Double trouble

The deer really like my backyard:  they eat my plants, they bed down in the wildflower garden leaving big depressions in the vegetation, they rest right under the bird feeder, and believe it or not, the half-grown fawns chase the foxes right out of the yard.  But I enjoy watching them parade through, so I just keep replanting the garden.

white-tailed fawns-

Make yourself comfortable…

white-tailed fawn-

By all means, help yourself to the garden perennials. This shrub rose may not recover, but oh well…

white-tailed fawns-

Yes, please do eat the buckthorn. I didn’t want that to spread in the backyard.

And where do these two learn where the best places to forage are?

white-tailed doe

From mom and dad, of course.

white-tailed buck-

This one has developed a taste for hostas.

Old friends in new places

Cave Creek ranch in the Chiricahua mountains near the New Mexico border is an idyllic haven for birders and hikers.  The scenery is pretty incredible too.

Cave creek near Portal, AZ

The view from my porch looks out over the creek and up into the rocks.

Cave creek near Portal, AZ

We’re set for an early morning hike up Cave Creek, to see if we can find some new birds we haven’t seen before.

Cave creek near Portal, AZ

Like the creek in Madera Canyon, sycamores line the banks of Cave Creek, stretching their limbs far and wide to create wonderful shade.

Sycamores can grow to be giants, but occasionally a limb snaps off, and we find animals taking advantage of the nook created by the amputated limb.

Great Horned Owl

This Great Horned Owl created a nest cavity in one of the huge clefts left after a limb dropped.  We also found a western Screech Owl seeking refuge during the daytime in a similar cavity in another sycamore.

Desert animals are often pale in comparison to others of their kind in other climates, as this Great Horned Owl is.  But there is more to the story than just differences in color.

Animals in this part of the U.S. seem to be entirely different geographic races of their parent species, and the extent of differences in their DNA, their color, their song, and their behavior have led scientists to begin splitting the southwestern desert species off from their representatives in other parts of the U.S. and Mexico.  That’s great for birders that like adding species to their life lists!

Coue's white-tailed deer

The white-tailed deer are much smaller than their relatives in my backyard in MN. In fact, they are technically known as Coue’s white-tailed deer, a dwarfed race, or is it a different species?

Hairy woodpecker, Cave Creek, AZ

Here’s a familiar bird, a male Hairy Woodpecker, but it looks quite different from the MN variety, as it lacks the spots on the wings, and has a broad white stripe down its back.  Would a MN female Hairy Woodpecker refuse to mate with this bird?  If so, then they would be considered separate species.

Brown Creeper, Cave Creek, AZ

Brown Creepers have been divided into four groups now, one in Mexico, and three others in the U.S. divided into eastern, Rocky Mt, and Pacific races.  Differences in song and plumage have been known for some time, but recent DNA analysis has confirmed the separations.

We met some new friends along the Cave Creek trail, but apparently our “old friends” may be new as well.

Feeling frisky

A light snow yesterday morning brought the local deer herd by the backyard to clean up all the spills under the bird feeders.  First, a small group of does wandered through the yard, and then a couple of young bucks, who were too cool to feed on fallen bird seed but felt frisky enough to put on a shoving match instead.

deer-butting-heads

“Big brother” shoved “little brother” (no doubt they are completely unrelated) several feet, repeatedly bumping heads.

deer-butting-heads-

Kind of unfair that one young buck has antlers and the other doesn’t in this shoving match. But ouch, this looks like a good way to get your eye poked by an antler tip.

deer-butting-heads-

Junior has had enough of this.

deer-butting-heads-

Completely disinterested in each other now, they went their separate ways. It must be lonely being a young buck in the winter… nobody to hang out with.

resting in the backyard

Back in Minnesota once again, I looked out my porch windows and found three deer resting on the neighbor’s lawn.  I assume this is the same doe and twin fawns that I saw perusing the flower beds in the backyard before I left town in August.

doe-and-fawns

My presence alerted the doe, but all three were resting comfortably in the shade when I first spied them, chewing their cud and digesting their morning repast.

early fall white-tailed deer fawn

This is notch-ear — observed earlier this summer. The fawns have now molted out of their spotted coat and acquired the mature tawny hair color.  This youngster seems a bit muddy on the nose and forehead.

early fall fawn

Its sibling couldn’t care less that I’m 100 yards away clicking the camera shutter.  I think I can see little antler buds on its forehead, making this a male-female pair of fawns.

whitetail fawns-

A month ago ( see post on lazy summer days) they looked like this.  Note, the notch-eared fawn on the right.  

white-tailed deer doe

The doe looks over at her twins as if to say, “Rest time is over; time to get out of here.”

lazy summer days

What do you do on a hot, summer day when soft, grassy lawns and the sweet aroma of wildflower blooms beckon?  It calls for a short nap in the grass, I guess, even for wildlife, and the backyard was the perfect place yesterday.

whitetail fawns-

A pair of fawns wandered by, one of whom decided on a short rest while munching on fallen leaves.

whitetail fawns-

Still spotted, although they’re now half the size of their mom.  The left ear of the fawn standing has a torn notch — perhaps it had an encounter with a predator early in life.

whitetail doe-

Mom watched me warily from the woods, as I snuck up on her darlings.

red fox kit-

A little later a red fox kit wandered by, checking out the squirrels at the bird feeder.

red fox kit-

And then settled down for a little rest near the wildflower garden while still watching those squirrels.

red fox kit-

Resting in the shade on a hot summer day…that’s the life.

“here’s looking at you”

With huge, globular eyes that make up about 50% of their head, dragonflies are amazing visual predators.

dragonfly eyes

A sampling of beautiful dragonfly eyes from a Google search

And those eyes are key to their success as highly visual predators.

halloween pennant-8111

Halloween Pennant dragonflies search from the tips of the highest plants in grassy fields, with their orange-banded wings fluttering in the breeze.

In fact, they are probably the most efficient predators in the animal kingdom, with an astounding 95% success rate per attempt.  In comparison, lions are lucky to succeed once every four to five tries and great white sharks only manage to catch what they are after half the time.  How do dragonflies do it?

Here's looking at you...

Here’s looking at you… the facial disk of the Horned Clubtail.  Depending on the angle of incoming light (and observer position), the eyes might look turquoise blue.

Enough clues? The eyes and more particularly, the wiring of retinal cells to the brain is key to their hunting success.

The eyes and more particularly, the wiring of retinal cells to the brain, is key to their hunting success.

Those giant optical domes on the top of their heads give them a 360 degree view, and contain as many as 30,000 optical units (ommatidia), each with a complement of photopigments that can process images separately.  Thus, instead of one retinal focusing area, they have thousands.

The eye of a dragonfly, showing the individual facets or ommatidia that contain visual pigments. Each facet can detect and send an image to the insect's brain. Imagine having 30,000 eyes!

The eye of a dragonfly, showing the individual facets or ommatidia that contain visual pigments. Each facet can detect and send an image to the insect’s brain. Imagine having 30,000 eyes! From Science Blogs, July 8, 2009.

In addition, where human eyes have three photo pigments, dragonflies have 15-30 pigments that can detect light in ranges beyond human capability, including detection of polarized light.  What if we could see images in UV or infra-red, or whatever other spectral wavelengths dragonflies can resolve?

A newly emerged male Common Whitetail has the wing markings of a male and the abdominal coloration of the female. Over the course of the next week, he will gradually transform to the powder-white abdomen typical of males.

A newly emerged male Common Whitetail has the wing markings of a male and the abdominal coloration of the female. Over the course of the next week, he will gradually transform to the powder-white abdomen typical of males.

Photopigments sensitive to blue and UV light are concentrated in the upper part of the compound eye, so that prey (or predators) above them stand out against a perceived white background.  Pigments sensitive to longer wavelengths (green, yellow, red) are concentrated in the lower part of the compound eye and allow prey flitting below the dragonfly in dense vegetation to be detected.

This Dot-tailed Whiteface continually moved its head up and down as it scanned for prey. Each time I tried to get in front of it to photograph its white face, it flew away.

This Dot-tailed Whiteface continually moved its head up and down as it scanned for prey. Each time I tried to get in front of it to photograph its white face, it flew away.

In addition to their heightened visual sensitivity and acuity, dragonflies exhibit single-object tracking, which means they keep a particular prey item exactly on a collision course with themselves. (Kind of sounds like a drone, doesn’t it?)

And that’s where the fancy flying comes in handy. To keep the image of the prey in exactly the same place in their visual field, a dragonfly might fly up, down, sideways, backwards, even upside down, if needed. Four wings that can move independently facilitate this maneuverability, and in fact, they don’t even need all four.

This female 12-spotted Skimmer has lost half of its hind wing, but it's doubtful that it comprises hunting success.

This female 12-spotted Skimmer has lost half of its left hind wing, but it’s doubtful that it comprises hunting success.

These amazing little machines have been around for several hundred million years, feasting on slower flying, less visually talented prey.  Such a visual formula for hunting success ensures that they will be around for a while, keeping those pesky mosquitoes in check.

[This is an edited version of a previous post from Backyard Biology]

Lost and found

The local deer herd wanders through the back yard several times a week.  There are three bucks of different sizes, all of which still have their antlers, and six good-sized does.  With one exception, they all seem to have come through the winter looking very healthy.  The exception looks a bit skinny and has a mangy coat — but will probably survive, since winter seems to have given up its hold here.

white-tailed deer bucks-

The two largest bucks seem to get along well, and I often seen them together, browsing or dozing in the sun. The bigger of the two (on the left) has a bigger rack and seems a bit beefier, or perhaps just didn’t lose as much weight over the winter as the other buck (in back).

This might be the same pair I observed hanging around together last December. They did some friendly sparring, but usually were quite docile around each other.

white-tailed deer bucks-

Big Buck does not like Little Buck however, and usually gives him a head butt or a threatening glance.

This is the time of year when bucks lose part or all of their antlers, as a zone of separation between their skull and the antler bone begins to break down and the connection is loosened.  The tangle of vegetation the deer wander through might be enough to dislodge a loosened antler, although I have never found any piece of an antler out in the part of the way backyard the deer inhabit.

white-tailed deer-

Does on high alert…as workmen (in yellow and orange) enter the far backyard to dredge out the ponds there.

The other day some workmen interrupted the deer herd’s exploration of my backyard, and the entire herd bolted.  Some ran up the hill toward the neighbor’s house, and one buck came galloping up toward my garage on a dead run headed for the front yard.  Now there is only a narrow three foot gap between the garage and some lilac bushes, but Mr. Buck must have negotiated the gap quickly because I didn’t even see him after his mad dash.  But look what he left behind.

white-tailed deer antler-

Either he hit the bushes or the side of the garage with his antler and it popped off.

white-tailed deer antler separation point-

A tiny spot of blood on the separation point of the antler, but it was obviously ready to be dropped.

white-tailed deer buck-

I’m guessing it might have been the medium-sized buck’s antler based on its size, but don’t know for sure.

white-tailed deer antler-

Your loss, Mr. Buck. But I think I’ll keep what I found.

Snow day

A “snow day” in Minnesota usually means kids get out of school, businesses close early, and we are warned to stay indoors until snow plows have made the roads manageable.  Although none of that happened, high winds and rapidly falling snow made it seem like much more of an emergency than it really was.  But the effect on the landscape was truly beautiful, as only heavy snowfall can be.  I gazed out my porch windows wishing some little animal would stop by and get framed in the puffy snowflakes that were accumulating on every surface.

Not more than 5 minutes later, the deer herd wandered into the yard, nosing around for fallen bird seed or scraps of months-old dead plants.  And this was the scene…

deer herd in the snow-

The deer seemed surprised that there was so much white stuff covering up the food. White splotches on the deer are the snowflakes closest to me as I shot the view through the porch window with my cell phone camera.

deer herd in the snow-

There is usually something to eat in the wildflower garden in the spring and summer, but not now.

deer herd in the snow-

Then it’s off to the neighbors yard to see if there is anything good to eat over there.

And that will be the last of snowy scenes on this blog for a couple of weeks, while I’m traveling to warmer, greener, and more scenic spots in tropical climates.

Blending in… or not

In the winter, everything seems to take on shades of gray and brown, even the several day’s old crusty snow.  When I looked out in the backyard early one morning recently, I saw a few members of the local deer herd wandering down the hill toward the pond, but didn’t think there was much of photographic interest there.  So I just snapped a quick couple of images.  When I finally got around to looking at those photos, I found the deer match their gray-brown background so well, I didn’t even see the large buck having a morning rest in the snow.

white-tailed buck resting

It’s easy to miss even large-bodied animals, like the buck in the left background, when they aren’t moving around.  When the light is dim in the early morning, and the world is gray-brown, whte-tailed deer blend in nicely with their surroundings.

white-tailed buck resting

A little photo “massage” makes the buck stand out a little better.

Most of the gaudy male birds wear their less conspicuous plumage in the winter — to better blend in and avoid being someone’s lunch.  But there’s always an exception to that general rule:

male Northern cardinal - wnter-

Mr. Cardinal doesn’t stay in one place long, and he is obviously the brightest thing visible in this monochromatic (almost) background.  He visits the feeder right at dawn and again at dusk, and stays tucked into dense vegetation during the rest of the day.

female cardinal - wnter

Mrs. Cardinal is less colorful, but she too only visits the feeders at dawn and dusk, when there is barely enough light for me to see which birds are there.

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.