Big predators hunt faster

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Capture that flag!

At high school I was a member of the ATC (Air Training Corp). We would meet each week at the Balclutha Primary School Hall where we would learn drill, information about planes and information about wilderness survival and first aid. Every fourth week we would go to the small-bore rifle range and shoot targets. Very occasionally we would go for flights on weekends and a couple of times a year we would go off on a tramp. Once a year we would do a capture the flag camp. A group of cadets would be dropped several hours away from the base-camp. We would have to slog our way to the camp becoming increasingly secretive as we got closer. You see a flag was raised in the camp and it was the job of ‘attacking’ group to get the flag without being seen by the defenders. That was a difficult task. You could wait for night-time which might help, although the defenders had torches. So various tactics needed to be devised. Once in a while someone might sneak in and get the flag on their own but usually we needed a diversion. One method that worked was sending most of the attacking party to raid one side of the camp while a couple of attackers waited at a different side. When the raid started (preferably at night) it would take most or all of the defenders to spot each attacker. While this was happening the sneaks could do their stuff capturing the flag while the defenders were occupied with processing the other attackers. Success!

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Hungry Thai water bugs !

These days of creeping through the darkness, invariably on one of the wettest days of the year, came back to me recently when I read about some research done by my Department of Ecology colleague Hannah Buckley. Hannah, with colleagues Robbie Weterings and Chanin Umponstira (from Naresuan University in Thailand), have just published the rather formidable sounding “Density-dependent allometric functional response models” in the journal Ecological Modelling. De-coding this a little, the research was interested in the relationship between predators and prey, particularly when considering how fast predators can handle prey. It has long been known that prey size can affect handling time (the bigger the prey individual the longer it takes to catch, process and consume and the fewer prey that will be taken in a time period). What Hannah and her colleagues wanted to know was whether predator size also plays a role (larger predators can handle prey faster than smaller predators).

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The prey: the mosquito, Armigeres sp

Predators for this study came from the aquatic Nepomorpha insect group (Hemiptera or bugs). Their prey were third and fourth instar mosquito larvae. Specimens were obtained from canals in the historic walled city of Kamphaeng Phet in Thailand. One to four nepomorphans were placed in 1.5l containers and 10-60 mosquito larvae were released in with them. Survival after 24 hours was measured. Each nepomorphan was measured in length. Hannah also developed various models that included prey density, handling time, change in prey density and predator size to see which best fitted the collected data. They found that increased predation rates in larger predators was mainly a result of decreased handling time. The bigger the predator the faster they could deal with an individual prey and then move onto another one. The models produced from this research will be useful for future research where predator populations are composed of individuals of different species, sizes or age-groups.

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The experimental set up

So could the younger Adrian, lying in the scrub with rain trickling down his neck, have used these findings to help his group of attackers to capture the flag? If we assume that a larger predator equates to a more experienced human then it would have made sense to rush the more inexperienced defenders (cadets like I was) who might not have handled targeting the attackers as well. Likewise, if we could tell where the more experienced officers were, we would have needed to send relatively more attackers against them to keep them occupied. Capturing the flag based on bug and mossie tactics. Success!

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