Exotic Animals

As I’ve been writing this blog, you’ve probably been noticing some common threads weaving in and out of various posts: the relationships between animal groups, the nature of evolution, and the modern evidence of evolution.

To start with, in any discussion of evolution, you need to define a theory.  In popular usage, a theory is basically a “best guess” as to why something happened; in science, however, a theory is a well supported supposition, explaining observed facts.

The next definition you need is for evolution.  In modern biology, evolution is simply the name given to the fact that species change over time, and that similar species are likely to be closely related genetically.

These two definitions make it clear that there is no one “theory of evolution.” Evolution is an observed fact; there are theories designed to explain the fact, and there is a great deal of debate among biologists about those theories.

So what are some of the theories which have been put out there to explain evolution?  Well, I am not a biologist, but I do like the field and try to read up on it, so here is my take on some theories of evolution:

1) The most venerable, of course, is Darwin’s theory of natural selection.  Darwin’s model describes how, when individual organisms act in their own best interest (defined as reproductive success; leaving the most surviving offspring), they will tend to pass favorable features on to succeeding generations.  As a result, populations will change over time.

2) Theories of genetic contraints on development.  These get complex.  Basically, in a strictly Darwinian natural selection, organisms vary randomly, and the fortuitously best adapted will survive and reproduce.  However, organisms are not truly random with respect to variation.  As complex systems in their own right, organisms are constrained in how they can change by their genetic code and body structure.  These constraints can guide the paths of evolution.

3) Punctuated Equilibrium is a theory about the pattern of evolution.  It takes the fossil record literally, and predicts that gradual change is not to be expected.  Rather, that species are in stasis for most of their history, and have bursts of evolutionary change at the beginning and end of stasis periods.  These bursts are incredibly long by human standards, 10,000 to 100,000+ years, but minute specks of time compared to the 500 million year history of animal life on Earth.

As you can see, one fact, evolution, can spur people to develop numerous theories.  These burgeoning theories do not mean that the fact is wrong; only that it is complex, with far reaching implications.  A fact like evolution, which predicts that all life arose from a single common ancestory, meets that definition.

Bugs are everywhere.  Oh joy.

Everyone in the Midwest knows by now, that it’s Cicada Time.

Cicadas are the famous insects that live underground for most of their lives, and only emerge every 17 years to mate, feed, and make a lot of noise, and die messily on the lawn, the sidewalk, the windshield of the car, etc, etc, etc…

Actually, that’s not quite accurate.  There are several species of cicada, with varying emergence cylces.  Some cycles are 5 years, some 7, some 9, and then there are the famous 13 and 17 year cicadas.  You can see these as a child, and forget all about them until your twenties….

Our focus on their emergence cycle is really a sort of human-parochialism.  Cicadas are not dormant while they are underground.  They have several molts between the time they hatch and the time they emerge, and the intervening larval and nymphal stages feed, move around, grow, and interact with each other and with their environment.  At the end of this multi-year growth period, the final molt occurs, and the adult insect (what we think of as a “cicada”) emerges from the ground, feeds on leaves, mates, lays eggs, and dies.

The multi-year cycle is most likely an evolutionary adaptation to avoiding predators. Cicadas are highly nutritious, and make excellent meals for blue jays, robins, crows, and rodents.  None of these predators, however, can depend on cicadas for food, since they can only hunt them when they are above ground.  And when the cicadas do emerge, they emerge in such numbers that the predators cannot possibly get them all.

So remember, no matter how much of a nuisance they are when they come out, cicadas’ lives are much longer than you normally think, and for the most part, they are completely unnoticed.

I got to meet, and help care for, a baby wallaby.

A few years ago, in the winter of 2001, I had the opportunity to help care
for a baby wallaby.  Why the chance came up is a long story; it will suffice to
say that I couldn’t turn it down.

So what’s a wallaby, and what kind of care do the babies need?

Wallabies are marsupials, native to Australia, and closely related to
kangaroos.  The main difference between wallabies and roos is size; while
kangaroos are person-sized or larger, wallabies are usually no bigger than a
medium sized dog.  Like all marsupials, wallabies are born at a very early
stage, and the mother holds them in a pouch until they mature enough to take
care of themselves.

Wallabies are herbivores.  In the wild, they graze on various grasses, and
browse on small shrubbs.  They are bipedal hoppers, meaning they move their back
legs in unison, and they have a long, heavy tail which helps to balance them
when they hop at full speed.

It’s illegal to export animals from Australia, but wallabies will breed
readily in captivity, and there are several breeders in the US, especially in
the western states.  The original stock was brought to the US before Australia’s
export ban went into effect.

The wallaby that I helped to foster was a few months old, and male.  He was
no longer nursing, so I didn’t have to bottle feed him, but he did have a big
quilted pouch that he didn’t like to leave.  He enjoyed being carried around in
the pouch.  He ate various grasses, moslty timothy, which are readily available
at pet stores as rabbit food.  He also enjoyed root vegetables, particularly
carrots.  He would eat these right from my hands.

When he wasn’t being carried around in the pouch, or allowed to run
supervised around my apartment, he lived in an ordinary porta-crib.  A heavy
blanket over the top kept him from jumping out, and an ordinary rabbit water
bottle was available when he got thirsty.

He was a pretty cuddly little guy, but not very smart, and not
house-trainable.  I won’t talk abou the cleanup required….

I wouldn’t recommend keeping a wallaby unless you have a ranch to let him
run.  This is why the breeder are mainly in the west; they can house the animals
outdoors, in a similar habitat to what they came from.  Still, helping to foster
this baby was an amazing experience.

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