On Earth Beat this week we nose around in our social environments. We want to know how many friends we should have and whether the virtual ones are as loyal as the offline ones. Plus online addicts, psycho beetles and everything in the ocean.

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How many friends do we need?
Anthropologist Robin Dunbar joins Marnie to explain Dunbar’s number; the 150 friends we need to function in society. Research suggests we are incapable of making more meaningful friendships than this. Robin says if you have fewer than this, don’t worry, you can count your family and you don’t need to even like all 150.
 
Hal’s Facebook friends
Writer Hal Niedzviecki wanted to put real vs virtual to the test: he decided to throw a party for all 700 of his Facebook friends when real ones were suddenly scarce.

Online suicide
This isn’t about killing yourself. Just your virtual connections. Dutchman Walter Langelaar developed a computer programme - Web 2.0 Suicide Machine - which allows users to delete themselves at the click of a mouse. This video shows how it works:

A couch, fresh air and a goat
Studies show that up to 20 percent of internet users between the ages of 18 and 28 are addicted to being online. One of the co-founders of the reStart Internet Addiction Recovery Program, Hilarie Cash, joins Marnie to discuss how a mix of good old therapy, the great outdoors and bonding with animals can offer the cure.

Reputation Defender
How do you protect your virtual profile? California-based company Reputation Defender says you need to call in the professionals to stop your details and reputation being used and abused on the online environment.

Psycho killer beetles
David Dunn is a composer. Richard Hofstetter is a beetle expert. They have joined forces to study a voracious pest, the bark beetle, which is destroying North America's pine forests. They have discovered that playing certain beetle noises back to the beetles sends them into a murderous frenzy and that this carnage could be used to control the pest’s population.

Bird scaring
Tourists are drawn to South East Peru by the exciting birdlife. However, their chatter is stressing the birds out. Stanford graduate Daniel Karp explored what our noise is doing to the local birds.

Census of Marine Life
Professor Carlo Heip, director of the Royal Netherlands Institute for Sea Research explains the importance of this 10 year global research program, which set out to answer the question "what lives in the sea"? The census results have just been published. Read a report on the census results.