiting for females. When the female came to the pond,
the male intercepted her in the air and both formed the
copulatory wheel. Copulation took place near the pond,
often perched on a plant support (Fig. 1a). After copu-
lation, the male detached himself from the female and flew
away. The female laid eggs (oviposition) solitarily without
male protection (Fig. 1b), unlike many other dragonflies
(Corbet 1999). Female became vulnerable to male coercion
at that time because conspecific males were constantly
patrolling each corner of the pond looking for a mate. To
overcome this pressure, females showed both preventive
and protective behavioral strategies to avoid coercion
during oviposition and departure from reproductive sites.
To reveal potential preventive behavioral strategies of
females, I estimated the vegetation density (percentage
of 1 m2 water area covered by vegetation) around ovi-
position sites of 56 and 46 ovipositing females during five
days in Arosa and Lenzerheide, respectively (Appendix
S1). I hypothesized that females choose sheltered areas
Ecology, 0(0), 2017, pp. 1–3
© 2017 by the Ecological Society of America
The Scientific Naturalist
Fig. 1. Moorland hawker (Aeshna juncea). (a) Reproductive pair; (b) oviposition of a single female.
2Ecology, Vol. 0, No. 0
of the pond to reduce its visibility to coercive males. On
average, females laid eggs in sites with high vegetation
density of 70.9% in Arosa (n = 56) and 69.2% in
Lenzerheide (n = 46). I conducted an experiment in which
I reduced male density by ≥50% in the two sites during
one day (Appendix S1), which reduced of the average
density of oviposition sites in vegetation (Appendix S1:
Fig. S1a) and decreased the number of male coercion
events (Appendix S1: Fig. S1b). These results suggest that
males shape habitat selection of females, and thus the
occupancy of densely vegetated parts of the pond during
oviposition could be a behavior to reduce male coercion.
To assess the protective behavioral strategies of females
during coercion, I assessed female behavior during
departure from the reproductive site, which is probably
the phase where the female is most vulnerable to coercion.
Fig. 2 illustrates behavioral responses of females to male
coercion after oviposition and Appendix S1: Table S1
presents the respective statistics for both sites. When the
female tried to leave the oviposition site, males always
chased her on the air. Females (n = 35) usually crashed
on the ground (88.6%, n = 31), and rarely kept flying
(11.4%, n = 4; chi- square test, P < 0.0001; Appendix S1:
Table S1). Females who did not crash to the ground or
vegetation were all intercepted by a male. Females crash-
landed (n = 31) more often within vegetation such as
bushes and dense grasses (71%, n = 22), than on open
areas on the ground (29%, n = 9; chi- square test, P = 0.02).
Following the crash, death feigning was observed in 27
out of 31 cases (87%). Of the 27 motionless females, 21
(77.7%) were successful in deceiving the coercive male.
The high frequency of sexual death feigning in both sites
suggests that this behavior is common for the species. In
addition, that males could not detect the motionless
females highlights the importance of movement for males
to detect females, which is the case for many odonates
(e.g., Bick and Bick 1961, Ubukata 1984).
To test whether females are sensitive to touching
during death feigning, I performed an experiment in early
August 2015 at Arosa pond in which I attempted to catch
by hand females performing death feigning after male
harassment. Usually, it is impossible to catch an active
dragonfly by hand because they rapidly escape. Of 31
catching attempts, 27 females successfully escaped (87%).
Therefore, when females display death feigning they are
perfectly conscious and readily avoid disturbance and
probably predators.
So how did sexual death feigning evolve? On one hand,
this behavior could have resulted from exaptation. Since
death feigning already exists in the behavioral repertoire of
dragonflies (Corbet 1999), females of the moorland hawker
expanded the use of this antipredatory function to avoid
male coercion. On the other hand, the origin of this exap-
tation is probably sexual conflict where each sex adopts
reproductive strategies that best serve its own survival and
reproductive success (Parker 1979). The mating system of
the moorland hawker is predisposed to sexual conflict
because the vulnerability of solitary oviposition, the fitness
costs of male harassment (Rice 1996, Crudgington and
Siva- Jothy 2000), and the highly male- biased sex ratio in
oviposition sites (Wildermuth 1993) put the females under
extreme reproductive conditions that require effective
Fig. 2. Death feigning of female (in red) against male (in blue) coercion of the moorland hawker (Aeshna juncea). Numbers refer
to the succession of the events. Numbers in black and white are males and females, respectively. When the female leaves oviposition
site (red 1), a male usually chases her (blue 1), which induces the female to flee (red 2). The female either keep flying or crash on the
ground or vegetation (red 3). She performs death feigning right after crashing (red 4) while the male is searching for her (blue 2). The
male does not detect the female and leaves the crashing area (blue 3). The female, knowing that she is no longer coerced, flies away
(red 5).
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THE SCIENTIFIC NATURALIST
behavioral responses to overcome survival and repro-
ductive costs. Thus, females that perform death feigning
probably undergo less coercion, survive longer and produce
more offspring, hypotheses that warrant testing.
Sexual death feigning is one of the rarest behaviors in
nature, and due to its scarcity, it has received little attention
in behavioral ecology. Currently, it is restricted only to
arthropods. It would be interesting to know whether this
scarcity is true or just an artefact related to the lack of
behavioral investigations or difficulty in detecting this
behavior. Further studies should investigate how wide-
spread sexual death feigning is among arthropods and
whether it occurs in other phyla. Moreover, it is time to
develop an informative classification for death feigning
behavior that takes into account both behavioral and
physiological information because death feigning could
be strictly behavioral in which the animal is conscious and
sensitive to touching and handling (moorland hawk-
er- like), but could also include physiological changes
where the animal is “unconscious,” physiologically shut
down and unresponsive to physical contact (opos-
sum- like). Finally, the new case of sexual death feigning
reported here demonstrates discoveries even in common
species and well- studied areas of the world remain.
Although the diversity of sizes, shapes, structures and col-
orations of organisms on earth is astonishingly high, the
diversity of behaviors might be surprisingly comparable.
Acknowledgments
Funded by the Swiss Government Scholarship for Excellence
2013.0051 and a Forschungskredit der Universität Zürich (Nr.
FK- 16- 087). Thanks to Brad Taylor and John Pastor for helpful
comments on the manuscript. I am grateful to Gregory
Goldsmith, Josh Van Buskirk, and the Lukas Keller group for
constructive discussion and advice.
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rAssim kheliFA
Department of Evolutionary Biology and Environmental Studies,
University of Zurich
Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
E-mail: rassimkhelifa@gmail.com
Manuscript received 2 November 2016; revised 24 January
2017; accepted 30 January 2017. Corresponding Editor: John
Pastor.
Additional supporting information may be found in the
online version of this article at http://onlinelibrary.wiley.com/
doi/10.1002/ecy.1781/suppinfo