Their destructive and unpredictable behaviour during the annual May to June mating season is always highly problematic for the Japanese capital. But this year the aggressive ink-black birds have created a new headache by developing a seemingly insatiable taste for fibre-optic internet cable.

Tokyo has become a victim of its own rush to go broadband. In the past six weeks, hundreds of homes and offices have reportedly been left without high-speed internet service after the crows discovered that broadband cable can be pecked into usable strips more easily than power cables or telephone copper wire ever could. Crows have discovered that the broadband cables, which are strung from telegraph poles across Tokyo, are the perfect consistency for building nests.

The thieving nature of Japan’s crows is well known — in the less technologically advanced days before fibre- optic cable was available, the birds regularly fashioned nests from stolen metal coat-hangers or even car windscreen wipers.

Although their appetite for fibre-optic cable was spotted last year, broadband service providers, including NTT and Tepco, have begun reporting a sharp surge in instances of cable-pecking, in line with the rising population of crows. Engineers called out to repair crow-ravaged cables say that the centre of destruction is generally around junction boxes, where an average of 30 cables meet and provide rich pickings.

The birds’ behaviour exacerbates Tokyo’s miserable experience with crows — fearsome, intelligent 60cm-long (nearly 2ft) creatures that are drawn to the capital because of the large quantities of discarded food available. Every year there are reports of attacks on domestic pets or very small children as the birds’ jungle instincts take over and they sense their nesting grounds are being attacked.

The destruction of the fibre-optic cable highlights the abject failure of a “war on crows” declared five years ago by Tokyo’s Metropolitan Governor, Shintaro Ishihara. Fifteen years ago Tokyo had a crow population of around 7,000; today it is estimated at around 33,000.

Members of the public are forbidden from taking the battle into their own hands so the Governor arranged for a professional team to take on the challenge. An initial burst of activity involving a network of traps around the city and a squadron of experienced crow-catchers met with success, with about 11,000 crows captured.

Unfortunately, crows from the countryside around Tokyo flew in to replace their ensnared comrades, and the population remained constant.

Scientists have suggested that the birds might have started pecking at the fibre- optic cables as a form of mating- season stress relief. Foremost among them is Professor Shoei Sugita, of Utsunomiya University, who is an ally of Mr Ishihara in the war on crows.

Two years ago the professor designed what he thought might be a solution to the crows’ habit of slashing at rubbish bags with their sharp beaks: a plastic rubbish bag infused with pepper and other pungent spices that would cause the birds to wince from shock.

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