NOTES 
Courtship Behavior of the Lined Shore Crab, 
Pachygrapsus eras sipes Randall 
Richard V. Bovbjerg 1 
In his definitive monograph on the biology 
of the lined shore crab of the Pacific, an im- 
portant member of the high intertidal com- 
munity and useful to physiologists, Hiatt 
( 1948) describes the copulation pattern of this 
species from repeated observations. Having seen 
little preliminary activity, he precludes exten- 
sive prenuptial behavior. On the basis of several 
observations of courtship behavior in this 
species that I have made, the opportunity to 
extend Hiatt’s data prompts this note. 
These observations were made on crabs kept 
in laboratory bowls in the course of ecological 
work to be reported elsewhere. The following 
sequence is typical of this courtship behavior. 2 
The pattern is overtly initiated by the male’s 
approaching a female in a threat posture with 
chelae extended. However, this is not followed 
by the usual strike. The female is instead pushed 
— one is tempted to say, gently — with the chelae 
flexed horizontally. The female reaction to this 
gesture is a deliberate retreat, in which she is 
closely followed by the male. Lateral movements 
by the female are countered by the male, in a 
manner which may best be described as herding. 
This initial phase may end in a radical escape 
movement by the female, and as such is identical 
to a male-to-male herding activity by the more 
dominant individual. This first phase may last 
from less than a minute to several minutes. 
If the female is acceptant, the second phase 
is marked by the cessation of herding and a 
1 Department of Zoology, State University of Iowa, 
Iowa City. Manuscript received November 13, 1958. 
2 Dr. Richard A. Boolootian, Department of Zool- 
ogy, University of California at Los Angeles, personal 
communication, has observed at least some aspects of 
this behavior and has recorded these in some of his 
motion picture studies. 
retreat by the male, closely followed by the fe- 
male. The tempo of movement increases as the 
activity becomes a courtship dance. The pair 
moves in complete synchrony, chelae to chelae 
but not grasping. The movements are of two 
sorts: a forward and backward as well as lateral 
walking, and a lateral swaying movement of 
the body without walking. The intensity and 
synchrony increase for a period up to a minute 
or two. This phase is culminated during a back- 
ward movement by the male as he rolls onto 
his back with the female walking over him in 
the characteristic dorsal copulatory position of 
the female described by Hiatt (1948). 
Sexual harmony is the striking product of 
this behavior; in the courtship activities the 
male at no time forcibly holds the female, nor 
(in corroboration of Hiatt’s observations) is 
there aggressive grasping during copulation. 
However, the initial phase is definitely a type 
of male aggression and may end in a strike or 
a fight. In like manner, the postcopulatory male 
behavior may return to the aggressive pattern. 
While some pairs separate and proceed inde- 
pendently, in others only one partner is re- 
leased from the sexual sequence. In one instance 
the female escaped following copulation and 
the male transferred immediately to a second fe- 
male. Conversely, another copulation ended 
with the female still in the following sequence 
and the male returning to the aggressive role 
with a violent strike at the female. This close 
relationship between sexual and aggressive be- 
havior would seem to be characteristic of many 
decapod crustaceans (Andrews, 1895; Chidester, 
1911; Crane, 1941; Bovbjerg, 1946) and indeed 
of many vertebrates. 
No investigation was made of the cues in- 
volved, though Hiatt (1948) notes sexual be- 
421 
