April blizzards create new challenges for wildlife, already limited by the diminished resources available. Can squirrels really remember where they hid some buried treasure last fall? Apparently so.
How picturesque, stumbling onto a mule deer herd in Calero county park east of San Jose, CA, as they munched their way through the spring wildflowers.
It may be a while before Minnesota takes on such a green glow!
If you google that question, you’ll find that gray squirrels can jump at least 4 feet straight up in the air, and at least 9 feet horizontally. I’ve had a peanut feeder hanging in the buckeye tree about 7 feet from the trunk of the tree all winter, and just today a gray squirrel finally figured out how to get to the feeder. (Shot through the window looking into the afternoon sun with a terrible reflection.)
The momentum of the landing creates a violent swing in the feeder, which can dislodge the squirrel that might be just hanging on with its toes.
After several failed attempts involving collisions with the plastic dome over the feeder,
the squirrel successfully launched itself from just the right height on the tree trunk, with just the right trajectory arc, to land most of its body on the side of the feeder.
Athletic and smart, that’s the gray squirrel key to success.
A great surplus of the fluffy white stuff has been accumulating in the backyard this past week, and there are predictions of more to come. Squirrels have been busy excavating in the snow looking for fallen seed. Every now and then, they seem to take a break and just hang out on a branch.
I don’t know what this frantic chasing up and down branches is all about, but I did notice that the red squirrels run toward birds in these same branches that have just come back from the feeder with a seed or a peanut. Maybe they are hoping the birds will drop whatever they are eating and fly off, leaving the tidbits for the squirrels to find?
I’ve noticed that the frenzied feeding activity at bird feeders (see yesterday’s post on “finch feeding frenzy“) usually coincides with a precipitous drop in temperature the next day, but I’ve wondered what enables birds to predict that occurrence.
Cardinals, Blue Jays, Nuthatches, Chickadees, Slate-colored Juncos, House Finches, and Goldfinches all made an appearance at the bird feeder during the morning hours the day before the frigid temperature drop.
But it’s not the temperature drop the birds are predicting, it’s the drop in barometric pressure. Low barometric pressure in one area means there will be air movement from a higher pressure area, and in the winter, that usually means Minnesota will receive a big blast of frigid Canadian air.
And the data bear this out: barometric pressure reached a low point at noon on the day of frenzied finch feeding and increased almost 30 mm by midnight the next day, bringing with it bright sunny weather but a 30 degree drop in air temperature.
It seems that birds are the only land vertebrates (with a couple of exceptions) that possess a paratympanic (i.e., next to the ear drum in the middle ear) barometric sense organ, and it is derived from the same hair cells in sharks and their relatives that provide those fish with information about their jaw movement relative to the prey they intend to gobble up.
So, is a 30 mm change in barometric pressure (a little over 1 inch) enough to trigger such a feeding response in my backyard finches? Yes, it is. Experimental data on White-throated Sparrows showed that they could detect a pressure change of as little as 10 mm: when barometric pressure was decreased artificially in a chamber holding migratory sparrows, they immediately began feeding when the lights were turned on; when the pressure was higher (and normal), they became active, preening and hopping around in the chamber, but not feeding.
And why is it just the birds that have evolved this magnificently sensitive sensor? In addition to predicting weather fronts, the barometric sensor is most useful for maintaining level flight at a particular altitude during migration.
What about mammals, especially humans? Can we detect changes in barometric pressure?
Only one species of bat possesses a physical sense organ that detects barometric pressure, but mammals, including humans, can sense changes in pressure in their ears, sinuses, sometimes joints, but there is no specific receptor for the sensation. Rather it is changes in pressure within a confined cavity that elicits the sensation, and not in everyone.
Although it is far easier to find birds in the southwestern deserts, more than 100 mammal species live there too, a few in some of the harshest and most challenging environments. Most are usually active only at night or in the twilight that precedes sunrise or follows sunset. Why? Because daytime temperatures can be very hot, water is limited so keeping cool by evaporation is dangerous, and there aren’t very many places to retreat to cool shade.
Mammals cope with the heat by avoiding it, storing it, unloading it, or offsetting it by consuming the water-filled bodies of their prey. Here are a few examples of these strategies in mammals of the Living Desert Zoo in Palm Desert, CA.
Avoiding the heat: bats, rodents, kit fox, coyote, mountain lion, bobcat
Big carnivores need to retreat to sheltered crevices or caves during the hot daytime hours, while mice can keep cool in underground burrows. Their dense fur is an adaptation to keep them warm on clear, cold desert nights, and in the winter. In addition, water lost by panting to keep cool can be replaced by the body water in their prey. Their home range might even include a water source like a spring or pool.
Storing the heat: pronghorn antelope, bighorn sheep
Large-bodied herbivores can’t escape the heat, so they tolerate it by storing it in their large body mass, and allowing their body temperatures to fluctuate several degrees over the course of the day. Heat gained during the daytime can be unloaded by radiation or convective cooling at night. Bighorn sheep can withstand dehydration for several days (to a level that would kill a human) and can replenish all of their body water immediately upon drinking.
Unloading the heat: jackrabbits, mule deer
Both deer and rabbits seek shade during the day, but use their very large and well vascularized ears to radiate heat away from their body.
Fennec foxes from Saharan and Arabian deserts use a similar strategy to unload heat from highly vascularized, over-sized ears. Apparently the large surface area of their ears also helps them hear prey moving around under ground. It’s interesting to see such convergence of strategies in unrelated animals from different continents.
And what about the unlovely Javelina?
Their solution to the challenges of desert life? Live near the water and stay in the shade, for example, under a trailer!
We hiked about a mile and a half out to the sand dunes at Año Nuevo state park, and were excited to find the giant forms of sleeping Elephant Seals there.
Elephant seals don’t eat or drink while on land, instead subsisting on the fat stores acquired during their many months at sea. When they leave the breeding beaches, males and females take differ routes to feeding grounds either along the coast (males) or open ocean (females), but both feed at extreme depths, up to 5000 feet deep in dives lasting almost 2 hours. (There are some special adaptations for that activity, to be discussed later). Preferred foods are usually benthic forms like rays, bottom-dwelling sharks, squid, hagfish, etc.
From David Attenborough’s “life in the freezer”
For those following the travelog, yes we made it to California, just an hour before a major winter snowfall hit Donner Pass. Cars were delayed 17 hours on I-80 and chains we didn’t have were required after 36 inches of snow fell on the Sierras over the weekend.
The grandkid cousins had a chance to play together and exercise the McNab border collie that lives here in CA. She’s great entertainment for the kids, and gave me a chance to practice my high speed (and she is definitely a high-speed chaser) photography.
Take the vast, open prairie of South Dakota, and remove the cows and farms, add some bunch grasses, sage brush, and pockets of stunted juniper, along with a few rolling hills, and you have Eastern Wyoming.
Somehow on our way from I-90 to I-80 in eastern Wyoming, we got off the beaten track and stumbled across a road through a picturesque canyon right before sunset. One of those construction signs with lighted messages warned us, “wildlife next 10 miles”. This was quite exciting because we had seen a total of exactly one hawk the entire day. Sure enough around one corner, there were three mule deer standing next to the road, but they quickly scurried away.
We spotted a raven or two as we drove along the smaller roads, but the winter landscape in this part of Wyoming seems devoid of wildlife: few hawks, no coyotes, no antelope, no jack rabbits, no cattle, no people. It might as well be the Gobi desert.
In the twilight we negotiated our way back to I-80 and were treated with a glorious sunset.
The next day, following I-80 west from Rawlings to Evanston and then into Utah, the Wyoming landscape got more and more interesting, as rolling hills of sagebrush gave way to rocky cliffs, deep canyons, and taller juniper interspersed with a few pines. But the sparseness of human settlement did not change. This is land for the very rugged, independent, individualists of us, who really enjoy their alone time.
Wyoming is challenging, and mystifying, and interesting, and welcoming. Towns have unusual names like Winner (where you introduce yourself by saying you’re a Winner-ite), Chugwater (how do you suppose it got that name?), and Guernsey (are there actual cows there?). Friendly hotel and restaurant personnel provide wonderful service, with nary a country twang in their speech. And I bet they are strong enough to throw a hay bale up on a pickup!
Our travels took us far and wide this year: Peru, England, Scotland, Iceland, California a few times, New England and Maritime provinces of Canada, Florida, and of course, northern Minnesota. There were so many interesting, colorful, and unique encounters with wildlife it was hard to pick favorites, but my choices are partly based on diversity of subject material. Of the ones below (that made my top 15 list), which are your favorites? (You can click or tap on each image to enlarge it to full screen and use the back arrow to return to the post.)