Predators hunt for a balanced diet
12 January 2012
Predators select their prey in order to eat a nutritionally balanced diet and give themselves the best chance of producing healthy offspring. A University of Exeter and Oxford-led study published yesterday (11 January 2012) in Proceedings of the Royal Society B shows for the first time that predatory animals choose their food on the basis of its nutritional value, rather than just overall calorie content.
By furthering our understanding of how food webs and ecosystems interact, this research could help scientists to manage environments, sustainably.
An international team of scientists from the Universities of Exeter and Oxford in the UK, University of Sydney (Australia), Aarhus University (Denmark) and Massey University (New Zealand) based their research on the ground beetle, Anchomenus dorsalis, a well-known garden insect that feasts on slugs, aphids, moths, beetle larvae and ants.
The team collected female beetles from the wild and split them into two groups in the laboratory. Half of the beetles were offered a choice of foods, some that were high in protein and some that were high in fat. The other half were not given a choice of what to eat: some were only given food that was higher in protein and others just had higher-fat foods, none of which provided the right nutritional balance. The beetles that were provided with a range of foods selected the balance of protein and fat that was optimal for producing healthy eggs. These beetles produced more eggs than the beetles that did not have the right nutritional balance.
Previous research on insects has shown that herbivores such as butterfly larvae and grasshoppers and omnivores like fruit flies and crickets select food that will give them a balanced diet. However, until now scientists have assumed that predators can only focus on obtaining sufficient calories in their diets. This is the first research to show that predators also select food on the basis of its nutritional value. Although this study focuses on one insect species, the researchers believe that this is likely to be true for predators across the animal kingdom.
Lead researcher Dr Kim Jensen of the University of Exeter said: "At a time of year when many of us are focused on healthy eating, it is interesting to see that predators are also selective about what they eat. Biologists have previously assumed that predators cannot afford to be fussy and that they are simply focused on getting the right quantity of food, rather than quality. We show for the first time that they do actually select the foods that will give them the right balance of nutrients.
"Our findings could help further our understanding of food webs and how communities of animals interact in the wild."
This study was funded by Biotechnology and Biological Sciences Research Council (BBSRC), with additional support from the Royal Society and Natural Environment Research Council.
About the University of Exeter
The University of Exeter is a leading UK university and in the top one percent of institutions globally. It combines world-class research with very high levels of student satisfaction. Exeter is ranked 9th in The Sunday Times University Guide, 10th in the UK in The Times Good University Guide 2012 and 11th in the Guardian University Guide 2012. In the 2008 Research Assessment Exercise (RAE) 90% of the University's research was rated as being at internationally recognised levels and 16 of its 31 subjects are ranked in the top 10, with 27 subjects ranked in the top 20.
The University has over 17,000 students and is developing its campuses in Exeter and Cornwall with almost £350 million worth of new facilities due for completion by 2012. For more information visit: www.exeter.ac.uk .
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