There was quick reaction to President Donald Trump's announcement last week that he plans to follow through on his campaign pledge to build a wall on the U.S.-Mexican border. Conservative and liberal commentators alike were channeling their inner Robert Frost, referencing his poem "Mending Walls" that starts "Something there is that doesn't love a wall" and contains the well-known proverb, "Good fences make good neighbors."
It is worth remembering that this border is an imaginary line we draw ourselves. It's true that the Rio Grande separates Texas and Mexico. But much of the rest of the border is dirt. The only way to see the border is to draw a line.
Animals don't really respect borders the way we'd like them to. The jaguars, gray wolves and ocelots which depend on ranges that cross the U.S.-Mexican border don't see it. Humans can detect the human signs of a border. But they tend to think about how to get across it rather than how to stay on one side. Even East Berliners in the days of the famously lethal Berlin Wall found ways to get across to West Berlin. They went up, around, under and through it again and again.