Rabu, 27 Maret 2013

Female Monogamy and Male Competition in Photinus collustrans

Female Photinus collustrans live in burrows and stay in close proximity to them throughout their adult life. Females live approximately 10 days and are sexually active for only about 18 minutes each night starting around 20 minutes after sunset. A female's complete mating history can easily be recorded because of the regularity of these habits, the specificity of her location, and this short span of time in which her matings occur.
This study indicates that most females mate only once in their life, which limits male prospects for mating. Competition among males for mating opportunities has led to the development of a series of male tactics to increase female susceptibility to mate more than once.


Of the 108 females studied, 104 mated only once. Typically, a female appears by her burrow each night until she attracts a male. The male lands nearby and walks towards her. When he has made contact, he climbs on top of her to mate. Copulation lasts about one minute, after which the male flies away in search of another female. After mating, the female usually paused, either briefly or for several minutes, during which time she did not respond to other males. She then reentered her burrow.
Of the four females that mated more than once, one female was forcibly dug from her burrow by another male; one was mated by what will be described as a "sneaky" male; and two females simply made themselves available on subsequent nights to respond to another mate.
Male tactics for mating
When two males were attracted to the same female, the first to reach her mated with her. The second, or rival male, also mounted her and attempted to break the pair apart. In these instances, the first male remained joined to the female for an extended period of time so as not to let the rival disturb their mating, even to the point of being dragged behind the female as she reentered her burrow. At this point the male would disengage from the female and fly away. The rival male often tried to dig the female out of her burrow to also mate with her. In one case observed, the rival male was successful and did mate with the female.

Some rival males tried a different, "sneaky" tactic. The "sneaky" male did not try to dislodge the mating male, but tapped the pair with his antennae, walked away, and returned to tap them again. The original mating male did not remain attached to the female for an extended time, but flew off immediately after mating. The "sneaky" male then mated with the female when she paused before reentering her burrow.


Because females are difficult to locate and are available for such a short period of time each night, males quickly leave the female after mating and fly off in search of another female.
The female rests for a short period of time before reentering her burrow. During this rest period, she does not respond to flashes of other males. If, however, another male can gain access to her, he can successfully mate.
Rival males may gain access to the female by forcibly prying the female and her mate apart, mounting her during her post-mating rest period, or digging her out of her burrow.
To prevent being prematurely separated from the female, the first mating male will stay attached to the female for an extended period of time, often being dragged by her into her burrow. While he is still attached, the rival male cannot mate with her.
The "sneaky male" circumvents that mate-guarding behavior by not interfering with the mating, and instead waits to mount the female after the first male flies off in search of another mate.
While the number of times that males encounter rivals will vary with the number of males in a given area, the rare occurrence of females mating more than once has led to these male strategies for both increasing multiple matings and counter-strategies for preventing matings by their rivals.

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