SAMPLINGS 



Pushy Pups, Passive "Parents" 



Banded mongooses live in extended-family 

 groups, with as many as ten females breeding 

 at the same time. When they're about a month 

 old, pups leave the communal den to forage 

 with the adults. That's when a pup usually be- 

 gins to associate exclusively 

 with one particular adult — not 

 necessarily a parent — that 

 provides nourishment and 

 protection. One might as- 

 sume that the adult chooses 

 the pup it wishes to assist. 



Not so, says Jason S. Gil- 

 christ of Napier University in 

 Edinburgh, Scotland, who has 

 long studied banded mon- 

 gooses in Uganda. His latest 

 research demonstrates that 

 the pups do the picking, 

 then establish and jealously defend a territo- 

 rial zone of about a yard radius around their 

 adult "escort." Other pups that venture too 

 close are chased away. 



In field experiments, Gilchrist separated 

 pups from their escorts and held them captive 

 for two days. During that time, the adults inter 



acted freely with other pups. When Gilchrist 

 returned the detained pups to the group, how- 

 ever, they quickly reasserted exclusive rights 

 to their escorts. The adults, it seems, are the 

 passive partners in the relationship. 



Banded mongoose pup sticks with its escort. 



Generally, when pups reach three months of 

 age, they no longer require their escorts' ser- 

 vices and begin to fend for themselves. Gilchrist 

 concludes that even in cooperatively breeding 

 societies, "conflict can be as rife as coopera- 

 tion." {Proceedings of the Royal Society B) 



— Harvey Leifert 



Tide Travelers 



Life is no beach for tidal creatures that must migrate in sync 

 with the waterline. Imagine trying to gauge the tides that sweep 

 through a Kenyan mangrove forest: how far the water rises up a 

 given tree depends on the season, the phase of the moon, and the 

 tree's position. Yet a pinkie-toe-size snail, Cerithidea decollata, 

 seems to predict the height of the incoming tide. It ascends a trunk 

 just high enough to escape inundation, then descends when it's 

 safe to forage in the mud below. 



To find out how, Marco Vannini of the University of Florence and 

 colleagues observed the snails on plastic pipes — imitation man- 

 grove trunks — that they stuck into the mud. The scientists tried 

 obscuring any chemical markers left behind by the tide line or the 

 snails themselves, and still, the snails climbed to the right height. 

 Nor do the predictive gastropods seem to be using visual cues 

 from overhead foliage. They aren't even counting the "steps" they 

 must creep to beat the tide: when the scientists tilted the pipes, 

 the snails readily climbed the extra length. 



When lead weights were glued to the snails' shells, however, they 

 adjusted their ascents; the heavier the weight, the shorter the climb. 

 So it seems that the snails' are sensitive to their own energy output. 

 Perhaps, Vannini suggests, they actually perceive the variations in 

 gravity that drive the tides: before a low tide, the snails feel heavier 

 and therefore don't climb very high. (Animal Behaviour) — Erin Espelie 



Green Biing 



When agriculture arose 

 about 11,000 years ago in the 

 Middle East, fields weren't 

 the only green things cropping 

 up. People's accessories were 

 growing greener too, accord- 

 ing to a comprehensive study 

 of stone beads — the bling of 

 yestermillennia — unearthed 

 at eight dig sites in Israel. 



The sites are between 

 8,200 and 13,000 years old. 

 Of the 221 beads found 

 there, report Daniella E. Bar- 

 Yosef Mayer of the University 

 of Haifa and Naomi Porat of 

 the Geological Survey of Israel 

 in Jerusalem, 89 beads , or 40 

 percent, are made of green 

 stone, including malachite, 

 turquoise, and fluorapatite. 

 The collections mark the 

 first substantial appearance 

 of stone beads, green ones 

 in particular, anywhere in the 

 archaeological record. In the 

 hunter-gatherer societies 

 that preceded the dawn of 

 agriculture, beads — typically 

 of antler, bone, tooth, ivory, 

 or shell — were white, yellow, 

 brown, red, or black, with 

 only a few examples of green 

 soapstone. 



The minerals used to fashion 

 the green beads discovered in 

 Israel came from as far away 

 as northern Syria and Saudi 

 Arabia. Thus, people must 

 have gone to great lengths to 

 obtain stones of the latest col- 

 or. Bar-Yosef Mayer and Porat 

 propose that with the advent of 

 agriculture, the color of young 

 leaves came to symbolize fer- 

 tility and good health. Green 

 beads, they say, were probably 

 used as fertility charms and 

 amulets against the evil eye, just 

 as they are today in many parts 

 of the Middle East. (PNAS) 



— Stephan Reebs 



natural history October 2008 



