Birds Tweet their Tweets on Twitter
Birds now tweet their tweets on Twitter. The microblogging service used for short, text-based messages known as tweets, has been used by an innovative biologist at Scotland's University of St. Andrews to monitor what happens when birds meet in the wild.
An inventive team at the University of Washington (UW) designed the electronic tag that was attached to crows and then used to see whether they might learn to use tools from one another. The findings were published in Current Biology and show an unexpected degree of social mobility in the crow community, with the crows often spending time near birds outside their immediate family.
The researchers investigated crows in New Caledonia, an archipelago of islands located in the South Pacific off the eastern coast of Australia. The crows are most commonly known for using different tools to extract prey from deadwood and vegetation. Biologists however had wondered how much, if at all, the birds might learn by watching each other.
The results, as reported by the St. Andrews researchers, reveal what they believe are 'a surprising number of contacts' between non-related crows. During one week, the technology recorded more than 28,000 interactions among 34 crows. While core family units of New Caledonian crows contain only three members, the study found all the birds were connected to the larger social network.
The use of UW tags to record animal social interactions is a first, and the paper is the first published study to use this technology. 'This is a new type of animal-tracking technology,' said co-author Brian Otis, a UW associate professor of electrical engineering whose lab developed the tags. 'Ecology is just one of the many fields that will be transformed with miniaturised, low-power wireless sensors.'
What normally happens is that biologists tag animals with radio transmitters which then broadcast at a particular frequency.
Field researchers then use a receiver to listen for that frequency and detect when the animal is present. The drawback is that any encounter between small animals would only be recorded if the researcher was nearby.
The UW system, called Encounternet, uses programmable digital tags that can send and receive pulses. 'Encounternet tags can monitor each other, so you can use them to study interactions among animals,' said co-author John Burt, a UW affiliate professor of electrical engineering. 'You can't even start to do that with other radio-tracking technology.'
The UW team is no longer alone in using the tag. Researchers at the University of Windsor in Canada are using it to study mating behaviour in Costa Rican long-tailed manikins; a researcher at Drexel University is using them to study the interaction between birds and army ants in Costa Rica; German researchers are putting the tags on sea lions in the Galapagos Islands to study their behaviour as they pull up on beaches; and researchers in the Netherlands are studying the social behaviour of great tits, a small woodland bird.
'It's a big topic right now, the idea that animals have social networks,' Burt said. 'There are other tags that can do proximity logging, but they're all very big and for larger animals. None is as small as Encounternet -- or even near to it.' The smallest of the UW tags weighs less than 1 gramme (0.035 ounces) and can be used on animals as light as 20 grammes (less than an ounce), about the weight of a sparrow.
Work is now underway to add a GPS component that will record the location of encounters, and to add an accelerometer and other sensors that could detect an animal's behaviour. 'People are excited about this because for the first time, it allows them to study smaller animal interactions and social networks on an incredibly fine scale,' Burt said. 'Social networks are turning out to be key to understanding many animal behaviours. People say Encounternet is the only thing they can find that can collect that information.'
Rutz C. et al.: Automated mapping of social networks in wild birds, Current Biology 22, R669-R671 (2012)