Love gifts in the animal kingdom

By Ella DaviesReporter, BBC Nature

On Valentine's day, what beau could possibly resist a hand-picked gift, wrapped in perfumed silk?

Certainly not female Paratrechalea ornata spiders, according to research by Dr Luiz Costa-Schmidt, an arachnid expert studying in Brazil.

Male spiders of this south-American species incorporate a chemical known as a pheromone into their silk gift wrap. This encourages females to accept them as mates.

Using a present, or "nuptial gift", to ensure a sexual engagement is a practice found throughout the animal kingdom but it can be startlingly different from our human perception of courtship.

Here are some of the weird array of presents that animals give to potential mates.

Perfumed package

P. ornata are not the only spiders to give gifts to their intended: the male nursery web spider (Pisaura mirabilis), commonly found in European grass meadows, also wraps offerings in silk.

With this presentation, however, all is not as it seems. The males do not always wrap up enticing morsels of prey for their mates.

Instead, beguiling packaging can disguise a multitude of disappointing items - from dried-out ant husks to worthless bits of plant.

"If a male finds a receptive female, but [he] doesn't have prey at that moment, any object could be easily be wrapped in silk to be offered," explains Pedro Ere Disconzi Brum, another member of the Brazilian research team.

"This may be a crucial step for this male to be chosen by the female in the early steps of the courtship process."

Moreover, Mr Brum explains, if the male is in poor condition, he can catch prey for himself and wrap up the leftovers to gain the attention of a mate.

http://www.bbc.co.uk/nature/16987410

How Male Spiders Use Eavesdropping to One-Up Their Rivals

ScienceDaily (Jan. 4, 2012) — Researchers have made a new discovery into the complex world of spiders that reflects what some might perceive as similar behavior in human society. As male wolf spiders go searching for a mate, it appears they eavesdrop, match and even try to outdo the mating dances of their successful rivals, a behavior seen mainly in vertebrate animals.

The study co-authored by David Clark, a professor of biology at Alma College; J. Andrew Roberts, an associate professor in the department of evolution, ecology and organismal biology at The Ohio State University at Newark; and George W. Uetz, a professor of biological sciences at the University of Cincinnati; is published this month in Biology Letters, a journal of the Royal Society of London.

"Eavesdropping on the communication of others is widespread among animals and often serves as a means of obtaining information. For example, studies of birds, mammals and fish have shown that male bystanders observing male-male contests can learn about the strengths of potential opponents, while female observers may copy the mate choices of others," says Clark, the lead author and co-investigator on the study. "This new discovery shows that male wolf spiders also eavesdrop on the visualsignals of courting males."

Read more at:  http://www.sciencedaily.com/releases/2012/01/120104115055.htm

Stag tries to impress the ladies with grass wig

Stags often go to great lengths to attract a female - but it moss have been love for one male who slipped on a grass wig to impress potential mates.
The stag was seem wandering alone for days in Richmond Park before it dived into a lake and came out with a grassy mop resting between its antlers.
After letting out a mating call he emerged from the water to find two females waiting for him.
Unfortunately, he also attracted the attention of another stag, who he had to fight off before strolling away with the two females in tow.
The incident was witnessed by keen photographer Robert Piper, 55, who couldn't believe his eyes as the extraordinary events unfolded.
He told the Daily Mail: 'Sometimes the stags adorn themselves with bracken to impress the females - and it must somehow strike a chord.
'But the head gear can also attract other stags and on occasions will end up with a fight exactly like what happened here.
'This stag did find a female but keeping her was another matter because other stags became jealous and tried to fight him.
'But he fought them off and eventually had two deer following him around.'

Read more: http://www.metro.co.uk/weird/879771-stag-tries-to-impress-the-ladies-with-grass-wig#ixzz1btEXzLpS

Scientists might have explained promiscuous behaviour

Scientists have shown that inbreeding can lead to female promiscuity.

The team, which reports its findings in the journal Science, witnessed a change in mating behaviour when they bred female flour beetles with their close relatives.

The researchers suspect that promiscuous females are avoiding the ill-effects of inbreeding by exposing themselves to a larger pool of sperm.

The results help explain why females of some species mate with several males.

For females, sex can be traumatic. In some insects, insemination involves wounding females and infecting them with dangerous microbes. In many other species, mating reduces females' lifespans.

Given that in most species, a single mating is generally enough to fertilise all a female's eggs, she has little incentive to mate again. And yet in many species, females mate multiple times with different males.

The new results help evolutionary biologists explain this perplexing phenomenon.

Driving extinction
By driving a population of flour beetles, Tribolium castaneum, to the brink of extinction, and then allowing their numbers to recover from a few individuals, the researchers at the University of East Anglia (UEA) created highly inbred populations.

The researchers found that females in these inbred populations were more eager to mate than those that had not been forced through a bottleneck.

Attempting to explain why unbridled mating was on the increase, the researchers went on to show that inbred females left twice as many descendents as those that mated with just one male.

"It is quite easy to imagine how promiscuity could spread through the population if [promiscuous females] leave more descendents," explained UEA evolutionary biologist Matthew Gage.

When a population is inbred, the chances of mating with a genetically similar male are heightened, so hedging your bets and mating with more suitors is a sensible strategy, he explained.

Dr Gage suspects that promiscuous females amass a large pool of sperm, and select ones that are more genetically dissimilar to them to fertilise their eggs. Mating with more males gives females a larger range of sperm from which to select.

However, Dr Gage warned that he and his colleagues might not have witnessed "the evolution" of a new mating behaviour.

Rather than changing genetically, he explained, the females might simply have been adjusting their behaviour to their new environmental conditions.

Dr Gage and his team are now looking into this.

By Jennifer Carpenter Science reporter, BBC News
http://www.bbc.co.uk/news/science-environment-15002277