03/14/2007
Planning Ahead
After writing about black holes, as I did last week, I like to return to more down-to-earth subjects, animal behavior being a favorite. I’ve mentioned seeing a very healthy looking red fox pass through our backyard recently, the first fox I’d seen in our town. Last Sunday our Lamb creator, Harry Trumbore, dropped by and told us of an intriguing incident with a fox in his backyard.
His backyard borders on a wooded area harboring deer and other creatures, notably wild turkeys. In past years, the turkeys were a novelty and would eat seeds that dropped from a generously supplied bird feeder. Harry would sometimes sprinkle feed on the ground to provide the turkeys added sustenance. However, the turkey troop has grown to over a dozen birds and has become more of a nuisance. Last week, he found the turkeys pecking on the glass door, demanding to be fed. However, Harry decided enough was enough and shooed the birds away.
The turkeys gave up and were leaving the yard when a large gray fox entered the picture. In such a situation, I would have expected the fox to end up with a turkey dinner, albeit without the cranberry sauce and stuffing. Not so. The turkeys grouped together with the puffed up males in front and, instead of retreating, marched towards the fox. In the woods behind the fox were four deer, totally ignoring both fox and turkeys. The sly fox, after a period of indecision, decided the turkeys had the upper hand and fled the scene. Harry recalled that some time ago a mailman in a neighboring town was attacked by wild turkeys and had to retreat back to his truck to escape bodily harm!
I especially enjoy writing about animals that appear to have a degree of intelligence that we humans normally reserve for ourselves. For example, a common view has been that humans are the only species that uses past experiences to plan ahead or think about the future. However, I only have to look out in our backyard and watch the squirrels digging up my lawn retrieving the nuts and acorns they stored there last fall. They obviously planned ahead for the winter. But, was this just something programmed in the squirrels’ genes and triggered by the changing seasons?
In the Newscripts section of the January 22 Chemical and Engineering News, Faith Hayden goes a step further and asks the question, “Are red squirrels psychic?” She cites work published last year in Science about the competition between trees and squirrels, the trees using a “swamp and starve” tactic to keep squirrels from eating all its seed. With lots of oak trees in our neighborhood, it’s clear that some years there are unusually large numbers of acorns, other years not so many. If we ascribe a motive to the tree’s variable production of acorns, it could be that the lean crops of acorns tend to starve the squirrels and reduce their population. With a smaller population, when the tree produces a bountiful crop of acorns, there won’t be enough squirrels to eat all of them and the seeds survive.
The study cited by Hayden says that both American and Eurasian red squirrels have found the secret as to the tree’s next year’s productivity of acorns. The squirrels will produce a second litter of baby squirrels in advance of a bountiful seed production by the trees. The female squirrel may even conceive a second litter while still nursing her first litter. This in itself is surprising because lactation in mammals generally tends to suppress ovulation. How do the squirrels know what the trees will produce? That’s a mystery. Do they “count” the number of flowers or buds or pollen cones? And aren’t we crazy to ascribe motivation to a tree? Maybe not!
We’ve discussed other examples of looking ahead in animals. Some time ago, I wrote about the work of Nicola Clayton and her colleagues on western scrub jays. There’s a profile of Clayton and her work by Virginia Morell in the February 23 issue of Science. In 1995, Clayton moved to the University of California at Davis from the UK. At Oxford, she had shown that Eurasian jays and tits had excellent memories in the caching of food and that the hippocampus region of these birds’ brains grew as they stored seeds in more and more different locations. When she moved to California, she found western scrub jays in abundance and began observing their behavior in the wild.
I wrote about her work that revealed the jays would steal from other jays and that a jay would store some food in one area but notice that another jay was watching. The first jay would then return when the other jay was not around and move the food to another location. This led her and a co-author at the University of Cambridge to publish a paper in Nature claiming that the scrub jays have so-called “episodic-like” memories. To store an episodic memory is to store a memory of a specific episode in the past, something we humans do all the time – even if we older folk have trouble dredging up these memories later in life! Her co-author, Anthony Dickinson, admits that when he first heard of Clayton’s assertion that the jay had an episodic memory he thought it was “outrageous”. He became a convert after collaborating with Clayton on further experiments on the jays.
Dickinson wasn’t the only convert. At UC Davis, Clayton met Nathan Emery, who was studying primates and would tell Clayton about the various things that his apes could do that no other animal could do. Clayton disagreed and said her birds were just as smart. Emery not only became Clayton’s collaborator but also ended up being her husband! In 2000, they moved to England and took some scrub jays with them.
Clayton and her colleagues have published many papers on the mental skills of food-storing birds, the latest being one in the February 22 issue of Nature and is co-authored with Dickinson and two of Clayton’s graduate students. This paper reinforces strongly the view that the jays have episodic memories and use the memories to plan for the future. The two grad students, Caroline Raby and Dean Alexis, put the jays into an interesting situation. They were placed in a “suite” with two adjoining rooms, where they stayed overnight in what I’ll call the living room. The next day they were moved to one of the adjoining rooms. One room was a jay bed and breakfast, supplied with a plentiful amount of pine nuts. The other room was devoid of any food items, not a place a hungry jay would enjoy. It was like the difference between the Ritz and a sleazy motel.
After spending a few days in the different rooms, the jays were placed in the suite with free access to either room. The “living room” contained a plentiful supply of pine nuts. What did the jays do? Without hesitation, they started taking nuts from the living room and stashed them away in the “motel” room! They certainly seemed to remember their times spent in that room and wanted to be sure that if they found themselves there again they wouldn’t go hungry. It sounds like episodic memory to me!
Once again, we see that the use of the term “birdbrain” used in a derogatory sense is quite unwarranted. Now if the trees start outwitting the squirrels again I’ll really be impressed!
Allen F. Bortrum
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