Fall harvest gone wild

This should be called the year of the fantastic nut crop: acorns by the ton, walnuts carpeting the lawn, and buckeyes remaining unharvested because there is a food surplus in the backyard like never before.

Ohio buckeye nuts

The Ohio Buckeye tree is loaded with nuts, which the squirrels should have harvested by now.

Why is this happening?  I don’t remember there being great spring weather; oh wait, I was in the UK during spring.  The summer was the usual blend of hot and humid interspersed with cold and rainy, so it must have been perfect for growing a huge nut crop.  But why have all the oak trees in the backyard gone crazy with acorn production?

Oak acorns

The forest floor has become crunchy with fallen acorns. This is just what the squirrels leave behind.

We are experiencing a “mast year” in oak tree production of acorns, which happens irregularly, every two to five to seven years.  And it’s happening in not just one species of oak, but simultaneously in the three most common Minnesota oak species — the northern pin oak, the northern red oak, and the bur oak.

Bucks eating acorns, photo by Charles Alsheimer

In a normal year of acorn production, animals consume or store most of the acorn crop, leaving little chance that the nuts could sprout into seedling oaks. Photo by Charles Alsheimer.

In a recent post (September 12), I discussed how trees “talk” to each other, and this synchronous boom production of acorns is a good example of the result of that communication, which can occur not only locally within a forest, but over broad distances.  Basically, mast production of acorns is the trees’ combined strategy of satiating the acorn consumers so that the leftovers can develop into seedlings.

The oaks must have been talking to the walnuts in the backyard as well, and the squirrels are just not able to keep up with the bounties of this fall harvest.

Gray squirrel husking a walnut

Bring all your friends, Mr. Squirrel, I’ve already raked up a garbage can full of walnuts.

The perfect response to this enormous fall bounty — “stop, I’m full already”.

National Geographic funny animal photos, 2018, Photo by Mary McGowan, CWPA, Barcroft Images

National Geographic funny animal photos, 2018, Photo by Mary McGowan, CWPA, Barcroft Images.

too cold…

It’s -13 F right now, and with a moderate wind blowing, the wind chill makes it -36 F.  That’s too cold for me, but not too cold for the hungry birds and squirrels in the backyard to come into the bird feeders for a meal.

basking gray squirrel-

Gray squirrels don’t venture out until the sun is well up on these really cold days. And before they cross snow patches to get to the feeders, they bask on the trees for a while to warm up, orienting the darker fur on their backs directly toward the sun.

basking chickadee-

Even the chickadees take a few minutes between trips to the feeder to bask a little, fluffing their feathers out to make their tiny bodies into an almost spherical shape.

basking blue jay-

The bluejay must have been too cold to move — it just sat there looking around, squinting into the sun.  I could see the wind ruffling up its feathers — brrrrrrr.

Basking to gain what little radiant heat the sun provides at this time of year can be effective in warming up, but wind currents that penetrate fur and feathers carry that precious heat away.  What can a small animal do to cope with this intense winter cold?  Activity helps, as muscles generate heat, but that comes at a cost to be repaid by eating more.  Shivering helps, and when animals are not active, muscles engage in isometric tremors that generate heat, which is also expensive, but not as much as flying or running across the snow and climbing trees.   The only animals that seem unperturbed by this weather are the feisty little red squirrels.

red squirrel-

Red Squirrels must generate a lot of heat dashing around, because they spend almost no time basking and a lot of time digging into the snow looking for buried treasures (food) and running up and down trees to stash whatever they find away.

gray squirrel for breakfast

I complain that I have too many gray squirrels in the backyard, clever ones that manage to defeat all the squirrel barriers on bird feeders.  It’s my own fault for supplying too much bird seed, but there is an unexpected benefit to attracting squirrels — attracting their much more photogenic predators.

red fox with gray squirrel kill-

I missed the actual fox-squirrel encounter, however, the fox was making sure the squirrel was dead by biting it in the neck several times.

red fox with gray squirrel kill-

checking for life from another angle…

red fox with gray squirrel kill-

bite it again, just to make sure…

red fox with gray squirrel kill-

So, eat it now, or save for later?

Save for later, was apparently the decision, as the fox picked the squirrel up in its jaws and trotted off behind bushes and the neighbor’s house to have some privacy.

Foxes and probably the Great Horned Owls in the backyard have been doing a fine job of keeping the local rabbit population in check.  In fact, I rarely see a rabbit munching on my flowers any more.  As is usually the case, when one population of prey decreases, there is increased pressure on other prey species, in this case, the gray squirrels that annually produce a new crop of naive youngsters that like to hang out near the bird feeders.  And therein lies the balance of nature…

Note: these are not the best photos of a photogenic fox; they were shot on a very gray day, early in the morning, through dirty windows, with a much too slow shutter speed — but the action was exciting!

Surviving the cold – part II

In yesterday’s blog post, I summarized the challenges of living in (and surviving) the harsh weather of northern latitude winters and described a few of the solutions to those challenges.  But there are more solutions available to animals — and humans.

4. Turn up the heat:  For those animals (and humans) that can afford to do so, the best solution to surviving cold temperature extremes is to fire up the metabolic furnace.  No one enjoys standing out in the cold shivering intensely, but that and physical exertion are the first line of defense in staying warm.  The trick is to preserve the heat inside the body by improving insulation.

red-bellied-woodpecker

Flying around looking for food generates body heat for this Red-bellied Woodpecker, but the bird must fluff out those feathers when sitting still to retain the heat produced by activity.

gray-squirrel-

Mammals, like this Gray Squirrel, fight the cold by increasing both shivering and non-shivering heat production, using an extra source of heat production from their “brown fat”.  It doesn’t hurt to have a furry tail to keep your back warm either.

Brown fat (more vascularized than regular white fat) is more prevalent in mammals acclimated to cold (even humans!) and especially in young mammals and in hibernators that undergo dormant sleep for most of the winter.  Localized in the trunk and back, brown fat heat production preferentially warms the spinal cord and brain.

5. Don’t spend what you don’t have:  In cases where food is limited or costly to obtain (i.e., resulting in a net loss of energy), the opposite strategy from #4 above is to be more conservative in expending energy by turning down the metabolic furnace when resting, decreasing activity, sleeping more, etc.  A variety of mammals, some birds, and even some humans employ this strategy in the winter.  Hibernation, or winter sleep, is key to survival in many rodent species (except tree squirrels), because there is little energy wasted on heating up their body that is essentially the same temperature as their burrow.

hibernating chipmunk-sni.schlastic.com

Hibernating chipmunks store food in their underground burrow, and rouse every couple of weeks from their torpid sleep to snack a little before becoming dormant again.  Photo from sni.scholastic.com

human hiberanation

The British Medical Journal described a case of “human hibernation” in a group of Russian peasants, living in an impoverished area with inadequate food, who typically slept through the winter, rousing only once a day to eat a little bread, drink some water, and add fuel to their fireplace.

Just turning down the furnace and lowering body temperature a few degrees at night can make the difference between survival and succumbing to the cold.  Birds as small as Black-capped Chickadees and as large as Red-tailed Hawks save 30-40% of their overnight energy expenses by cooling off a few degrees.

Red-tailed Hawks sitting on phone poles

It’s not unusual to see Red-tailed Hawks perched on telephone or light poles along highways in the winter, where they can get a good view of potential prey moving around below them.  But if these hawks miss a few meals, they may not have enough energy reserves to make it through the night. Better to reduce night-time costs and save energy.  Photo by Allan Block

6.  Tolerating net energy loss:  This is kind of a last-ditch effort to survive winter, but may be a viable strategy in larger-bodied, well-fed animals.  For example, White-tailed Deer may not find enough forage to sustain themselves over an entire winter, so they put on weight by eating a lot in the Fall and coast through the winter, using up their reserves.

white-tailed-fawns-feeding

Winter cold must be especially tough on smaller-bodied fawns with less energy reserves than the adults.

Longer winters with more extreme temperatures may mean lower survival rates, and may even compromise an animal’s ability to recover in the spring.

white-tailed-deer-late winter

This White-tailed buck looks pretty emaciated after a long, cold winter.  He may not be able to rebuild his muscle mass over the summer in time for the Fall rut season.

A more atypical illustration of this strategy is that of hibernating bears.  They aren’t really hibernating in the true sense, since their body temperatures are only a few degrees lower than normal, but they purposely fatten up in the fall, and then metabolize that fat over the months of winter sleep, losing 25-40% of their body weight before they emerge from the den in the spring.  Females use an additional portion of energy reserve to nurse cubs born during the winter sleep.

black-bear-hibernating - bearlakereserve.com

Hibernating Black Bear and cub; photo from blackbearreserve.com

In summary, animals use a variety of strategies to offset the cost of surviving winter cold; it’s not really mysterious or magical, but is a product of selecting what works best in a particular situation.  Animals using the wrong strategy are quickly removed from the breeding pool, and thus solutions get better and better over time.

I can’t eat another thing, not even a “wafer thin mint”

I think the squirrels have become satiated with all the walnuts and buckeye nuts falling on the ground this past week.  Here is what they left behind as I tried to clean up their messy harvest.

ohio buckeye nuts-

I raked up an entire mixing bowl full of buckeye nuts left behind by the squirrels at the base of the tree. A few of the nuts had a bite or two out of them, but most were unscathed.  They are so heavy and slick, they slide right into any crevice in the lawn and get more or less buried there — ready to germinate next Spring and create a little Buckeye forest.

Meanwhile the squirrels look like this…

gray squirrel-

“I’m so full — I can’t eat another thing, not even a wafer thin mint”.

A la Monty Python’s sketch in “The Meaning of Life”

wafer-thin-mint

The strategy of satiating predators with an over-abundance of food ensures that some of the seed crop (or animal prey in the case of carnivores) remains unharmed, able to carry on the next generation.  Who said trees weren’t smart?

The buckeye harvest

Our Ohio Buckeye tree is rapidly being harvested by the local gray squirrel population.

gray squirrel eating buckeye nuts

Gray Squirrels make quick work of this large nut, by stripping off the outer spongy hull to get to the larger brown seeds inside.

A half dozen squirrels race up and down the trunk and branches, cutting the nuts from the terminal parts of the branches, then quickly de-hulling them, and carrying the brown seeds off to their hidden caches.

gray squirrel eating buckeye nuts

It takes some acrobatic maneuvers to get to some of the nuts on the tree.

gray squirrel eating buckeye nuts

A young squirrel copying the example of his elders — but going the wrong direction (up the tree) with his prize.

Nuts of the Ohio buckeye

1-3 shiny brown nuts can be found within the spongy hull of the buckeye.  Carrying buckeye nuts around in your pocket is supposed to bring good luck….  (Photo by H.Zell, from Wikimedia Commons.)

It’s somewhat surprising that the squirrels place such value on these toxic nuts, which are so poisonous to domestic animals and pets.  Indians apparently found a way to detoxify their high tannic acid and alkaloid content by roasting, grinding, and leaching the nuts before pounding the extract into a powder for a nut-bread concoction.

gray squirrel eating buckeye nuts

Those are some sharp lower incisors that can chip through the tough outer shell of the nut.

gray squirrel eating buckeye nuts

The aftermath of the harvest is a big pile of leaves and hull debris on the lawn, which is pretty difficult to rake up.

gray squirrel eating buckeye nuts-

Enjoying the fruits of the harvest. I’m just glad these squirrels prefer buckeye nuts to my Honeycrisp apples!

the walnut harvest

Walnuts drop like big chunks of hail in the backyard these days, as the gray and red squirrels begin their fall harvest of the nut crop.  A few of the nuts are shelled and eaten on the spot, which leaves a nice coating of dark brown walnut varnish on sidewalks and deck boards.  But most are carried off to their winter larder.  The strategy for this harvest is apparently to scale the tree and climb down the ends of the walnut branches, liberate a dozen or so walnuts, and then scurry to the ground and carry them off, while fending off the interlopers.

red squirrel harvesting walnuts

Walnuts ripe for harvest attract this red squirrel, who is quickly cutting off a dozen or so nuts.

red squirrel harvesting walnuts

Hanging upside down is sometimes the best tactic for removing some of the nuts.

The problem with dropping all those nuts on the ground at once is that it attracts other walnut lovers, who can then help themselves without putting in the work of harvesting them.

red squirrel harvesting walnuts

The red squirrel in the tree dropped most of the nuts in a concentrated patch, but another red squirrel made off with a few of them before the one in the tree could get down. 

gray squirrel with walnuts

A gray squirrel made off with a few of the nuts too.

red squirrel harvesting walnuts

Red squirrel in the tree is quite upset at all the thievery going on. A lot of squirrel chatter ensues.

Down the tree the squirrel came in a flash, chased away a couple of other red squirrels and took off after a much larger gray squirrel (unfortunately these guys were just too fast for me to photograph).

red squirrel chasing gray squirrel

You can just see the red squirrel (at the top of the photo) chasing the walnut thief.

red squirrel harvesting walnuts

Finally taking control of its hard-earned harvest of walnuts.

red squirrel harvesting walnuts

Off the squirrel goes to stash a nut in its larder; repeated at about 2 minute intervals until the entire pile on the ground was gone.

Ninja squirrel

I have tried many different feeder styles and placements in my backyard, but the gray squirrels have defeated every one of my squirrel-proofing attempts.  Nothing had worked to prevent the squirrels from empyting the bird feeders when I’ve been gone for several days, until we covered the trunk of the feeder tree (the Ohio Buckeye) with stove pipe sheet metal to keep them out of the tree altogether.

squirrel-proof bird feeders

But is this really squirrel-proof?  

No, because now they try to jump to the feeders from the porch railing.

flying gray squirrel

I think it might be just one ninja gray squirrel that is doing all the pilfering. He’s quite an athlete.

flying gray squirrel

It looks like he might have the distance and the height for this jump.

flying gray squirrel

But it’s not just the distance that must be covered, it’s the grab at the end of the jump that’s important.  Note outstretched paws ready to make the grab.

flying gray squirrel

No joy. A clean miss. But the jump is not fruitless because he is usually able to knock some seed out of the feeder onto the grass below.  The angle of this shot is deceptive.  The feeder is really about 6 feet from the tree trunk.

This squirrel must have tried to make the jump at least 12 times before he finally landed — and I missed the successful attempt unfortunately, because I wanted to see how he did it.

gray squirrel on feeder

Success!

Based on Ninja Squirrel’s prodigious feats of athleticism, I moved the feeder closer to the tree trunk.  We’ll see how he manages now.

Backyard drama

I just missed the drama by seconds.  The lone wandering coyote that occasionally visits the backyard had just chased a squirrel up a tree, when I spotted him wandering over to the neighbor’s yard.  Since I missed the action, I’m not sure how this squirrel got injured, but it has sustained severe damage to its left front leg.

The squirrel waited until the coyote had left to come back down the tree and resume his foraging.  It looks like the left foot is broken, some fur is missing from  the upper part of the limb and the tail is a bit frayed at its tip.  He was lucky to escape, but might not be very nimble at this point.

The squirrel waited until the coyote had left to come back down the tree and resume his foraging. It looks like his left foot is broken, some fur is missing from the upper part of the limb and the tail is a bit frayed at its tip. He was lucky to escape, but might not be very nimble at this point.

Coyotes subsist on scavenging from deer carcasses as well as hunting rabbits and mice in the winter. Squirrels make up little of their winter prey, so it’s possible that the squirrel’s injury is the result of an encounter with another predator.  Perhaps the coyote noticed that this squirrel was injured and thought it would be an easy meal.

Listening for mice in the snow below...

In the neighbor’s back yard, the coyote paused to listen for voles (meadow mice) moving about in the ground below the snow…

There's definitely something interesting there, but the snow has frozen into solid ice blocks and is too hard to excavate.

There’s definitely something interesting there, but the snow has frozen into solid ice blocks and is too hard to excavate.

This hunt was a bust, so the coyote moves on.

This hunt was a bust, so the coyote moves on.  Looking back at what might have been a substantial meal.

Basking tree

The trunk and top branches of the Buckeye tree outside my (somewhat dirty) porch windows are brightly illuminated with the morning sun, making it the perfect place to bask in whatever heat the sunlight can provide on this chilly morning.

A chilly start...

A chilly start…

Early in the morning, I’ve noticed a variety of birds and squirrels using the buckeye as a basking spot.

You don't normally see White-breasted Nuthatches at rest in this posture (head up).  Notice how the bird is plastered right up next to the trunk of the tree with its feathers maximally fluffed.  Is it possible that the tree surface is actually "warm"?

You don’t normally see White-breasted Nuthatches at rest in this posture (head up). Notice how the bird is plastered right up next to the trunk of the tree with its feathers maximally fluffed. Is it possible that the tree surface is actually “warm”? (well, probably warmer than the air…)

Red-bellied Woodpeckers apparently like the buckeye as a basking spot as well.

Red-bellied Woodpeckers apparently like the buckeye as a basking spot as well.  This bird was sitting at rest, not foraging in this spot.

Even the much, much larger-bodied Gray Squirrels enjoy a little basking time on the trunk of the tree when the temperatures dip into the -20 F range.

Even the much larger-bodied Gray Squirrels enjoy a little basking time on the trunk of the tree when the temperatures dip into the -20 F range. Belly and tail are plastered tightly to the trunk of the tree to soak up whatever warmth it can provide.

Usually we associate basking behavior with reptilian thermoregulation — sun-loving turtles and lizards, for example.  Even crocodilians lie around in the sun letting its heat warm them while they digest their latest meal.  But basking becomes important to birds and mammals as a means of economizing on the high metabolic expense of staying warm in extreme cold.

Here's a bird that specializes in basking to warm up on cool mornings.

Here’s a bird that specializes in basking to warm up on cool mornings.