Animals split into smaller groups to avoid costs of living in groups!
Animals choose to be in groups because it offers advantages like reduced risk of predation. However, being in groups comes with costs like increased competition for food. But animals are smarter than we think! To strike a balance between such costs and benefits of group living, a few species split into smaller subgroups while doing daily activities and the groups merge again, at a later time. Such societies in which the group configuration changes continuously and the groups split and merge are called 'FISSION-FUSION SOCIETIES'. Fission-fusion systems offer advantages of being in groups while reducing the costs of group living! Chimpanzees, hyenas, lions, dolphins, elephants and even spotted deer are known to show fission-fusion group systems.
Another example of such a fission-fusion system is that of giraffes. Giraffes can be seen solitary or in groups of varying sizes. Female giraffes are more likely to be seen in all-female groups or ‘NURSERY GROUPS’. Nursery groups comprise of adult females, their calves and sub-adult females. Such groups provide various advantages to all members in the ‘nursery’. Mother-calf bonds in giraffes are extremely strong. Bulls mostly prefer to be solitary but can also be seen in all-male groups. There has been accumulating evidence that giraffes prefer being with certain individuals more than others, and they do not form groups randomly! However, in spite of quite a few studies focusing on giraffe grouping structure, it is still not very well understood!
A nursery group with females, their calves and sub-adult females. Adult females get help with raising their young, while sub-adult females get experience of raising young!
A handsome male with an oxpecker on its horn! -- The oxpeckers eat the ticks and other parasites from bodies of large mammals -- the birds get food and the mammals get clean!
A calf -- look at how cute he is! :) We had named him "Dell"
I got the opportunity of studying such a fission-fusion system in giraffes as a part of my masters thesis (2010-11) in a nature reserve in South Africa, with Francesca Hinman. I was trying to understand if giraffes prefer being with certain individuals more than others, when they form groups. In short, I was studying if giraffes have best friends! To study group formation in giraffes, we had to identify every individual and collect data on whom they were seen with. Individual giraffes were identified from the pattern on their body, which is unique, just like our fingerprints. But what was the biggest challenge faced while collecting data? – Strangely enough, we faced a tough time even spotting giraffes, which is one of the biggest living animal – forget identification! If they were successfully spotted, to identify individuals, we needed a photo of their neck/body. And most of the times what we saw was just the legs or head, thanks to the vegetation (Check picture)! But in the end, we managed to identify 31 individual giraffes (would have been impossible without Francesca), observe these identified individuals multiple times, and successfully complete my project, which I thought I would never get data for! Challenges in field ecology studies just cannot be predicted! :-s
Know what frustration is? -- THIS! When you are desperately trying to get a good picture of their body or neck for individual identification and all that you see for weeks is THIS!