Biology Reference
In-Depth Information
(a)
(b)
Fig. 6.11
Sentinels in:
(a) meerkats and
(b) pied babblers.
These individuals
watch for
predators from
look-out perches
while the rest of
the group
forages. Is the
sentinel altruistic
or selfish? Photos
© Tom Flower.
(b)
(a)
9
0.4
8
0.35
7
0.3
6
0.25
5
0.2
4
0.15
3
0.1
2
0.05
1
0
0
Background
noise
Sentinel calls
Background
noise
Sentinel calls
Fig. 6.12
The watchman's song. Sentinels give quiet vocalizations while on guard.
Playback of sentinel calls to foraging pied babblers leads to lower vigilance (a), and
improved foraging success (b) by the foragers in the group, compared to control
playback of background noise. From Hollen, Bell and Radford (2008). With permission
from Elsevier.
foragers. Each individual is simply choosing the best option for itself, depending on its
own state and the action of others in the group.
Observations of both meerkats and Arabian babblers,
Turdoides squamiceps
, support
this selfish view of sentinel duties (Clutton-Brock
et al
., 1999a; Wright
et al
., 2001).
Both species feed in the open desert, digging for invertebrates in the sand. While
foraging, it is difficult to spot approaching predators. Individuals are more likely to
become sentinels when they are satiated, either after a natural feeding bout or after
experimental provisioning with extra food. Furthermore, sentinels are not at increased
risk of predation; in fact, they usually detect predators first and are often the first to flee
Selfish sentinels
in meerkats and
babblers
