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Hi Jim & All, Dec 28, 2006
I don't have any perennial physiology sources at home, so must rely
on memory, but I think 1) that flowering buds of perennial woody plants
in general (and fruit starts such as 1-yr pine cones and 1-yr acorns)
tend to be more rich in organic and mineral nutrients than vegetative
buds and 2) both flowering and vegetative buds tend to be richer just
before a heavy seed year or on fruiting year.
So these squirrels are likely just responding to better nutrition.
Yt, Dave Webster, Kentville
Jim Wolford wrote:
> Globe and Mail, Thurs., Dec. 28, 2006 -- on-line Globe? [not in newspaper]
>
>
> Red squirrels time babies to big crops
>
>
> Larger litters are born when evergreens produce extra seeds,
> scientists discover
>
> STEVE LILLEBUEN
>
> Canadian Press
> EDMONTON -- In the eat-or-be-eaten animal kingdom, red squirrels have
> found a way to stay one step ahead of their food source.
>
> Biologists have discovered that the furry critters can anticipate when
> evergreens will produce bumper crops of seeds, and they respond with
> larger than usual litters.
>
> It's no coincidence, according to an article published in the latest
> edition of the journal Science. Rather, it's perfectly timed behaviour.
>
> "We usually predict that animals will just track resources and respond
> at a later date, so this is very surprising," lead author Stan Boutin,
> a University of Alberta biologist, said yesterday.
> "It's quite a story in the scientific world because we haven't seen
> this before, and more importantly, we hadn't even thought to look."
> Typically, spruce and pine trees use a boom-and-bust strategy in their
> seed production to counter a squirrel's big appetite.
>
> In lean years, Prof. Boutin said, trees starve squirrels so that when
> larger seed crops are produced randomly, there are fewer squirrels
> around to eat their future seedlings.
>
> Monitoring red squirrels near Kluane National Park in the Yukon,
> however, led to surprising results.
>
> Months before a big cone season started, squirrels went into a
> reproductive frenzy. The pattern repeated itself in 1993, 1998 and 2005.
>
> "Lots of animals breed well ahead of the spring flush when babies are
> born, and they can do that each year because temperature and daylight
> changes are such good predictors of upcoming changes," Prof. Boutin said.
>
> "It's a little bit tougher when things are unpredictable like seed
> production years, but the squirrels obviously figured out a cue."
>
> Squirrels also take quite a chance, he said, because they end up
> having their offspring during seasons with no resources in order to
> outwit the trees' swamp-and-starve mechanism.
>
> There's no danger that the squirrels will wipe the trees out, he said.
> Lots of seed still escapes to produce young seedlings.
>
> The same patterns were observed by scientists in Europe, where
> Eurasian red squirrels cranked up their reproduction so that their
> young could feast on a burst of seeds from oak and beech trees.
>
> Exactly how the squirrels have become smart enough to predict the
> future availability of seeds is not yet known.
>
> Prof. Boutin figures the animals may be aware of some as-yet-unseen cue.
>
> It takes roughly 18 months for a tree to produce a cone, he said.
> Cones start off as either reproductive or vegetative buds. The
> reproductive buds sit dormant over winter, giving the squirrels
> something to feed on until spring arrives.
>
> The reproductive buds may somehow give the squirrels a trigger to know
> that a big crop is on its way.
>
> It could be simply a matter of observing the abundance of reproductive
> buds, or plant hormones could be tapping into some kind of
> reproductive trigger in the squirrels' physiology.
>
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