Courtship Behavior of Spiders
The next time you take a date to the movies you may want to consider opting for an extra large popcorn, or else risk getting walked out on -- or worse, eaten! This may seem like a ludicrously unlikely scenario from a human perspective, but a male spider of the Pisauridae family would not be laughing. Research conducted at the Institute of Botany & Zoology in Masaryk University in the Czech Republic and the Department of Ecology & Genetics in Aarhus University in Denmark has delved into the courtship behavior of spiders of the family/genus Pisaura mirabilis (see cite 1). The research focused on the conditions that determine whether a female spider will mate or not. When presented with an offering of an egg sac, unwrapped fly, or a wrapped fly, the female's behavioral response was observed. It was hypothesized that the female's preoccupation with the egg sac may distract her into mating. It was opposingly proposed that the female may focus her attention on eating while mating takes place.
The experiment involved the pairing of each male spider in the study with one of three food offerings: an egg sac, an unwrapped fly, and a wrapped fly. Male spiders were then paired with female spiders, and presented their offerings. The condition of the females fell into four different categories: starved or well fed, and lacking in mating experience or experienced. Male spiders with one of the three varieties of offerings were paired with each of the four varieties of females. The investigators found that the majority of females showed no preference for food type. It would appear that motherly care on behalf of the female plays little role in her decision to eat the egg sac. The female’s desire to eat did play a role in her behavior, as starved females stole or accepted the food more quickly than fed females.
What of the instances when females are compelled to devour males? Bilde and his co-investigators concluded that as a result of females eating males during mating attempts, male food giving is selected for. The researchers further reference Randy Thornhill, who incorporating Trivers, states:
“ ..It is the relative parental investment of the sexes in their offspring that controls the operation of sexual selection. In most species a female’s investment per offspring greatly exceeds that of the male” (Thornhill 1976 on Trivers 1972).
In light of this hypothesis, it would seem appropriate that male behavior would change given the desire of the females to eat. Males that did not offer food were selected against and likely eaten, while males that offered a meal and distracted the female were more likely to be spared during mating (and thereby able to spread their “giving” genes) (Bilde). The take home message is that, along with protection, it would behoove all of us to bring an extra candy bar along …just in case.
Buabbud6 and defuria6 both included that the act of the female eating the male is not restricted to this species of spider (or only spiders for that matter). Defuria6 brought up the example of the praying mantis, a non-spider species which often exhibits eating of the male during mating. Buabbud6 offered a profound statement, "what hurts more to a spider, rejection, or death?". Across these species it seems that some "risks" are taken on behalf of the male in order to obtain mating attempts. Some of the evidence would suggest that mating is important enough to risk one's life. Additionally, the low occurance of male killing (in the spider) may be outwieghed by the advantages of mating and spreading ones genes (Blide and co-authors). Chances are that a male will not be killed during a mating attempt. Thus, it is probably in the male's favor to take the risk.
Alvarez6 asked," is there another way for the male to avoid being eaten or left behind?". Discussed in the article is the concept of thanatosis (faking death). The male, when presenting the food offering, will sometimes "fake" being dead in order to avoid provoking the female. This tactic may result in the survival of many males who would otherwise be noticed and eaten.
Posted by AKE(2)
(cite 1.) Trine Bilde, Christina Tuni, Rehab Elsayed, Stano Pekar, Soren Toft
Institute of Botany & Zoology, Masaryk University, Czech Republic
Department of Ecology & Genetics, Aarhus University Denmark
Animal Behaviour, Volume 73, Issue 2, February 2007, pages 267-273: Nuptial gifts of male spiders: sensory exploitation of the female's maternal care instinct or foraging motivation?
Randy Thornhill
The American Naturalist, Volume 110, No. 974, Juy- August 1976: Sexual Selection and Nuptial Feeding Behavior in Bittacus Apicalis (Insecta: Mecoptera)
posted by PWH @ 9:54 PM
13 comments
13 Comments:
This is quite an interesting and relevant insight into the subject of mating in different species. Evolutionarily, mating is probably the most important aspect of survival, seeing as genes cannot be passed on if no fertilization occurs. On the other hand, what is also important is that once the mating does occur, whether or not the offspring be capable of survival. Mating is one way for that question to be answered. As a female spider, it is important to mate with a worthy male whose genes will endow the offspring with survival. So if the male is not capable of providing food, another large aspect of survival and evolution (one cannot live if he or she starves), or is not clever enough to create the right distraction for a female, then his genes are not worth passing on after all of the work that the female does. In a world with numerous spiders, to a starving female, such a useless male is probably looking mighty tasty. Interesting research, not extremely different from other animal mating rituals save for the cannibalism, where in most the male is simply rejected. But what hurts more to a spider, rejection, or death?
I thought this entry was really interesting. It demonstrates the theory of selection that we are learning about in a very real and understandable example. If your method is not to offer food then you might get eaten and those genes will not be passed on. I know that different adaptations are very important in the mating of different animals so it was fun to learn about spiders. I also thought the tone with which the entry was written was very entertaining, laid back, and made it more fun to read.
- colesk5
It would be interesting to see how this behavior developed. Why can't it just be the male cohort's job to supply nourishment for the female? In addition, it would be interesting to observe if males resist or just give in. Over than just hunger, is the size of the male one factor which may come into the female spider's mind when deciding to eat its partner?
This entry discusses a fascinating topic. It gives an insight into how female spiders, in their own way, are looking out for their offspring. By allowing only the males who are able to provide food to survive, they are improving the odds that their offspring will have enough to live off of. Also, the genes that are being passed on include the ones of a male who knew how to search for and find food. I would find it interesting to discover if the provision of food is all that the female spider looks for or if there is any other qualities that she uses to determine whether or not to eat her mate. Also, if the female is full when she is approached by a male, will she still eat him or simply ignore him if he tries to present her with a gift or if he does not have one? I think that this post is very well written as it is informative while still keeping the reader interested.
-doylea6
This was an entertaining article to read because its content and the way it was composed. Its interesting to read about the different mating techniques of species. I was curious to know if there would be a different reaction by the female if perhaps a different kind of spider were to come along and perhaps not offer food. Besides food, is there another way for the male to avoid being eaten or left behind? I guess it would be safe to say that the males would suffer a lot if there were a food shortage.
alvarez6
I thought this article was written quite cleverly. The human to spider scenario right from the beginning had caught my attention. I am an extreme arachnophobic so i had never really thought about spiders mating rituals. I never knew that male spiders brought food to their female companion in order to win her over. I was confused however. It stated that in the experiment the male spiders that had brought food along were less likely to be devoured themselves, but then again, some were eaten. When a female eats a male spider, is that a way of showing them that she isn't interested or is it just something they do because they are hungry?
This is very interesting, but at the same time, not too surprising. Mating and reproducing takes a lot of energy. If a male cannot supply the goods then he becomes the goods. It was interesting that regardless of whether the females were well fed or starving, they all ate the food offering. It gives me the impression that this is a behavioral expectation for the males. If males don't bring an offering, that could be a sign that they aren't strong enough to feel more than one spider. In this case, killing the male would prevent these "weak genes" from proliferating. Anyway, I think it's great, the female spiders are keeping chivalry alive.
I have always found spiders to be interesting. Throughout history, nature has always had a way to bring out the best in a species. Most of the time, if an organism isn't fit for survival, their life will be short because of preditors, poor survival skills, or just lack the physical capability to handle the enviroment. In this case, it is interesting because instead of the spiders dying from situations listed above, their own kind gets rid of them if they are not worthy of survival. In this case, not bringing an overing of food to the female defines not worhty of survival.
It's important to look at other species mating habits to appreciate our own. Think if female humans ate their companion male humans. This would cause a plethora of problems. Many types of insects use this behavior. One example that comes to mind is the praying mantis. Why does the female eat regardless of being hungry or not. I agree with caseyl6's reasoning on the matter, because it would make sense for the weak genes to be taken out. Courtship does prove to be an interesting topic among animal species.
This is quite an interesting article and its interesting to point out that other insect species and arachnids share similar mating patterns. There are many species of spiders and insect where the male gets eaten or his head bit off and so what influences this outcome is certainly interesting. I think I would like to find out more about this in relation to these other species. This article was well written and certainly caught my eye. It's an interesting article for the casual reader and keeps one interested and entertained.
Robert Carmona
I believe that the courtship behavior of all species is quite interesting and spectacular. I think the spider is even more fascinating in the fact that is the women that gets to dominate over her male companion. I think that the idea of gift giving from a male to a female in order to win her over is also intriguing. Actually being able to read and understand research and stuides that have been done in this field is also quite interesting to see these things in action. From a woman's point of view is interesting the difference in sexual role reversal in other species when it comes to mating and the need for sexual preference by females to ensure that their offspring are given the best genes possible.
I knew that many times female spiders devoured their mates but I did not know that there were instinces where the males would offer food. It makes sense, however. I found it interesting how an egg sack could be offered as food. Like others have commented, I would also like to know how something like this might have evolved.
I found your blog particularly interesting.You had a very good and strong introduction on this subject. I wounder if the femaler would react differently in the presence of another spider that is smaller and/or a tiny bit larger then its size?
Mike
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