Early on in this blog I did a report on the Peacock spider that dances and flashes his pretty colours to attract females. I have chosen to do another spider, the Jumping spider, who also dances but instead of colours he uses ‘hypnotism’. It’s not real hypnotism of course but the use of seismic vibrations to essentially mesmerise the female.

In a study conducted on a male jumping spider (Habronattus dossenus), the scientists found that in addition to the ornaments and movements, the males also use a complex repertoire of seismic signals for courtship. Virgin females were paired with either one of two males: they were either muted or non-muted. In this context the term ‘muted’ refers to unable to sense vibration.  

The results showed that females were significantly more likely to mate with a non-muted male to a muted one and that the latency to copulation, and the likely hood of cannibalism (the price for not putting on a good show), were both shorter in the non-muted males. This infers that the use of seismic vibrations is a critical component in the successful courtship of female H. dossenus.

References

Elias D. O, Hebets E. A, Hoy R. R & Mason A. C. (2005). Seismic signals are crucial for male mating success in a visual specialist jumping spider (Araneae: Salticidae). Animal Behaviour, 69(4), 931-938.

Unlike most courtship in animals, this week I have chosen an example where it is the female who courts the male. It is the courting behaviour of the Capuchin monkey.

A study was conducted on the tufted Capuchin monkey, Cebus apella, to observe their courtship and sexual behaviour. Courting typically takes place between a female and an alpha male. It starts as a one-way exchange by the females who court by trying to get the attention of the males. This only becomes a two-way exchange once the male is actively involved. Females will essentially conduct a hit and run approach on the males i.e. they will poke and/or grab parts of the male while he is not looking and then quickly run away. Quite often the male will ignore these advances at first or even get a little agitated. If the female eventually initiates a positive reaction from the male, he will reciprocate her advances with an eyebrow raise and then the mating will take place not long after.

More recently, studies on Capuchin monkeys in Brazil have shown that females in certain populations have resulted to throwing rocks at the males to get their attention. This could be a safety precaution as the males could be well known to be grumpy and throwing something at them from a distance is safer then actually grabbing them.

References

Carosi M & Visalberghi E. (2002). Analysis of tufted capuchin (Cebus apella) courtship and sexual behavior repertoire: Changes throughout the female cycle and female interindividual differences. American journal of physical anthropology, 118(1), 11-24.

It is often the case that males use their bright colours and strong presence to attract females and also to warn off other males. Male Augrabies flat lizards, Platysaurus broadleyi, have brightly coloured appendages that are used for both courtship and to deter other males. For courtship, males use visual cues for gender recognition and chemical cues for enticing females. If she permits close proximity then the male will use a tongue-flicking technique at her posterior end which is presumed to be in order to assess her reproductive viability. Males only use visual cues to present their masculinity to other males.

This system of honest signalling can be problematic for young males as gaining territory and proximity to females can be quite tough with other mature males around. Therefore some males employ a tactic known as female mimicry.

This involves delaying the onset of their colours, therefore their male appearance, to look like a female. This allows them to walk around other males with a decreased chance of getting into an altercation, as males can be very territorial, and get close to females without other males knowing. This can work as its mainly chemical cues that females use to assess the males.

There are limits to this adaptation though as the disguise only works in a visual sense. If these young males stay far enough away from other males they will be fine however if they stray too close, mature males will sense, through chemical cues, that they are males, not females, and therefore are more likely to frighten off or hurt the young males.

References

Whiting M. J, Webb J. K & Keogh J. S. (2009). Flat lizard female mimics use sexual deception in visual but not chemical signals. Proceedings of the Royal Society B: Biological Sciences, 276(1662), 1585-1591.

Frigatebirds are a family of seabirds which have a scope for strong sexual selection. This due to the striking ways that males attract females and that through observation in a study population, only 55% of males successfully obtained a mate. The species used for the study was the Magnificent frigatebird, Fregata magnificens.

When females are looking for a mate, they fly around male display sites and look for that bright red pouch being inflated by the males. This is the gular pouch that males present along with a drumming sound. When females are inspecting, males turn their body to makes their pouch look as big as possible and produce loud and deep drumming sounds. As it may be difficult for females to accurately assess the males due to height or the way the male is positioned, it was thought that there was a relationship between pouch size and the frequency of the drumming sound and that the pouch acts as some kind of resonance chamber.

69 males were assessed during their courtship, their pouch sizes noted, and their drumming sounds recorded for analysis. It was found that there was a negative correlation between the two variables. As the size of the pouch increased, the frequency of the drumming sound decreased thus providing evidence to support the hypothesis that the pouch acts as a resonance chamber. This correlation suggests that, as the females might not be able to accurately see the pouch size, the frequency of the drumming sound helps them get an idea and therefore helps them make their decision.

Reference

Madsen V, Balsby T. J, Dabelsteen T & Osorno J. L. (2004). Bimodal signaling of a sexually selected trait: gular pouch drumming in the magnificent frigatebird. The Condor, 106(1), 156-160.

One of the most remarkable animals in the animal kingdom is the Superb Lyrebird (Menura novaehollandiae). Its ability to mimic the sounds of a variety of species is nothing short of astonishing. The males use their vocal ability, along with their flashy tail, to attract potential mates. In fact, up to 70% of their vocalisations consist of imitations from up to 20 local species of bird.

It has been thought that females are impressed by the repertoire of sounds that a male can produce. This hypothesis does seem plausible in the case of M.  novaehollandiae as his repertoire is quite extensive however, for other species of bird, this is not the case. A new hypothesis is not how large a repertoire is but how accurate the mimicry of the sounds is.

A study from 2012 set out to test just how accurate the mimicry of M.  novaehollandiae is. They assessed the accuracy with which the lyrebird was able to imitate the complex song of the Grey shrike-thrush, Colluricincla harmonica. The accuracy of the imitation was found to be extremely strong and the only deviation came from the fewer amount of repetitions that were produced by the lyrebird. It was so accurate that it was able to fool the grey shrike-thrush itself.

This idea of accuracy being driven from female preferences has also been examined specifically and with the use of spectrograph cross-correlations, they were able to provide ample evidence to support this alternative hypothesis to the previous repertoire idea.

References

Coleman S. W, Patricelli G. L, Coyle B, Siani J & Borgia G. (2007). Female preferences drive the evolution of mimetic accuracy in male sexual displays. Biology Letters, 3(5), 463-466.

Dalziell A. H & Magrath R. D. (2012). Fooling the experts: accurate vocal mimicry in the song of the superb lyrebird, Menura novaehollandiae. .Animal Behaviour, 83(6), 1401-1410.

This week I am talking about an artistic fish that creates elaborate, and time consuming, pieces of artwork to impress and attract females. This artwork was discovered by divers in 1995 and it wasn’t until 2011 that scientists were able to say who or what created them. It was a small male puffer fish Torquigener sp.

Many marine animals are known to create nest sites on the seafloor however; the puffer fish creates unique characteristics not found anywhere else in the ocean. Radially aligned peaks and valleys that are created outside the actual nest site; the peaks are decorated with shells; and the sand is altered to create irregular patterns in the nest site itself. These patterns were created before mating and after a female has visited the site, they collapse. Females were found to evaluate the artwork and make their mate choice based on the nest construction, although what exactly they look for in a nest site is still unknown.

The specific patterns created provide more than just an aesthetic function. The radially aligned peaks that the fish constructs aids in providing lots of soft sand that can be deposited in the nest site.  The males flap their fins in order to dig up the sand and create the valleys and peaks. Also, due to fluid dynamics, and the construction of the outer nest, the sand that the fish stirs up will be propelled towards the centre of the nest and not outside it so the males efforts are not done in vain.

References

Kawase H, Okata Y & Ito K. (2013). Role of huge geometric circular structures in the reproduction of a marine pufferfish. Scientific reports, 3.

I thought I would do my first, but not my last, bird of paradise. Certainly one of the best cases of elaborate courtship displays and extreme sexual dimorphism. With so many birds to choose from, it was difficult to know where to start but I think I landed on a good bird to start with. The Twelve-Wired Bird of Paradise, Seleucidis melanoleuca.

In this dramatically sexually dimorphic species, the males, aside from being brightly coloured, has a set of highly modified display plumes and a pair of coral coloured legs and feet. This is in stark contrast to the females who are smaller and have a mixture of black and brown plumage.

As in real estate, courtship is all about location, location, location. Males begin the process by finding a bare, dead tree snag from which to display from. Once there he lets out three distinct vocalisations, two of which appear to be for advertisement and one is for the display. Once the female has arrived the real singing begins.

In company with the singing comes the dancing, holding the wings open to maximise display of his brilliant colours. This includes leg postures that better present his beautiful coral legs are one of two factors of the display that are unusual. The other gives the bird its name, the wire-wipe display.

During this, the male performs many slow and exaggerated body movements by hopping to this alterante foot postions, all the while pointing his wires towards the female so that he can, very delicately, brush them across her face which impresses her. The paper goes into great detail in explaining the whole process but its too much writing so I will just put a video up.

References
Frith C. B. & Beehler, B. M. (1997). Courtship and mating behaviour of the twelve-wired bird of paradise seleucidis melanoleuca. Emu, 97(2), 133-140.

It is often the case that sexual dimorphism in animals leaves the males more colourful and with extra appendages that are used to impress females. However this is not the case in socially monogamous birds, such as the Blue-footed Booby, Sula nebouxii.

Both male and female Blue-footed Booby’s both have brightly coloured blue feet used during courtship. The reasons behind the females having ornamental structures like the males have seldom been documented. In this case it is in the interest of both the females and males to have nice blue feet.

A study has found that the bluer and brighter a females feet, the more attractive she is to the males. Through an experiment of temporarily changing females feet to a duller shade of blue, scientists found that they received less intra- and extrapair courtship than the control females. They concluded that the blue colour of the feet is favoured by sexual selection through male preference.

In a similar study, the opposite was tested. Scientists found that the brightness of the males feet colour was related to the overall health of the bird. When deprived of food for 48hrs, the blue colour became duller as an indication of its ill health. This study also found that this had an influence on how much reproductive investment the female put in.  After the first egg was laid, the male responsible was taken and his feet were temporarily modified to appear duller and less attractive. In response females decreased the size of their second egg as their partner appeared to be in ill condition. They concluded that female Blue-footed Booby’s continually evaluate the health of their partners to determine the amount of their reproductive investment.

References

Torres R & Velando A. (2005). Male preference for female foot colour in the socially monogamous blue-footed booby, Sula nebouxii. Animal Behaviour, 69(1), 59-65.

Velando A, Beamonte-Barrientos R & Torres R. (2006). Pigment-based skin colour in the blue-footed booby: an honest signal of current condition used by females to adjust reproductive investment. Oecologia, 149(3), 535-542.

This week I will talk about animal that would not immediately come to most people’s minds when discussing elaborate courtship displays. It is the Peacock spider, Maratus volans.

Although male jumping spiders are known for being quite ornamented compared to the female, peacock spiders, which are endemic to Australia, are an exceptional example. When courting, a male peacock spider will display his brightly coloured opisthosomal flaps that usually stay tucked away around its abdomen. This will be waved around in synchrony with a pair of ornamental legs to impress the female.

A study on the courting behaviour of the male peacock spider however, has found that they employ a multi-modal signalling structure i.e. using multiple tactics when trying to impress. In particular the study showed that the males use visual cues and vibratory modalities in their display. As far as visual displays, certain behaviours were observed such as pedipalp flicker, opisthosomal bobbing, 3^rd leg wave, fan dance, fan-flapping, and pre-mount display.

These behaviours can be observed in the accompanying video where we see one of these amazing courtship displays taking place.

References

Girard MB, Kasumovic MM, Elias DO.2011. Multi-Modal Courtship in the Peacock Spider, Maratus volans. PLoS one 6(9): e25390.

Hey everyone

My name is David Clarke and I have decided to make the main topic of my blog sexual selection throughout the animal kingdom.  It will include many facets that include evolution, sexual dimorphism and the variety of mate finding behaviour that is utilised by different species. My plan is to give an example of sexual selection from a different species each week with information taken from the literature.

For this first post I thought, seeing as though this is an evolution class, I would start with an example from back in the Jurassic, which is also an example of a very simple way of attracting females (in animals), showing off your enlarged genitalia. In this instance it is an extinct insect in the order Mecoptera that existed in the late Middle Jurassic.

Scientists discovered the fossils of two, now new, genera of scorpionfly in the Jiulongshan formation at Daohugou village Ningcheng County in Inner Mongolia, China. Through examinations of the specimens they found that, although similar in size to other Mecopterans in the same era, these new specimens, Miriholcorpa forcipata (Figure 1) and Fortiholcorpa paradoxa (Figure 2) had enlarged male genitalia and extremely long and extended terminal abdominal segments.

The scientists proposed an evolutionary scenario in which these abdominal segments were used to intimidate/compete with other males and/or were used to attract females by showing off their large “penis”. Having these large abdominal segments and  enlarged genitalia could be seen to be quite a burden to carry around however as  they were alive for quite a while  it is thought that the sexual selection and display of these characteristics outweighed the possible poor mobility and bulky body plan in the evolutionary process.

Figure 1 - Photograph and line drawing showing abdominal segments on Miriholcorpa forcipata   Figure 2 - Photograph and line drawing showing abdominal segments in Fortiholcorpa paradoxa  References

ANG, Q., SHIH, C. & REN, D. 2013. The Earliest Case of Extreme Sexual Display with Exaggerated Male Organs by Two Middle Jurassic Mecopterans. PloS one, 8, e71378.