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Stealthy surreptitious scrub-jays are as quiet as a mouse to protect stored food from rival birds
9 September 2009
When it comes to protecting hidden food stores, scrub-jays – a member of the crow family, renowned for its large brain and clever tricks - show abilities in social cognition that rival the great apes and give important clues about the evolution of intelligence. Research funded by the Biotechnology and Biological Sciences Research Council (BBSRC) at the University of Cambridge and Queen Mary, University of London shows that when a competitor can hear but not see what is going on, scrub-jays keep as quiet as possible and choose the least noisy place they can find to hide the food. The research will be published in 11 September edition of Biology Letters.
Lead researcher Professor Nicola Clayton said: “Members of the crow family – Corvids – are remarkably clever and have huge brains for their body size. They are exceptionally fast learners and great innovators, as you can see from their impressive tool use and manufacture. But their cognitive capabilities are not restricted to the technological domain, for they also demonstrate rather sophisticated social skills.
The scrub-jays hide food for the future, but these caches can be stolen by others and so the birds go to great lengths to reduce the likelihood that their stash is stolen in the future. They will use distance, shade and barriers to minimise the chance of being seen while they are hiding food. If they know they’ve been seen, they may come back later and move the cache to another place when the potential thieves have left the scene. They only move the food, however, if they themselves have been a thief in the past! Perhaps even more remarkable is their awareness that even when they can’t be seen by another individual they might still be heard.”
The researchers offered scrub-jays a choice of two trays in which to hide food. One was filled with small pebbles that make a noise when the birds cache food in it and the other with soft soil, which makes little if any sound. In the presence of another, out-of-sight, individual the birds showed a strong preference for the tray with soil rather than the noisier pebbles.
Professor Clayton continued: “The birds know when it’s crucial to conceal auditory information”.
The jays make a judgement based on the likelihood that they may be heard, even if they aren’t seen, and will choose to be as quiet as possible if they assess the risk to be high. If they are alone in the room, or if they know that they are being watched, they don’t show the same preference for the quiet substrate as when they are in the ‘heard but not seen’ scenario and in fact will often choose to hide their food in the noisy tray instead.
“It’s really a case of Corvid crime prevention – something akin to setting your house alarm,” said Professor Clayton. “If you are in bed and an intruder sneaks in the back door at night, you probably can’t see them. But if the alarm sounds then you know that something is afoot downstairs. It’s the same for the jays: even if they can’t see the spot where the food is hidden, if they hid food in the noisy tray then they might have a chance of hearing the sound and intercepting the thief.”
This work is part of a body of results that show that birds demonstrate complex cognition. They are able to make judgements about other individuals and can recognise particular individuals. They have knowledge of the intentions of their competitors – knowledge that depends on who the individual is and the bird's past experience or lack thereof. This complex cognition had previously been thought to be unique to primates. In fact, these findings show us that the Corvid mind is much more closely related to the human mind that previously thought and therefore can inform our understanding of human cognitive development and the evolution of intelligence.
Professor Clayton said: “The experiments we use with our birds can actually be applied to other non-human animals as well as pre-school children allowing us to investigate the evolution and development of cognition.”
The work also has medical implications: Using this research paradigm neuroscientists have been able to refine an animal model of episodic memory (personal memories of past events) – an ability that, before the research on jays, was thought to be unique to humans. This is extremely useful in research about neurodegenerative diseases of the mind such as Alzheimer’s.
About Queen Mary, University of London
Queen Mary, University of London is one of the UK's leading research-focused higher education institutions with some 15,000 undergraduate and postgraduate students.
Amongst the largest of the colleges of the University of London, Queen Mary’s 3,000 staff deliver world class degree programmes and research across 21 academic departments and institutes, within three sectors: Science and Engineering; Humanities, Social Sciences and Laws; and the School of Medicine and Dentistry.
Queen Mary is ranked 11th in the UK according to the Guardian analysis of the 2008 Research Assessment Exercise, and has been described as ‘the biggest star among the research-intensive institutions’ by the Times Higher Education.
The Biotechnology and Biological Sciences Research Council (BBSRC) is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £450 million in a wide range of research that makes a significant contribution to the quality of life for UK citizens and supports a number of important industrial stakeholders including the agriculture, food, chemical, healthcare and pharmaceutical sectors. BBSRC carries out its mission by funding internationally competitive research, providing training in the biosciences, fostering opportunities for knowledge transfer and innovation and promoting interaction with the public and other stakeholders on issues of scientific interest in universities, centres and institutes.
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