Diurnal Activity Cycles

My wife and I (both writing theses this spring) and two cats share a very small studio apartment. One way we make maximum use of the space is by having different sleep-wake schedules. I do my most effective writing between 9PM and 1AM. Iris gets the most done from 6AM to 10AM. I have the easiest time concentrating at that time, and only partly because everyone else is asleep. FeLion, our older cat, does some of her best suckling on inanimate objects in the middle of the day. Tigrinum, the kitten, expends most of his energy from 2AM to 6AM, charging around the house and leaping from the top of his cat-tree onto his sleeping humans. Come to think of it, it makes a pretty lousy system.

There is a well established pattern of individuals of different ages waking and sleeping at different times. Older adults and young children tend to go to sleep early and wake up early. Teenagers tend to stay up late and go to bed late. People in all the ages in between are pretty variable. These patterns are well known to most people, but I'm not sure we understand their evolutionary basis. Why did humans evolve to have sleep schedules that vary individually and with age as much as they do? My guess is that it had to do with avoiding competition within groups for space and forage. The old people and the little kids left the cave or the hut early in the morning and foraged before everyone else was up. In the evening, after everyone else was asleep the young people would stay up and try to impress potential mating partners. That was probably the easiest time to find some privacy without straying too far from the village. One thing I wonder about, do other primates have similar variation in their diurnal activity cycles? That right there is a good evolutionary biodemography question.

Elastic replacement

I've been thinking on an off for several years about the concept of 'elastic replacement.' That is term I made up to mean when the rate at which new things arise increases in response to the effort to remove old things. The example that got me started thinking about this was a political one. For the early years of the US occupation of Iraq, the Bush administration frequently cited statistics on how many terrorists had been killed or captured as a result of US action in Iraq. What they never seemed to consider was that US action in Iraq might also be increasing the replacement of terrorists by making it easier for terrorists to find and recruit young people who might have otherwise been non-violent. The size of any population is determined by not only the number leaving, but also the number entering, and by measuring only one portion of our effect, the US government necessarily got a biased picture of our effect. The CIA has confirmed that the number of active terrorist in Iraq rapidly increased rather than decreasing through the first years of the Iraq war.

This general idea carries over into all sorts of arenas. When a giant old tree falls, it makes space for hundreds of seedlings. When I comb my cat to remove loose hairs, I loosen lots more hairs and possibly even stimulate increased hair growth. WWII caused far fewer deaths of US soldiers than the ensuing baby-boom caused births of US babies. Eating all the chocolate so that my wife won't be tempted by it inspires her to go out and buy more chocolate. Responding to all the emails I should have responded to a long time ago brings in even more emails that need to be responded to.

Elastic replacement seems to be an extremely common class of unintended consequences. Humans don't seem to be good at considering it, but we should try.

Can't live with'em can't live without 'em.

Biologists and Ecologists have (mostly) learned to give at least some forethought to the consequences of introducing non-native species. The problems invasive species cause are often most sever on islands, where the native species often have limited evolutionary experience dealing with the relative of the invaders. For example, many island endemic bird species were flightless, as there were no land based predators to need to fly away from, so why bother building all that expensive escape equipment when there is nobody to escape from. Other island nesting birds, like those on Macquarie Island can fly (except the penguins) but don't seem to have the right tricks in their behavioral repertoires to escape from introduced predators.

A recent attempt to help these birds is making ecologists aware that one has to be very careful not only about introducing invasive species, but also about removing them. A commentary in Nature describes the story:

Cats were introduced to the Macquarie Island in 1818; sealers introduced rabbits 60 years later.

The rabbits tore through the island's vegetation. In 1968, the rabbit flea was introduced. Once that had established the lethal myxomatosis virus — which the flea spreads — was introduced in 1978.

Rabbit numbers crashed, but then the cats, which had previously eaten rabbits, switched their attentions to the island's birds.

But once the cats were gone, the few hardy rabbits that had survived both the cats and the myxomatosis emerged and began doing what rabbits do best — breeding and eating.

So the island has cats, rabbits, rabbit fleas, rabbit viruses as well as rats and mice, all introduced. The cats were bad for the birds because they ate them. The rabbits were introduced and were bad for the birds because they destroyed the vegetation, but good in that they distracted the cats. And the cats were at least partly good for the birds, because they ate the rabbits. Some kind of unstable plateau was reached. And then disease was introduced to reduce the rabbit population, leaving a whole bunch of hungry cats, which were bad for the birds. But then the cats were killed off, which was bad for the birds and everything else (except the rabbits, rats and mice) because for the first time there were rabbits without cats on the island. The rabbits, unchecked, ate through most of the island's plants. And this, of course, is a vast over simplification.

The Australian authorities who run Macquarie Island are now trying to figure out how to exterminate the rabbits, rats and mice without harming other native populations, such as the seals and sea lions that breed on the island. They estimate it will take tens of millions of dollars, and that may be optimistic. Few efforts to irradicate rodents from any land mass of decent size have succeeded. Macquarie Island, at 128 km², offers a lot of hiding places big enough for a rat. Miss one pregnant rat and in just few years you are back to square one. And who knows what effect the rats would have without rabbits around harboring disease and eating potential cover? Rats eat bird eggs, and have been known to finish off large bird colonies in just a few years.

The lesson learned is that just because introducing species is generally bad, removing those introduced species from an ecosystem that has started to adjust to their input isn't always good. At least it has to be done very carefuly.

Picture of Science! Kitten in an Academic Household

Picture of Science! Tiger Salamander Larvae

My wife and I were walking up to Cecret Lake, at 10,000 ft. in Little Cottonwood Canyon, above Salt Lake City. When we got there, I said, "Oh fish!" Iris pointed out that they had too many dangley bits, and I took a closer look. "Tadpoles!" I said, but then I remembered that tadpoles don't have external gills along the back of the head like that. So I eventually figured out they must be salamander larvae. But what salamader has 6 inch long larvae? The tiger salamander, Ambystoma tigrinum.
This struck us as particularly fortuitous, as we only a month ago named a kitten Tigrinum, in honor of this species. Quite a resemblance, wouldn't you say?


Tiger salamanders often breed in mountain lakes and streams, and their populations often die out when fish are introduced to their previously fishless breeding grounds. Those big slow larvae are easy prey for predatory fish.

Catnip -> Olfaction -> Happy

My Friend Terry Johnson is a lecturer in Bioengeneering at UC Berkeley. He also writes the Ask a Biogeek column for io9.com. Now he is one of the judges for their Mad Science Contest: Build a Lifeform. And, in investigating my idea for an artificial organism, I came across this abstract:

Hart BL, Leedy MG.1985. Analysis of the catnip reaction: mediation by olfactory system, not vomeronasal organ. Behav Neural Biol. 44(1):38-46.

Pet owners and behavioral scientists alike are fascinated by unique behavioral reactions that cats show in the presence of catnip. These experiments explored the possibility that the catnip reaction might be triggered by chemosensory stimulation of the vomeronasal organ. In the chewing and mouthing of the catnip source, substances might be dissolved in saliva and transported to the vomeronasal organ. The rolling and rubbing during a catnip reaction might be a sexual response activated by the accessory olfactory system since the system projects to parts of the brain involved in mediation of sexual behavior. However, removal of the vomeronasal organ did not attenuate any of the behavioral reactions to catnip. Olfactory bulbectomy immediately eliminated catnip responding, revealing that the chemosensory stimulus evoking the catnip reaction is undoubtedly mediated through the main olfactory system. Catnip activates behavioral elements associated with several species-specific behaviors, including sniffing and chewing as associated with oral appetitive behavior, rolling and rubbing characteristic of female sexual behavior, batting the catnip source characteristic of play behavior, and a type of kicking associated with predatory behavior. These behavioral reactions occur randomly and intermittently.

The moral of the story seems to be that:
A. Cats respond to catnip through their olfaction, the type of smelling that humans do fairly well, rather than through the vomeronasal organ, the part of smelling that humans don't seem to do at all.
B. Catnip elicits from cats behaviors associated with almost every active things cats enjoy (eating, playing, sex and hunting). Catnip does not elicit the calming and resting behaviors such as self-grooming and napping that cats also enjoy. Catnip also does not elict behavior associated with things cats don't enjoy (fighting, danger, housechoirs).

Based on this, and my own observations, it seems likely that catnip is a quick-acting stimulant, extremely pleasant to the cat and absorbed through the olfactory epithelium.

Stefanie Schwartz, in her book "Psychoactive Herbs in Veterinary Medicine" list some other useful facts. Catnip response is not associated with any know histological or physiological effect, (meaning that while it certainly does something in the body, it is something subtle) catnip is not toxic even at relatively high doses, and the physiological and psychological effects are very different in cats than in humans. In humans, catnip is mild sedative, and smoked catnip is said to have similar psychtrophic effects to smoke marijiana. In cats, it is clearly a stimulant. In neither species does it have any known side effects.

Nepetalactone, the active ingredient, is also aparrently a powerful insect repellant, driving off both lice and cockroaches many times more powerfully than does DEET.

Three Birds, Two Cats and a primate

It was an awful lot of croaking for a Friday afternoon. I went out on the patio to investigate. The Ravens were in an uproar about something. My first thought was that one of their nestlings had fledged and was hiding in our yard. They were flying back and forth, low over the top of the apple tree, scolding and creaking and booming. I decided their fledgling must be in the top of the tree, and they must be trying to tell it that this was not a safe place. My eyes scanning the trees for a fledgling, I was impressed and intimidated to see these two birds, each the size of a large hawk, diving and screaming just over my head. And just as I was starting to think they might really be screaming directly at me, I heard something moving only a couple of yards from my feet. Looking down, I saw this:

A turkey right in our garden, and clearly the focus of the Ravens' ire. They were responding to it as they would any large animal (except humans and deer, which they seem to be used to ) getting too close to their nest tree: by screaming and scolding, "you better git the hell off our land if you know what's good fer ya!" The turkey had apparently responded by hunkering down by Betty's compost bin.


I pulled out my cell phone and started to take pictures. After a couple of minutes the ravens went off to scream at something else and the turkey and I were left to talk amongst ourselves. I went for my better camera, but finding the batteries dead, knocked on Betty's door and said, "Hi Betty, sorry to bother you, but there is a turkey in the backyard. You should bring your camera please."

It was a very tame turkey. I taking photos with my cellphone and Betty with her big digital SLR each stood about 10 feet from it. "People have been feeding it." I said as it watched us hopefully and I resisted the urge to feed it. It rooted around in the garden.

FeLion wandered out onto the patio and saw the turkey. Her response seemed perfectly split between, "That is the biggest bird I have ever seen, I'm gonna eat it." and "that is the bigest bird I have ever seen, I hope it doesn't try to eat me." She was frozen with indecision.


Betty's cat Sophie, on the other hand, was not at all reluctant to charge a bird twice her weight. She burst out of the bushes and sprinted toward the turkey, who turned tail and ran up the step to the very top of our yard.


When I caught up, the turkey was defending a position on top of the garden gate arch, and Sophie was attempting to storm the battlements.

Eventually she succeeded, and the Turkey took to the air, at which point the Ravens resumed their harrying. The turkey, pursued from above an below. stopped in a tangle of low Eucalyptus branches. Betty and I snapped a few more shots and then took the cats inside.

Duetting Alone

I attended a seminar yesterday given by a former lab mate of mine, discussing her work to understand the duetting call of the California Towhee.

(An article in the Berkeley Alumni Magazine discusses the work and links to a sound file of the call.)

She described how this squeal-call is almost never given by just one bird, and is almost always a duet by the pairs who mate for life (and cheat on each other like mad).
It has been called the "reunion squeal" because the pair always fly towards each other while duetting, and end the duet side by side.

So this morning I was in my neighbor's backyard and noticed a pile of feathers on the ground. They have four outside cats, so I was not surprised. I bent over to examine the feathers and see who the victim was. Drab brown feathers. The wing and tail feathers were too small for a robin or a jay, but too big for most of the sparrows and finches around here. Then I noticed the clump of orange feathers, just the color of a towhee's undertail coverts. A California Towhee, one of the most common birds in the neighborhood, had bit it.
As I stood up, I heard the squeal. A rather half hearted squeal I thought. Then I looked up to see the towhee, sitting on the fence, squealing. It wasn't a half hearted squeal, it was that this bird was doing its half of the duet alone. It was initiating the reunion squeal, but couldn't reunite, because its mate wouldn't squeal back. It squealed twice more in the next several minutes, far more often than is common among pairs.
The cats sat on their lawn chairs and looked smug.

DUDES (Diurnal Urban Detritus Eating Sparrows)

There are at least a dozen outdoor housecats on my block. And, as you might expect, not a whole lot of ground dwelling small wildlife. A few salamanders, the very occasional rat (the only times I've seen these there were at least two cats in purrsuit) and some squirells which can outclimb any of the cats. And there is really only one bird species that spends much time on the gound, a big drab brown sparrow called the California Towhee.

Today I saw two of them fighting. A frantic ball of beaks and feathers twisting crazily through the air. They were so intent on mauling each other, they crashed first into the neighbors' fence, then onto the driveway. The instant they touched down, still rolling and pecking, a cat appeared a few yards from them, coming for them at full speed. The cat pounced, and while it was in the air the towhees joined it, but as it began to come down, they accelerated straight upwards. The cat got nothing but the feathers they had torn from each other.

I've seen birds escape preditors before, but nothing quite that close or sudden. These birds clearly had practice. How could they not, given the feline density around here? But somehow, California Towhees seem to thrive, feeding on the ground, in exactly the kinds of neighborhoods that are full of cats.

Like most species able to exploit human created niches, they've got a bright future ahead of them. The cats could even be good for them, keeping out rodents and other birds that would compete with the Towhees for food.

And that is how we get from natural history observation to testable hypothesis.