Fun with Science Club®


			Can not being hungry make you a better guard? Carrie Straight 05.18.01 Cooperatively breeding animals sometimes have sentinels, or guards, who stand watch over the group. Usually an animal will stand guard from a position from which they can see potential threats easier. When sentinels spot danger, they sound the alarm, letting the other animals get away. This allows the other animals in the group to hunt for food and not have to be as concerned with watching out for danger. The sentinel will watch for danger. Many scientific reasons could explain why an animal would choose to be a sentinel. Maybe they do it to help relatives, or maybe being a sentinel will make the individual look better to all the others in the group. But what things can effect how good of a job a sentinel does? Are sentinels better with smaller groups or when more food is available? Scientists wanted to answer how food affected the sentinels among Arabian babblers (Turdoides squamiceps). These researchers wanted to test if the amount of food available to the sentinels could change their behavior. Two male babblers are usually the sentinels. They predicted that as the amount of food they gave to the sentinels increased their guarding activity would increase. They also predicted that there would be an equal increase in activity of the dominant (alpha) male and the subdominant (beta) male, but if one sentinel increased its activity the other sentinel on duty would slack off some. They tested these predictions by an experiment using 40 different groups of babblers. It was easy for the researchers to identify sentinels because the sentinels sat on an elevated perch and held their head up looking for predators. The researchers gave additional food to some of the sentinels and not others. The researchers identified the sentinels as either dominant or subdominant and systematically observed all of their behavior. The results of the study showed that when a sentinel (either alpha or beta) had extra food the number of minutes it spent scanning increased. The results also showed that when one sentinel increased its effort the other sentinel decreased its effort. Full sentinels are better at their job, probably because they have more energy reserves.


			Wright, Jonathan, Alexei A. Maklakov, and Vladimir Khazin. 2001. State-dependent sentinels: an experimental study in the Arabian babbler. Proceedings of the Royal Society of London. Biological Sciences Series. 268: 821-826.