TROOP­ING THE NUM­BERS UMBERS

BBC Wildlife Magazine - - Wild News -

Ba­boons troops can con­tain any­thing from a hand­ful to hun­dreds of in­di­vid­u­als. But Univer­sity of Ox­ford bi­ol­o­gists have dis­cov­ered that some group sizes are more com­mon than oth­ers and, what’s more, that there’s an in­trigu­ing math­e­mat­i­cal re­la­tion­ship be­tween them – 20, 40, 80 and 160.

Part of the rea­son is that ba­boon troops di­vide in two once they reach an up­per thresh­old. That’s be­cause, as so­cial com­plex­ity in­creases, fe­males pro­duce off­spring at a slower rate. The re­sult is that any given troop os­cil­lates be­tween a high and low pop­u­la­tionn size – 20 and 40, 40 and 80 or 80 and 160.

Which pair of sizes a troop os­cil­lates be­tween seems to de­pend onn the lo­cal risk posed by preda­tors.ors. Larger groups are bet­ter at de­fend­ing them­selveses against the likes of leop­ard­sopards and lions. So, inn re­gions where the den­sity of preda­tors is high and there is lit­tle­tle shel­ter, it pays to os­cil­late be­tween a higher pair of troop sizes. zes.

Ba­boon troop num­bers tend to fol­low a se­quence.

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