I live in an ecotone, a kind of blend between the coniferous forest of the Transition Zone, and the oak woodlands and savannahs of the Upper Sonoran Zone. The "life zones" of Merriam have fallen out of favor in recent decades, but I still find them very apt. Merriam recognized that, as elevation increases, in a mountain range, vegetation changes in very much the same way as if elevation remained constant, but latitude increased. To ascend the Sierra Nevada to the 5,000-foot contour and the realm of the White Fir is much the same as to go north into southern Canada. Merriam did his seminal research near Fort Valley, Arizona, where my grandfather Leland Towle worked as a forest ranger, at the time.
That was almost a century ago. Here, on Moody Ridge, in this ecotone between two different assemblages of vegetation, one sees two different assemblages of animals, also. For instance, both the Scrub Jay of lower elevations, and the Steller Jay of higher elevations, are here.
Today a young squirrel is slowly dying in my yard. It is a California
Ground Squirrel, Citellus beecheyi, and is more closely identified
with the Upper Sonoran life zone of the Scrub Jay, than with the
Transition life zone of the Steller Jay. And, since my yard is on the
cusp between the two zones, there are many Gray Squirrels in the area, as well. And Flying Squirrels, for that matter, although these are rarely seen.
The Ground Squirrel lives up to its name, only rarely venturing into
trees, and when it does, never climbing more than, oh, fifteen or
twenty feet. It will clamber into Ceanothus bushes and harvest the
seeds, storing them in cheek pouches, and then find some conspicuous
perch and slowly work through the seeds it has saved. It is strange
that they like these highly exposed perches, on a large boulder,
perhaps, for they are preyed upon by Golden Eagles.
It may be that another predator worries them much more than mere
eagles. The Western Rattlesnake, Crotalus viridus, is an avid hunter
of the Ground Squirrel. One might almost say, given ground squirrels,
rattlesnakes are sure to follow.
In this little clearing in the woods, in this ecotone, there has
always been a colony of ground squirrels, at least, for the
thirty-three years I have been here, there have been ground squirrels.
They fall victim to foxes, to bobcats, and, although one is extremely
unlikely to actually see it happen, to rattlesnakes.
This summer brought many a baby squirrel into the colony. The colony burrows are scattered over a broad area, and have multiple entrances, and may also be shared between individual squirrel families. It seems there are more squirrels now than ever before. One develops a sense of their lives and habits. I can recognize their metallic "alarm squeak," and sometimes, hearing the squeak, and taking a look around, I will see the fox, or the bobcat, which inspired that squeak.
The squeak is repeated, every second or so, for minutes, sometimes tens of minutes, at a time. It is painful to listen to this squeak. With a roar, and a hurled rock, I will sometimes try to quiet that squeak.
So. There are many squirrels, hence, as night must follow day, there must also be many rattlesnakes.
And there are. Four or five different snakes have visited the yard this summer. The hotter days seem to somehow inspire them to visit. Years ago, when my children were small, I killed rattlesnakes in the yard. In recent years I do not bother them. Live and let live. And yet ... and yet, they are so very hard to see if not moving, and they do not always rattle, and they coil up in places one can't really see well, anyway. It is a bit nerve-wracking. To have four or five different snakes visit, in one summer month, is a first in my several decades here.
I recently learned, on the Internet, that adult ground squirrels are immune to rattlesnake venom, and also, that they will wave their tails back and forth while facing a rattlesnake, and that the temperature of those waving tails increases by some five degrees at the time.
Yesterday I heard a doubled alarm squeak, in the sultry smoky heat of the afternoon, and walked slowly towards the sound, expecting to find a rattlesnake.
An adult and a juvenile squirrel were atop one of their favorite Ceanothus-seed-eating perches, just above their burrow, both facing a spot a foot and a half away, and every two or three seconds, at exactly the same time, they would rapidly wave their tails, and squeak. It was as if they were telepathically connected. I could not see anything for them to squeak at, and slowly ventured closer.
The young squirrels are much more fearful of humans, than their parents, and they (there turned out to be a second juvenile, perched a few inches below) scampered away once I was within six or eight feet. The adult remained, steadfastly squeaking and waving its tail. Finally I saw the snake. It was occupying a crevice between two boulders, directly above one of the burrow entrances. The head and upper part of the snake's body were already coiled and still, the tail was extended away a foot or so, and was slowly being drawn into the coil.
I kept an eye on that snake as the afternoon dwindled into darkness. It never moved. I saw the adult squirrel enter the burrow, only a foot from the snake. The snake never moved. It seemed to be waiting for the squirrels to forget its presence.
At dawn I returned. The snake had gone. There seemed a peculiar lack of squirrels in the yard. This is common after a fox or bobcat visits.
An hour later I looked around again; an adult ground squirrel was on a large boulder, seemingly surveying its domain. And a few feet away, a juvenile was stretched out on the ground, its eyes open, alive, but hardly able to move. It had been bit by a rattlesnake in its right hindquarters, paralyzing its right hind leg. Over the next hour it painfully dragged itself twenty or thirty feet, downhill, towards one of its family burrows. The adult surveyed its child's progress. But then the venom's force overcame the young squirrel. It stopped moving. Its eyes closed. An hour later, it was dead.
There was absolutely no sign of the snake. All the squirrels entered their burrows and stayed within for hours, in mourning.