Filed under: biology, carnivores, mammals, vertebrates, zoology | Tags: biology, zoology, animal, behavior, animals, mammal, carnivore, pet, cat, vision
Part of my move to the Missouri River Valley included the acquisition of three cats. Or should I say the acquisition BY three cats. They belong to my host here and they’re wonderful.
The cats all love to play with water if it’s moving. They’ll spend long minutes staring and batting at a dripping faucet. Like most cats they’ll also play with just about anything that moves.
So how come?
Cats’ vision is actually different than our own. They do not see a static environment very well, but they are immediately attracted to and able to clearly see any movement against a background.
Their prey in the wild (and sometimes around the house), of course, is mostly small creatures. Often these creatures are well camouflaged. The one thing they can’t camouflage is their movement and cat vision takes advantage of that.
A dripping faucet, bouncing light or rolling cat toy are attractive to cats because their instinct is to chase small moving prey. And their vision is tuned to seeing it better.
In fact, a cats’ eyes are so keenly adapted to see motion more clearly (and so comparably poor at seeing non-moving things) that if you look very very closely into a cat’s eyes, you’ll see they vibrate! Just a little, but this vibration puts the whole world into motion. This way the cats can see things much more clearly.
This adaptation also helps them to see in the dark – cats are, really, nocturnal animals after all. In dim light their eyes can see the motion against a background, even if they can’t see the background details.
So if you want to attract the attention of a cat, move!
Filed under: biology, birds, vertebrates, zoology | Tags: animal, animals, behavior, biology, birds, nature, zoology
With my migration to the center of the country came an opportunity to put out a bird feeder. I’ve had it up for a little over a week now and there are birds coming regularly now.
It often takes a week or more for birds to discover a new feeder. Birds establish daily patterns of movement to make the most out of local resources (food and water) and it can take some time for them to break out of those patterns.
Actually, some birds, like House Sparrows (Passer domesticus) are better at breaking out of those patterns than others. In the case of the House Sparrow, they’re very good at it. This often means they’re the first ones to a new feeder.
Once one bird, such as a House Sparrow, has found the feeder, other birds start to notice. Birds are always watching out for what’s going on around them, even with other species of birds.
Some species are more alert to predators and some (like the House Sparrows) are more alert to new feeding opportunities. This way all the birds in an area benefit from taking advantage of the strengths of others.
This also happens, of course, within a species. Birds that flock pay attention to the birds around them. As different species have their strengths, some individuals are more alert to predators or food sources than others. All the birds in the flock benefit from watching the others.
And rarely is the same bird the one who always spots a danger or opportunity. Different birds in a flock and different species in an area will notice things at different times. Sometimes the House Sparrows will lead and sometimes the Jays will lead.
This same type of behavior is common to all animals that collect in groups. A herd of antelope is better than watching for a lion than a single antelope simply because there are more eyes pointed in more directions. A school of fish is more likely to notice a patch of food than a single fish.
We humans do it too. A group of people is more likely to see an oncoming car when crossing a road, or notice the sign of the restaurant they’re looking for.
In some neighborhoods too, there is a flocking behavior among humans. Once one person starts feeding birds and showing enjoyment, often some of their neighbors start doing it too.
The day before the first snow, I took this picture at Heron Haven, a small nature interpretation area in Omaha, Nebraska.
Less than 20 hours latter, the snow was piled high on the leaves of this maple tree.
Filed under: biology, botany, plants | Tags: biology, botany, nature, plants, trees
Having just posted about autumn, here in the Missouri Valley winter has hit. Yesterday we had our first snow of the year. It was very early, but does happen occasionally.
We’ve had generally unusually cold weather the past couple weeks. This has led to some interesting patterns in the fall color in the trees.
The fall color comes about when the plant essentially reabsorbs the green chlorophylls that allow the plant to undergo photosynthesis and make food for themselves. The other pigments in the leaves, usually melanins (black and brown colors) and xanthins (yellow colors) then can show off.
In the last post, I talked about the tilt of the earth in relation to the sun which causes a change in the length of daylight (called photoperiod). In many plants this change in daylight is what triggers the loss of chlorophyll. In other plants, it’s a change in temperature.
In the case of the plants here, the plants that are triggered by temperature and usually wait longer in the year, have been changing color already. Some of the other plants, that are triggered by daylight length, still have all their bright green leaves, and they are the ones that might be damaged by this early cold weather and snow.
The reason for the possible damage is partly in the answer to the question “why do the plants change at all?”.
Plants essentially are “cold blooded”. Their temperature is approximately the same as the surrounding environment and they don’t make their own “body” heat.
Like animals, plants do need to move things around inside their bodies. They move water, generally from the roots up to the leaves. They make food in the leaves through photosynthesis and have to move the food to the rest of the body so they can continue to grow. This food travels dissolved in some of the water that is brought up to the leaves.
The movement of water and food in plants is mostly due to gravity (for the food moving from the leaves) and evaporation (which pulls water up to the leaves).
When it gets too cold, the water doesn’t evaporate from the leaves so the movement upward stops. This means there’s no water coming in to the leaves to take the food down to the rest of the plant. In very cold conditions, the water may freeze, causing damage to the plant cells.
If a plant that normally drops its leaves in the fall is “caught” in a cold snap still with it’s fully functioning green leaves, the water in the leaves may freeze and kill the leaves before the plant has had a chance to take the nutrients out of the leaves to store for the winter non-growing season. This may make it more difficult for the plant to grow in the spring.
Evergreens, by the way, have a different way to cope with cold temperatures. I’ll cover that in a future post.
Filed under: biology, birds, botany, plants, seeds, zoology | Tags: biology, zoology, botany, birds, animal, behavior, nature, animals, plants, seeds, trees, astronomy, climate, geography
It’s that time of year in the Northern Hemisphere when the hours of daylight are getting shorter and temperatures in most places are getting cooler.
But at this same time, the Southern Hemisphere is starting to warm up. The hours of daylight are getting longer and while many may still it Fall (or Autumn), the season’s heading for summer.
The change has to do with the tilt in the axis of the Earth in relation to the sun. The planet’s rotation axis (the imaginary line through the earth between the north pole and the south pole) is tilted at about a 45 degree angle. As the planet takes its trip around the sun (which takes about 365 days), for about half that trip the north pole is closer to the sun than the south pole. For the other half of the trip, the south pole is closer.
The change-over happens on the days we call the “solstice”. Starting at the winter solstice (December 21st or 22nd), the north pole gradually points more an more toward the sun. At the summer solstice (June 21st or 22nd) the north pole starts pointing away from the sun.
These days are also known as the shortest and longest days of the year. The daylight in the northern hemisphere is longest on the summer solstice, and shortest in the southern hemisphere.
There are also two “equinox” days – around September 21 and March 20th. These are the “flip days” where the daylight and night time are of equal length. The north and south poles are, at those times, changing between pointing toward and away from the sun.
The length of daylight also affects the temperature. Less daylight means there’s less time for the sun to heat the earth (rocks, dirt, water), so the overall temperature drops.
Okay, what has all this got to do with biology? Lots.
Many plants and animals react to the length of daylight or to the change in temperature. Sometimes it’s difficult to figure out whether the organism is responding to light or heat.
But, as day length gets shorter (and temperature drops), some animals begin to migrate toward the hemisphere that’s getting more daylight. Some start eating more so they can put on weight for hibernation. Many plants set seed or flower as days get shorter.
As daylight gets longer, many animals get ready to breed. Many plants start their growth season and put out their flowers for pollination.
These changes in animal and plant behavior are, of course, more pronounced the farther north and south the organisms live. Near the equator the changes are not nearly as dramatic.
The Amazon and Congo Rainforests, for instance, don’t have as much daylight change as here in the north-central Great Plains of North America. The sun is always nearly overhead for them. So, temperatures there (except in the highlands) rarely get really cold. While here, we’re expecting snow already this weekend, just about three weeks after the equinox.
So, all those changes in the world around you – trees budding or losing their leaves, animals migrating, flowers blooming, are responses to the way the Earth is tilted in space.
Happy southern summer and northern winter.
Filed under: biology, birds, vertebrates, zoology | Tags: animal, animals, biology, bird feeding, birds, chickadee, nature
About a week ago I hung up a bird feeder in my new backyard. It’s a tube feeder filled with safflower seeds.
Here in the Missouri River Valley, that’s apparently a good seed to put out to attract birds other than grackles (which come to the yard anyway).
Today I got the first birds to visit! The first I saw was a House Sparrow, which is introduced and nothing special. But it was quickly followed by a White-breasted Nuthatch. Also nothing special to me, as they come to feeders where ever they’re found.
The third bird, though! It was a Black-capped Chickadee. Of course that’s not too surprising, since they’re a common bird at feeders, but it’s the first one I’ve ever had at a feeder.
I’ve fed birds in Mississippi and in California, two places where you’re not likely to get Black-capped Chickadee.
In Mississippi I would get Carolina Chickadees, which do hybridize with the Black-capped, and are difficult to tell apart except for song (at least at first glance). In California the Chestnut-backed Chickadee was the feeder chickadee. Mountain Chickadees also occur in California, but not in the lowland areas I lived.
Chickadees are some of my favorite birds. They belong to the family Paridae that includes the chickadees, tits and titmice. They are some of the most intelligent of birds, and individuals of several species have learned extremely complex behaviors. All are small, generally much smaller than blackbirds.
So. I’m going to enjoy my bird feeders and watching those chickadees.
Filed under: biology, botany, plants | Tags: biology, botany, nature, plants, trees
Autumn is upon us and non-human animals are not the only migrants.
Since my last post I’ve migrated from the Sierra Nevada foothills to the northern Great Plains. A completely different ecosystem indeed.
I’m now living in the Missouri River Valley on the eastern edge of the great plains, just where the eastern deciduous forest begins. The equinox occurred on the this week (September 21st) and almost immediately the leaves started falling from the trees.
We mowed the lawn today and by the time we were through there were already a sprinkling of leaves on the lawn. As the days shorten and the temperature cools the chlorophyll is drying up in those leaves, some being chemically broken down and used or stored as food for the plants.
During the growing season the chlorophyll masks other pigments in the leaves. As it diminishes, it leaves behind the yellow, red and brown pigments (melanins and xanthins and such) which show through. Those are the pigments that make the trees those glorious fall colors. They’re present all the time, they’re just “covered up” by the green.
Of course in California and the southwest, the rainy season is coming around. Many plants will be undergoing the opposite effect. The summer-dry plants that have been brown all summer will start to grow new leaves and the landscape will brighten up and turn green.
Meanwhile, of course, in the southern hemisphere spring has just started and the plants will be heading into their colorful flower shows.
Filed under: biology, botany, plants, seeds | Tags: biology, botany, nature, plants, trees
Still up at the ranch in the Sierra foothills and having a great time.
The habitat here is, as are much of the foothills, a mix of oak/gray pine savannah and woodland.
Most of the oaks here are blue oaks (Quercus douglasii). They’re a tall, mostly upright tree, the typical “foothills oak” through much of California. The leaves are “oak shaped” (broadly lobed) and covered with a grayish wax that helps to prevent the leaves from drying out. This is an adaptation to their dry environment. The gray waxy coating gives the leaves a blue-green cast in the right light, which gives them their common name.
There are also some interior live oaks (Quercus wislizeni) here too. Those are more variable and have both “entire” (no lobes or prickles on the leaves) and spiny leaves on the same tree, usually on the same branch. The trees are generally less upright and more spreading than the blue oaks.
I’ve been told that the spiny leaves only appear once a branch has been disturbed by having leaves eaten or otherwise pulled from the tree. I’ve not been able to confirm this. I’ve seen trees where this would explain the pattern of where the spiny leaves are growing, but I’ve seen some where it’s not so obvious. I have not spent enough time with the species to do the obvious experiment of pulling off a smooth-edged leaf and seeing what happens.
The area here is heavily grazed. There are cattle on the ranch, and sheep in the house “yard” so no much goes unmolested unless fenced. Most of the oaks are fully mature specimens. There are several young oaks (about six inches or less in diameter) around the house, which is good to see, but there are no seedlings. The cattle and sheep would eat many of the acorns (oak seeds) and the California ground squirrels (Spermophilus beechyii) that seem to be everywhere will eat them too. That gives the oaks very little chance to reproduce.
This is a problem all over California with most of the oak species here. Oak woodland and oak savannah (grassland with occasional oaks in it) are great places to build orchards, farms and houses. They’re also great places to run cattle. All of those activities are bad for oak reproduction, of course.
For many years there has been a concerted effort to replant oaks, and make sure that the stands remaining have a chance to regenerate. This is more important in the central valley where there is very little wild habitat left – most of it having gone to agriculture 50 to 100 years ago.
Since many of the more endangered oaks live to 400 or more years old and with the mature trees being fairly common, it may seem like it’s not an urgent problem to some. However, when Sudden Oak Death Syndrome (SODS) hit, it became one. The older mature oaks started dying and there still were no replacements for them.
Now that Some species could face extinction it’s become much more urgent to make sure the oaks are able to reproduce. Progress is being made in slowing the spread of SODS as well as in replanting. Hopefully the work will prevent the collapse of any of the oak species – and the habitat they support.
Filed under: biology, botany, mammals, plants, seeds | Tags: biology, botany, grass, mammal, nature, plants, seeds
I’m staying at the ranch of some friends for a few weeks in the Sierra Nevada foothills in central California. Right now it’s high summer here and most of the annual plants have all gone to seed and dried out.
There are two ranch dogs that also spend a lot of time in the house. When we go out for a walk or after they’ve been outside they return covered with burrs and awns and have to be combed out.
Burrs and awns are specialized seed packets, allowing plants to send their seeds off into the distance. This allows the parent plants to not have to compete with their offspring, and also allows the plants to colonize new areas.
Burrs are round or oval packets of seed that are covered with small hooked “hairs” that will grab on to the fur of a passing animal (or the clothes of a passing human). These “hairs” of some burrs were apparently the inspiration for the original brand of hook-and-loop fastener (Velcro). Burrs can be quite sticky – and the hook-and-loop fastener design is used to hold the tiles on the outside of the U.S. Space Shuttle.
Awns are usually arrowhead shaped and have barbs on them that also catch on the hair of passing animals. More generally, awns are also the flower of many grasses. You may be familiar with “foxtails”, which are large grass awns.
While the animals give a ride to the next generation of plants, there seems not to be much benefit to them from these sticky hangers-on. They can get badly tangled in fur and the area may become irritated. Awns are structured, like an arrowhead, so that when the animal moves the awn is propelled forward. Since the tips of awns are sharp, they can pierce the skin of an animal and have been known to travel completely through their “host” and out the other side of the body.
In environments where burrs and awns are common, such as the open lands of the western U.S., most native mammals have short fur. The shorter the fur, the fewer burrs and awns are picked up. That’s illustrated by the dogs here – one has a fairly short coat, the other has a coat just a bit longer. We spend twice or three times as much time combing out the longer haired dog.
One very special burr is the Devil’s Claw (Proboscidea louisianica) of the southwestern United States. The fruit of this flower has huge curving hooks on one end. It’s thought by some that the only thing these hooks might be useful for it catching hold of the long fur of a mammoth. Even though the he plants do get around on their own today, though.
Photos and more information about Devil’s Claw plants can be found at CalFlora
Filed under: biology, carnivores, dinosaurs, evolution, mammals, paleontology, vertebrates, zoology | Tags: animal, animals, biology, carnivore, dinosaurs, mammal, paleontology, zoology
Dinosaurs may have weighed less than previously thought.
According to Scientific American, a paper published in the Jun 21, 2009 issue of the Journal of Zoology, (http://www.wiley.com/bw/journal.asp?ref=0952-8369) has reexamined the calculations upon which our understanding of the weights of non-avian dinosaurs.
The old calculations, used for several decades, apparently are full of flaws and end up estimating weight at about twice the actual weight. The authors of the paper have proposed new calculations that are much more accurate. In estimating an elephant’s weight from a single femur, the new calculations were only seven pounds off the actual recorded weight of the elephant (1300 actual, 1307 estimated). The old calculation estimated the elephant’s weight at over 20,000 pounds.
As the Scientific American article says, this has the potential to change much of what we think we know about dinosaurs. Tyrannosaurus rex, for instance, goes from a six ton to a three ton carnivore. Still a mighty beast, not something you want to meet on a dark night in a jungle.
However, a three ton (6000 pound) carnivore could require much less food. New estimates of weights for the large dinosaurs should help solve several apparent riddles about how such creatures could find enough food to sustain themselves.
There are many more exciting potential ramifications for this change in calculation. Look for new insights to be coming out of paleontology – and not just for dinosaurs. There are lots of mammals that will need their weight recalculated.
