Friday, August 24, 2007
I believe this is a lodgepole chipmunk (Tamias speciosus), but I am not certain. The old addage, "if it looks like a duck and sounds like a duck. . ." may apply to chipmunks in general, but it doesn't apply to species of chipmunks. Some chipmunk species are remarkably similar in coat color and size, and only diligent study reveals their true identify. This one, photographed at Lassen National Park among the Jeffrey pines, could also be the yellow pine chipmunk (T. amoenus).
Californians proudly boast 13 species of chipmunks. (Well, they should anyway.) Yes, 50% of the world's species of chipmunks live in the golden state. Most of the other species live in the intermontane parts of the western US, Canada, and Mexico.
Chipmunks are basically mini-tree squirrels with racing stripes. They occur from sea level to treeline, and fill an ecological niche between the terrestrial world of ground squirrels and the largely arboreal world of tree squirrels.
The sexes show variable dimorphism in body size. In more extreme habitats females tend to be larger than males, while males are the larger sex in other areas. This infers that big female chipmunks have certain advantages, perhaps in energetics and reproduction--though the subject needs more study. Their best known trait is their internal cheek pouches, which allow them to haul food from feeding areas to hoards and nests.
The two most widespread species, the eastern chipmunk (Tamias striatus) and the Siberian chipmunk (T. sibiricus) have the largest geographic ranges. They also have more generalized traits, so mammalogists believe they are a bit closer to the ancestral chipmunk. The hotbed of chipmunk evolution is western North America. Here where the forces of nature have created a quiltwork of habitats they have evolved into many forms.
The debate isn't settled on where exactly chipmunks came from--Eurasia, North America, or perhaps somewhere in between, like Beringia. If the ancestral chipmunk was Eurasian or North American, however, it had to cross the Bering land bridge, like a lot of other mammals in the past.
Contrary to popular belief, the word chipmunk does not owe its derivation to the resemblance of these rodents to cheerful Jesuit monks, or men of any particular monastic order. The word comes from the Algonquian "achitamon" for "one who descends trees headlong". In other words, chipmunks can rotate their hindlegs and climb down tree trunks headfirst. They share this trait with tree squirrels. Their small size gives them advantage when it comes to negotiating shrubby vegetation that bears nutlets, berries, and drupes. Thus they get around much better in the brushlands, chaparral and forest understory than ground squirrels and tree squirrels.
Like ground squirrels, they nest and hibernate in burrows, but apparently some species, like the lodgepole chipmunk, make tree nests in cavities or exposed on a limb close to the trunk. These are used by mother and young after the munklets develop their climbing skills. This practice of using both subterranean and arboreal nests is just another example of how chipmunks live between two worlds.
Best, T.L., R.G. Clawson, and J.A. Clawson. 1994. Tamias speciosus. Mammalian Species, No. 478:1-9.
Broadbooks, H.E. 1974. Tree nests of chipmunks with comments on associated behavior and ecology. Journal of Mammalogy, 55(3):630-639.
Levenson, H. 1990. Sexual size dimorphism in chipmunks. Journal of Mammalogy, 71(2):161-170.
Levenson, H., R.S. Hoffmann, C.F. Nadler, L. Deutsch, and S.D. Freeman. 1985. Systematics of the Holarctic chipmunks (Tamias). Journal of Mammalogy, 66(1):219-242.
Ralls, K. 1976. Mammals in which females are larger than males. The Quarterly Review of Biology, 51:245-276.
Sutton, D. A. and D.B. Patterson. 2000. Geogrpahic variation of the western chipmunks Tamias senes and T. siskiyou, with two new subspecies from California. Journal of Mammalogy, 81(2):299-316.
Wilson, D.E. and D. M Reeder. 1993. Mammal species of the world, a taxonomic and geographic reference. Smithsonian Institution Press, Wasgington D.C. and London.
Thursday, August 23, 2007
Indeed she does, and you can't blame her. It's been hot here, and bear baths seem to be more about cooling off than personal hygiene.
Like . . . "Ahhhh...this sure feels good."
The bears here rarely bathe at night. Their visits to this creek, now just a series of pools, have been in the morning, around noon, or in late afternoon.
Last week I changed memory sticks in the creek cam, and found that three bears had visited the pool.
If you'll indulge my anthropomorphism, this selection from 27 pictures on August 1 tells the best story.
It was 12:40 PM when the camera woke up and started taking pictures. She was just settling in the pool.
After her initial luxuriation, she drank deeply of her bath water. (This is not recommended.)
"Oh no, there's that damn camera flashing at me again. Oh well. I'll ignore it for now. I can always check it out later."
"Wait a minute! What's that? I heard something . . ."
"Waaaahhhh! I'm outta here!"
Tuesday, August 21, 2007
When H. Ross Perot declared 'I'm all ears' early in the 1992 presidential campaign, he really meant he was listening intently. But the articulate entrepreneur was blessed with robust ears and his statement earned him belly laughs that Jerry Seinfeld would envy.
Now that we're talking ears, how many times have you wondered why rabbits have such long ones? I mean, when you are cruising along and see a roadkilled jackrabbit, or think about the energizer rabbit . . .do you knit your brows and ponder:
"Why? Why is it that they have such large ears? Is it all about good hearing, or is something else going on?"
What? The question has never crossed your mind? You've got to be kidding!
Well then, how about this: the antelope jackrabbit (L. alleni) of our American southwest has ears that are 25% of its body surface. On the other hand, the ears of the black-tailed jackrabbit that you see at my water trough make up 19% of its body surface. Still impressive structures.
Back in the late 1800s a naturalist named J.A. Allen, who spent a lot of time measuring museum specimens (including the ears of rabbits) had a revelation. He noticed that birds and mammals from cold climates have smaller extremities than their relatives from warmer climates. He had hit on a general principle of the natural world, and he wrote it up and published it. Thus we got Allen's Rule.
Since then biologists have spent countless years measuring more museum specimens, and have found Allen's Rule to be less comprehensive than Allen thought. It does not apply to all species, nor to all extremities (legs, tails, ears, noses, beaks). In cottontails and brush rabbits, for example, no extremities 'obey' the rule. But it does apply to the ears (and tails) of jackrabbits.
It makes sense, because the ears of rabbits are like automotive radiators. You need bigger radiators in hot climates. The difference is that jackrabbits have more sophisticated thermostats than cars, and thanks to the studies of Professor Richard Hill and his associates, here's how they work in a nutshell.
Jackrabbits crank down blood flow to their ears when they are resting at temperatures below 24 C (=75F). Under these conditions their ear temperatures are slightly above air temperature (from 0.3 to 2.5 degrees C). When it's freezing on the plains, jacks have chilly ears. That way they conserve body heat.
At warm temperatures (above 31C = 88F) the ears' arteries dilate, blood flow increases, and the ears shed body heat by convection and radiation.
But when jackrabbits are exercising, their body temperature increases just as it does in people. Of course, running jackrabbits pant and thus cool their snouts by evaporation, but their ears can become considerably warmer than the air, and they also vibrate, which to some extent can help shed body heat by convection. After 15 to 25 minutes of rest the ears have cooled off, and the rabbits are back to their resting body temperature of 38C (=100F).
What about when it gets really hot? When temperatures reach 45.5C (=114F) jacks rely on panting and evaporation to shed body heat. Most of the time the ears stay cooler than the air because body temperature is less than air temperature, and their blood flow is restricted. However, every several minutes the arteries engorge for 10 to 20 seconds, at which time they absorb heat from the air. This adds significantly to the animal's overall heat gain.
If you are trying to get rid of heat this seems counterproductive. So, why let those big ears absorb more heat? Why not minimize their blood circulation so this doesn't happen? The most logical answer is that hot ears have their own metabolic demands for oxygen, blood sugar, and waste removal.
If you like the car radiator analogy, think of it this way. You've got to flush your radiator if you want to keep it working.
Griffing, J.P. 1974. Body measurements of black-tailed jackrabbits of southeastern New Mexico with implications of Allen's Rule. Journal of Mammalogy, 55(3):674-678. [the temperature data in this paper were in error, as noted in Hill et al (1980)].
Hill, R.W. and J.H. Veghte. 1976. Jackrabbit ears: surface temperatures and vascular responses. Science, 194(4263):436-438.
Hill, R.W., D.P. Christian, and J.H. Veghte. 1980. Pinna temperature in exercising jackrabbits, Lepus californicus. Journal of Mammalogy, 61(1):30-38.
Hinds, D.S. 1977. Acclimatization of thermoregulation in desert-inhabiting jackrabbits (Lepus alleni and Lepus californicus). Ecology 58(2):246-264.
Stevenson, R.D. 1986. Allen's Rule in North American rabbits (Sylvilagus) and hares (Lepus) is an exception, not a rule. Journal of Mammalogy, 67(2):312-316.
Sunday, August 19, 2007
[Basking harbor seals at Bolinas Lagoon, Marin County, California]
It's a neighborly thing to do -- walking your neighbor's dog. And it doesn't have to be drudgery, especially when you live in a small seaside community like Jenner, at the mouth of the Russian River on California's Sonoma County coast. There you can take the pooch to the beach, and play retrieve the stick. This is exactly what Angel Garcia was doing when a huge Northern Elephant Seal torpedoed from the surf and seized the pit bull in its jaws. Sativa, the pooch managed to break free. For a few moments, man and dog stood defiant before the great hulk. Then they decided 'discretion is the better part of valor'.
Meet Nibbles, an elephant seal with a checkered past. Since he was an adolescent, five years ago, he has been visiting this beach and forcing himself on female harbor seals. Yes, that's what I said. He has been trying to have sex with them, and in the process he kills them. I should also mention that the oaf weighs about 10 times more than his victims. Bull dozer deaths.
At first it seemed to be accidental, the errors of confused and testosteronized youth, frustrated by the bullying of larger males. Then last year Nibbles started to kill the seals with a head bite. More recently he started to eat the dead victims. It seems rather bizarre, but as Mark Twain said, "truth is stranger than fiction". [If you haven't viewed the video, now is the time, but be forewarned -- it's gory.]
What do people make of this? The public is more likely to rush to judgment and pronounce the animal a degenerate miscreant. Biologists know that our knowledge of seal behavior may be incomplete, and that such events may not always be abnormal.
So I wrote to Daryl Boness, a good friend who is an expert on pinniped behavior.
Daryl replied that while raping and pillaging is not common among pinnipeds, elements of Nibble's bizarre behavior are known in a number of species. He has observed adult male grey seals raping female harbor seals. "While I have not witnessed the harbor seal being killed or eaten, I did get a report from someone of harbor seals being killed by a male under such conditions, but there was no indication of eating the carcass.
"However, there is a published report of male New Zealand fur seals occasionally stealing, killing and eating pups of their own species. There was no evidence of sex with the pups, but young South American fur seals will steal pups from mothers and have sex with them, which often leads to their death. Males of this species also will group together and steal females from a territorial male."
It's not pretty stuff, but there you have it. Male seals and sea lions are aggressive by nature. When you are talking about seals and sex, the word courtship seems an egregious malapropism. Copulation in pinnipeds is a brutish thing. The fumbling and bumbling sexual attentions of adolescent males are at times directed to inappropriate subjects such as immature animals. You can add to this the fact that some pinnipeds (walruses, northern sea lions, and leopard seals) prey on smaller pinnipeds, and the lines between normal and abnormal start to blur.
The point I want to make is that some aspects of animal behavior may seem immoral or indecent by human standards, but may not be abnormal.
That isn't to excuse Nibbles.
As Daryl said, "I think these young males are driven by sex hormones and things get out of hand. It is likely a learned behavior. Killing and eating the carcass is the most aberant part of it. You see lots of young grey seal males raping weaned pups on Sable Island, but you don't see them killing and eating the pups.
"Your elephant seal male may be the equivalent of a human nut case. How's that for being scientific?"
Daryl is obviously a little uncomfortable about being anthropomorphic. But I agree with him . . . we can always rely on our own species for the best examples of the bizarre and abnormal.
Campagna et al 1988. Group raids: a mating strategy of male southern sea lions. Behaviour, 107:44-60
Campagna et al 2000. Pup abduction and infanticide in southern sea lions. Marine Mammal Science, 16(2):494-500.
Mortenson, J. and Follis, M. 1997. Northern elephant seal (Mirounga angustrirostris) aggression on harbor seal (Phoca vitulina) pups. Mar. Mamm. Sci. 13(3): 526-530
Friday, August 17, 2007
Scat: feces, dung.
Scattraction: the attraction to scat. (A contraction of scat + attraction) (I made it up).
As you already know, mammalian carnivores have a powerful attraction to stinky things. So why not use scat as a "lure"? Sooner or later some one is going to come along, take a sniff, and make a deposit. Right?
Last month I set two cameras on a fire road where coyotes and gray foxes leave their calling cards. The cameras were aimed at places where one species had "over-marked" the feces of the other. Presumably this tells the passing coyote or gray fox who visited the site most recently.
The only visitors who allowed themselves to be photographed were striped skunks and gray foxes. Since better than half the pictures were blank, many visitors escaped detection.
I suspect some of them were clever coyotes. (This is a frustration I have learned to live with, but I am confident that one of these days I will get their pictures too.)
I didn't want to tamper with the site, but a couple weeks ago I found the hide of a squirrel that had probably been skinned by a bobcat. I added it to the site, which became a kind of olfactory smorgasbord.
The fox sprinkled the scat pile, but he didn't make a deposit.
Instead he decided to make a withdrawal.
But he didn't carry through. The squirrel hide was lying a few feet away. He only rearranged the smorgasbord.
Sunday, August 12, 2007
We named her meatloaf. She was rounded on top and squared off on the bottom edges. She looked solid. Actually, there were several meatloafs in the campground, all adult mantled ground squirrels.
There were also smaller ones, perhaps yearlings . . .
and certainly some of the most trim squirrels were young of the year.
I want to talk about fat squirrels. It's a relevant topic in light of the American addiction to junk food, rampant childhood obesity, and our obsession with dieting. They can teach us something. They have a good reason for getting fat, and they have a successful way of dieting.
First, a few words for those of you not familiar with this charming rodent.
Mantled ground squirrels inhabit the open coniferous forests of the Sierra Nevada and Rocky Mountains. These are great places to live in the summer when it's dry, sunny, and warm. In the spring the mountains offer nutritious fodder. Tender young plants are high in protein and fiber, so the squirrels don't gain much weight, and rest assured they have no complaints about "irregularity". As the forbs and herbs set seed and dry up, the mountains yield their gourmet luxuries. The squirrels then root about for hypogeous fungi, which we know as truffles. Still, they keep their mesomorphic physiques.
Then in late summer the conifers drop their cones, and our squirrels gorge on the protein and oil-packed manna from heaven. During the month of August they start to "plump out". By September, adults have three times the body fat they had in the summer. Juveniles on the other hand only gain about twice their summer fatness.
The seasons change. The dog days of August give way to freezing night-time temperatures, and then moisture-laden air from the Pacific drops a blanket of snow -- often as early as September. The mountains are a hard place to live when snow covers the countryside and temperatures are below freezing. Making it through the winter depends on getting enough food.
Squirrelly creatures have made two evolutionary choices: stay active and feed daily, or hole up and hibernate. Tree squirrels opted for an active athletic winter; they get bigger appetites, burn more energy, and tough it out. Chipmunks and mantled squirrels have opted for a restful comatose condition known as hibernation. Their appetite and metabolism shut down. They sleep and slowly burn fat. Chipmunks also have a lot of larders so they can snack periodically through the winter. Mantled squirrels tend not to hoard larders, and seem to rely almost entirely on their body fat.
Mantled squirrels undergo another mysterious change. As winter approaches their body water decreases. The point is this -- a critter whose body temperature hovers dangerously close to freezing may protect itself by lowering its own freezing point.
And what about the skinny mantled ground squirrels?
They have a problem, because without fat their bodies don't tell them it's time for winter sleep. Hunger drives them to continue their quest for food. With limited food they can't make a go of it. They are doomed.
We can draw only one conclusion: sometimes it's better to be fat.
Bartels, M.A. and D.P. Thompson. 1993. Spermophilus lateralis. Mammalian Species No 440:1-8.
Blake, B.H. 1972. The annual cycle and fat storage in two populations of golden-mantled ground squirrels. Journal of Mammalogy, 53(1):157-167.
Jameson, Jr. E.W. and R.A.Mead. 1964. Seasonal changes in body fat, water, and basic weight in Citellus lateralis, Eutamias speciosus and E. amoenus. Journal of Mammalogy, 45(3):359-365.
Jameson, Jr. E.W. 1964. Food consumption of hibernating and nonhibernating Citellus lateralis. Journal of Mammalogy, 46(4):634-640.
McKeever, S. 1964. The biology of the golden mantled ground squirrel, Citellus latralis. Ecological Monographs 34(4)383-401.
Pengelley, E.T. and K.C. Fisher. 1963. The effect of temperature and photoperiod on the yearly hibernating behavior of captive golden-mantled ground squirrels (Citellus lateralis tescorum). Canadian Journal of Zoology, 41:1103-1120.
Tevis, Jr., L. 1956. Observations on chipmunks and mantled squirrels in northeastern California. American Midland Naturalist 53(1):71-78.
Tevis, Jr., L. 1956. Invasion of a logged area by golden-mantled squirrels. Journal of Mammalogy 37(2):291-2.
Wednesday, August 8, 2007
Though I set three camera traps for mountain beavers, there was no escaping the brush rabbits. "Briar Jennies" thrive in the coastal scrub.
Kids may believe rabbits lay eggs, but grown-ups deem rabbits to be commonplace, uncharismatic, and often a nuisance.
I've always wanted to believe that knowledge begets appreciation, so my goal today is to convince you that these benign-looking creatures are an evolutionary success.
Let's start with the generalized rabbit body plan (we're talking rabbits and hares here). It's an enduring 50 million-year-old design that first appeared in the middle Eocene when the Lagomorpha split from rodents.
Rabbits and hares (of the family Leporidae) are built for speed. Elongated limbs and feet endow them with a long stride, while their speed comes from the concentration of muscles in the upper legs. They represent two basic models: hares are lanky high-speed runners that out-distance and out-manuever their pursuers. Rabbits are compact sprinters that rely more on cover to elude their predators. Generally speaking, these differences reflect their use of more open versus more closed habitats.
They have a remarkable digestive system that begins with the split upper lip. The "hare-lip" works like two fingers with the jaws, incisors and tongue to select plant parts with magical effect. The single pair of lower incisors cuts vegetation against two pairs of upper incisors, one in front of the other. An effective apparatus for pruning plants.
The two-cycle digestive engine is also uniquely lagomorph. During their wakeful nocturnal phase rabbits frequently churn out numerous bunny beans, which are recycled products of digestion. During the restful daytime hours they eat partially-digested soft feces from the caecum, which is essentially a large appendix or "fermentation vat" attached to the intestine. It sounds yucky, but it works quite well when you have to extract energy from a diet heavy on fiber. The first passage through the gut doesn't quite do the job. That's why rabbits and hares spend their inactive hours dozing, grooming, and eating partially digested feces (refecation).
When it comes to reproduction, evolution has tinkered less with rabbits than hares. The nestbuilding habits of rabbits, and the often naked, blind and helpless condition of their young are more primitive characteristics shared with most rodents. Hares on the other hand, use a dirt depression as a birth site, and the furry and wide-eyed young are hopping about in a few days.
But neither rabbits nor hares are stay-at-home moms. They stoke their young with highly nutritious milk only once a day. With an average litter size of 3 young, and as many as five litters during the 7-month breeding season, the brush rabbit can produce 15 young a year, and an ample food source for predators.
Predators hit the "dumb bunnies" hardest. The complacent and dreamy-looking weanlings are sitting ducks for bobcats, foxes, coyotes, and weasels. Only the quick-witted survive to reproduce.
The brush rabbit seen here looks to be a young of the year. Indeed it was visited by a larger rabbit, possibly its mother.
It spent most of the day lingering in front of this mountain beaver burrow, which it used no doubt for escape. When the weasel visited, it "made itself scarce". Thus, this rabbit seems to have advanced beyond dumb bunnyhood.
If all goes well, it will become a Briar Jenny, and in a few more months will go forth and procreate.
And if it doesn't go well? Then another rabbit will be there to take its place.
Asher, R. J., J. Meng, J. R. Wible, M. C. McKenna, G. W. Rougier, D. Dashzeveg, and M. J. Novacek. 2005. Stem Lagomorpha and the antiquity of Glires. Science 307(5712):1091-1094.
Chapman, J.A. 1974. Sylvilagus bachmani. Mammalian Species No. 34:1-4.
Howell, A.B. 1965. Speed in animals, their specializations for running and leaping. Hafner Publishing Company, New York.
Orr, R.T. 1940. The rabbits of California. Occasional papers of the California Academy of Sciences, XIX. 207 pp.
Monday, August 6, 2007
Butte Lake Campground, Lassen National Park:
The grandkids were swimming at Butte Lake when I overheard the camp host mention otters to a family near by. It piqued my interest, and later that afternoon I was lucky enough to engage the host as he was making the rounds checking camp sites.
"I overheard you mention otters today down at the boat launch. Are they stealing fish?"
"No, but we had one bite a swimmer here on the 4th of July. He was checked in right here at this camp site." Small coincidence.
The victim, I learned, was a young man in his thirties, who had planned to spend a few days at Butte Lake with his wife and 8-month old baby. They arrived at 5:00 that afternoon, unpacked, and went to the lake for a swim. The husband swam out about 100 yards, while mother and baby waited on the beach. Then he turned around and headed for shore. His wife saw the otter swimming towards him when he was about 50 feet from the beach.
It was NOT a member of the local welcoming committee. The otter sunk its teeth into the man's upper calf, and worked its way forward, biting him above the elbow, on the latissimus (under the arm), and twice on the face below the eye. I gathered that the body bites were on the right side, and the facial bites were on the left.
So much for a happy family camping trip. They left at 8:00 that evening, and headed for the nearest hospital in Susanville, an hour and a half away. The face bites required 11 stitches, and the doctors started rabies inoculations. One aggressive otter curtailed a three day camping trip to 3 hours, and the National Park Service posted a warning.
Apparently otter attacks are becoming more common in the US, and the most likely explanation is that human recreation is becoming more common in otter habitat. Otters are highly territorial and don't tolerate the intrusions of neighboring otters. Thay also have strong maternal instincts. So it is NOT unnatural for a mother to defend her youngsters against large swimming mammals that splash about and make loud noises. To a wild otter people can be scary as hell.
Perhaps that's what happened at Butte Lake. The otter birth peak is in March and April, and the young aren't weaned for another three months. This puts the mother and her mobile but inexperienced youngsters in the water in June and July, when they forage together as a family. You can expect such mothers to be protective.
That would explain the other July otter attack in the Sierra Nevada and one that took place in April when an otter attacked a crew team on the Connecticut River.
More difficult to explain however are otter attacks on pets. One would expect a territorial otter to drive a frisky lab out of the water, but wildlife biologists scratch their heads when an otter attacks and drowns an Eskimo dog. Is this normal behavior? Have they been eating bad (=chemically contaminated) fish? Or are they suffering from rabies?
Inevitably the call goes out to remove the animals.
Which raises the question. Where else but in nature do we punish healthy maternal instinct?
As this codger sees it, if you you want to live close to nature, be prepared for the risks. Isn't it better to be bitten by an otter than the Taco Bell chihuahua?