A new study suggests that male chimpanzees that befriend the alpha male are more successful at mating. This leads to a greater number of offspring, and a higher chance of passing their genes on.
A new study suggests that male
chimpanzees that befriend the alpha male are more successful at mating.
This leads to a greater number of offspring, and a greater chance of
passing their genes on
from Arizona State University studied the behaviour of the animals over
the course of 36 years, and found that male chimpanzees that befriended
the top-ranking male were more successful at mating with preferred
females when in the alpha male's presence.
While alpha males usually mate more than other chimpanzees, they do not have complete control over access to preferred mates.
Bray, lead author of the study, said: 'Alpha males may concede mating priveleges
to subordinates in exchange for social favors, such as support in fights
against other males.'
The researchers' analysis revealed
that subordinate males that groomed the most with the alpha, were also
more successful at mating when the alpha was nearby
the subordinate males benefit in the short-term by having the chance to
mate, the alpha males gain long-term benefits by staying at the top of
Mr Bray said: 'Social exchanges are thus a win-win.'
researchers looked at several thousand matings over the course of 36
years, and eight alpha male tenures – the largest study of its kind.
analysis revealed that subordinate males that groomed the most with the
alpha, were also more successful at mating when the alpha was nearby.
This suggests that the alpha male tolerates the subordinates' mating attempts.
Mr Bray said: 'These results are very exciting because they demonstrate one potential function of social bonds.
for subordinate males, it gives them an opportunity to mate
successfully even if they are not of high rank, as long as they befriend
the chimp at the top.'
Ian Gilby, co-author of the study, said: 'The next step is to investigate these relationships in more detail.
'Is grooming evenly distributed? Are alpha males more tolerant if they have recently had attention from the lower ranking male?'
'In the future, we also want to look at whether alpha males vary in the degree to which they concede matings.
males that are firmly in control may have little to gain, whereas
smaller alphas with a more tenuous hold on their dominance position may
benefit by offering favours to subordinates to placate them or earn
their support in fights.'
The findings suggest that if chimpanzees groom with the alpha male, it will tolerate the subordinates' mating attempts
Roman Wittig, from the Max Planck Institute for Evolutionary
Anthropology and his colleagues looked into how chimpanzees reacted
after stressful experiences, like natural encounters with a rival
chimpanzee band and mimicking of rivals’ tree-drumming signals by
compared levels of glucocorticoids, a class of stress-related hormones,
in the urine of 17 wild chimpanzees following rest, grooming, or a
study showed when a chimp interacted with one of its friends during a
stressful event, the level of stress hormone did not increase.
Grooming by a social partner also reduced glucocorticoid levels below those observed during resting.
findings suggest social interactions play an important role in reducing
stress levels and potentially in maintaining health.